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^r6U 


HARVARD    UNIVERSITY 
-^ 

Library  of  the 

Museum  of 

Comparative  Zoology 


3-t\/A  -  Prov  o 

Brigham  Young  University 
Scienc  Bulletin 


THE  PEREGRINE  FALCON  IN  UTAH, 

EMPHASIZING  ECOLOGY  AND 

COMPETITION  WITH  THE 

PRAIRIE  FALCON 

MUS.  COMP.  ZOOl- 
L/BRARY 

SEP  24  1973 

HARVARD 
byUNJVERSlTY 

Richard  D.  Porter  and  Clayton  M.  White 

in  collaboration  with 
Robert  J.  Erwin 


BIOLOGICAL  SERIES— VOLUME  XVIII,  NUMBER   1 
JUNE  1973/ISSN  0068-1024 


BRIGHAM  YOUNG   UNIVERSITY   SCIENCE  BULLETIN 
BIOLOGICAL  SERIES 

Editor:   Stanley  L.  Welsh,  Department  of  Botany, 

Brigham  Young  University,  Provo,  Utah 

Acting  Editor:   Vernon  J.  Tipton,  Zoology 

Members  of  the  Editorial  Board: 

Ferron  L.  Andersen,  Zoology 
Joseph  R.  Murdock,  Botany 
WiLMER  W.  Tanner,  Zoology 

Ex  officio  Members: 

A.   Lester  Allen,  Dean,  College  of  Biological  and  Agricultural 
Sciences 

Ernest  L.  Olson,  Director,  Brigham  Young  University  Press 

The  Brigham  Young  University  Science  Bulletin,  Biological  Series,  publishes 
acceptable  papers,  particularly  large  manuscripts,  on  all  phases  of  biology. 

Separate  numbers  and  back  volumes  can  be  purchased  from  University  Press 
Marketing,  Brigham  Young  University,  Provo,  Utah  84602.  All  remittances  should 
be  made  payable  to  Brigham  Young  University. 

Orders  and  materials  for  library  exchange  should  be  directed  to  the  Division 
of  Gifts  and  Exchange,  Brigham  Young  University  Library,  Provo,  Utah  84602. 


Brigham  Young  University 
Science  Bulletin 


THE  PEREGRINE  FALCON  IN  UTAH, 

EMPHASIZING  ECOLOGY  AND 

COMPETITION  WITH  THE 

PRAIRIE  FALCON 


by 
Richard  D.  Porter  and  Clayton  M.  White 

in  collaboration  with 
Robert  J.  Erwin 


BIOLOGICAL  SERIES— VOLUME  XVIII,   NUMBER   1 
JUNE  1973/ISSN  0068-1024 


Frontispiece.  Male  (tierce!)  Peregrine  Falcon  on  rock  in  front  of  eyrie  (Table  1,  site  7);  it  is  clutching  a  young 
American  Avocet  ( Recurvirostra  amcricuna),  that  was  fed  to  tlie  young  falcons,  c.  New  York  Times  Co.,  1971. 
Photo  by  R.  D.  Porter,  1952. 


TABLE  OF  CONTENTS 

ABSTRACT    1 

INTRODUCTION     1 

GEOGRAPHIC  DISTRIBUTION  IN  UTAH  2 

Historic    Records    2 

Specimen   Records   2 

Nesting    Records    2 

Postnesting  Season  and  Winter     Records      9 

DENSITY  DISTRIBUTION  OF  PEREGRINE  EYRIES  IN  UTAH  12 

TOPOGRAPHY.    CLIMATE,    AND    PLANT    COVER    IN  UTAH  13 

ECOLOGICAL   DISTRIBUTION   OF   UTAH  PEREGRINES  14 

Climate    14 

Altitude   '. 15 

Habitat    Niche   15 

Nesting   Sites   19 

Cliff   Orientation   19 

Rock  T)pe,  Cliff  Size,  and  Eyrie  Height  19 

Hunting    Sites    21 

Food  Niche  28 

NESTING  BEHAVIOR  IN  UTAH  32 

History  of  Nesting  at  a  Wasatch  Mountain  Eyrie  32 

Egg   Laying   38 

Incubation  41 

PEREGRINE  DECLINE  IN  UTAH  41 

Climatic  Change  Hypothesis  for  Peregrine  Decline  42 

Pesticide  Hypothesis  for  Peregrine  Decline  44 

Pesticide  Syndrome  in  Utah  Peregrines  44 

Residues  of  Pesticides  in  Peregrine  Prey  Species  46 

Mosquitocide   Usage  in   Utah   46 

Disease   Hypothesis  for  Peregrine  Decline  47 

Human  Activity  Factors  in  the  Decline  of  the  Peregrine    47 

FACTORS    INFLUENCING   PEREGRINE    DISTRIBUTION   AND   ABUNDANCE   IN   UTAH   48 

Water,  Food,  and  Nesting  Sites  as  Limiting  Factors   49 

Interspecific  Competition   during  Nesting  Season  50 

Some  Factors  Modifying  Competition  and  Success  51 

Competition  with  the  Prairie  Falcon  for  Food  52 

Competition  with  the  Prairie  Falcon  for  Eyrie  Sites  55 

Directional   Exposure  Preferences   55 

Height  Preference  for  Cliffs  and  Eyrie  Sites  56 

Eyrie   Type   Preferences   56 

Size  Preference  for  Nesting  Area  58 

Aggressive    Interactions   between   Peregrines    and   Prairie    Falcons    59 

Date  of  Egg  Laying  as  a  Competitive  Factor  61 

Reproductive  Potential  as  a  Competitive  Factor  62 

PLEISTOCENE  AND  PREHISTORIC  PEREGRINE  AND   PRAIRIE   FALCON   DISTRIBUTIONAL 

RELATIONSHIPS     62 

Pleistocene  Distributional   Records   62 

Post- Pleistocene  Distributional  Records  63 

Lake  Bonneville  and  Peregrine  Distribution  in  Utah  63 

SUMMARY  AND  CONCLUSIONS  65 

Addendum    70 

ACKNOWLEDGMENTS     70 

APPENDIX     —ADDITIONAL  HISTORY  OF  DDT  USAGE   AS   A   MOSQUITOCIDE   IN   UTAH   70 

LITERATURE   CITED   71 


THE  PEREGRINE   FALCON   IN   UTAH,   EMPHASIZING 
ECOLOGY  AND  COMPETITION  WITH  THE  PRAIRIE  FALCON 


by 

Richard  D.  Porter^  and  Clayton  M.  White^ 
in  collaboration  with  Robert  J.  Erwin^ 

ABSTRACT 


This  study  was  undertaken  to  record  the 
known  history  of  the  Peregrine  Falcon  ( Faico 
peregrinus)  in  Utah  as  we  have  been  able  to 
construct  it  from  both  the  hterature  and  from 
our  original  research  that  extends  over  about  a 
30-year  period  in  the  state.  The  present  total 
population  of  the  peregrine  in  Utah  is  possibly 
only  10  percent  of  what  it  has  been  in  historic 
times.  In  an  effort  to  find  explanations  for  the 
decline,  we  have  explored  hypotheses  of  ch- 
matic  changes,  impact  of  pesticides,  disease, 
and  human  disturbances.  We  conclude  that 
pesticide  contamination  and  climatic  changes 
mav  have  been  the  major  reasons  for  their  de- 
cline in  Utah. 

A  general  background  of  the  geographical 
and  ecological  distribution  of  the  species  in 
Utah  is  provided  as  are  also  details  of  its  nest- 


ing behavior  from  some  Wasatch  Mountain 
eyries.  Our  data  suggest  that  its  nesting  density 
along  the  Wasatch  Mountains  was  about  the 
same  order  of  magnitude  as  nesting  densities 
in  other  regions  of  North  America  that  are  gen- 
erally considered  more  favorable  to  the  pere- 
grine. 

We  have  considered  some  of  the  environ- 
mental factors  that  may  limit  the  species  in  Utah 
and  especially  its  relationship  with  a  congener, 
the  Prairie  Falcon  {Falco  mexicanus).  We  con- 
clude that  the  peregrine  may  live  jointly  with 
the  Prairie  Falcon  with  a  minimum  of  intra- 
specific  competition.  We  present  evidence  which 
suggests  that  the  peregrine  has  been  in  Utah 
since  the  late  Pleistocene  and  that  it  has  had  a 
long  history  of  sympatric  existence  with  the 
Prairie  Falcon. 


INTRODUCTION 


Breeding  populations  of  the  Peregrine  Falcon 
(Falco  peregrinus)  have  declined  sharply  over 
much  of  its  historic  range  in  North  America  and 
Europe  during  the  last  two  decades.  Although 
this  decline  has  been  well  documented  for  many 
areas  (Hickey,  1969),  little  has  been  published 
on  the  status,  past  or  present,  of  the  species  in 
the  Great  Basin,  especially  as  a  breeding  bird  in 
Utah,  an  area  encompassing  84,916  sq  miles 
(219,932  km-). 

We  wish,  therefore,  to  place  on  record  our 
obscr\'ations  of  the  peregrine  in  Utah  from  data 
collected  over  the  past  .30  years.  In  presenting 
these  data,  it  is  our  purpose  to :  ( 1 )  describe 
the  ecological  distribution  of  the  species  in  the 
state,  (2)  delineate  the  ecological  factors  which 


may  have  Hmited  its  distribution  and  breeding 
success  there,  (3)  describe  its  food  and  habitat 
niches,  (4)  discuss  its  competition  with  related 
species,  especially  the  Prairie  Falcon  (Falco 
mexicanus),  and  (5)  compare  its  present  levels 
of  population  with  those  formerly  known, 
since  peregrines  in  Utah  have  not  been  immune 
to  the  decline  that  afflicted  its  populations  else- 
where. Because  the  known  active  eyries  of  this 
species  in  the  state  are  now  only  about  10  per- 
cent of  those  known  to  have  been  present  earlier 
in  the  century,  another  of  our  objectives  is  to 
(6)  discuss  and  evaluate  the  factors  which  may 
have  led  to  the  near  extirpation  of  this  species 
in  the  state. 


^Present    address:    Bureau    i>f    Sport    KiOieries    and    Wildlife.    Inteniiountain   Forest   and   Range   Experiment   Station,  Federal   Building,   Rm   B2, 
West  First  North,  Provo,  Utah  84t)()l 
^Department   of  7,ooIogv.    Brigham    Young   University.   Provo,    Utah   84(i02 
'892  East  3250  North,  Ogden,  Utah  H+404- 


Bricham  Young  Univehsity  Science  Bulletin 
GEOGRAPHIC  DISTRIBUTION 


Historic  Records 

The  percgriiu'  was  not  mentioned  in  the  or- 
nithological literature  for  Utah  until  1871,  when 
it  was  reported  by  Allen  (1872)  to  prey  on 
waterfowl  about  the  marshes  of  the  Great  Salt 
Lake  near  Ogden.  He  found  it  to  be  common 
there  in  September.  The  next  to  mention  the 
presence  of  the  species  was  Henshaw  (1874), 
who  with  Yarrow,  collected  600  specimens  of 
birds  representing  165  species  on  a  trip  from  Salt 
Lake  City  to  St.  George  between  July  and  De- 
cember 1872.  The  peregrine  was  considered  by 
Henshaw  to  be  a  rather  common  resident  in 
Utah  and  to  nest  in  the  state.  Henshaw's  later 
account  (1875)  mentions  only  an  observation 
of  this  species  by  Allen  (1872)  in  the  vicinity 
of  Ogden,  thus  opening  to  question  the  source 
of  his  data  supporting  the  status  of  the  species 
in  Utah. 

The  lack  of  observations  by  Allen  (1872) 
of  the  Prairie  Falcon  in  the  Great  Salt  Lake  Val- 
ley and  the  complete  absence  of  this  species  in 
his  account  of  the  birds  encountered  in  Kan- 
sas, Colorado,  Wyoming,  and  Utah  is  difficult 
to  understand,  since  the  peregrine  apparently 
was  noted  at  all  but  two  of  Allen's  collecting 
localities  and  a  specimen  (young  bird)  was  ob- 
tained by  him  (ibid.)  at  Fairplay  (South  Park), 
Colorado  Territory.  Did  Allen  ( ibid. )  overlook 
the  Prairie  Falcon  or  did  he  consider  all  large 
falcons  to  be  peregrines?  Nevertheless,  his  ob- 
servations of  the  peregrine  along  the  Great  Salt 
Lake  marshes  probably  were  accurate,  as  the 
species  has  been  seen  there  many  times  since 
then.  Although  Ridgway  ( 1S74,  1877)  found 
the  Prairie  Falcon  to  be  common  in  the  rocky 
canyons  of  the  Wasatch  Mountains  and  a  rare 
breeder  along  cliffs  of  canyons  and  valleys  in 
Salt  Lake  Cit)'  and  neighborhood  in  1869,  he 
apparently  made  no  observations  of  the  pere- 
grine in  Utah.  Several  earlier  naturalists  and 
explorers  (Fremont,  1845;  Stansbury,  1852; 
Baird,  1852;  and  Remy  and  Brenchley,  1861) 
also  failed  to  mention  the  presence  of  the  pere- 
grine in  Utah. 

Specimen  Records 

Specimens  from  both  the  arctic  tundra  pop- 
ulation (F.  ;;.  timdriu.s)  and  the  more  southern 
population  ( F.  p.  amitttm)  have  been  taken 
in  Utah  during  the  winter  months.  A  specimen 
of  the  tumhius  race,  identified  b)'  C.  M.  White 
(CMW),  was  found  shot  and  wounded  by  R. 
Vem  Bullough  on  15  December  1956,  near 
Famiington    Ba\-,    Davis    County.    (For    a    dis- 


cussion   of    peregrine    systematics,    see    White, 
1968b.) 

A  male  specimen  of  unknown  racial  affinity 
was  collected  by  Wolfe  ( 1928 )  near  St.  George, 
Washington  County,  on  5  February  1926.  John 
Hutchings  (Bee  and  Hutchings,  1942)  collected 
a  specimen  of  anattan  (sensii  lata;  western  sub- 
group) (CMW)  near  Pelican  Point,  Lake  Moun- 
tains, Utah  County  (date  not  given,  Woodbury, 
Cottam  and  Sugden,  unpubl.  ms,  indicate  speci- 
men was  taken  alive,  2  August  1935).  Five 
specimens  (Twomey,  1942)— a  male,  molting  into 
adult  plumage;  an  adult  female,  collection  date 
not  given;  and  three  males,  collected  on  23 
April  and  5  and  23  August  in  1935  at  the  Ash- 
ley Creek  marshes,  Uintah  County— were  as- 
signed to  the  race  anatinn  {scnsu  lato;  western 
subgroup)   (CMW). 

Woodbury  et  al.  (unpubl.  ms)  record  the 
following  additional  specimens  by  countv:  Box 
Elder,  at  Bear  River  marshes,  specimens  taken 
1  Julv  and  6  September  1914;  14  September 
1915; '2<S  July  and  28  September  1916  (U.S. 
Biol.  Surv.);  18  August  and  7  September  1927 
(Phil.  Acad.  Sci.);  all  aimtum  (sensu  lato; 
western  subgroup)  (CMW).  Davis,  Jordan  Fur 
Farm,  W  of  Bountiful,  5  January  1939  (Univ. 
Utah  Coll.;  UU)  anatum  (sensu  /afo).SaIt  Lake, 
near  Salt  Lake  Cit>-,  4  September  1947  (UU). 
Iron,  near  Cedar  City,  12  May  1936  (Chicago 
Field  Mus.;  LBB),  anatum  (sensu  lato;  western 
subgroup)  (CMW).  Uintah,  Ashley  Creek 
marshes,  a  young  male  in  1937  (Carnegie  Mus.). 
Washington,  Zion  Canvon  (Zion  National  Park), 
16  July  1939  (Zion  Park  Museum)  anatum 
(sensu  lato;  u-estern  subgroup)    (CMW). 

Additional  specimens  of  F.  p.  anatum  (sensu 
lato;  western  subgroup)  have  been  examined 
by  C.  M.  White  for  Emerv  Count)',  two  speci- 
mens, July;  and  Salt  Lake  Countv,  two  speci- 
mens, Januar)'  and   November. 

Nesting  Records 

Historically,  the  peregrine  is  known  to  have 
nested  in  13  counties  of  Utah  and  is  suspected 
of  nesting  in  at  least  three  others.  Figure  1  shows 
the  pattern  of  known  and  suspected  breeding 
distribution  in  Utah,  and  Table  1  gives  their 
known  histories  in  the  state. 

The  first  recorded  eyrie  for  the  state  was  an 
observation  by  Johnson  (1899),  who  in  May 
1898,  found  three  \oung  peregrines  in  a  shallow 
cave  under  an  overhanging  rock  of  an  80-foot 
(24  m)  cliff  [Land  Rock]  in  Lake  Mountains, 
west  of  Utah  Lake,  Utah  Count)',  and  five  eggs 


Biological  Series,  Vol.  18,  No.  1        Peregrine  Falcon  in  Utah 


m 


UTAH 


Fig.  1.  Pattern  of  known  and  suspected  breeding  distribution  of  the  Peregrine  Falcon  in  Utah.  Letters  for  the 
regions  and  numbers  correspond  to  those  on  Table  1.  The  hne  running  nearly  vertically  through  the  center 
of  the  state  separates  the  Great  Basin  from  the  Colorado  River  Basin.  The  west  face  of  the  Wasatch  Moun- 
tains bisects  area  A  and  is  encompassed  within  the  northern  and  southern  boundary  of  the  area.  Lightly 
stippled  area  between  regions  A  and  B  delimits  the  Great  Salt  Lake  Desert,  although  there  are  also  other 
areas  of  salt  flats  at  the  southwest  edge  of  the  Great  Salt  Lake  that  are  not  classified  within  the  confines 
of  the  desert. 


Bricham  Young  University  Science  Bulletin 


Table    1.     Peregrine   eyries   in    Utah.    Eyrie   site  numbers    and    letters    for   regional    areas   correspond   with   those 
given  in  Figure  1. 


Site 
No. 


First  Located  and  Subsequent  History 


Last  Known  to  be  Active 


Date 


Observer 


Date 


Observer 


1 

2' 

3 
4 


9 
10 


11 
12 
13 


1898 

1940 
1939-42 
1935 
ca.    1926-27 
1939-42 
1954 
1956 
1940s 

1939-42 
1939-42 
1943 


ca.   1900-20? 

1939-42 
1943 

1939 
1939-42 
1950 
1955 

1939-42 
1939-42 
1940s 


1951 


14 

ca.   1900-20 

1926-27 

1939-42 

1940s 

15 

1930 

16 

1943 

1940s 

17 

1930s 

1940s 

1950s 

1967 

18 

1930s 

1939-46? 

19 

1930-32 

20 

1946-? 

A — Great  Basin  Region — Surrounding  Utah  and  Great 
Salt  lakes,  and  North  Central  Utah 

H.  C.  Johnson  (1899) 


R.  G.  Bee  (field  notes) 

Nelson   (1969)° 

Bee  and  Hutchings  (1942) 

L.  R.  Wolfe  (in  letter) 

Nelson  (1969)° 

Porter  et  al.  (unpubl.  ms) 

C.  M.  White 

Morlan  Nelson  (pers.  comm.,  1971) 

Boyd  Shaeffer  ( pers.  coinin. ) 

Nelson  (1969)° 

Nelson   (1969)° 

R,  D.  &  R.  L.  Porter 

R.  J.  Erwin,  J.  F.  Poorman 

(unpubl.  data) 

Trcganza  ( in  Woodbury  et  al., 

unpubl.  ms) 

Nelson  (1969)° 

R.  D.  Porter  &  R.  ].  Erwin 

(unpubl.  data) 

Morlan  Nelson  (pers.  comm.,  1971) 

Nelson  (1969)° 

C.  Wilson   (pers.  comm.) 

Lorin  Carsey  (pers.  comm.),  one 

young  female  taken  for  falconry 

Nelson   (1969)° 

Nelson  (1969)° 

Boyd  Shaeffer  (pers.  comm.) 

reported  eyrie  to  have  been 

found  and  photographed  in 

tlie  1930's  by  a  different  party 

R.  D.  Porter  and  Jack  Hagan 

(unpubl.  data),  birds  seen, 

eyrie  not  located 

Treganza  ( in  Woodbury  et  al., 

unpubl.  ms) 

L.  R.  Wolfe  ( in  field  notes 

of  R.  G.  Bee),  seen  carrying 

food  toward  cliffs,  and 

Wolfe  (1928) 

Morlan  Nelson   (pers.  comm.,   1971) 

Boyd  Shaeffer  (pers.  comm.), 

took  young  from  eyrie 

Dr.  Harold  Austin  (pers.  comm.) 

R.  D.  &  R.  L.  Porter,  and  R. 

J.  Erwin  (unpubl.  data) 

Boyd  Shaeffer  (pers.  comm.) 

Clyde  Ward  ( pers.  comm. ) 

Boyd  Shaeffer  (pers.  comm.) 

C. 'M.  White  (unpubl.  data) 

Del  Diamond  (pers.  comm.) 

Clyde  Ward  (pers.  comm.) 
Morlan  Nelson  ( pers.  comm. ) 

Clyde  Ward  (pers.  comm.) 
Boyd  Shaeffer  (pers.  comm.) 
Marcus  Nelson? 


Early  H.  G.  Johnson  (field  notes 

1900s  of  R.  G.  Bee) 

1940  R.  G.  Bee   (field  notes) 

Nelson  (1969) 

1957-58     C.  M.  White  (unpubl. 
data) 


1953  R.  J.  Erwin   (unpubl. 

data) 


1969  C.  M.  White  (unpubl. 

data),  single  bird 


1956  C.  M.  White   (unpubl. 

data ) 


1952  R.  J.  Erwin  (unpubl. 

data) 


1968?         Clyde  Ward 


19.54  Clyde  Ward 

1969  H.'  Austin  and  L.  Wakefield 

one  adult  seen. 
1930-32      Clyde  Ward  (pers.  comm.) 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


Table  1   ( Continued ) 

21   (SNV)=  ca.  1926-27 


22  (SNV) 

1939-4S 

23' 

1942 

24 

1942 

25       ca. 

1939 

26 

1969 

27  (SNV) 

1960 

28 

1961 

29  (SNV) 

1916  & 

1936 

30  (SNV) 

1958 

1959 

31  (SNV) 

1953 

32 

1958 

33  (SNV) 


1958-59 


34 

1937 

35  (SNV) 

1935-? 
1965-66 

36  (SNV) 

1961 

37 

1936 

38 


1939 


39  (SNV)  1963 

40  (SNV)   ca.   1926 


L.  R.  Wolfe  ( ill  field  notes  of 

R.  G.  Bee) 

Morlan  Nelson  ( pers.  comm.,  1971) 


1970  C.  M.  White   (unpubl. 

data) 
B — Great  Basin  Region — Great  Salt  Lake  Desert 

1959-60      C.    M.    White    and    Gary    D. 

Lloyd  (unpubl.  data) 


H.  Webster  (letter,  1961) 

H.  Webster  (letter,  1961) 

C — Central  Utah,  eastern  edge  Great  Basin,  western 
Colorado  River  Basin  (Plateau) 

Gunther  and  Nelson  ( in  Woodbury 

et  al.,  unpubl.  ms.) 

C.  M.  White  (unpubl.  data)  1969 

G.  G.  Musser,  A.  D.  Stock,  and 

C.  M.  White  (unpubl.  data) 

White  and  Lloyd  (1962)  1964 

D — Colorado  Plateau  and  Navajo  Country 

Woodbury  and  Russell   (1945)  1961 


edge 


R.  J.  Erwin  (unpubl.  data)  1962 

R.  D.  Porter  (unpubl.  data) 

Behle  (1960) 

G.  L.  Richards  (pers.  comm.), 

saw  fledged  young 

C.  M.  White  (pers.  comm.  from 

M.  Hopkins,  unpubl.  data) 

E — Uinta  Basin  and  Upper  Colorado  River  Basin 

Twomey  (1942)  1961 

Twomey  (1942) 

E.  Peck,  W.  Pingree,  and  J. 

Gaskill   (pers.  comm.) 

F — Southwestern  Utah,  edge  Great  Basin;  and  Virgin  River  Valley 


C.  M.  White  (unpubl. 
data) 


C.  M.  White  and  G.  D. 
Lloyd  (unpubl.  data) 

C.  M.  White  and  G.  D. 
Lloyd   (unpubl.  data), 
pair  seen  in  area 
G.  D.  Lloyd  (unpubl.  data), 
adult  in  general  area 


G.  L.  Richards  (pers.  comm.), 
at  nearby  locahty 


C.  M.  White  and  G.  Worthen 
(unpubl.  data) 
W.  S.  Long  ( breeding  female 
collected ) 

Grater  (1947) 


Wauer  and  Carter  (1965) 
Wolfe  (1928) 


1961  G.  M.  White  (unpubl. 
data) 

1962  C.  M.  White  and  G.  D. 
Lloyd  (unpubl.  data), 
an  adult  in  area 

1964  Wauer  and  Garter  (1965) 

1966  C.  M.  White  (unpubl. 

data),  lone  adult  seen 


JMay   be  an   alternate  site   for  number   1:   located  only  2  or    3  miles    (3.2    or   4.8    km)    from   site   number    1,    but   nearly  40   years   later. 
-SNV,    (suspected,    but    not    verified)    adults   were    observed    at    these   localities,    but  eyrie   sites  not  actually   located;  although   adult   birds 
have    been    >cen    one    nr    nir>re    time^,    m    the    authors'    opinions,    the    sites    need    further    verification.     The    validity    of    these    sites   is    probable. 
■The    eyrie   proper    is   about   0-5    mile    (0.8   km)    into   Nevada. 

"These   sites    are    the    ones    referred    to    by    Nelson    (1969);    their    locations    were    commimicated    to    us    in    a    letter    from    Nelson    dated    25 
April    1969. 


on  the  same  ledge  on  30  March  1899  (Figs.  1-5; 
Table  1,  site  1).  While  circling  Utah  Lake,  John- 
son (ibid)  noted  Long-billed  Curlew  (Ntimenius 
americamts) ,  snipes  (Capella  gallinago),  bitterns 
(Botaurus  lentigino.nis),  and  a  goodly  number 
of  ducks  of  various  species  which  probably 
served  as  a  food  supply  for  the  peregrines. 

Bee  and  Hutchings  (1942)  report  finding  a 
nest  containing  four  fresh  eggs  on  a  ledge  over- 


looking Utah  Lake,  (5  miles  south  of  the  Land 
Rock  site)  near  Pelican  Point  in  the  Lake  Moun- 
tains, 20  May  1935  (Fig.  1,  Table  1,  site  3). 
Thev  collected  the  adults  to  verify  identification. 
Local  residents  report  that  peregrines  had  been 
observed  nesting  there  for  many  years  ( ibid. ) .  A 
visit  to  the  sites  on  22  April  1950  by  R.  D.  Por- 
ter and  R.  J.  Erwin  revealed  no  indications  of 
recent  occupancy.   In  recent  years  lime  mining 


Bhicham  Young  Univehsity  Science  Bulletin 


Fig.  2.  Land  Rock,  west  side  of  Utah  Lake;  location 
of  first  known  peregrine  eyrie  site  in  Utah.  It  is 
a  marginal  site,  which  in  some  recent  years  has 
been  occupied  by  Prairie  Falcons.  Note  scrubby 
nature  of  vegetation  in  foreground.  Photo  by  Kim 
Despain,   197L 


operations  have  destroyed  the  Pehcan  Point  site 
(Fig.  6)  and  Prairie  Falcons  have  occasionally 
occupied  the  Land  Rock  site. 

Nelson  ( 1969 )  located  9  or  10  eyries  ( in 
letter,  25  April  1969,  Nelson  gave  9  eyrie  loca- 
tions) in  the  area  surrounding  the  Utah  and 
Great  Salt  lakes  during  the  period  1939-1942. 
This  area  included  parts  of  Box  Elder,  Weber, 
Davis,  Salt  Lake,  Utah,  and  Tooele  counties. 
Treganza  (in  letter,  5  January  1930;  Woodbury 
et  al.,  unpubl.  ms)  found  the  species  breeding 
on  the  cliffs  fronting  the  lake  from  Brigham  to 
Ogden  [at  least  four  eyries  overlooked  the  Bear 
River  Marshes  in  the  18  miles  from  Ogden  to 
Brigham  City  (Woodbury,  pers.  comm.,  in  White, 
1969b)].  Although  he  located  nests,  he  was 
unable  to  negotiate  the  cliffs;  one  was  over  1,000 
feet  (305  m)  high  (Fig.  7).  Females  were  col- 
lected off  the  nests,  but  precise  nesting  data 
were  not  obtained. 

Gunther  and  Nelson  (Woodbury  et  al.,  un- 
publ. ms)  noted  the  species  nesting  at  a  site 
in  the  Great  Basin  Desert  of  west  central  Utah 
during  the  nesting  season  (vear  not  given).  Gun- 
ther (Woodbury  et  al.,  unpubl.  ms)  saw  the 
species  at  a  large  reservoir  in  Wasatch  County 
in  the  summer  of  1938. 


Fig.  3.     Utah  Lake  and  adjacent  habitat  as  presently  seen  from  atop  the  Land  Rock  eyrie  site;  marshes  former- 
ly were  more  extensive  than  today  and  came  closer  to   the   eyrie.    Photo   by   Kim   Despain,    197L 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


Fig.   4.     A   view  of  Land   Rock  eyrie  showing  nature  of  terrain   and  vegetation.   Photo   by  Kim   Despain,   1971. 


Grater  ( 1947 )  recorded  peregrines  at  Angel's 
Landing  in  Zion  Canyon,  Washington  County, 
from  March  to  August  1939,  where  adults  fre- 
quently were  seen  carrying  food  to  a  high  ledge 
on  the  face  of  the  peak.  On  16  July  1939  (the 
more  precise  dates  from  Woodbury  et  al.,  un- 
publ.  ms )  a  young  female,  only  a  few  weeks  old, 
was  accidentally  killed  in  the  canyon  (Figs.  1 


Fig.  5.  A  different  view  of  the  Land  Rock  eyrie  show- 
ing terrain.  Flat  area  formerly  contained  some 
marsh  habitat.   Photo  by  Kim  Despain,    1971. 


and  8,  Table  1,  site  38).  Wauer  and  Carter 
( 1965 )  reported  this  site  to  be  active  as  late  as 
19&4. 

In  the  Uinta  Basin,  Twome)'  ( 1942)  re- 
ported an  inaccessible  eyrie  about  40  feet 
(12.2  m)  up  on  a  deep  shelf  of  a  cliff,  east  of 
the  Green  River,  near  Venial  ( Fig.  1;  Table  1, 
site  34),  Uintah  Count)'.  Actions  of  the  adults 
indicated  that  young  were  in  the  nest  and  im- 
mature birds  were  seen  at  the  Ashley  Creek 
marshes  in  early  August  and  in  the  vicinity  of 
Jensen  from  August  through  September.  G.  L. 
Richards  ( pers.  comm. )  saw  a  pair  in  the  marsh- 
es in  1961,  the  most  recent  evidence  of  activity 
at  this  eyrie. 

In  southern  Utah,  single  falcons  were  seen  at 
Kanab,  Kane  County,  on  28  April  1935,  and  6 
April  1947,  and  two  were  recorded  along  Kanab 
Creek  on  20  May  1947  (Behle,  Bushman,  and 
Greenhalgh,  1958).  Behle  (1960)  also  noted  the 
species  near  the  Colorado  River  at  Dewey  on 
21  May  1953  (Fig.  1;  Table  1,  site  31),  and  in 
Glen  Can\'on  on  6  August  1958.  Peregrines  were 
seen  several  times  in  July  and  August  at  Navajo 
Mountain,  San  Juan  County,  by  Woodbury  and 
Russell  ( 1945)  in  1936,  and  by  C.  M.  White  and 
G.  D.  Lloyd  (unpubl.  data)  in  1960  and  1961 
(Fig.  1;  table  1,  site  29).  White  and  Lloyd 
(1962)  reported  on  the  predation  of  young 
peregrines  which  had  not  yet  fledged  from  an 
eyrie  in  the  Colorado  River  Basin  (Figs.  1,  9, 
and  10;  Table  1,  site  28). 


Bricham  Young  University  Science  Bulletin 


Fig.  6.     Pelican  Point  eyrie  site  (Table  1,  site  3,  Fig.  1)   showing   lime   mining  operation,   which   in   recent   years 
destroyed    the   nesting   cliff.    Photo    by    Kim    Despain,   1971. 


^-\/'- 


JS^w"-*^^ 


Fig.   7.     Treganza   noted   a   pair  of   peregrines   nesting  on  the  distant   1,000  ft.    (305  m)   cliff  in  the  early  1900s, 
but  he  was  unable  to  reach  the  eyrie  site  (Woodbur)'   ct  al.   unpubl.   ms).   Photo  by  R.   J.   Erwin,   1971. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


■mm.-  '■  ■  I    '     -^  '"''J\A 


A: 


■4-J^ 


it^ 


.a#tr- 


:^ 


Fig.  8.     Angel's  Landing,  Zion  Canyon.  Cliff  in  center  where  Grater   (1947)   saw  peregrines  nesting  high  on  face 
of  peak   (Fig.   1,  Table  1,  site  38).  Photo  by  Grant,   1  September  1929,  Courtesy  U.  S.  National  Park  Service. 


Postnesting  Season  and  Winter  Records 

The  species  is  present  in  the  state  through- 
out the  year  (Woodbury,  Cottam,  and  Sugden, 
1949).  Postbrceding  adults,  immatures,  migrants, 
and  wintering  falcons  congregate  near  marshes 
where  a  plentiful  supply  of  food  is  available, 
especially  near  the  marshes  of  the  Great  Salt 
Lake  (Woodbury,  Cottam,  and  Sugden,  unpubl. 
ins).  At  the  Bear  River  marshes,  for  example, 
records  extend  back  to  1915,  when  Alexander 
Wetmore  found  the  peregrine  to  be  a  regular 
and  frequent  visitor  after  mid-July  (ibid.).  The 
Christmas  bird  censuses  taken  loy  Vanez  T.  Wil- 
son et  al.  (in  Bird  Lore  42,  1940;  Audubon 
Magazine  43-48,  1941-1946;  and  Audubon  Field 
Notes  1-24,  1947-1970)  at  the  Bear  River  Migra- 
tor\  Waterfowl  Refuge,  indicate  that  the  spe- 
cies wintered  there  in  small  numbers  until  the 
early  1960s  (Fig.  11).  The  greatest  number  of 
peregrines  seen  during  the  seven-  to  eight-hour 
censuses  was  seven,  in  1940.  The  Christmas  bird 
counts  at  the  Bear  River  marshes  were  exception- 
ally consistent  from  one  vear  to  the  next  begin- 
ning in  19.39  through  1960  as  regards  the  number 
of  participants.  th(>  area  covered,  and  the  party 
hours  afield.  .Vdditionallv,  V.  T.  Wilson  directed 


and  participated  each  year  until  1960,  after 
which  other  observers  were  involved  and  a 
greater  area  was  covered,  although  the  number 
of  party  hours  afield  remained  essentially  the 
same. 

Tlie  racial  affinity  of  specimens  taken  at 
the  Bear  River  marshes  between  1  July  and  28 
September  (anatum,  sensu  lato;  western  sub- 
group), suggest  that  most  of  the  postbreeding 
and  fall  peregrines  in  these  marshes  were  from 
local  eyries.  The  steady  decline  in  the  numbers 
of  peregrines  recorded  at  the  Bear  River  marshes 
during  thi'  Christmas  bird  counts  (ibid.)  from 
1939  to  the  early  1960s  (Fig.  11)  closely  cor- 
responded with  the  decline  in  the  number  of  ac- 
tive eyries  in  the  area  surrounding  the  marshes. 
This  correspondence  suggests  that  most  pere- 
grines wintering  in  the  marshes  of  Great  Salt 
Lake  probably  were  from  local  breeding  popu- 
lations, although  they  also  mav  have  been  from 
some  other  sharply  declining  population  of  the 
anatum  race.  It  is  probable  that  only  a  small 
percentage  of  these  wintering  birds  were  from 
the  arctic  populations  (F.  p.  twidrius),  because 
arctic  birds  normally  winter  farther  south,  and 
because  the  arctic  populations  were  not  known 


10 


Bricham  Young  University  Science  Bulletin 


to  have  declined  between  1939  and  the  late 
1960s. 

Peregrines  also  have  been  reported  on  Christ- 
mas bird  counts  both  at  Ogden  and  Salt  Lake 
Cit)'  over  the  past  30  years.  In  addition,  they 
have  been  recorded  at  Parowan,  Iron  County, 
on  27  December  1963  (Audubon  Field  Notes 
18;  1964)  and  at  St.  George,  Washington  County, 
on  1  January  1969  (Audubon  Field  Notes  23; 
1969).  Cliristmas  bird  count  data  for  the  areas 
other  than  the  Bear  River  marshes  are  either 
too  spotty  or  are  too  heterogeneous  in  their 
method  of  collection  to  be  evaluated  statistically. 

The  peregrine  was  recorded  at  Clear  Lake 
State  Waterfowl  Management  Area  by  R.  Wil- 
liams on   16  September  1939,  and  by  Gunther 


Mi:^^'^5«^-»i 


Fig.  9.  Peregrine  cliff  in  desert  of  Colorado  Plateau, 
reported  by  White  and  Lloyd  (1962)  (Fig.  I, 
Table  1,  site  28).  Distance  from  the  rock  at  point 
A  to  the  eyrie  ledge  at  point  B  is  70  ft  (21.3  m). 
Poplar  trees  (Popidus  fremotitii),  along  a  water 
course  in  foreground  (C)  are  40-50  ft  (12.2- 
15.2  m)  in  height.  Photo  by  J.  B.  Piatt,  May  1971. 


and  Nelson  on  24  October,  10  November,  and 
4  December  1941  (Woodbury  et  al.,  unpubl. 
ms),  indicating  that  the  species  winters  at 
other  marshes  as  well  as  at  those  near  the  Great 
Salt  Lake.  Members  of  arctic  populations  (F.  p. 
tundrius)  apparently  utilize  Utah's  marshes  both 
as  stopping  places  during  migration  and,  spar- 
ingly, as  wintering  grounds.  This  is  suggested 
by  Lincoln's  ( 1933 )  report  of  a  peregrine  banded 
as  a  juvenile  at  King's  Point,  Yukon  Territory, 
within  the  geographic  range  of  tundrius  on  30 
July  1924;  by  its  recovery  at  Duchesne,  Du- 
chesne Countv',  Utah,  on  20  February  1925; 
and  by  the  collection  in  December  of  the  pre- 
viously mentioned  specimen  of  tundrius  from 
Famiington  Bay. 

Late  summer  sightings,  which  could  repre- 
sent either  resident  birds  or  early  migrants,  have 
been  recorded  from  several  other  areas.  Twomey 
(1942)  reported  peregrines  at  Hill  Creek,  40 
miles  (64.4  km)  south  of  Ouray,  Uintah  Coun- 
ty, on  5  August  [1935?],  at  Strawberr)'  Reser- 
voir, Wasatch  County,  on  17  August  [1935?],  and 
Bchle  ( 1960)  recorded  the  species  at  Glen  Can- 
von  near  Wahweep  Creek,  Mile  17,  on  6 
August  1958  and  at  10,500  feet  (3,200  m)  on 
the  north  slope  of  Mt.  Ellen,  Henry  Mountains, 
on  8  September  1957.  Finally,  a  subadult  was 
seen  near  Park  City,  Wasatch  County,  in  late 
August  1959  (M.  Nelson  and  F.  Welch,  pers. 
comm. ) . 


Fig.  10.  Two-day-old  young  and  an  addled  egg  on 
nesting  ledge  at  desert  eyrie  in  Colorado  Plateau 
(site  28)  shown  in  Figure  9.  Photo  by  G.  D.  Lloyd 
and  C.  M.  White,  10  June  196L 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


11 


y=.38l+(-.OI4X) 


Fig.  11.  Linear  regression  analysis  of  the  number  of  Peregrine  Falcons  recorded  per  party  hour,  during  Christ- 
mas bird  counts  at  the  Bear  River  Migratory  Waterfowl  Refuge  between  1939  and  1970.  Each  circle 
represents  the  observations  for  one  Christmas  bird  count.  Downward  trend  is  statistically  significant  (p<0.01). 
This  analysis  suggests  that  the  peregrine  had  essentially  disappeared  as  a  wintering  bird  in  the  Bear 
River  marshes  by  1965. 


12 


BnicnAM  Young  University  Science  Bulletin 

DENSITY  DISTRIBUTION  OF  PEREGRINE  EYRIES  IN  UTAH 


Utah's  desert  climate  should  seem  to  be  a 
significant  barrier  to  the  nesting  of  the  pere- 
grine, yet  we  have  compiled  a  list  of  about  40 
eyries  in  the  state  (Table  1),  which  appear  to 
have  been  active  at  one  time  or  another.  On 
the  basis  of  density,  if  all  40  eyries  were  active 
simultaneously,  there  would  be  about  2,123  sq 
miles  (5,499  km-)  per  eyrie  site.  If  the  11  sus- 
pected but  unverified  eyries  (SNV,  Table  1) 
are  excluded,  the  density  would  be  reduced  to 
one  eyrie  site  for  every  2,928  sq  miles  (7,584 
km=). 

Density  of  peregrine  nesting  sites  in  Utah 
appears  to  be  directly  related  to  the  availability 
of  food  and  suitable  cliffs  for  nesting.  The  im- 
portance of  these  two  factors  to  the  distribution 
and  density  of  the  peregrine  in  the  state  will  be 
discussed  separately  in  a  later  section.  Eyrie 
sites  usually  were  situated  near  marshes,  lakes, 
or  rivers,  where  there  was  a  plentiful  supply  of 
prey  species.  Where  the  nesting  habitat  was  ex- 
tensive, such  as  in  the  area  of  the  Great  Salt 
Lake  (  Fig.  1,  Table  1 ),  eyrie  sites  were  clustered 
around  the  marshes  in  a  pattern  conforming  to 
the  availability  of  nesting  sites  (Fig.  12).  Else- 
where in  the  state,  where  suitable  habitat  is 
greatly  restricted,  each  eyrie  site  usually  was 
located  many  miles  from  its  closest  known  neigh- 
bor (Fig.  1). 


The  density  of  peregrine  eyries  in  Utah,  ex- 
clusive of  the  area  surrounding  the  Great  Salt 
Lake  (4,500  mi-;  11,655  km-),  is  one  site  per 
4,232  sq  miles  ( 10,962  km-),  if  the  19  additional- 
ly known  and  suspected  eyries  were  all  active 
simultaneously.  If  the  10  suspected  eyries  in  the 
remainder  of  the  state  are  excluded,  the  aver- 
age area  per  nest  site  would  be  8,935  sq  miles 
(23,142  km-).  There  were  20  known  eyries  in 
the  area  surrounding  the  Utah  and  Great  Salt 
lakes  (Fig.  1,  Table  1,  e}rie  sites,  1-20).  This  is 
exclusive  of  eyrie  site  22  (Table  1)  which  is 
outside  of  the  region.  One  other  probable  eyrie 
is  suggested  by  the  presence  of  adults  on  each 
of  several  visits  by  L.  R.  Wolfe  ( field  notes  of 
R.  G.  Bee)  to  one  other  site  (site  21,  Table  1). 
If  all  20  known  eyries  were  active  concurrently, 
there  would  have  been  one  eyrie  site  for  about 
every  225  sq  miles  (583  km-)  in  an  area  cover- 
ing about  4,500  scj  miles  (11,655  km-),  sur- 
rounding and  including  the  Utah  and  Great  Salt 
lakes  (Fig.  1,  Table  1). 

The  average  distance  between  13  eyries  ( sites 
5,  7-10,  12-19,  Table  1)  located  along  130  linear 
miles  (209  km)  of  the  west  face  of  the  Wasatch 
Mountains  from  the  south  end  of  Utah  Lake  to 
the  north  end  of  the  Great  Salt  Lake  was  10.0 
linear  miles  ( 16.1  km).  The  closest  eyries  to  each 
other  were  about  2  miles  ( 3.2  km )  apart  and  the 


Fig.  12.  Looking  east  from  the  peregrine's  hunting  habitat  at  a  large  Utah  marsh  toward  its  nesting  habitat 
along  the  escarpment  of  the  Wasateh  Mountains.  Two  pairs  of  peregrines  ami  tliree  pairs  of  frairie  FiJcons 
nested  on  the  portion  of  the  ejiffs  seen  in  tlie  distanee  and  both  species  utilized  tlie  marshes.  Photo  by  R.  J. 
Erwin,  August  1971. 


Biological  Sehies,  Vol.  18,  No.  1        PEREcniNE  Falcon  in  Utah 


13 


farthest  were  20  miles  (32.2  km)  apart.  How- 
ever, since  cliffs  make  up  only  about  25  miles 
(40  km)  of  the  130  linear  miles,  including  side 
canyons  (estimated  from  U.  S.  Geological  Sur- 
vey topographic  maps),  peregrine  eyries,  on  the 
average,  were  only  about  two  miles  (3  km) 
apart  on  the  cliff  sections  of  the  mountain.  Sev- 
eral additional  eyries  near  the  western  edge  of 
Utah  Lake  and  the  eastern  and  southern  edges 
of  the  Great  Salt  Lake  were  not  included  because 
they  did  not  fall  in  a  direct  line  with  the  13 
eyries  mentioned  above. 

It  is  possible  that  populations  of  the  pere- 
grine were  substantially  greater  prior  to  arrival 
of  the  first  white  settlers  than  historically,  con- 
sidering the  apparent  abundance  of  food  that 
was  available  in  nearby  marshes,  the  number  of 
cliffs  which  appear  to  be  suitable  (but  which 
lia\'e  not  been  known  to  harbor  peregrines ) ,  and 
the  probable  lack  of  human  disturbance. 

Population  densities  of  the  magnitude  of 
those  occurring  around  the  Great  Salt  Lake 
seeminglv  did  not  differ  greatly  from  some  of 
those  present  in  other  regions  of  North  America 
where  the  environment  is  considered  more  con- 
genial to  the  peregrine.  For  instance,  Herbert 
and  Herbert  (1965)  recorded  nine  eyries  along 
55  miles  (88.5  km)  of  the  Hudson  River  (eight 
on  the  west  side)  for  an  average  of  6.1  miles 
(9.8  km)  per  eyrie.  Berger  and  Mueller  (1969) 
found  14  eyries  along  a  198.4-mile  (319  km) 
stretch  of  upper  Mississippi  River  for  an  average 
of  14.2  miles   (22.8  km)  between  eyries. 

White  and  Cade  ( 1971 )  recorded  a  peregrine 
density  along  the  Colville  River  in  1967-1969  to 
be  one  pair  per  8.3  miles  (13.4  km)  above 
Umiat  Mountain  and  one  pair  per  3.7  miles 
(6.0  km)  below  Umiat  Mountain,  giving  an 
overall  average  of  6.03  river  miles  (9.7  km)  be- 
tvveen  eyries.  The  distance  between  active  eyries 
ranged  from  0.4  miles  (0.64  km)  to  27  miles 
( 4.3.4  km ) .  There  were  32  nesting  pairs  of  pere- 
grines along  183  miles  (294  km)  of  the  Colville 
River  in  Alaska  in  1952,  40  pairs  in  1959,  and 
27  pairs  in  1967,  for  an  average  distance  in  miles 
between  eyries  of  5.7,  4.6,  and  6.8  (9.2,  7.4,  and 
10.9  km),  respectively  (Cade,  I960;  White  and 
Cade,  1971). 


The  average  distance  between  19  eyries  along 
172  miles  (277  km)  of  the  Yukon  River  in  Alas- 
ka was  9.3  miles  (15  km)  (range,  2.75-31  mi; 
4.4-49.9  km)  in  1951  and  10.1  miles  (16.3  km) 
(range,  2-31;  3.2-49.9 km)  in  1966  (Cade,  White, 
and  Haugh,  1968).  Cade,  White,  and  Haugh 
(1968)  believed  that  the  peregrine  probably 
was  never  more  common  along  the  Yukon  than 
in  1966. 

For  the  Aleutian  Islands,  White,  Emison,  and 
Williamson  ( 1971 )  found  the  average  distance 
between  peregrines  defending  territories  to  be 
about  5.8  miles  (9.3  km)  (range,  0.81-21  mi; 
1.3-34  km)  for  Amchitka  Island,  similar  densi- 
ties on  Rat  and  Semisopochnoi  islands,  and 
ec|ual  or  perhaps  greater  densities  on  Kiska 
Island    (M.   Nelson,  pers.   comm.,    1971). 

On  the  other  hand,  no  locality  in  Utah  had 
populations  approaching  the  densities  found  in 
several  other  regions.  Hickey  (1942),  for  exam- 
ple, in  a  local  area  of  the  eastern  United  States, 
reported  five  pairs  of  peregrines  on  7  miles 
(11.3  km)  of  escaqiment.  In  Great  Britain,  Rat- 
cliff  e  ( 1962 )  found  three  pairs  residing  along 
a  linear  distance  of  1,000  yards  (914  m)  of  sea 
chff,  and  15  pairs  along  a  17-mile  (27.4  km) 
distance.  The  highest  densities  known  are  for 
the  Queen  Charlotte  Islands,  where  five  to  eight 
pairs  of  falcons  utilized  a  linear  distance  of  a 
mile  (1.61  km)   of  sea  cliff  (Beebe,  1960). 

Hickey  (1942)  listed  19  pairs  of  peregrines 
in  an  area  of  about  10,000  sq  miles  ( 25,900  km^ ) 
around  New  York  City,  for  an  average  of  one 
pair  for  evers'  526  sq  miles  (1,362  km-).  Cade 
( 1960 )  estimated  a  probable  density  of  200  and 
300  sq  miles  (518  and  777  km')  per  pair  in 
the  Colville  and  Yukon  river  systems,  respec- 
tively, and  one  known  pair  per  2,000  sq 
miles  (5,180  km-)  in  the  Yukon  countr\'.  Bond 
( 1946 )  considered  the  peregrine  to  be  common 
along  the  western  coast  of  the  United  States 
and  Baja,  Mexico,  where  there  was  an  average 
of  less  than  2,000  sq  miles  (5,180  km=)  per 
known  pair.  Judging  from  the  data  presented 
above,  the  peregrine  was  relatively  common  in 
the  area  of  the  Great  Salt  Lake  and  uncommon 
elsewhere  in  Utah. 


TOPOGRAPHY,  CLIMATE,  AND  PLANT  COVER  IN  UTAH 


Utah  is  in  a  region  of  generally  high  inland 
plateaus  and  mountains  which  have  been  dis- 
sected by  numerous  canyons  and  dotted  with 
manv  lakes  and  inland  valle\s.  A  chain  of  moun- 
tains and  high  plateaus  beginning  at  the  comer 


of  Wyoming  and  extending  southwest\vard  ap- 
proximately two-thirds  of  the  length  of  Utah 
separate  the  major  part  of  the  state  into  the 
Colorado  and  Great  Basin  drainage  areas  (see 
Fig.  1 ) .  The  elevation  of  this  central  mountain 


14 


BniGHAM  YouNO  Univeksity  Science  Bulletin 


chain  ranges  from  9.000  to  12,000  feet  (2,743- 
3,658  m).  Tlie  Wasatch  Mountains  make  up  the 
northern  third  of  the  central  cliain  ( to  the  south- 
em  end  of  Utah  Lake)  and  high  plateaus  the 
remainder. 

Nearly  all  of  Utah  west  of  the  central  moun- 
tain chain  lies  in  the  Great  Basin  and  contains 
the  entire  drainage  of  ancient  Lake  Bonneville, 
of  which  Utah,  Sevier,  and  Great  Salt  lakes  are 
remnants.  The  Great  Salt  Lake,  which  is  about 
83  miles  (134  km)  long  by  51  miles  (82  km) 
wide,  has  fluctuated  in  area  from  2,400  sq  miles 
(6,216  km-)  in  1870  to  950  sq  miles  (2,461  km-) 
in  1961  (Nelson,  1969).  It  contains  high  concen- 
trations of  salts  (about  25  percent)  comprising 
principally  sodium  chloride  and  sodium  sul- 
fate. Utah  Lake,  which  is  about  23  miles  (37 
km)  long  and  15  miles  (24  km)  wide,  is  fresh 
water.  Water  comprises  nearly  three  percent  of 
Utah's  area  due  mainly  to  these  lakes.  The  low- 
lands on  the  floor  of  the  basin  range  from 
4,200  to  5,550  feet  (1,280-1,692  m)  in  elevaHon. 
Just  west  of  the  Great  Salt  Lake  lies  the  Great 
Salt  Lake  Desert,  one  of  the  most  formidable 
deserts  in  North  America.  In  its  greatest  length 
and  width  it  exceeds  150  by  60  miles  (240  by 
97  km)  (see  Fig.  1). 

Tlie  eastern  half  of  the  state  is  in  part  of  the 
Colorado  Plateau  or  Colorado  River  Basin.  The 
Colorado  River  Basin  is  bordered  on  the  north 
by  the  high  Uinta  Mountains,  some  peaks  of 
which  exceed  13,000  feet  (3,962  m),  and  con- 
tains the  Uinta  Basin  immediately  south  of  the 
mountains  and  the  eanvonlands  farther  south. 
It  is  dissected  from  north  to  south  by  the  Green 
and  Colorado  rivers.  The  basin  floor  ranges  in 
elevation  from  about  4,300  feet  to  6,000  feet 
(1,311-1,829  m).  The  Virgin  River  Basin,  in 
southwestern  Utah,  is  about  2.250  feet  (686  m) 
in  elevation. 

Because  Utah  lies  in  the  rain  shadow  of  the 
high  coastal  ranges,  it  is  one  of  the  drier  regions 
in  North  America,  with  an  average  of  onlv  4 
to  10  inches  ( 10.2-25.4  cm )  of  annual  precipita- 
tion  in  the  desert  lowlands.   The  precipitation 


generally  increases  with  an  increase  in  altitude 
and  may  reach  30  to  50  inches  (76.2-127.0  cm) 
annually  in  the  higher  mountains.  Daily  and 
seasonal  temperatures  in  Utah  vary  widely.  The 
summer  maximum  may  exceed  100°F.  The  rela- 
tive humidity  is  extremely  low  and  the  evapora- 
tion rate  is  high. 

The  desert  lowlands  are  dotted  with  salt 
desert  shrubs  consisting  chiefly  of  greasewood 
(Sarcobatus  vermiculatus)  and  shadscale  (Atrt- 
plex  confertifolia)  in  areas  below  5,.500  feet 
( 1,676  m)  in  elevation,  and  sagebrush  (Artemisia 
tridentata)  in  areas  higher  than  5,500  feet  (1,676 
m)  throughout  much  of  the  Colorado  Plateau 
and  the  Great  Basin.  This  low  scrubby  vegeta- 
tion ranges  from  several  inches  to  several  feet 
in  height.  Desert  scrub,  consisting  predominantly 
of  mesquite  (Prosopis  glandtiliflora) ,  creosote 
bush  ( Larrea  divaricata ) ,  and  black  brush 
( Coleogtjne  Tamosissima ) ,  occurs  in  the  southern 
desert  of  southwestern  Utah. 

The  more  arid  foothills  in  the  Great  Basin 
and  Colorado  Plateau,  which  receive  10  to  15 
inches  (25.4-38.1  cm)  of  rainfall  annually,  are 
covered  with  pinon-junipcr  forests  (Pinus  and 
Jimipems).  10  to  30  feet  (3.0-9.1  m)  in  height. 
Foothills  receiving  16  to  20  inches  (40.6-50.8 
em)  of  rainfall  are  covered  with  a  variety  of 
scrubbv  trees  and  bushes  called  chaparral,  con- 
sisting of  oak  (Qiiercus),  maple  (Acer),  service- 
berry  (Amelancliier),  mountain  mahogany  (Cer- 
cocarpus),  mountain  laurel  (Ceanothus),  and 
manzanita  (Arctostaphtjlos).  Above  the  foot- 
hills lie  montane  forests  of  spruce  (Picea),  fir 
(Abies),  and  aspen  (Populus  tremnloides) .  The 
aforementioned  data  on  relationships  between 
precipitation  and  vegetation  are  modified  from 
Woodbury  and  Cottam  (1962). 

Utah's  numerous  mountain  ranges,  its  ex- 
tensive plateaus,  and  its  high  cliffs  and  mesas 
supply  a  plentitude  of  suitable  nesting  sites 
for  birds  of  prey.  The  low  scrubby  vegetation 
of  its  foothills  and  desert  lowlands  provides  the 
extensive  hunting  areas  preferred  by  the  larger 
falcons. 


ECOLOGICAL  DISTRIBUTION  OF  UTAH  PEREGRINES 


Climate 

The  peregrine,  as  represented  by  a  cosmo- 
politan assortment  of  geographically  variable 
races,  has  adapted  to  a  wide  variety  of  environ- 
mental conditions.  This  is  true  also  for  the  ana- 
tum  race,  which  ranges  from  the  tree  line  of 
the  North  American  Arctic  south  sparingly  into 
northern  Mexico  and  the  southern  tip  of  Baja 


California.  In  Utah,  the  peregrine  has  been 
known  to  nest  in  the  Great  Salt  Lake  Desert, 
one  of  the  more  arid  regions  known  to  be  in- 
habited by  this  cosmopolitan  species.  At  Wen- 
dover,  for  example,  the  monthly  rainfall  for  the 
critical  breeding  period  of  March  through  July 
averaged  onlv  0.44  inches  (1.12  cm)  over  a  49- 
vear    period;    the    mean    monthlv    temperature 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


15 


ranged  from  42°  F  (6°C)  in  March  to  79°F 
(26°C)  in  July  (U.  S.  Dept.  of  Commerce, 
1965).  Bond  ( 1946)  tells  of  peregrines  nesting  in 
the  hot,  arid  climates  along  the  lower  Colorado 
River  in  California,  in  northeastern  California, 
and  eastern  Oregon. 

Climate  along  the  Wasatch  Mountains  of 
Utah,  where  the  peregrine  historically  attained 
its  maximum  density  in  the  state,  is  more  mod- 
erate. Here  (Salt  Lake  City)  the  monthly  rain- 
fall for  March  through  July  averaged  1.03  inches 
(2.62  cm)  over  a  32-year  period;  the  monthly 
temperature  ranged  from  40°F  (4.4°C)  in  March 
to  77°F  (25°C)  in  July  (U.  S.  Dept.  of  Com- 
merce, 1965). 

Figures  13-15  delineate  some  of  the  climatic 
extremes  associated  with  nesting  peregrines  in 
Utah.  The  hythergraphs  given  in  Figure  13 
are  composites  of  the  mean  monthly  extremes 
of  daily  temperature  (for  record  period)  and 
the  mean  monthly  precipitation  for  weather  sta- 
tions near  18  known  peregrine  eyries  distrib- 
uted throughout  Utah.  Tlie  breeding  period, 
March  through  August,  is  indicated  also.  Tlie 
composite  hythergraphs  are  constructed  the 
same  as  those  given  by  Twomey  (1936)  and 
Linsdale  ( 1937 ) ,  except  that  these  authors  used 
mean  nionthlv  averages  of  daily  temperature 
rather  than  extremes  (data  from  U.  S.  Dept.  of 
Commerce,  1965). 

In  Figure  14  we  have  plotted  the  monthly 
a\'erage  of  the  daily  minimum  temperature 
against  the  monthly  average  of  the  daily  maxi- 
mum relative  humidit>'  (from  readings  taken  at 
three-hour  intervals,  1965  through  1969)  and  the 
monthly  average  of  the  daily  maximum  tempera- 
tures against  the  monthly  average  of  the  daily 
minimum  relative  humidity  for  Salt  Lake  City 
( U.  S.  Dept.  of  Commerce,  Local  Climatol.  Data 
1965-1969). 

Figure  15  gives  a  composite  of  the  mean 
number  of  days  per  month  that  the  precipitation 
was  equal  to  or  exceeded  0.1  inch  (0.25  cm) 
and  the  mean  number  of  davs  per  month  in 
which  the  temperature  was  equal  to  or  exceeded 
90°F  (.32.2°C),  averaged  for  the  18  stations  util- 
ized in  Figure  13  (data  from  U.  S.  Dept.  of 
Commerce,   1965,    [for  record  period]). 

We  used  the  extremes  of  climate  since  they, 
more  than  means,  are  likelv  to  influence  the 
general  distribution  of  a  species.  According  to 
Odum  (19.59:116-117): 

.  .  .  temperature  exerts  a  more  severe  limiting  effect 
on  organLsm.s  when  moishire  conditions  are  extreme, 
that  is,  either  very  high  or  very  low,  tlian  wlien  such 
conditions  are  moderate.  Likewise,  moisture  plays  a 
more  critical  role  in  the  extremes  of  temperature. 


It  is  at  the  environmental  extremes  that  the 
evolutionary  processes  for  a  species  are  most 
pronounced  in  regards  to  the  development  of 
new  limits  of  tolerance.  By  comparing  the  cli- 
matic extremes  at  the  periphery  of  the  ecologi- 
cal range  of  a  species,  such  as  the  peregrine  in 
Utah,  one  may  gain  an  insight  into  the  climatic 
factors  which  may  hmit  its  range. 

Altitude 

For  western  North  America,  Bond's  data 
( 1946 )  indicate  that  the  peregrine  rarely  nests 
above  5,000  feet  (1,524  m)  in  elevation,  with 
a  few  nesting  up  to  10,000  feet  (3,048  m)  in 
California.  However,  many  of  the  18  eyries 
cited  by  Enderson  (1965)  for  Colorado  were 
above  5,280  feet  (1,610  m),  while  the  majority 
of  them  were  above  6,000  feet  (1,829  m)  (En- 
derson, pers.  comm.),  with  one  eyrie  in  a  high 
mountain  region  of  Colorado,  situated  at  an 
elevation  of  12,000  feet  (3,658  m)  (Thomas  D. 
Ray,  pers.  comm.).  It  may  be  that  the  habitat 
requirements  of  the  peregrine  are  best  satisfied 
in  Colorado  at  these  higher  elevations.  The 
paucity  of  eyries  known  to  Bond  ( 1946 )  to  be  at 
the  higher  elevations  may  be  due,  in  part,  to  the 
difficulties  encountered  in  reaching  and  search- 
ing the  cliffs. 

Nelson  (1969)  reported  that  peregrines  in 
Utah  nest  at  elevations  up  to  tree  line,  between 
6,000  and  7,000  feet  (1,829  and  2,134  m).  The 
only  eyrie  in  Utah  exceeding  6,000  feet  (1,829 
m),  that  is  known  to  us,  is  at  an  elevation  of 
6,700  feet  (2,042  m)  (Table  1,  site  36),  but  two 
are  at  6,000  feet  (Fig.  1,  Table  1,  sites  22  and 
37),  and  the  elevations  of  four  others  approach 
6,000  feet  (Fig.  1,  Table  1,  sites  26,  28,  35,  38). 
One  suspected  eyrie  site,  however,  is  at  an  ele- 
vation of  8,500  feet  (2,591  m)  (Fig.  1,  Table  1, 
site  29)  and  another  is  at  9,750  feet  (2,972  m) 
(Fig.  1,  Table  1,  site  27),  suggesting  the  possi- 
bility that  if  higher  areas  were  searched,  others 
would  be  found.  The  mean  elevation  of  pere- 
grine eyries  in  Utah  is  about  5,000  feet  (1,524 
m)  (Table  2).  They  ranged  from  3,360  to 
6,750  feet  (1,024-2,057  m),  with  a  prepon- 
derance of  eyries  (89  percent)  between  4,000 
and  6,000  feet  (1,219  and  1,829  m)  in  eleva- 
tion, and  with  nearly  50  percent  of  them  at 
elevations  between  4,500  and  4,999  feet  (1,372 
and  1,524  m).  A  frequency  distribution  of  the 
elevations  of  Utah  eyries  is  given  in  Table  2. 

Habitat  Niche 

The  habitat  niche  of  the  peregrine  may  be 
divided  into  two  parts:  (1)  the  cliff  or  substrate 
upon  wliich  it  lays  its  eggs  and  rears  its  young 


16 


Bhicium  YdUNC  University  Science  Bulletin 


100- 


2C>- 


10- - 


Maximum 


oV 

0 


■M- 


4- 


M 


NIMUM 


I    I    I    I    I    I    I    I 


2  3  0  12 

Inches  of  Precipitation 


Fig.  13.  Composite  hythcrj^raph  for  18  stations  situated  near  known  peregrine  eyries  in  Utah.  Mean  total 
monthly  precipitation  is  represented  in  inches  and  mean  monthlv  extremes  of  temperature  (daily  ma.\i- 
mum  and  minimum,  for  record  period)  are  represented  in  degrees  F;  they  were  constnicted  the  same 
as  those  given  by  Twomev  (1936)  and  Linsdale  (1937),  except  that  these  authors  used  mean  monthly 
temperatures  (U.S.  Dept.  Commerce,  1965).  The  diagonalK  lined  area  depicts  the  climatic  conditions  for 
the  egg-laying  and  incubation  period  (March-May);  the  stippled  area  represents  the  hatching  and  nestling 
period   (May  and  June);  the  vertically  lined  area  shows    the    fledging    period     (June-August). 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


17 


IOOt 


SO- 


SO' 


UJ 

S60- 
Q 


-50- 

LlI 

a: 

<40- 

Ixl 

a. 

^30' 


20-- 


10- - 


0' 


MIN  TEMP  :  MAX  REL  HUM 


■'•     K. 


MAX   TEMP-.  MIN  REL  HUM 


1         I  I  I  I  I  I  I 

0        10       20       30      40       50      60      70 

Percent  of  Humidity 


-I 


80      90      100 


I'ig.  14.  Climographs  for  Salt  Lake  City.  Utah.  Daily  maximum  temperatures  (averaged  monthly  for  years 
1965-1969),  represented  in  degrees  F  are  plotted  against  the  mean  daily  minimum  relative  humidity  for  the 
same  period;  and  the  mean  daily  minimum  temperatures  for  the  same  period  are  plotted  against  the  mean 
daily  maximum  relative  humidity.  Humidit)-  vahies  were  average  from  the  maximum  and  minimum  readings, 
taken  at  .3-hour  intervals  for  196.5  through  1969  (U.S.  Dept.  Commerce,  Local  Climatological  Data).  Num- 
bers  beside   points   designate  month.s   of   the  year. 


18 


Bhigham  Young  University  Science  Bulletin 


3a 


25- 


20 


o 

o 

< 
Q 
10- 


N=I8 
Mean- 


EXTREMES 


/ 


/ 


/ 


-r- 


^^ 


\ 


•4- 


Mar  Apr  May  Jun 

MONTHS 


Jul 


Aug 


30 


25 


20 


15 


\0 


O 

Al 


i^^--^^ 


N=I8 
Mean 


Extremes  a;:^' 


—(I 


^•~. 


I 


0^ 


,<i- — 


Mar  Apr  May  Jun 

MONTHS 


Jul 


Aug 


•0 


Fig.  15.  Composite  graph  for  18  stations  near  peregrine  eyries  in  Utah  depicting  the  mean  number  of  days 
per  month  in  which  precipitation  was  0.1  inch  (0.25  cm)  or  more  and  the  average  number  of  days  per  month 
in  which  the  temperature  was  90°F  (32.2°C)  or  higher.  (For  record  period,  U.S.  Dept.  of  Commerce, 
1965.)  Values  were  averaged  (dashed  hues)  for  tlie  same  18  eyrie  sites  u.sed  in  Fig.  13;  extreme  values 
are  represented  by  sohd  triangles. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


19 


Table  2.     Frequency  distribution  of  peregrine  eyrie  site 
elevations  in  Utah. 


Elevation 

(500-ft.  inter\als) 

n 

Percent 

Elevation 
( intervals  in  meters ) 

3000-3499 

1 

3.2 

914.4-1066.7 

3500-3999 

0 

0.0 

1066.8-1219.1 

4000-4499 

3 

9.7 

1219.2-1371.5 

4500-4999 

15 

48.4 

1371.6-1523.9 

5000-5499 

6 

19.4 

1524.0-1676.3 

5500-5999 

4 

12.9 

1676.4-1828.7 

6000-6499 

1 

3.2 

1828.8-1981.1 

6500-6999 

1 

3.2 

1981.2-2133.3 

Totals: 

31 

100.0 

xelev.  4987  ft  (1520  m) 
Range  3360-6750  ft  ( 1024-2057 

m) 

and  around  which  its  reproductive  activities  take 
place  (nesting  sites),  and  (2)  the  surrounding 
environs  or  territor)'  where  it  obtains  its  food 
(hunting  sites). 

Nesting  Sites 

Most  peregrine  eyries  in  Utah  were  situated 
on  a  high  ledge  on  the  face  of  a  cliff,  but  one 
female  peregrine  was  reported  to  have  laid  her 
eggs  in  1946  (Boyd  Shaeffer,  pers.  comm.)  on 
one  of  the  dikes  (elevated  roadways)  that  sep- 
arated two  impoundment  lakes  at  Ogden  Bay 
State  Waterfowl  Management  Area  (Table  1, 
site  20).  Additionally,  an  ornithologist  (verbal 
report,  to  J.  H.  Enderson  at  AOU  meeting,  1964 ) 
reported  seeing  an  adult  peregrine  carry  food 
to  a  \oung,  nonflving  falcon  on  the  Monnon 
Temple  in'Salt  Lake  City  in  1962,  although  we 
can  find  no  corroborative  evidence  that  falcons 
ever  nested  there. 

CHff  OrientaHon 

The  ledges  on  which  most  Utah  peregrines 
nest  are  in  extensive  mountain  ranges  which  lie 
in  a  north-south  direction.  The  escarpments  of 
these  mountains  provide  east-  and  west-facing 
cliffs,  while  their  side  canyons  provide  both 
north-  and  south-facing  cliffs  (Fig.  12).  As  il- 
lustrated in  Figure  16,  most  peregrine  eyries  in 
the  state  were  found  in  east-  and  north-facing 
cliffs.  .Although  the  escarpment  along  the  Wa- 
satch Mountains  provided  cliffs  which  faced  all 
directions  (Fig.  12),  10  of  12  eyries,  for  which 
data  are  available,  were  at  sites  facing  north- 
ward (five  evries)  and  eastward  (five  eyries); 
three  of  the  12  faced  slightly  westward  (NNW 
and  NW),  four  faced  southward  (ESE  and  SE), 
one  faced  directlv  west,  and  one  faced  directly 
south.  This  suggests  a  directional  orientation 
by  the  peregrine  to  the  sun's  exposure.  Cliffs 
facing  north  or  east  should  provide  the  eyrie 


better  protection  from  the  hot  afternoon  sun  than 
would  those  facing  south  or  west. 

These  findings  tend  to  corroborate  those 
of  Nelson  (1969),  who  has  documented  the 
death  of  nestling  Golden  Eagles  {Aquila  chrysae- 
tos)  due  to  direct  exposure  to  the  hot  rays  of 
the  sun.  He  considers  tlie  peregrine  to  be  more 
sensitive  to  the  extremes  of  temperature  and  to 
the  direct  rays  of  the  sun  than  the  Prairie  Fal- 
con. He  has  pointed  out  that  the  later  nesting 
of  the  peregrine,  compared  to  that  of  the  Golden 
Eagle  and  Prairie  Falcon  makes  the  peregrine's 
young  more  vulnerable  to  heat  and  sun  than  are 
the  young  of  either  of  the  other  t^vo  species. 
McGahan  (1968)  found  a  preference  by  the 
Golden  Eagle  in  Montana  for  southern  exposures. 
He  suggested  that  nest  site  preference  was  in- 
fluenced by  the  direction  of  the  sun  and  noted 
that  exposure  should  be  important  when  tem- 
peratures are  below  freezing  as  well  as  during 
the  warmer  months  of  June  and  July. 

In  Alaska,  Cade  ( 1960)  found  that  peregrines 
nesting  along  the  Yukon  River  preferred  cliffs 
facing  an  easterly  direction  and  that  this  orienta- 
tion had  some  relation  to  the  sun.  He  noted 
no  such  correlation,  however,  for  eyries  along 
the  Colvillc  River  and  hypothesized  that  the 
Yukon  eyries  faced  eastward  because  of  strong 
prevailing  summer  \vinds,  whereas  the  lack  of 
special  orientation  along  the  Colville  was  due  to 
the  absence  of  such  winds. 

On  the  other  hand,  in  Great  Britain,  where 
the  climate  is  more  moderate,  Ratcliffe  (1962) 
found  that  suitable  cliffs  faced  all  directions 
and  that  British  peregrines  are  indifferent  to  di- 
rectional facing.  He  argues  further  that  more 
intensive  ice  action  on  shaded  north  and  east 
slopes  have  resulted  in  more  extensive  develop- 
ment of  cliffs  or  crag  ranges  on  these  slopes. 
Hence,  he  concludes  that  cliff  exposure  is 
unlikely  to  influence  the  deliberate  choice  of  a 
nesting  cliff  or  site. 

Our  data  and  those  of  Cade's  (1960)  suggest 
that  sun  and  wind  exposure  in  the  harsh  ex- 
tremes of  climate  such  as  those  in  the  desert 
and  in  the  Arctic  may,  indeed,  elicit  a  deliberate 
choice  of  nesting  sites.  In  Great  Britain  peregrine 
eyries  probably  are  not  subjected  to  such  harsh 
extremes  of  climate,  and  thus,  peregrines  have 
less  need  for  making  deliberate  choices  there. 

Rock  Type,  Cliff  Size,  and  Eyrie  Height 

The  physical  characterisHcs  of  the  cliff  play 
an  important  role  in  their  use  by  the  peregrine 
as  a  nesting  site.  The  geological  formation,  in- 
volving type  of  rock  and  height  of  cliff,  con- 
tributes to  the  suitability  of  the  cliff  as  a  nest- 
ing site.  Tliirty  peregrine  eyries  in  Utah  were 


20 


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Fig.  16.  Directional  facings  of  Peregrine  Falcon  and  Prairie  Falcon  eyries  in  Utah,  both  in  areas  of  sympatry  and 
in  areas  of  allopatry.  The  values  in  the  outer  ring  are  for  the  peregrine;  those  in  the  inner  ring  are  for  the 
Prairie  Falcon.  The  directional  relationships  shown  here  were  statistically  significant  at  /;  <0.01  (X"  test; 
calculated  .\=  value,  7.37,  1  df)  for  the  Prairie  Falcon  and  p<0.05  (X=test;  calculated  X=  value,  4.48,  1  df) 
for  the  Peregrine  Falcon. 


situated  on  cliffs  composed  principally  of  four 
types  of  rocks:  limestone,  nine  e\'rics;  sandstone, 
nine  eyries;  quartzite,  six  eyries;  and  volcanic 
rock,  three  eyries.  One  additional  eyrie  each 
was  located  on  volcanic  agglomerate,  granite, 
and  metamorphic  gneiss. 

According  to  Hickey  (1942),  the  height  of 
the  cliff  is  involved  in  the  species'  fidclit)  at  the 
eyrie  site  over  many  generations  of  occupancy, 
and  this  concept  is  supported  h\-  Ratcliffe  ( 1962, 
1969)  in  Great  Britain;  iMsclu-r  (1967)  has  dis- 
cussed the  concept  for  eyries  elsewhere  in  Eu- 


rope. Hickey  (1942),  on  the  basis  of  height  and 
c()ntinuit\'  of  use,  classified  cliffs  in  the  eastern 
United  States  into  three  classes.  Bond  (1946) 
believes  Hieke\"s  (op.  eit. )  classification  to  bi'  an 
oversimplification  in  the  western  United  States. 
Peregrines  in  Utah  selected  a  wide  variety 
of  e\  rie  sites.  .-Mthough  the  histor\-  of  occupancy 
of  indi\'iduai  eyries  in  Utah  is  largely  unknown, 
there  is  some  evidence  to  support  Hickey's 
( op.  cit. )  hypothesis,  at  least  in  regards  to  height. 
I']\rie  sites  on  the  low,  marginal  cliffs  were  the 
first  to  be  abandoned  in  Utah,  whereas  several 


Biological  .Series,  Vol.  18,  No.  1       Pereghine  Falcon  in  Utah 


21 


that  were  situated  high  up,  on  massive  cliffs 
that  were  difficult  to  climb,  have  the  longest 
histories  of  occupancy. 

A  frequenc\'  distribution  of  heights  of  cliffs 
which  supported  nesting  peregrines  in  Utah  are 
gi\'en  in  Table  3.  These  cliffs  ranged  from  40 
to  400  feet  (12.2-122  m)  in  height.  The  mean 
height  of  21  such  cliffs  in  Utah  was  178  feet 
(.54.3  m).  An  additional  cliff,  first  noted  by 
Treganza  earlv  in  this  centur)'  and  reported  by 
\\'oodburA-  et  al.,  (unpubl.  ms),  was  in  excess 
of  1,000  feet  (304.8  m)  in  height  (Figs.  1  and 
7;  Table  1,  site  8).  We  excluded  it  from  our  cal- 
culations so  as  to  not  disturb  unduly  the  more 
normal  range  of  heights  (see  footnote.  Table  3). 

For  14  evries  the  distance  from  the  base  of 
the  cliff  to  the  evrie  site  averaged  105.5  feet 
(32.2  m)  and  ranged  from  28  to  330  feet 
(8.5-100.6  m).  These  measurements  do  not 
include  the  talus  slope  and  mountain  side.  If 
these  distances  were  included,  the  values  given 
above  would  be  considerably  higher  for  most 
sites,  especially  those  on  the  escaq^mcnt  of  the 
Wasatch  Mountains.  Ratcliffe  (1962)  has  dis- 
cussed the  importance  of  the  steep  slopes  as  a 
relevant  factor  in  attracting  peregrines  to  the 
cliff. 

From  the  brink  of  the  cliff  to  the  eyrie 
sites  below,  the  distance  averaged  68.6  feet 
( 20.9  m )  and  ranged  from  12  to  250  feet  ( 3.7- 
76.2  m )  for  13  e\ries. 

The  values  given  here  for  cliff  heights  aver- 
age somewhat  higher  than  those  reported  by 
Cade    (1960)    for  "the   Yukon   River   in   Alaska, 


and  by  White  and  Cade  (1971)  for  the  Colville 
River.  Distances  from  the  base  of  cliffs  to  the 
nest  sites  in  Utah,  however,  averaged  nearly 
twice  those  reported  by  Cade  ( 1960)  in  the  Arc- 
tic. 

Hunting  Sites 

Marshes  apparently  play  an  important  role 
in  the  breeding  ecology  of  the  peregrine  in 
Utah  (Figs.  12,  17,  and  18),  because  nearly  all 
peregrine  eyries  are  situated  near  them.  We 
measured  the  distances  from  each  of  20  known 
eyrie  sites  in  the  Great  Salt  Lake  and  Utah 
Lake  valleys  to  the  closest  nonflowing  surface 
water,  to  the  closest  marsh  320  acres  (130  ha) 
or  larger,  and  to  the  closest  marsh  with  no  re- 
gard to  size.  The  surface  areas  of  the  closest 
nonflowing  water  and  the  size  of  the  closest 
marsh  were  also  determined.  Measurements  were 
taken  from  U.S.  Geological  Survey  topographic 
maps  which  were  constructed  from  aerial  photo- 
graphs taken  between  1945  and  1956;  they  are 
summarized  in  Table  4. 

Of  the  4,.500  sq  miles  (11,655  km=)  sur- 
rounding and  including  these  two  lakes,  marshes 
covered  about  100  sq  miles  (259  km-),  while 
open  water  comprised  about  1,443  sq  miles 
(3,737  km=).  With  exclusion  of  the  Utah  and 
Great  Salt  lakes,  with  their  surface  areas  of 
about  138  sq  miles  and  1,661  sq  miles  (358 
km-  and  4,302  km-),  respectively,  the  surface 
area  of  water  would  be  80  sq  miles  (207  k-m"). 
If  the  three  large  impoundment  lakes  (surface 
area,  about  55  mi";  142  km-)  at  the  Bear  River 


Table  3.     Frequency  distribution  of  heights  of  cliffs  containing    Peregrine 
Utah  and  the  vertical  distances  of  eyrie  sites  above  bases  of  the  cliffs. 


Falcon    and    Prairie    Falcon    eyries    in 


Distance 

CLIFFS 

EYRIES 

Distance 

in 

Peregrine 

Prairie 

Peregrine 

Prairie 

in 

Feet 

n           Percent 

n 

Percent 

n 

Percent 

n 

Percent 

meters 

0-24 

0              0.0 

1 

2.3 

0 

0.0 

10 

19.6 

0.0-7.5 

25-49 

1             4.5 

11 

25.0 

3 

21.4 

19 

37.3 

7.6-15.1 

50-74 

1             4.5 

10 

22.7 

3 

21.4 

8 

15.6 

15.2-22.8 

75-99 

4           18.2 

8 

18^2 

3 

21.4 

7 

13.7 

22.9-30.4 

100-124 

4           18.2 

5 

11.4 

0 

0.0 

2 

3.9 

30.5-37.9 

125-149 

1            4.5 

0 

0.0 

1 

7.1 

0 

0.0 

38.0-45.6 

150-199 

3           13.6 

3 

6.8 

0 

14.3 

2 

3.9 

45.7-60.9 

200-249 

1            4.5 

2 

4.5 

0 

0.0 

1 

2.0 

61.0-76.1 

250-299 

1            4.5 

1 

2.3 

1 

7.1 

1 

2.0 

76.2-91.3 

300-349 

2            9.1 

2 

4.5 

1 

7.1 

0 

0.0 

91.4-106.6 

350-399 

1            4.5 

0 

0.0 

0 

0.0 

0 

0.0 

106.7-121.8 

400-449 

2            9.1 

0 

0.0 

0 

0.0 

0 

0.0 

121.9-137.0 

450-499 

0            0.0 

0 

0.0 

0 

0.0 

1 

2.0 

137.1-152.3 

500  > 

1            4.5 

1 

2.3 

n 

0.0 

0 

0.0 

152.4> 

Totals: 

22           99.7 

44 

100.0 

14 

99.8 

51 

100.0 

X 

178.0  ft" 

101.7  ft 

105.5  ft 

64.2  ft 

(54.3  m) 

(31.0  m) 

(32. 

,2  m) 

(19.6  m) 

Range: 

40--400  ft 

7-500  ft 

28-330  ft 

2, 

.5-450  ft 

(12.2-121.9) 

(2.] 

1-152.4  m) 

(8.,5-100.6  m) 

(0.76-1.37.2  m) 

•Excludes   one   ground   nestcr  and   one  eyrie  on  a    1.000   ft    ( ^On   m)    cliff. 


22 


Bricham  Young  University  Science  Bulletin 


I 


\ 


Fig.   17.     Saltgrass    (Distichlis  stricta)   marsh  at  Ogden  Bay  Refuge,  Black-necked  stilts  (Himantopus  mexicantis), 
a  prey  species  of  the  peregrine,   in  the  foreground.  Photo  by  R.  D.  Porter,  1953. 


Fig.  18.  View  to  the  west  toward  Promontory  Mountains  from  Ogden  Bay  Waterfowl  Management  Area. 
Marshes  in  foreground  are  typical  of  those  adjacent  to  Great  Salt  Lake  from  which  peregrines  and  prai- 
ries nesting  along  the  Wasatch  escarpment  and  adjacent  mountains  obtained  their  major  food  source.  Photo 
1)V  R.  J.  Erwin,  August  1972. 


Biological  Series,  Vol.  18,  No.  1       Pehecrine  Falcon  in  Utah 


23 


Table  4.  Distances  from  peregrine  e)rie  sites  in  the  Great  Salt  Lake  Valley  and  Great  Basin  De.sert  to  open, 
nonflowing  water  and  marsh  liiinting  areas  and  the  size  of  these  areas  in  relation  to  distance  (measured 
from  U.S.  Geological  Sursey  topographic  maps  which  were  constructed  from  aerial  photographs  taken  be- 
tween   1946    and    1956).    Values    in    parentheses   represent  metric  equivalence  in   kilometers   or  hectares. 


MARSHES 

SURFACE  WATER' 

Mi.  to 

Mi.  to 

Number  of 

Mi.  to 

closest 

Acres  in 

Mi.  to 

closest 

acres  in 

closest 

marsh   > 

closest 

closest 

water   > 

closest 

Area  &  Sta-           marsh 

320  acres 

marsh 

water 

320  acres 

water 

tistic                        ( km ) 

(130  ha) 

(ha) 

(km) 

(130  ha) 

(ha) 

Wasatch  Mountains 

( Utah  &  Great  Salt 

Lake  valleys) 

n                         19 

19 

17= 

19 

19 

14' 

x±SD           3.3  ±2.6 

7.6±5.1 

17.5  ±20.6 

2.5+2.0 

5.2±4.3 

59.6  ±344 

(5.3  ±4.2) 

(12.2±8,2) 

(7.1±8.3) 

(4.0  ±3.2) 

(8.4±6.9) 

(24.1  ±13.9) 

Range          0.19-9.7 

0.19-18.6 

3.7-82.6 

0.10-6.7 

0.10-13.6 

1.2-188.8 

(0.31-15.6) 

(0.31-29.9) 

(1.5-33.4) 

(0.16-10.8) 

(0.16-21.9) 

(0.49-76.4) 

Desert,  Great  Basin 

n                         3 

3 

3 

3 

2* 

3 

x±SD           1.3  +  1.3 

1.3  +  1.3 

7,302  ±10,396 

1.7  +  2.0 

4.0 

406  ±701 

(2.1±2.1) 

(2.1±2.1) 

(2,955  ±4,207) 

(2.7  ±3.2) 

(64) 

(164  +  284) 

Range          0.19-2.8 

0.19-2.8 

640-19,281= 

0.19-4.0 

4.0-4.0 

1.0-1,216 

(0.31-4.5) 

(0.31-4.5) 

(259-7,803) 

(0.31-64) 

(6.4-6.4) 

(0.40-492) 

'nonflowing  waters;  lakes  and  ponds,  -excludes  Iwo  large  marshes,  one  5,598  acres  {2,2G()  hal,  the  other  1,114  acres  (-lol  ha), 
^closest  water  to  five  eyries  was  either  Utah  Lake  or  Great  Salt  Lake;  hence,  they  were  excluded.  Mata  for  one  desert  eyrie,  which  was 
nearly  100  miles  (Ifil  km)  from  large  bod,y  of  water,  was  excluded.  ^Nelson  (19(36)  gives  4,700  acres  (1.000  ha)  for  Clear  Lake  Water- 
fowl Management  .\rea,  but  topographic  maps  show  an  additional  14,5-Sl  acres  (5,901  ha),  contiguous  with  the  management  area,  and  a 
total   of  53,000  acres   (21.449  ha)    are  shown  within  about  20  miles  radius  of  the  Clear  Lake  e.vrie, 


Refuge  were  also  excluded,  the  amount  of  sur- 
face w'ater  would  be  reduced  to  25  sq  miles 
(65  km-).  If  both  surface  waters,  exclusive  of 
the  Utah  and  Great  Salt  lakes,  and  marshes  were 
divided  equall\-  by  the  20  known  peregrine 
eyries  for  the  area,  each  pair  of  birds  at  these 
evries  would  use  prey  species  from  4.0  sq  miles 
('10.4  km-)  of  water.'S.O  sq  miles  (13.0  km=)  of 
marsh,  and  9.0  sq  miles  (23.3  km-)  of  the  two 
combined.  Nelson  ( 1966),  on  the  other  hand,  re- 
ports that  there  are  234  sq  miles  (606  km=)  of 
managed  marshlands  surrounding  the  Great  Salt 
Lake  (see  Fig.  19),  to  which  may  be  added 
several  sq  miles  of  unmanaged  marshes  con- 
trolled bv  duck  clubs.  The  disparitv  between 
Nelson's  measurements  and  ours  probablv  is  due 
to  the  fact  that  we  used  onlv  marsh  areas  as 
shown  on  topographic  maps  and  excluded  mud 
flats  and  water,  whereas  Nelson's  measurements 
probabU'  include  all  lands  and  water  within  the 
Waterfowl  Management  Areas. 

Marshes  were  the  dominant  features  near 
three  eyries  in  the  Great  Basin  desert  (Figs. 
1  and  20,  Table  1,  sites  4,  23,  and  25),  and 
Twome\-  (1942)  reported  the  use  of  the  Ashley 
Greek  marshes  by  peregrines  nesting  in  Uintah 
Gount)-.  The  desert  eyrie  in  the  Colorado  Plateau 
reported  by  White  and  Lloyd  (1962)  was  by 
a  river  (Fig.  9).  Figure  21  gives  an  aerial  view 
of  a  river  site  in  the  desert  of  northern  Arizona, 
tspical  of  those  in  parts  of  Utah,  and  Figures 


22  and  23  show  marshes  near  eyrie  sites  in  the 
Great  Salt  Lake  Desert. 

Peregrines  nesting  along  the  Wasatch  es- 
carpment traveled  long  distances  to  obtain  shore 
and  marsh  birds,  which  made  up  the  bulk  of 
the  food  items  found  in  their  nests  (Table  4), 
and  the  marshes  where  they  hunted  were  rather 
extensive.  In  general,  the  Great  Basin  desert 
eyries  were  closer  to  marshes  and  to  open 
water  than  were  the  Wasatch  escarpment  eyries 
( Table  4 ) .  One  marsh  supporting  an  eyrie  in  the 
Great  Salt  Lake  Desert  is  onlv  about  a  square 
mile  (2.6  km-)  in  extent,  and  is  only  about  a 
mile  (1.6  km)  from  the  eyrie  (Fig.  20).  It  is 
about  the  same  size  as  the  Ashley  Creek  marsh 
(Stewart  Lake  Waterfowl  Management  Area, 
Nelson,  1966)  near  the  eyrie  found  by  Twomey 
( 1942 ) .  The  marsh  at  one  other  e^'ric  in  the 
Great  Salt  Lake  Desert  covers  about  2^4  square 
miles  (5.8  km-)  and  is  less  than  a  mile  from  the 
e\rie  site.  An  additional  eyrie  site  (Woodbury 
et  al.,  unpubl.  ms)  was  2.8  miles  (4.5  km)  from 
a  marsh  that  covered  over  30  square  miles 
(78  km-')  (Table  4).  The  surface  area  of  fresh 
water  at  two  of  the  desert  sites  is  only  a  few 
acres  in  extent  (Fig.  23),  whereas  that  at  the 
additional  site  was  about  2  square  miles  (5.2 
km-)  in  extent. 

Of  the  40  eyries  and  suspected  eyries  in 
Utah  for  which  we  have  data,  three  were  along 
rivers  with  marshes,  streams,  or  lakes;  five  were 


24 


Bricham  Young  Universiti-  Science  Bulletin 


GRANTSVlLLfc 


Fig.    19.     Distrihiition   of  maiuigcd   marshlands   concciitratnl    aniviiul    tlu-    Cr^at    Salt    Lake   region.    Photo   by   per- 
mission of   Utah   Oivisioii   of  Wildlife  Resources,  in  Nelson,   1960. 


Biological  Series,  Vol.  18,  No.  1       Pehegrine  Falcon  in  Utah 


25 


^^j"-*' 


Fig.  20.  View  across  a  marshy  area  adjacent  to  an  eyrie  in  the  Great  Basin  at  the  edge  of  the  Great  Salt 
Lake  Desert.  R.  D.  Porter  is  standing  in  foreground  ;ind  is  about  1  mile  (1.6  km)  east  of  the  eyrie  shown 
in  Figure  44.  Photo  by  R.  J.  Erwin,  August  1972. 


Fig.  21.  Aerial  view  of  a  river  eyrie  site  in  the  desert  of  northern  Arizona  typical  of  those  in  southeastern 
Utah.  View  looking  NNE.  Peregrines  nested  on  the  canyon  wall  on  the  right  hand  side  of  tile  photo. 
Photo  by  G.  D.  Lloyd,  1960. 


26 


Bricham  Young  University  Science  Bulletin 


along  major  rivers;  25  were  near  marshes  with 
lakes  and  streams;  five  were  along  streams  only; 
and  there  was  one  each  near  a  marsh  and  a  lake 
only.  All  but  two  of  the  21  eyries  near  the  Great 
Salt  Lake  were  adjacent  to  a  stream,  which  usual- 
ly comprised  the  closest  source  of  water.  The 
smaller  passerine  birds  associated  with  the 
streamside  vegetation  provided  the  peregrines 
with  a  source  of  food  which  frequently  was 
within  the  immediate  area  of  the  eyrie. 

The  marshes  originate  from  desert  springs, 
from  the  overflow  of  rivers  and  creeks,  from 
deltas  at  the  junctions  of  rivers  and  lakes,  and 
in  more  recent  times,  from  artificial  damming 
of  streams  or  from  the  fomiation  of  ponds  re- 
sulting from  the  drilling  of  wells.  Bulrush  (Scir- 
pus  sp. ),  saltgrass  {Distichlis  stricta)  (Figs.  17 
and  18),  and  cattail  (Tijpha  sp. )  (Fig.  12)  are 
the  principal  plants  in  these  marshes. 


The  marshes  supply  food  for  peregrines  dur- 
ing all  seasons  of  the  year,  but  are  especially  im- 
portant during  nesting  season.  The  presence  of 
an  abundant  food  supply  in  the  marshes  at  Og- 
den  Ba\'  undoubtedly  was  the  major  ecological 
factor  responsible  for  the  groundnesting  of  a 
peregrine  there.  Several  easily  accessible  eyries 
that  were  mentioned  by  Beebe  (1960)  in  the 
Queen  Charlotte  Islands  mav  have  been  due  to 
an  abundant  source  of  pre)'  and  to  the  absence 
of  mammalian  predators. 

The  combination  of  marshes  adjacent  to  suit- 
able cliffs  for  nesting  may  be  considered  an 
"ecological  magnet"  (Hiekey,  1941)  for  the  pere- 
grine in  Utah,  especially  along  the  Wasatch  es- 
carpment, where  extensive  marshes  border  the 
Utah  and  the  Great  Salt  lakes.  Here,  marshes 
are  formed  at  the  deltas  of  three  major  rivers 
that  flow  into  the  lake   (Fig.   19).  Typical  of 


M 


i^'  '>-%'^ 


Fig.  22.  Eyrie  site  near  the  eastern  limits  of  the  Great  Salt  Lake  Desert.  The  eyrie,  when  first  located  by 
Porter  in  the  early  19.5()s,  was  on  a  small  cliff  in  the  left  foreground  which  does  not  show  in  this  photo  be- 
cause it  was  removed  to  make  a  road  bed.  The  peregrines  were  last  .seen  using  the  cliffs  near  the  top  right 
of  the  photo.  Prairie  l'"alc()iis  also  used  the  same  eyrie  that  was  last  used  by  the  peregrines  at  least  three 
years  after  the  peregrines  were  last  seen  there.  Photo  by  K.  J.  Krwin,  August  1971. 


Biological  Sebies,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


27 


their  vegetation  is  that  at  the  delta  of  the  Weber 
River  (Ogden  Bay),  which,  from  salt  flats  to 
river  channels,  consists  mainly  of  glasswort 
(Salicornia  sp. ),  saltgrass,  alkali  bulrush  (S. 
pahi(losus).  hardstem  bulrush  (S.  acutiis),  cat- 
tail (T.  latifoJia  and  T.  angustifolia) ,  and  sago 
pondwecd  (Potamogeton  pectinatus)  (Nelson, 
1954).  For  a  more  comprehensive  description 
of  plant  ecology  in  Utah  marshes,  see  Nelson's 
( 1954 )  studies  of  a  marsh  near  the  Great  Salt 
Lake  ( Ogden  Bay )  and  Bolen's  ( 1964 )  discus- 
sion of  a  spring  fed  marsh  in  the  Great  Salt  Lake 
Desert  (Fish  Springs). 

Numerous  remains  of  nine  species  of  water- 
birds,  including  grebes,  ducks,  rails,  avocet, 
gulls,  and  terns,  from  anthropological  sites  at  the 
northwest  side  of  the  Great  Salt  Lake,  some 
dating  back  at  least  8,350  years  (Hai^per  and 
Alder,  in  press ) ,  suggest  that  marshes  were  pres- 
ent in  the  Great  Salt  Lake  valley  long  before 
the  arrival  of  the  white  man.  Some  of  the  early 
hunters  and  explorers  to  enter  the  valley  re- 
ported the  presence  of  numerous  waterfowl  and 
shorebirds.  Father  Escalante,  who  visited  Utah 
Lake  in  1776,  wrote  that  the  lake  "abounds  in 
man\'  kinds  of  fish  and  in  geese  and  waterfowl" 
(Harris,  1909).  Osborne  Russell,  a  trapper,  saw 
"miriads  of  Swans,  Geese  Brants,  and  Ducks 
which  kept  up  a  continuous  hum  day  and  night 
.  .  ."  at  Bear  River  marshes  on  2  April  1842 
(Haines,  1955).  Fremont  (1845),  who  visited  the 


Bear  River  Delta  on  3  September  1843,  men- 
tioned the  thunderous  noise  made  by  multitudes 
of  waterfowl  in  the  marshes  and  described  the 
area  as  being  covered  with  rushes  and  canes. 
Captain  Stansbury  (1852)  made  similar  observa- 
tions on  22  October  1849  from  a  vantage  point 
on  the  east  side  of  Promontory  Point.  He  re- 
corded that  ".  .  .  thousands  of  acres,  as  far  as  the 
eye  could  reach,  were  covered  with  them  [water- 
fowl]. .  .  ."  Fremont  (1845)  reported  that  "the 
stillness  of  the  night  [8  September  1843]  was  en- 
livened by  millions  of  waterfowl,"  this  time  at 
the  mouth  of  the  Weber  River  near  Little  Moun- 
tain; and  on  9  September  he  reported  that  the 
shallow  delta  of  the  river  was  "absolutely  cov- 
ered with  flocks  of  screaming  plover."  Stansbury 
( 1852 )  noted  innumerable  flocks  of  ducks,  geese, 
white  swan,  and  long-legged  plover  around  the 
shallows  at  the  mouth  of  the  Jordan  River  on 
4  April  1850.  It  is  probable  that  the  "plover" 
were  mostly  American  Avocet  {Recurvirostra 
americana).  Black-necked  Stilt  (Himantopus 
viexicarms).  and  Willet  {Catoptrophorus  semi- 
pahnattis) . 

Vegetation  at  the  river  sites  was  comprised 
mostly  of  cottonwoods  {PopuJus  fremontii  in  the 
Lower  Sonoran  desert  areas;  P.  angustifolia  in 
the  Upper  Sonoran  areas)  and  willows  (Salix 
exigua  was  most  frequently  present,  with  S. 
hitea,  S.  gooddingi,  and  S.  caudata  occasionally 
present  also).  Other  plant  species  known  to  oc- 


Fig.  2.3.     View  from  hilLsiile  below  eyrie  in  Figure  22,  Brackish   marsh   can    be   seen   in   the   midgroiind,   and   salt 
flats  from  the  Great  Salt  Lake  can  be  seen  in  the  background.   Photo  by   R.  J.   Erwin.  August   1971. 


28 


Brigham  Young  University  Science  Bulletin 


cur  with  the  cottonvvoods  and  willows  include: 
squawbush  (RIius  trilohata),  wildrose  {Rosa 
sp. ),  tamarix  (Tamarix  ramosissimu) ,  Joshua  tree 
(Clistoyucca  hrevifolia),  box  elder  (Acer  ne- 
gundo ) ,  ash  ( Fraxinus  sp. ) ,  baccharis  ( Baccharis 
emonji),  hackberrv  (Celtis  douglasii),  and  even 
scrub  oak  {(^)uercus  gambelii).  Tlie  presence  or 
absence  of  the  latter  species  is  dependent  upon 
altitude,  latitude,  and  local  ecological  conditions. 

Food  Niche 

Little  has  been  published  on  the  diet  of  the 
peregrine  in  the  intermountain  region.  Wet- 
more's  ( 1933:49-50)  account  of  the  hunting  tac- 
tics of  the  peregrine  on  the  Bear  River  marshes 
has  been  quoted  elsewhere  ( Bent,  1938 ) .  It  is  re- 
peated here  because  it  gives  a  remarkedly  vivid 
picture  of  the  peregrine  in  its  native  haunts 
along  marshes  of  the  Great  Salt  Lake  earlier  in 
the  present  century. 

The  birds  [falcx)ns]  at  rest  perched  in  low  willows,  or 
on  logs  or  bits  of  drift,  where  tliey  had  clear  view  of 
the  teeming  bird  life  about  them.  Wlien  hungry,  they 
dashed  across  the  open  flats  at  high  speed,  striking 
ruthlessly  at  any  birds  that  appeared,  from  small  s;md- 
pipers  to  large  ducks. 


Their  appearance  in  the  air  was  always  the  signal 
for  chattering  cries  of  akirm  from  blackbirds  and  avo- 
cets  that  put  all  tlieir  bird  neighbors  on  the  watch. 
These  warnings  had  little  effect,  however,  as  the  duck 
hawk,  killing  practically  at  will,  was  truly  despot  of 
this  realm. 

I  have  seen  this  falc-on  dash  through  closely  massed 
flocks  of  flying  sandpipers,  striking  out  two  or  three 
with  as  mimy  thrusts  of  the  claws,  allowing  each  bird 
to  drop  and  then  wheeling  swiftly  to  seize  the  falling 
prey  in  mid-air  before  it  reached  the  ground.  Again,  I 
liave  seen  one  in  a  stoop,  swift  almost  ;is  light,  knock 
a  redhead  duck  to  the  ground,  where  it  landed  with 
a  broken  wing  and  other  injuries. 

On  one  occasion  a  pair  of  duck  hawks  harried  a  help- 
less nighthawk,  stooping  at  it  playfully  until  one  in 
passing  gave  it  a  f[uick  squeeze  with  one  foot.  It 
then  ;Ul()wed  the  nighthawk  to  fall,  when  it  was  seized 
by  the  other  duck  h;uvk.  Tlicn  the  pair  flew  away, 
and  the  one  with  the  booty  at  intervals  dropped  it,  so 
that   it   could   be   seized   in   air  by   its   mate. 

Food  items  found  in  several  Utah  eyries  are 
summarized  in  Tables  5  and  6.  We  collected  107 
individual  prev  items  representing  20  species 
of  birds  and  at  least  one  species  of  mammal  from 
two  eyries  along  the  escarpment  of  the  Wasatch 
Mountains  between  1943  and  1957.  The  Ameri- 
can Avocet  was  represented  in  the  greatest  num- 
bers ( Fig.  24 ) .  It,  the  Mourning  Dove  ( Zenai- 


I"ig.  24.  Avoccl  at  nest.  This  species  was  the  most  important  food  species  found  in  the  eyries  of  the  pere- 
grine in  the  valley  of  tin;  Great  Salt  Lake  and  also  the  most  fre(iuent  shorebird  species  in  the  eyries  of  the 
Prairie  Falcon  in  the  same  localit)-.  I'hoto  by  R.  J.  Erwin,  8  Jiuie  19.59. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utaii 


29 


Table  5.     Prey  species  in  Peregrine  Falcon  and  Prairie  Falcon   eyries   in  areas   of  sympatry  along  the  escarpment 
of  Utah's  Wasatch  Mountains',  facim'  the  marshes  v(  the  Great  Salt  Lake. 


Prey  species 


Weight  class 
in  grams" 


Duck  sp.  (yng. )' 
Killdeer 

( Charadrius  lociferous ) 
Willet 

( Catotrophorus  semipalmatus ) 
Greater  Yellow-legs 

( Totanus  melanoleucus) 
Long-liillcd  Dowitcher 

( Limnodromus  scolopaceus) 
Sanderling 

(Crocethia  alba) 
American  Avocet 

( Rccurvirostra  americana ) 
Black-necked  Stilt 

( Himantopus  rncxicnnus ) 
Wilson's  Phalarope 

( Stcganopus  tricolor ) 
Franklin's  Gull 

( Lurus  pipixcan  ) 

Shorebird  and  Gull 

Subtotal 
California  Quail 

( Lophortijx  californiciis) 
Ring-necked  Pheasant 

{Phasianus  colchicus) 

Gallinaceous 

Bird  Subtotal 
Mourning  Dove 

(Zetuiidura  macroura) 
Rock  Dove 

{Coluniba  livia) 

Dove 

Subtotal 
Red-shafted  Flicker 

(Colaptcs  cafer) 
Western  Kingbird 

(Tijranrws  vcrticalis) 
Homed  Lark 

(Eremophila  alpestris) 
Scrub  Jay 

(Aphelocoma  coeridescens) 
Robin 

(Tiirdui-  migratoriiis) 
Bohemian  WiLwving 

(Bombi/cilla  garrula) 
House  sparrow 

(Passer  domcsticus) 
Western  Meadowhvrk 

(Sturnclla  ncglecta) 
Redwinged  Blackbird 

(Agelaius  phocniceus) 
Brewer's  Blackbird 

( Euphagus  cijanoccphalus ) 
Unidentified  blackbird 
Green-tailed  Towhee 

(Chlorura  chlorura) 
Rufous-side  Towhee 

( Pipilo  en/throphthalmus) 

Passerine 

Subtotal 
Big  brown  bat 

(Eptcsicus  fuscus) 
Unidentified  bat 


150 

106 

203 

165 

86 

63 

281 

152 

58 

295 

198 
807 

115 
318 

137 

42 

29 

77 

82 

56 

26 

89 

54 

68 

61 
30 

.37 


n 

Peregrine 
Percent  of 
total 

Falcon 
Percent  of 
biomass 

3 
2 

2.80 
1.87 

2.75 
1.29 

10 

9.35 

12.38 

3 

2.80 

3.02 

2 

1.87 

1.05 

Prairie  Falcon 
n       Percent  of    Percent  of 

total  biomass 


22 

20.56 

1 

0.93 

6 

5.61 

1 

0.93 

50 

43.92 

13 

12.15 

5 

4.67 

18 

16.82 

8 

7.48 

0.93 
1.87 
1.87 


9 

8.41 

4 

3.74 

3 

2.80 

5 
2 

4.67 
1.87 

37.10 
0.93 
2.12 
1.80 

59.69 


9.12 

9.70 

18.82 

6.69 


0.47 
0.99 
0.68 

4.89 

1.32 

1.24 

1.86 
0.37 


28 

26.16 

11.82 

18 

1 

0.93 

0.11 

10 

2 

1.87 

0.12 

9 
18 

1 
1 

2 
40 


2.63 
11.84 

6.58 


1.32 
7.89 


21 

27.63 

1 

1.32 

2 

2.63 

3 

3.95 

2 

2.63 

1 

1.32 

3 

3.95 

1 

1.32 

1 

1.32 

1 

1.32 

9.21 

11.84 
23.67 

1.32 
1.32 

2.63 
52.63 


2.60 
8.26 

8.79 


0.55 
14.60 


32.20 
1.71 
13.97 
15.68 
1.99 
2.75 
4.74 
1.19 
0.36 
0.25 

4.97 

2.03 

13.87 

0,59 
0.53 

0.64 
23.24 


30 


Bricham  Young  Univebsity  Science  Bulletin 


Table  5  (Continued) 


Uintah  groiintl  squirrel 
{Cilelius  trrmatus) 

250 

_ 

_ 

_ 

2 

2.63 

4.33 

Rock  siniirrel 

696 

_ 

_ 

_ 

2 

2.63 

12.04 

(Citellus  variegatus) 

Unidentified  ground 

400 

_ 

_ 

_ 

1 

1.32 

3.46 

squirrel  (Citellus  sp) 

Meadow  mouse 

60 

_ 

_ 

_ 

1 

1.32 

0.52 

( Microtus  sp ) 

Mammal 

3 

2.80 

0.23 

6 

7.90 

20.35 

Subtotal 

Totals 

107 

99.98 

20  species 

100.00 

76 

100.01 
21  species 

100.00 

'Mo.':t  prey  itcni^  for  both  species  origmated  Irom  the  Peregrine  Falcon  and  Prairie  Falcon  eyries  at  site  7  (Table  1,  Fig.  1);  hence,  ior 
the    most    part,    they    represent    prey    species    from    n    common    resource. 

'Weights  of  all  avian  species,  with  exception  of  tlie  common  pigeon,  were  obtained  from  Porter,  Bushman,  and  Behle  (impubl.  ms); 
the  value  for  the  common  pigeon  w.is  obtained  from  Roxie  I.ayboume.  of  the  U.  S.  Bureau  of  Sport  Fishencs  and  Wildlife;  weights  of 
mammalian  species  were  estimated  from  those  given  by  Hall  I194C).  Those  of  xmidentified  bats,  ground  squirrels,  and  young  ducks  were  esti- 
mated  by  the  authors. 

^Weight  of  the  young  ducks  is  estimated;  voimg  pintails  iAnas  titutti)  not  vet  feathered  were  in  the  peregrine  e\Tie  on  13  and  14 
June    19+7. 


dura  macruura),  Willct  (Fig.  25),  Western  Mead- 
owlark  ( Sturnella  neglecta ) ,  Red-shafted  Flicker 
{Colaptes  cafcr),  Wilson's  Phalarope  {Stegano- 
piis  tricolor).  Rock  Dove  {Columha  livia),  and 
two  species  of  blackbirds  (Agelaius  phoenicetts 
and  Euphagus  cijanocephalus)  made  up  nearly 
79  percent  of  the  food  items  at  the  eyries.  How- 
ever, in  both  total  biomass  (59.7  percent)  and 
in  numbers  (4.3.9  percent),  the  shorebirds  com- 
prised the  largest  segment  of  the  diet,  of  which 
the  avocet  (37.5  percent  biomass)  (also  see 
White,  1963)  and  Willct  (12.4  percent  biomass) 
were  by  far  the  most  frequent.  Tliis  is  probably 
a  reflection  of  the  availabilit)'  of  shorebirds  in 
the  Great  Salt  Lake  marshes. 

Aside  from  being  common,  both  avocet  and 
Willet  ma\'  have  some  conspicuous  behavior  that 
makes  them  easv  to  capture  and  that  accounts 
for  the  numbers  taken  b\'  the  falcons.  Tinbcrgen 
( 1940 )  has  shown  that  various  behavioral  pecu- 
liarities of  certain  passerine  birds  enhance  their 
vulnerability  to  predation,  and  F.  and  J.  Craig- 
head (1956),  based  on  the  study  of  the  food 
remains  at  20  peregrine  eyries,  have  suggested 
that  the  flash  patterns  of  meadowlarks,  redwings, 
and  the  Blue  |a\  {Cijanocitta  cristata)  and  the 
eonspieuous  Hight  of  flickers  ma\'  increase  the 
vuliKTability  of  these  species  to  predation  by  the 
peregrine.  This  hypothesis  may  be  applicable  to 
the  Willet  and  avocet,  both  of  which  have  con- 
spicuous flash  patteiTis. 

Mourning  l^oves  and  Rock  Doves  were  im- 
portant columbiforme  items  (  hS.S  percent  of  bio- 
mass and  16.8  percent  of  total  items).  Passer- 
ines, woodpeckers,  and  bats  were  represented 
in   smaller  numbers  and  biomass    (Table  5). 

The  use  of  bats  for  food  by  peregrines  has 
been  reported  from  Texas  by  Stager  ( 1941 ),  and 
desert  nesting  Shaheen  Falcons  ( Falco  pelegri- 
nokles  hahtjloniciis)  of  the  Middle  East,  which 
are  either  peregrines  or  are  very  closeh'  related 


to  them  (Vaurie,  1961;  White,  1968b;  Brown 
and  Amadon,  1968),  reportedly  hunt  bats  at 
dusk  (Dementiev,  1951  and  1957).  In  Indonesia, 
Mees  (1949)  reports  that  wintering  tundra  fal- 
cons seem  to  be  specialized  for  feeding  on  bats. 
He  saw  one  falcon  kill  seven  bats  one  after  an- 
other. Fischer  ( 1968 )  reports  that  the  subspecies 
of  peregrine  (F.  ;}.  ernesti)  indigenous  to  Indo- 
nesia also  hunts  bats. 


Fig.  25.  Willet  {Catoptrophortis  scvtipahiatus)  on  nest. 
The  Willet  was  an  important  prey  species  in  pere- 
grine cvries  of  the  CJreat  Salt  Lake  Valley.  This 
species  is  inconspicuous  while  on  nest  but  in  fUght 
it,  like  the  stilt  and  avocet,  shows  a  striking  flash 
pattern.    Photo   by   R.   J.   Erwin    19.59. 


Biological  Series,  Vol.  18,  No.  1       Pehecrine  Falcon  in  Utah 


31 


Table  6.     Prey  species  in  two  Peregrine  Falcon  eyries  in  Utah's  desert  (sites  4  and  28,  Table  1,  Figs.  1,  9,  and 
22).*     C  =  Colorado  Plateau,  GB  =  Great  Basin. 


Weight 

class 
in  grains 


No. 


Percent 

of 

total 


Percent 

ot 
biomass 


Chukar  {Alectoris  graeca)   (C)'" 

American  Coot  (Fulica  americana)   (GB)°" 

Mourning   Dove    {Zeimidura   macroura)    (C,    GB) 

Common  Nightliawk  (Chordeiles  minor  )   (GB)°° 

Ash-throated   Flycatcher   {Myiarchus  cincra'icens)    (C)"" 

Sav  s  Phoebe   (  Sayrnis  saya )    ( C )  °  ° 

Horned  Lark  { Eremophila  alpcslris)   (C,  GB)"" 

Pinon  Jay  {Gijmnorhinus  cyanocephala)   (C)°° 

Western  Meadowlark  (Sturnella  ncglccta)  (GB) 

Yellow-headed  Blackbird  ( Xanthocephahis 

xanthocephalus)   (C)" 
Redwinged  Blackbird  {Agelaiits  phocniceus)  (C,  GB) 
Lark  Sparrow  (Chondestes  grammacus)    (GB)"" 
Unidentified  Passerines  (C) 

Passerine  Subtotal 

Desert  Totals 


520 

1 

5.26 

26.52 

365 

1 

5.26 

18.60 

115 

2 

10.53 

11.73 

62 

1 

5.26 

3.16 

29 

2 

10.53 

2.96 

21 

1 

5.26 

1.07 

29 

3 

15.79 

4.44 

116 

1 

5.26 

5.92 

89 

1 

5.26 

4.54 

92 

3 

15.79 

14.07 

54 

2 

10.53 

5.51 

29 

1 

5.26 

1.48 

14 

73.68 

39.99 

19 

99.99 

100.00 

'Sro  fonttinte  for  Table  5 
•'Not    recorded    in    Wasatch    Moiinlain    eyries    (see    Table    5). 

Eyries  adjacent  to  the  Great  Salt  Lake  con- 
tained no  full-grown  waterfowl  despite  the  abun- 
dance of  waterfowl  in  the  adjacent  marshes,  al- 
though the  peregrine  has  been  observed  eating 
or  pursuing  full-grown  ducks  of  several  species 
during  the  breeding  season.  These  include  the 
Gad\\all  ( Anas  strepera )  ( observed  5  May  1938, 
field  notes  of  R.  G.  Bee),  a  teal  (H.  Austin, 
pers.  comm.),  a  teal  on  10  April  1948  at  Ogden 
Bay  (Porter),  and  the  Redhead  {Aijthya  ameri- 
cana) (Wetmore,  19.33).  Calvin  Wilson  (pers. 
comm.)  has  watched  peregrines  from  an  eyrie 
in  the  Wasatch  Mountains  eating  Ruddy  Duck 
(Oxytira  janmicensis) ,  Cinnamon  Teal  {Anas  cij- 
anoptera).  Pintail  (Anas  acuta),  and  American 
Coot  {Fulica  americana)  on  dikes  of  a  nearby 
marsh.  R.  J.  Erwin  (unpubl.  data)  flushed  a 
peregrine  from  the  side  of  a  highway  in  Grand 
County  in  April  1958,  where  it  had  just  cap- 
tured an   adult   Mallard    {Anas  platjtrhynchos). 

Cade,  White,  and  Haugh  ( 1968),  on  the  other 
hand,  found  that  waterfowl  constituted  nearly 
50  percent  (biomass)  of  the  food  items  in  the 
eyries  of  the  Alaskan  taiga  peregrine  (F.  p. 
anatum,  sensu  lata).  Utah  peregrines  are  smaller, 
however,  than  those  of  interior  Alaska.  The 
absence  of  ducks  in  the  Wasatch  Mountain  ey- 
ries mav  possibly  be  explained  on  the  basis  of 
the  weight  of  the  prev  item  in  relation  to  the 
distance  that  peregrines  must  earn,'  it  to  their 
evries.  A  full-grown  duck  may  be  too  heavy  for 
peregrines  to  carry  the  several  miles  from  the 
Great  Salt  Lake  marshes  to  eyries  along  the 
Wasatch  escarpment. 

Shorcbirds  were  not  present  in  two  desert 
eyries.  One  e\rie  was  located  near  a  marsh  in 


12  species 


the  Great  Basin  and  the  other  near  a  river  in 
the  desert  of  the  Colorado  Plateau.  The  avail- 
ability of  a  variety  of  marsh  and  shorcbirds  to 
the  peregrines  at  the  desert  eyries  in  the  Great 
Basin  (Table  6)  accounts  for  the  presence  of  the 
coot.  The  coot  in  the  Great  Basin  desert  eyrie 
probably  came  from  a  pond  (desert  spring) 
which  was  only  about  1,200  yards  ( 1,097  m ) 
from  the  eyrie  site.  Since  its  weight  (400  g)  is 
about  the  same  as  that  of  a  duck,  it  is  possible 
that  its  absence  from  the  Wasatch  Mountain 
eyries  may  have  been  for  the  same  reason  that 
ducks  were  missing  from  these  eyries.  The  small 
sample-size  of  food  items  probably  accounts 
for  the  absence  of  shorcbirds  in  this  desert  eyrie. 
At  a  Wasatch  Mountain  eyrie,  observed  by 
R.  D.  Porter  (site  7,  Table  1)  for  the  first  two 
weeks  after  hatching,  only  one,  and  at  most, 
two,  prey  items  were  found  each  day  in  the 
nest;  these  usually  consisted  of  Redwinged  Black- 
birds, Mourning  Doves,  Willets,  and  meadow- 
larks.  But  as  the  nesting  season  progressed, 
a  greater  number  of  species  and  items  were 
brought  to  the  nest.  On  28  June  1952,  for  ex- 
ample, about  three  weeks  after  hatching  of 
the  young  falcons,  the  female  returned  with  a 
young  Willet  at  11:00,  a  robin-sized  bird  at  11:50, 
and  an  unidentified  item  at  17:20.  The  male  re- 
turned with  a  young  avocet  at  15:20  and  a  leg 
of  a  young  avocet  at  15:45.  The  next  day  the 
male  brought  a  Wilson's  Phalarope  to  the  nest 
and  the  female  an  avocet.  Other  items  found 
in  the  nt^t  on  29  June  were  Scrub  Jay  ( Aphelo- 
coma  coerulescens) ,  unidentified  blackbird,  big 
brown  bat  {Eptesicus  fuscus)  and  one  adult  and 
one  immature  Wilson's  Phalarope.  Of  the  shore- 


32 


Brigham  Young  UNrvERsiTY  Science  Bulletin 


birds  brought  to  the  young  at  this  eyrie  (site  7, 
Table  1)  during  the  years  it  was  observed,  33 
percent  were  partially  fledged  young  of  the  sea- 
son. Peregrines  nesting  along  the  face  of  the 
Wasatch  Mountains  traveled  several  miles  to 
obtain  the  marsh  and  shorebirds  (Table  4); 
other  species  were  obtainable  much  closer  to  the 
eyries. 

Despite  the  peregrine's  reported  antipathy  to 
capturing  food  on  or  near  the  ground  (Bond, 
1936a),  mammalian  prey  species  such  as  the 
brush  rabbit  (Sijlvilagus  bachmani)  (Bond, 
1936c),  rats  [Rattus  sp.)  (White,  et  al,  1973), 
and  certain  gallinaceous  birds  (ptamiigan, 
Lagopus  sp.)  '(Cade,  I960;  White  and  Cade, 
1971 )  also  are  taken  for  food  occasionally.  Bond 
( 1946 )  reported  that  peregrines  commonly 
brought  Horned  Larks  to  their  small  young. 
The  Homed  Lark,  which  is  essentially  a  ground- 
dwelling  species,  is  one  of  the  most  abundant 
birds  in  Utah's  salt  desert  scrub  vegetation.  It 
was  present  in  peregrine  evries  in  both  the 
Colorado  Basin  and  Great  Basin  deserts  of  Utah 
(Table  6). 

Much  of  the  desert  lowlands  and  foothills 
of  Utah  are  vegetated  with  desert  scnib  and  with 
pigm\'  conifer  forests,  respcctivelv,  yet  the  pere- 
grine was  not  known  to  nest  far  from  water  in 
those  areas  where  the  Homed  Lark  of  necessity 
would  have  been  an  important  item  in  its  diet. 
Javs  (ApliclocoDia  and  Gymnorliinus),  king- 
birds {Tyranmis),  Ash-throated  Flvcatcher 
[Miiiarclius  cinerascens).  Lesser  Nighthawks, 
Red-shafted  Flickers,  Robins,  Mourning  Doves, 
and  Black-throated  Cra\'  Warbler  (Dcndroica 
nigrescens).  some  of  which  are  kTiown  to  be  used 
as  prev  bv  the  peregrine,  are  available  in  the  pig- 
mv  forests,  vet  the  peregrine  nests  in  these  areas 


only  when  water  or  marshes  are  nearby. 

A  more  intensive  study  of  the  peregrine's 
food  habits  in  Utah  during  nesting  season  un- 
doubtedh'  would  have  revealed  a  much  wider 
variety  of  prey  species,  especially  the  smaller 
passerines.  In  terms  of  biomass,  however,  the 
smaller  species  of  birds  probably  would  not  have 
altered  appreciably  the  percentages  of  each 
categor)'  of  birds. 

The  abundance  of  doves  in  Utah  eyries  is 
not  surprising,  despite  the  availability  of  marsh 
and  shorebirds,  since  the  domestic  pigeon  has 
been  found  to  be  a  favorite  prey  species  of  the 
peregrine,  not  only  in  the  eastern  United  States, 
but  also  in  many  other  areas  of  the  peregrine's 
cosmopolitan  distribution  (Hickey  and  Ander- 
son, 1969). 

The  Utah  peregrines  utilize  a  wide  variety 
of  prev  species  (at  least  29  species,  see  Tables 
5  and  6)  during  the  nesting  season,  and  in  this 
respect  their  diet  is  more  comparable  to  that  of 
populations  elsewhere  in  North  America  than  to 
tliat  of  populations  in  the  Queen  Charlotte  Is- 
lands, where  Beebe  (1960)  found  them  limited 
mosth'  to  one  and  not  more  than  four  prey  spe- 
cies during  the  nesring  season.  On  Amchitka  in 
the  Aleutian  Islands,  White,  Emison,  and  Wil- 
liamson ( 1973,  in  press )  list  32  species  in  the 
peregrine's  diet,  most  of  which  were  found  in 
the  nests,  and  comprised  principally  marine 
birds,  waterfowl,  gulls,  and  shorebirds.  Shore- 
birds  were  represented  frequenth'  in  the  eyries 
of  peregrines  along  the  Colville  River  of  Alaska 
(White  and  Cade,  1971).  Cade,  White,  and 
Haugh  ( 1968)  reported  49  prev  species  in  eyries 
located  in  the  taiga  zone  of  the  Arctic,  and  Cade 
(1960)  found  21  species  in  nests  located  in  the 
tundra  zone. 


NESTING  BEHAVIOR  IN  UTAH 


History  of  Nesting  at  a  Wasatch  Mountain  Eyrie 

Eyrie  sites  of  the  Peregrine  and  Prairie  Fal- 
con at  a  chff  on  the  escarpment  of  the  Wasatch 
Mountains  (Table  1,  site  7;  Fig.  26)  were  ob- 
served by  R.  D.  Porter,  R.  J.  Erwin,  and  others 
from  1943  through  1952,  exclusive  of  two  war 
years,  1944  and  1945.  We  obtained  data  at  this 
cliff  on  interspecific  competition  between  the 
two  species  and  on  productivity,  incubation  peri- 
ods, and  rcproduetive  failure  for  the  peregrine, 
all  of  wliieh  will  be  discussed  under  s(>parate 
headings. 

The  cliffs  were  composed  of  quartzite  and 
faced  westerly  along  the  west-facing  escarpment 
of  the  mountains  and  southerK-  along  a  south- 


facing  edge  of  a  side  canyon.  Peregrines  were 
first  noted  there  on  3  April  1943,  the  year  the 
cliff  was  first  under  our  observations,  by  R.  J. 
Erwin  and  J.  F.  Poorman,  and  again  that  year 
by  J.  F.  Poorman  and  R.  L.  Porter  on  15  April. 
A  nest  containing  three  eggs  was  found  on  26 
,\pril.  Prairie  Falcons  were  also  first  noted  at 
this  cliff  in  1943.  A  summary  of  the  reproductive 
history  of  the  peregrines  at  this  site  is  given  in 
Table  7.  The  phvsical  characteristics  of  the  var- 
ious peregrine  and  Prairie  Falcon  sites  utilized 
during  the  period  of  studv  are  given  in  Table  8. 
The  photographs  represented  by  Figures  27-39 
were  taken  in  1947,  1948,  and  1952. 

In    1949  the  peregrines   defended   a   nesting 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


33 


Fig.  26.  A  cliff  along  the  escarpment  of  the  Wasatch  Mountains  which  contained  eyries  of  both  the  Peregrine  Fal- 
con and  tlie  Prairie  Falcon  (Table  1.  site  7).  The  Peregrine  Falcons  used  site  A-3  in  194.3,  1952,  and  1953; 
site  B  in  1946  and  1947;  and  site  C  in  1948  and  1951.  The  Prairie  Falcons  used  site  2  in  1948;  site  A-3, 
1949;  and  site  1,  to  the  north  (not  shown  in  photograph)  of  site  A-3,  in  1943  and  1950.  Sites  B  and  C 
faced  south,  sites  1,  2,  and  A-3  faced  west.  Photo  by  R.  J.  Envin,  1972. 


ledge,  which  contained  two  nest  scrapes,  but 
apparently  laid  no  eggs.  They  defended  several 
sites  on  the  cliff  in  1950  but  with  less  tenacity 
than  usual.  Although  they  made  20  to  25  scrapes 
along  several  hundred  feet  of  ledge,  no  eggs 
were  found.  Between  4  March  and  early  June 
the  cliffs  were  searched  for  an  eyrie  10  times 
without  success.  The  behavior  of  the  birds  sug- 
gested the  presence  of  a  nest  at  numerous  places 
along  the  cliff.  However,  each  new  section  of 
chff  was  defended  with  nearly  equal  spirit. 

In  1952,  the  two  young  at  site  A  (Fig.  26 
and  Tables  7  and  8)  were  measured  and 
weighed  from  date  of  hatching  until  13  August. 
They  were  removed  from  the  nest  on  5  July. 
R.  J.  Erwin  banded  three  young  peregrines  at 
the  194.3  site  in  1953.  He  obtained  no  informa- 
tion on  egg  number  or  occurrence  of  Prairie 
Falcons. 

A  new  female  peregrine  nested  at  alternate 
site   A    in    1952.    She   still   had   some   immature 


,0^' 


•t 
V 


Fig.  27.  Five-egg  clutch  of  Peregrine  Falcon  (eyrie 
site  7-B,  Table  1,  1947).  Note  the  wood  rat  {Neo- 
toma  sp. )  scat  on  ledge  and  about  the  eggs.  Photo 
by  R.  D.  Porter. 


34 


Brigham  Young  University  Science  Bulletin 


Fig.   28.     Female  peregrine  entering  eyrie.   Photo  by   R.  D.  Porter  and  R.  J.  Erwin,  1948. 


Fig.    29.     Female    peregrine    settling    down    over    nestling.s  which  are  only  a  few  days  old   (Table  1,  site  7,  alt. 
.site  C).  Photo  by  R.  D.  Porter  and  R.  J.  Erwin.  1948. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


35 


Fig.   30.     Female   peregrine   brooding  young.   Note  addled  egg.  Photo  by  R.  D.  Porter  and  R.  J.  Erwin, 


1948. 


Fig.   31.     Female  peregrine  with  young,  in  defensive  attitude.  Photo  by  R.  D.  Porter  and  R.  J.  Erwin,   1948. 


36 


Bricham  Young  University  Science  Bulletin 


». 


Fig.  32.     Female  peregrine  feeding  young.  Photo  by  R.  D.  Porter  and  R.  J.  Erwin,  1948. 


\^1\    V 


u^ 


« 


t-'' 


Fig.  33.     Female  peregrine  feeding  young  which  were  nearly   3   week.s   old    (eyrie   site   7,   alt.   site   B,   Table    1). 
Photo  by  R.  D.  Porter,  1947. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  F.alcon  in  Utah 


37 


A     - 


Fig.   34.     Young   peregrines   at   approximately  4   weeks   of  age   (eyrie  site  7,  alt.   site  C).   Photo  by  R.   D.   Porter 
and  R.  J.  Erwin,  1948. 


Fig.   3.5.     Young  peregrines   about  6  weeks  of  age,  nearly  old  enough  to  fledge  (eyrie  site  7,  alt.  site  C).  Photo 
bv  R.  D.  Porter,  1947. 


38 


Bhicham  Young  University  Science  Bulletin 


Table  7.   Reproductive  history  of  the  peregrines  at  a  Wasatch 
Figs.  26-29). 


Mountain  eyrie   ( site  7,  see  Tables   1   and  8,   and 


Alternate 

EGGS 

NESTLINGS 

Probable 

Incubation 

Other 

site 

Dates 

date  of 

period 

Dates 

dates  of 

Year 

location 

recorded 

No. 

1st  egg 

(in  days) 

No. 

hatched 

record 

Misc.  Data 

1943 

A 

26  April 

3 

- 

^37  (3rd  egg) 

3' 

unknown 

31  May 

1946 

B 

- 

- 

- 

unknown 

4 

unknown 

26  June 

Young  nearly 
fledged,  two  taken 

1947 

B 

26  April 
17  May 

3 

5? 

21-22  April 

35-37  (3rd  egg) 

3 

unknown 

31   May 

Downy  young 

1948 

C 

16  April 
19  April 
27  May 

3 
4 

5 

11-12  April 

42-44  (3rd  egg) 
39-41   (4th  egg) 

4 

28-29  May 

29  May 

29  June 

5  July 

17  July 

5  eggs,  1  pipped 
27  May;  4  young  -|- 
1  addled  egg,  29  May 
4  young,  2  taken' 
young  fledged' 
young  full  grown' 

1951     C 

2  May 

3  May 
13  May 
19  May 

3 
3 
2 
0 

unknown 

0 

-^ 

1952     A 

29  April 

1   May 

27  May 

V 
V 
3 

29  April 

37  (cggl) 

0' 

2 

4  June 
5  June,  07:00     5  June 

2  eggs  pipping 
1  hatclied,  1° 
nearly  hatched 

31   May 

3 

- 

2 

7  June 

both  hatched 

1  June 

3 

- 

1953     A 

-       - 

- 

- 

unknown 

3 

- 

^Three  young  were  about  ready  for  flight  when  two  were  taken  for  falconry  s-iinetime  in  early  July.  -29  June:  4  young,  2  males, 
2  females;  females  taken  for  falconry;  oldest  male,  tail  half  grown,  flew  from  nest.  5  July:  I  young  male,  still  on  nest  ledge,  flew  at 
approach  of  observer,  first  male  to  leave  nest  on  rock  above  nest.  \7  July:  females  taken  from  nest  about  full  grown.  ^Marked  with  a 
numeral  1  in  India  ink.  ^Two  eggs  pipping,  one  with  small  bole  (egg  1),  other  barely  dented,  young  peeping  inside  both  eggs,  loudest 
in  egg  marked  with  numeral  1 ;  marked  egg  weighed  47  g,  other  pipped  egg,  50  g,  and  impipped  egg,  48  g.  ^Shell  around  abdomen  and 
legs;    it    probably    hatched    on   6   June;    third   egg   addled. 


feathers  (see  Figs.  36-38),  and  was  undergoing 
a  molt  as  evidenced  bv  the  fact  that  on  28  June 
the  upper  surface  of  the  wings  had  just  begun 
to  molt  into  the  adult  plumage.  The  molt  on  the 
back  (capital  and  spinal  feather  tracts)  and  the 
lower  breast  (ventral  tracts)  was  nearly  com- 
plete, while  that  of  the  primaries  and  rectrices 
had  only  begun.  The  capital  tracts  of  the  head 
were  only  partially  molted.  While  the  female 
was  in  flight,  it  was  noted  that  at  least  one  pri- 
mary was  missing  on  each  wing  as  well  as  at 
least  one  retrix  on  each  side  of  the  tail. 

The  plumage  condition  of  this  bird  indicates 
that  she  probably  was  no  more  than  three  years 
of  age.  Records  of  breeding  peregrines  while 
still  in  their  immature  plumage  are  not  common. 
Beebe  (1960)  noted  no  instances  of  mated  pairs 
in  immature  plumage,  or  even  in  plumage  show- 
ing traces  of  immaturity,  in  a  rather  large 
sample  of  pairs  along  the  northwest  Pacific 
Coast.  However,  Herbert  and  Herbert  (1965) 
pointed  out  two  instances  of  immatiux'-plum- 
aged  females  occupying  an  eyrie,  neither  of 
which  was  found  to  lay  eggs.  Hickcy  (1942) 
reported  on  three  immature,  one-vi-ar-old  fe- 
males that  failed  to  lay  eggs  and  a  fourth  that 
brooded  a  clutch  of  t\vo  eggs,  making  a  total 
of  only  one  first-year  f(-male  out  of  .34  falcons 


over  a  two-year-period  in  New  York.  A  report 
by  Herbert  of  two  females  believed  by  him  to 
be  two-vear-old  birds,  both  of  which  laid  only 
two  eggs  in  different  )ears,  also  was  mentioned 
by  Hickcy  ( 1942).  White  and  J.  R.  Haugh  (pers. 
ol)ser. )  found  one  female,  out  of  17  pairs  breed- 
ing on  the  Yukon  River  in  1966,  that  was  essen- 
tially still  in  the  streaked  brown  immature  plum- 
age. Therefore,  it  was  thought  to  be  but  one 
year  old.  She  laid  Uvo  fertile  eggs,  one  of  which 
hatched. 

Egg  Laying 

At  the  alternate  site  A  eyrie  (Table  1,  site 
7)  egg  la\ing  began  between  12  and  29  April 
( 1943-1952)  as  estimated  by  counting  back  from 
known  dates  certain  eggs  were  laid  (Table  7). 
Published  records  for  the  state  range  from  about 
22  March  (counting  back  from  30  March  as 
given  by  Johnson,  1899)  to  the  second  or  third 
week  in  NIa\-  (counting  back  from  20  Ma\'  given 
by  Bee  and  Hutchings,  1942).  The  first' egg  of 
a  three-egg  clutch  found  by  White  and  Lloyd 
(Table  1,  site  28)  was  probably  laid  around  6 
Ma\',  as  indicated  by  the  date  of  hatching.  At 
the  aforementioned  e\rie  in  the  Wasatch  Moun- 
tains (Table  1,  site  7),  3.8  (\ggs  (range  .3-5)  on 
the  average  were  laid  per  year  during  the  five 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


39 


..v;-^ 


Fig.  36.     A  view  of  female  peregrine  with  unmolted  immature  plumage.   Her  two  young  are  about  3  weeks  old 
(eyrie  site  7,  alt.  site  A).  Photo  by  R.  D.  Porter,  1952. 


Fig.  37.  Same  female  as  in  Fig.  36.  This  bird  is  c(;rtainly  not  more  than  three  years  old  because  of  the  amount  of 
immature  plumage  retained.  Note  tiiat  most  of  the  tail,  secondary  wing  feathers,  and  greater  wing  coverts 
are  immature  feathers.  Photo  by  R.  D.  Porter,  1952. 


40 


Bhigham  Young  University  Science  Bulletin 


Table  8.  Physical  characteristics  of  eyrie  sites  at  a  cliff  in  the  Wasatch  Mountains  (Table  1,  site  7,  see  Figs. 
26-39)  used  by  botli  peregrines  (Pe)  and  Prairie  Falcons  (Pr).  Values  in  parentheses  represent  metric  equiva- 
lents. 


Approx.  dist. 

Dist.  Eyrie 

Dia. 

in  ft   (in) 

Species' 

Cliff 

Eyrie 

Ledge 

Ledge 

below 

Nest 

nest 

Depth 

from 

and 

height. 

height, 

length. 

width. 

overhang. 

area 

scrape. 

.soil, 

Alt. 

site  A 

year 

ft 

ft 

Direct 

inches 

inches 

inches 

ft= 

inches 

inches 

site 

to  site 

used 

(m) 

(m) 

facing 

(m) 

(m) 

(m) 

(m=) 

(m) 

(m) 

A-3= 

0 

Pe  1943 

110 

85 

W 

72 

62 

20 

7.42 

6.9 

2 

1952 

(34) 

(26) 

(1.8) 

(1.6) 

(0.,51) 

(0.69) 

(0.18) 

(0.051) 

1953 

Pr  1949 

B 

320 

Pe  1946 

135 

90 

S 

120 

60 

18 

6.45 

- 

- 

(98) 

1947 

(41) 

(27) 

(3.0) 

(1.5) 

(0.46) 

(0.60) 

C 

350 

Pe  1948 

135 

90 

S 

156 

48 

35 

6.55 

6.4 

(107) 

1951 

(41) 

(27) 

(4.0) 

(1.2) 

(0.89) 

(0.61) 

(0.16) 

- 

1' 

300 

Pr  1943 

110 

(91) 

1950 

(34) 

- 

w 

- 

- 

- 

- 

- 

2' 

55 

Pr  1948 

110 

95 

w 

61 

90 

21 

21.8 

- 

2 

(17) 

(34) 

(29) 

(1.5) 

(2.3) 

(0.53) 

(2.0) 

- 

(0.051) 

M^rairie    Falmiis    wrie    not    reinrded    in     1**47.    1952.    and    lOji,    were  seen,  bul  no  nest  was  found  in  1951. 

'All    values    were    obtained    by    direct    measurements    at    eyrie    sites;   all   other   values  given  in   the  table,  except  cliff  and  ej-rie  heights, 
distances    between    e>Tie   sites,    are   approximations    from    photographs,    using  a   peregrine's  egg  or  the  adult   peregrine  as  a   unit  of  measurement. 
^Exact  e>xie  site  was  not  reached. 


years  that  eggs  were  found  (see  Fig.  27),  and 
2.4  of  the  eggs  (range  0-4)  on  the  average 
hatched.  The  eyrie  produced  a  total  of  19  young 
during  the  seven  years  it  was  known  to  have 
been  active,  for  an  average  of  2.7  young  per 


year.  Although  the  number  of  fledged  young 
was  not  ascertained,  no  )Oung  were  known  to 
have  died  in  the  nest.  Eight  young,  however, 
were  removed  for  falconr>'  when  nearly  fledged. 
These  values  approach  those  for  the  peregrine 


Fig.  .38.     A  close-up  of  same  female  as  in  Fig.  36.  Photo  by  R.  D.  Porter,  1952. 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


41 


in  eastern  North  America,  where  Hickey  (1942) 
found  the  average  clutch  size  to  be  3.72  and 
the  average  number  of  downy  young  to  be  3.0. 
For  western  North  America,  Bond  (1946)  re- 
ported an  average  clutch  size  of  3.7  and  Cade 
( 1960 )  recorded  an  average  of  2.7  eggs  per 
clutch  in  northern  Alaska  and  3.1  eggs  per  clutch 
in  other  locations  in  the  Arctic. 

Incubation 

The  eggs  are  laid  usually  at  two-day  inter- 
vals, and  occasionallv  at  three  ( Cade,  1960;  Her- 
bert and  Herbert,  1965;  Dcmandt  in  Fischer, 
1967).  On  the  Hudson  River,  incubation  gener- 
ally began  on  the  fifth  day  with  the  laying  of 
the  third  egg  and  averaged  32-33  days  from  time 
of  commencement  until  the  hatching  of  the 
last  egg  (Herbert  and  Herbert,  op.  cit. ).  The 
incubation  period  is  detennined  best  by  check- 
ing the  time  between  the  last  egg  laid  and  the 
last  \oung  hatched  (Nice,  1954),  providing 
that  all  eggs  hatch.  Although  the  incubation 
period  in  the  peregrine  is  said  to  be  28-29 
days  (Witherby,  et  al,  1939;  Dementiev,  1951; 
Herbert  and  Herbert,  1965),  there  is  still  some 
unccrtainb."  regarding  its  exact  length,  as  sug- 
gested also  by  Nelson  ( 1972),  who  believes  it  to 
be  closer  to  32  to  34  days  in  F.  p.  pealei.  If  the 
incubation  period  for  the  fifth  egg  is  28  to  29 
davs,  and  not  more  than  two  days  elapse  be- 
tween the  laving  of  each  egg,  the  period  be- 
tween la\'ing  of  the  fourth  egg  and  the  hatching 
of  the  fifth  egg  would  be  30  to  31  days;  be- 
tween the  la\ing  of  the  third  egg  and  the  hatch- 
ing of  the  fiftii,  .32  to  33  days;  between  the 
second  and  the  fifth,  34  to  35  days;  and  between 
the  first  and  the  fifth  egg,  36  to  37  days.  In 
four-egg  clutches,  the  intervals  between  the  lay- 
ing and  hatching  of  the  third  and  fourth  egg 
would  be  30  to  31  days;  between  the  second  and 
the  fourth  egg,  32  to  33  days;  and  between  the 
first  and  fourth  egg,  34  to  35  days.  For  three-egg 
clutches,  the  intervals  between  the  laving  of  the 
second  and  third  eggs  would  be  30  to  31  days; 
and  between  first  and  third  eggs,  32  to  .33  days. 
If,  as  reported  b\'  Nelson  (ibid.),  the  incubation 
period  is  32  to  .34  days,  4  to  6  additional  days 
must  be  added  to  each  of  the  above  values. 

At  the  Wasatch  Mountain  eyrie  (Tables  1 
and  7,  site  7),  the  incubation  period  in  1947  and 


1952  was  close  to  that  given  by  Nelson  ( op.  cit. ) 
for  pealei.  In  1948,  however,  it  seemed  to  have 
lasted  abnormally  long.  The  period  from  laying 
to  hatching  was  about  40  days  (39  to  41)  for 
the  fourth  egg  and  at  least  42  days  (42  to  44) 
for  the  third  egg,  which  is  about  10  days  longer 
than  that  expected  using  the  28  to  29  day  period. 
This  could  be  explained  if  the  first  clutch  was 
destroyed  within  a  day  or  so  after  the  fifth  egg 
was  laid  and  if  the  first  egg  of  a  new  clutch 
was  laid  a  day  or  two  later.  This  would  increase 
the  observed  incubation  period  by  about  10 
davs.  This  phenomenon  has  been  reported  in 
captive  American  Kestrels  {Falco  sparverius) 
(Porter  and  Wiemeyer,  1972). 

In  19.52,  the  period  between  the  laying  and 
hatching  of  marked  egg  number  one  was  about 
37  days.  It  likely  was  laid  the  day  it  was  first 
found  or  the  day  before.  Unfortunately,  the 
period  of  36  to  37  days  corresponds  closely  to 
the  expected  incubation  period  for  the  first  egg 
of  a  five-egg  clutch,  if  the  incubation  period  is 
28  to  29  days,  as  well  as  that  expected  for  the 
first  egg  of  a  three-egg  clutch  if  the  incubation 
period  is  32  to  .34  days. 

Tlie  32-  to  34-day  period  seems  to  fit  our  data 
better  than  does  the  28-  to  29-day  period.  Addi- 
tional observations  are  needed  to  resolve  this 
problem. 

Two  da\'s  elapsed  between  the  pipping  of 
the  first  egg  to  hatch  and  the  fourth  egg  to 
hatch  (a  fifth  egg  did  not  hatch)  in  1948. 
Only  one  day  elapsed  between  pipping  and 
hatching  of  egg  number  one  in  1952  and  the 
same  was  probably  true  of  the  second  egg  as 
well.  This  appears  to  agree  with  Hall's  (1955) 
observation  in  1943  on  the  Sun  Life  peregrines, 
which  hatched  two  eggs  on  each  of  t\vo  succes- 
sive days.  Porter  and  Wiemeyer  (1972)  reported 
a  two-dav  interval  between  the  hatching  of  the 
first  and  the  last  egg  of  five-egg  clutches  of 
captive  kestrels.  The  kestrels  frequently  began 
incubation  wath  the  laying  of  the  fourth  egg. 
Unlike  the  peregrines  of  the  lower  latitudes, 
those  in  the  Arctic  reportedly  initiate  incubation 
with  tlie  la\ing  of  the  first  egg  (Cade,  1960; 
Dementiev,  ■  1951).  Cade  (1960)  reported  as 
much  as  a  week's  difference  between  the  ages 
of  the  youngest  and  oldest  nestlings  in  four-egg 
clutches  in  the  Arctic. 


PEREGRINE  DECLINE  IN  UTAH 


The  peregrine  in  Utah,  as  elsewhere  in  the 
United  States  and  in  Europe  (Hickev,  1969), 
declined  precipitously  in  the  past  two  decades. 


To  our  knowledge,  only  two  or  three  of  the  29 
eyries  known  to  occur  in  Utah  over  the  past 
several  decades  are  still  active.   Nelson   (1969) 


42 


Bhigham  Young  University  Science  Bulletin 


reported  that  before  1942,  50  percent  of  the 
"9  or  10"  (9,  Nelson,  pers.  comm.  1969,  see 
Table  1)  eyries  located  by  him  between  1939 
and  1942  around  the  Great  Salt  Lake  were  taken 
over  bv  Prairie  Falcons,  and  by  1948  onlv  three 
or  four  of  them  were  left.  White  (1963),  how- 
ever, noted  that  five  of  these  eyries  (Table  1, 
sites  4,  7,  8,  10,  and  13)  were  still  active  as  late 
as  1952,  and  two  additional  eyries  (sites  17  and 
18)  are  known  to  have  been  active  in  1952  (C. 
Ward,  pers.  comm.),  indicating  that  some  of 
them  were  overlooked  b\'  Nelson  (1969)  or  else 
previously  unoccupied  eyries  were  reactivated 
later.  However,  White's  (1969b)  report  of  the 
occupancN'  by  peregrines  in  19.54  of  an  eyrie 
which  earlier  in  the  ccnturv'  ( 1927)  was  used  by 
Prairie  Falcons  (Wolfe,  1929)  suggests  that  the 
reverse  situation  also  may  have  taken  place. 

The  usurpation  of  peregrine  eyries  by  Prairie 
Falcons  nia\'  not  have  been  permanent,  as  sug- 
gested bv  our  observations  of  the  two  species 
utilizing  one  another's  eyries  in  Utah.  Nelson 
(1969)  indicates  that  he  was  unaware  of  the 
utilization  of  alternate  nesting  sites  by  the  pere- 
grine between  1939  and  1942,  which  increases 
the  possibility  that  some  of  the  peregrine  loca- 
tions believed  to  have  been  taken  over  by  Prairie 
Falcons  at  that  time  were  still  being  utilized  by 
peregrines  nesting  at  alternate  eyries. 

By  19.56,  onlv  four  of  the  20  known  eyries 
along  the  Wasatch  Front  were  active.  No  young 
have  been  known  to  fledge  from  an\'  of  these 
eyries  since  then  (White,  1963),  although  one 
adult  was  seen  at  each  of  two  eyries  in  1969 
(Table  1,  sites  8  and  18),  and  a  third  is  report- 
edly still  active.  Onh'  two  or  three  eyries  were 
believed  to  have  been  active  by  1969  in  the 
entire  state,  which  represents  only  about  10 
percent  of  the  total  known  to  occur  earlier.  On 
the  other  hand,  there  are  vast  areas  in  Utah 
with  seemingl)'  appropriate  ecological  condi- 
tions that  have  remained  virtuallv  unexplored 
for  falcons.  It  is  possible  that  10  or  more  eyries 
exist  in  these  areas.  It  is  interesting  to  note  that 
the  eyries  in  the  more  remote  parts  of  Utah 
remained  active  nearly  a  decade  longer  than  did 
those  in  the  more  populous  and  more  intensive- 
ly c>iltivat(>d  areas. 

Climatic  Change  Hypothesis  for 
Peregrine  Decline 

Nelson  (1969)  has  hypothesized  that  the  re- 
duction in  numbers  of  active  eyries  in  Utah 
was  caused  by  a  combination  of  rising  average 
temperature  and  drasticalK'  reduced  precipita- 
tion, starting  about  1870.  He  suggested  that  these 
changes  resulted  in  the  dr\ing  up  of  small  lakes 


and  ponds  and  the  lowering  of  the  surface 
water  areas  of  larger  lakes,  causing  a  critical 
reduction  in  the  habitat  for  the  prey  species  of 
the  peregrine  in  Utah  and  in  other  areas  of  the 
northwestern  United  States.  According  to  Nelson 
(ibid.)  b\'  1961  the  drought  gave  way  to  more 
moderate  conditions  resulting  in  habitat  changes 
more  suitable  to  the  peregrine. 

Besides  the  drought  conditions  reported  by 
Nelson  (1969),  river  waters  were  diverted  for 
irrigation  and  the  vegetation  adjacent  to  the 
marshes  was  overgrazed  by  livestock  (Behle, 
1958).  By  1910,  thousands  of  once  productive 
acres  of  heavily  vegetated  marshlands  along 
the  shores  of  the  Great  Salt  Lake,  with  their 
smaller  lakes,  ponds,  and  channels  of  frt^h  water, 
became  mud  flats  with  stagnant  pools  of  alkaline 
water.  Ultimately  these  changes  caused  the 
death  of  thousands  of  ducks,  shorebirds,  and 
marshbirds  due  to  botulism  (Wehnore,  1915, 
1918;  Behle,  1958).  It  was  not  until  after  the 
completion  of  the  Bear  River  Migraton'  Water- 
fowl Refuge  between  1932  and  1935  and  tlie 
Ogden  Bav  and  Fannington  Bay  refuges  in  about 
1941  that  these  marshes  regained  much  of  their 
former  vitality  and  productivity. 

Some  changes  took  place  as  late  as  the  early 
19.50s  in  the  marshes  fm-ther  removed  from  the 
lake.  Weller,  Wingfield,  and  Low  (1958),  for 
example,  recorded  a  drastic  change  in  the  size 
of  the  Knudson  Marsh,  four  miles  west  of  Brig- 
ham  City,  Utah,  between  1950  and  1955.  They 
attributed  the  changes  to  a  deepening  of  the 
water  channel  entering  Bear  River  Refuge,  an 
increased  demand  for  irrigation  waters,  a  below 
average  rainfall  between  1952  and  1954,  and 
overgrazing  bv  cattle.  The  change  in  size  of  the 
Knudson  Marsh  resulted  in  a  decline  of  one- 
third  in  the  number  of  species  and  two-thirds 
in  the  number  of  birds  nesting  there. 

Bv  1960,  the  total  acreage  of  marshland  in 
Utah  was  reduced  bv  nearly  50  percent  ( Smith, 
1961)  of  the  1,174,400  acres  (475,279  ha)  known 
to  exist  originally  (Low,  1966).  Smith  (1961) 
reported  the  existence  in  1960  of  600,000 
acres  (242,820  ha)  of  wetland  habitat  in  Utah 
of  variable  value  to  wildlife.  Of  this  acreage, 
83,000  (33,590  ha)  were  owned  bv  the  U.S. 
Fish  and  Wildlife  Service  and  60,()00  (24,282 
ha)  were  owned  and  operated  by  the  State  Fish 
and  Game  Department.  The  remaining  acreage 
was  in  private  ownership,  either  as  managed 
clubs  or  as  unmanaged  natural  wetlands.  Un- 
fortunately, the  effects  of  these  environmental 
changes  on  the  peregrine  were  never  docu- 
mented adeHjuatelv. 

Morlan  Nelson  (Hickey,  1969:  96)  has  sug- 
gested   that    in    1965    there    was    only    enough 


Biological  Series,  Vol.  18.  No.  1        Peregrine  F.alcon  in  Utah 


43 


habitat  left  in  tlie  Bear  River  marshes  to  sup- 
port one  pair  ot  peregrines.  This  would  seem  to 
he  an  underestimation,  since  we  know  of  several 
evrie  sites  in  the  western  United  States  where 
peregrines  have  bred  successfully  adjacent  to 
marshes  much  smaller  and  much  less  productive 
than  are  the  Bear  River  marshes. 

In  discussing  the  decline  of  the  peregrine  in 
Utah.  Nelson  (1969)  indicated  that  the  pere- 
grines nesting  in  1939  at  the  Ul  site  (site  11, 
Table  1 )  adjacent  to  the  Bear  River  Migratorv 
Bird  Refuge  did  not  return  to  nest  by  1941  be- 
cause the  drought  dried  up  their  hunting  sites. 
So  that  we  might  critically  assess  Nelson's  im- 
plication, we  measured  the  extent  of  the  marshes 
and  open  waters  within  a  fi\e-mile  ( 18  km )  radi- 
us (if  tlu'  Ul  e\  rie,  using  U.  S.  Geological  Sur- 
\e\'  topographic  maps  (aerialh-  photographed, 
1953-19.56).  The  resulting  measurements  tend 
to  weaken  Nelson's  argument,  since  there  were 
still  16.6  sq  miles  (43  km-)  of  marsh  and  5.8 
sq  miles  ( 15  km- )  of  open  water  within  the 
five-mile  radius.  Moreover,  the  Bear  River  Ref- 
uge, with  its  extensive  marshes,  was  only  seven 
miles  away.  However,  this  is  based  on  the  as- 
sumption that  these  marshes  did  not  increase 
appreciabh'  in  size  between  1941  and  1956.  We 
cannot  comment  on  the  latter  premise  because 
we  have  no  infomiation  on  the  extent  of  these 
marshes  for  the  earlv  1940s. 

Since  we  consider  the  cliff  at  the  Ul  site 
to  be  marginal  in  terms  of  accessibility  to 
humans  and  predators,  we  believe  that  human 
disturbance  may  have  been  the  major  factor 
causing  the  abandonment  of  this  evrie,  although 
habitat  change  and  competition  with  the  Prairie 
Falcon  probablv  played  a  subordinate  role. 

Further  evidence  which  tends  to  weaken 
Nelson's  climatic  change  h\pothesis  was  ob- 
tained from  Noland  F.  Nelson,  manager  of  the 
Ogden  Bay  State  Waterfowl  Management  Area. 
Nelson  spent  man\  hours  at  the  Bear  River  and 
Ogden  Bav  marshes  prior  to  the  completion  of 
the  refuges.  He  noted  that  there  was  not  a 
dearth  of  shorebirds  and  marshbirds  at  these 
marshes  before  the  dikes  were  constructed  (N. 
F.  Nelson,  pers.  comm.,  1971)  and  that  the  de- 
velopment of  the  Ogden  Bav  area  increased  the 
numbers  of  nesting  and  migrant  shorebirds 
(Nelson,  1954).  Nevertheless,  he  does  believe 
that  the  shorebird  populations  at  Ogden  Bay 
have  declined  in  the  past  several  years  (N.  F. 
Nelson,  pers.  comm.,  1971). 

Furthermore,  it  is  of  interest  to  note  that 
Noland  Nelson  observed  fewer  peregrines  at 
Ogden  Bay  in  the  1950s  than  in  the  i940s.  He 
saw  them  there  occasionallv  in  the  1940s  (Nel- 
son, 1954),  but  rarely  after  the  early  1950s  (N. 


F.  Nelson,  pers.  com.,  1971).  The  occasional  ob- 
servation of  peregrines  at  Ogden  Bay  during 
the  1940s  is  about  all  one  would  expect,  con- 
sidering that  these  marshes  were  supporting  at 
most  only  three  pairs  of  active  eyries  during 
these  years.  These  observations  correspond  with 
the  reduction  of  breeding  pairs  along  the  Wa- 
satch escarpment  between  1940  and  the  1950s. 
The  Great  Salt  Lake  has  been  subject  to 
major  cyclic  fluctuations  in  size  twice  historical- 
ly, and  perhaps  many  times  in  the  past  several 
thousand  vears.  Early  historical  evidence  indi- 
cates that  in  1850,  when  the  Great  Salt  Lake 
was  first  sur\'eyed  bv  Captain  Howard  Stans- 
bury,  it  was  much  reduced  in  size  compared  to 
earlier  and  later  reports.  James  Clvman,  who 
with  a  parts'  of  trappers  first  circumnavigated 
the  Great  Salt  Lake  in  a  bullboat  in  1826,  wrote 
the  following  in  his  journal  on  1  June  as  he 
passed  through  the  Great  Salt  Lake  Valley  in 
1846  on  a  trip  east  from  California. 

proceeded  ne.irlv  ea,st  to  the  point  of  a  liigh  mountain 
[Oquirrh  Mountains]  that  Bound.s  the  Southern  part  of 
the  greate  salt  lake  I  observed  that  this  lake  like  all 
the  rest  of  this  wide  spread  Sterility  ha.s  nearly  wasted 
away  one  half  of  its  surface  since  1825  [1826]  when 
I  floated  around  it  in  mv  Bull  Boate  and  we  crossed  a 
large  Bay  of  this  lake  with  our  horses  which  is  now 
dry  .  .  .  (Koms.  19.51:36). 

Four  \ears  later  when  the  lake  was  sur- 
veyed bv  Stansbur\'  (1852),  it  covered  1,750  sq 
miles  (4,433  km-) '(Powell,  1879).  By  1S69,  the 
lake  had  increased  in  size  to  2,166  sq  miles 
(5,610  knr)  (ibid.),  and  bv  1870  to  2,400  sq 
miles  (6.216  km-)  (Bue,  1963  in  Nelson,  1969). 
By  1961,  the  Great  Salt  Lake  had  receded  to  an 
unprecedented  low  (950  mi-;  2,461  km-)  fol- 
lowing several  decades  of  drought  (ibid.),  and 
b\'  1971  it  had  risen  about  seven  feet  (2.1  m) 
above  its  historic  low,  with  a  surface  area  of 
1,461  s(i  miles  (3,784  km')  (U.S.  Geol.  Survey, 
1971).  Powell  (1879)  considered  the  lake  to  be 
at  its  highest  level  in  1869,  which  exceeded  a 
level  to  which  it  had  long  been  subjected,  and 
that  its  old  mean  area  was  1,820  s((  miles  (4,714 
km-).  A  drawing  of  the  lake  in  18.50  by 
Stansbury  (Powell,  1879)  is  a  near  duplicate 
of  the  size  and  shape  of  th(>  lake  shown  on  U.S. 
Geological  Sur\'ey  topographic  maps  constructed 
from  photographs  taken  in  1953.  Anthropologi- 
cal studies  in  Utah  b\'  Antevs  (1948)  and  Har- 
per and  Alder  (in  press)  and  the  studies  of 
Blackwelder  (1948)  suggest  that  the  lake  prob- 
ably was  subjected  to  fluctuations  in  size  many 
times  prior  to  written  history;  this  will  be  taken 
up  in  more  detail  imder  a  separate  heading. 

Despite  these  periods  of  drought  and  their 
corresponding   changes   in   aquatic   habitat,   the 


44 


BmciiAM  YouNo  University  Science  Bulletin 


peregrine  persisted  until  the  late  1950s.  Although 
the  relationsiiip  between  the  changes  in  climate 
and  coneoiiiitant  ilnetuations  in  tlie  size  of  the 
lake  and  the  effects  of  these  changes  on  peregrine 
populations  of  the  area  may  never  be  fully  un- 
derstood, it  is  clear  that  never  before  had  these 
populations  been  so  adversely  influenced  by  the 
actixities  of  man  as  in  the  past  century. 

Data  from   Utah  Lake  also  do  not  seem  to 
fully  support  Nelson's    (1969)   hypothesis.   Data 
on  the  fluctuations  of  water  surface  and  com- 
promise le\els  have  been  plotted  for  the  period 
1883  to    1960    (from   several  sources,   including 
Bureau  of  Reclamation  and  Utah  State  Fish  and 
Game).  The  lake  oscillated  around  the  compro- 
mise level  (4,488.95  ft;   1,. 368.2.3  m)  between  a 
plus  and  minus  five  feet  (1.5  m)  through  1925. 
Between    192.5    and    19.30,    the    lake    remained 
around  the  minus  five-foot  (1.5  m)   level,  and 
starting  in  1930  the  lake  level  gradually  lowered 
to  its  lowest  level,  slighth   below  minus  10  feet 
(.3.0  m),  in    19.34  and   1935.  There  was  a  slow 
regain,  remaining  near  the  minus  five-foot  ( 1.5 
m)  level  through  the  mid-1940s,  until  it  reached 
above  the  compromise  le\el  in  19.52.   However, 
the   lake  has   remained  below   the   compromise 
level  since  then.  At  its  lowest  level   ( 1934-35) 
about  .37  percent  of  the  surface  area  was  lost 
(data  through  D.A.  White  from  the  Utah  Lake 
Research    Shition).    PresumabK    many    marshes 
around  the   i-dgc-  of   the  lake   dried   up   during 
this  low  period^  thereby  reducing  shorebird  and 
water  bird  habitat.   However,  this  may  not  be 
a  totally  satisfacton'  index  to  the  availability  of 
marshes.  Man\-  areas  fomierly  covered  by  water 
l)ut  appareiitl>-  dr\   during  the  low  water  years, 
such   as   Provo   Bay,   were   fed   b\    springs   and 
doubtless  maintained  some  habitat  for  the  prime 
avian   pre\    species.    Some   of   these  areas   were 
situated  opposite  acti\-e  peregrine  eyries.  Thus, 
tlie  impact  of  tlie  drought  \ears  on  peregrines 
is  difficult  to  evaluate.  Even  so,  it  is  clear  that 
it   was   not   until   well   after  the   drought  years 
and   after   the    19.50s    that    some    of    the    eyries 
around   Utah   Lake  became   inacti\e    (Table    1, 
sites  17  and  18,  for  example). 

As  mentioned  earlier,  tlie  nunilxT  n)  pere- 
grines wintering  in  the  marshes  adjacent  to 
the  Great  Salt  Lak(>  declined  steadilv  from  1939 
(;><0.01,  linear  regression  analysis),  the  vear 
Nelson  (  U)69)  located  his  first  e\  ries  in  Utah, 
until  the  early  1960s  when  tlie  species  disap- 
peared as  a  resident  in  tlie  iiiaishes  (Fig.  1  \).  The 
decline  correlated  closely  in  tiiiu-  with  the  aban- 
dcmment  of  local  eyries.  The  desertion  of  some 
e\ries  during  the  early  194()s  and  perhaps  earlier 
in  the  centun'  is  explainable  on  the  ba.sis  of  Nel- 
son's   (ibid. )    cliniatie  change  hypothesis.   How- 


ever, the  magnitude  of  the  decline  which  fol- 
lowed later  in  the  decade  and  on  into  the  late 
195()s  is  not,  since  management  methods  by  then 
iiad  brought  about  stabilit\  to  the  marshes  and  a 
concomitant  increased  population  of  prey  spe- 
cies. If  climate  had  been  the  sole  cause  of  the 
decline  in  Utah,  one  should  have  expected  the 
reactivation  of  e\ries  b\-  the  early  1950s  fol- 
lowing the  development  of  the  migratory  water- 
fowl lefuges  in  Utah,  yet  this  did  not  happen. 

( Additionalh',  a  reported  increase  in  nesting 
peregrines  since  19.39  in  Arizona  at  the  expense 
of  tlie  Prairie  Falcon  is  still  unexplained  [Phil- 
lips, Marshall  and  Monson,  19641.) 

We  do  not  ciuestion  thi'  \alidity  of  Nelson's 
(op.  cit. )  climatic  change  hypothesis  for  Idaho 
and  elsewhere  in  the  Northwest,  where  peregrine 
food  producing  marshes  and  waters  disappeared. 
We  do  believe,  however,  that  the  more  penna- 
nent  nature  of  the  Great  Salt  Lake  marshc^s  great- 
l\-  lessened  the  impact  of  these  climatic  changes 
in  Utah,  resulting  in  the  abandonment  of  a  few 
marginal  e\ries  (Table  1,  sites  11  and  25)  that 
were  situated  near  smaller  and  less  pemianent 
marshes  or  that  were  located  on  small,  relative- 
l\  accessible  cliffs.  Howe\'er,  the  number  of 
e\ries,  if  anv,  that  disappeared  prior  to  Nel- 
son's (1969)  19.39-1948  observations  in  Utah  is 
not  known.  Furthermore,  a  10-year  reversal  of 
the  prolonged  drought  of  the  preceding  half 
centurv  \\'hich  purporti'dl\  caused  the  peregrine 
decline  has  not  \et  resulted  in  an  appreciable 
recolonization  of  old  e\  lie  sites  or  the  estab- 
lishment of  new  sites. 

Nelson  ( op.  cit. )  also  suggested  that  Utah's 
peregrines  ina\-  have  made  altitudinal  adjust- 
ments during  periods  of  drought  to  compensate 
for  the  changes  in  climate.  Our  data  show  no  in- 
ilication  whatever  of  shifts  in  the  species  nesting 
populations  from  lower  tn  higher  elevations 
(see  Table  2).  On!\  one  known  eyrie  (site  36, 
Table  1)  and  two  suspected  e\  ries  (sites  27  and 
29,  Table  1)  in  I'tah  weii'  above  6.000  feet 
(1,829  m)  in  elexatioii.  Two  oi  these  were 
known  earlier  in  the  eentun  (early  1900s  and 
middle  19.3()s).  whereas  the  third  is  of  more  re- 
cent iibseixation  in  an  area  that  was  not  investi- 
(fated  l)i(ili)L;ieall\    earlier  in  the  eentur\'. 

Pesticide  Ilvpothesis  for  Peregrine  Decline 

Pesticide  Si/;u/ro(»ic  in  Utah  Fere<irines 

Because  climatic  change  did  not  appear  to 
be  the  complete  answer  to  the  peregrine  decline 
in  Utah,  we  hav<-  investigated  th(>  possibility 
tli.it  pesticides  max  ha\-e  been  iinohed  during 
the    later   stages    oi    the   decline. 


Biological  Series,  Vol.  18,  No.  1        Pehegiune  Falcon  in  Utah 


45 


Abnomial  boha\ior  and  increased  reproduc- 
tive failure  were  recorded  at  several  Utah  e\rii's 
durins;  tlie  period  follo\vin<j;  World  War  II 
(Table  1). 

As  mentioned  earlier,  the  birds  at  site  7  in 
the  Wasatch  Mountains  either  failed  to  lay  in 
1949  and  1950  or  if  they  laid,  their  eggs  were 
destroyed  and  the  adults  showed  little  inclina- 
tion to  defend  their  nests  during  these  years.  In 
1951  the  eyrie  contained  three  eggs,  but  they 
disappeared  one  b\"  one  over  a  17-da\'  period, 
and  in  1952  the  nesting  female  at  the  e\'rie  was 
a  ni'w  one  ( see  Table  7 ) . 

A  pair  of  peregrines  at  an  eyrie  which  was 
located  several  miles  away  (Table  1,  site  13), 
reacted  similarK'  when  they  were  first  observed 
on  20  Ma\  1951.  An  adult  male  and  immature 
female  dived  at  us  onh-  halflieartedly  once  or 
twice,  otherwise  they  circled,  screamed,  or  just 
perched.  A  third  falcon  which  flew  by  at  this 
time  elicited  no  response  from  either  bird.  A 
pair  was  seen  there  again  on  1  June  1952  by 
R.  J.  Erwin.  Although  they  apparently  had  no 
eggs.  the\'  responded  more  nomially  to  human 
intrusion  than  the\-  had  the  previous  year. 

The  occurrence  of  immature  females  at  these 
two  evries  suggests  the  possibilit)'  of  a  break- 
down in  the  nonnal  ratios  of  adult  to  immature 
peregrines  during  the  early  19.50s.  The  two 
aforementioned  eyries  were  visited  again  by  us 
in   1961,  but  no  falcons  were  seen. 

One  of  the  four  eggs  in  a  Great  Basin 
desert  evrie  (Table  1,  site  4)  was  partially  caved 
in  on  one  side  and  contained  a  small  hole  about 
one-fourth  inch  ( 0.64  cm )  in  diameter  when  the 
nest  was  first  located  on  13  May  1954.  The  male 
was  not  seen  at  this  time,  but  the  female  dis- 
played little  if  an\'  of  the  expected  aggressive- 
ness toward  our  intrusion  (Porter,  et  al.,  unpubl. 
ms).  When  the  evrie  was  next  visited  on  24 
June,  only  one  voungster  was  present,  and  both 
adults  screamed  incessantlv  at  the  observer.  The 
e\rie  was  still  active  in  1954  (White).  It  was 
last  observed  to  be  active  in  1957  or  1958  by  a 
local  falconer,  who  trapped  the  adults  after  a 
complete  clutch  of  eggs  was  said  to  have  dis- 
appeared. 

White  and  Lloyd  (1962)  found  two  freshly 
killed  peregrines,  about  28  days  old,  at  an  eyrie 
in  the  dissert  of  the  Colorado  Plateau  (Table 
1,  site  28,  Figs.  9  and  10).  The  two  young  were 
located  near  their  nest,  70  feet  (21  m)  from  the 
top  of  a  4(X)-foot  (122  m)  vertical  cliff  com- 
posed of  smooth  Navajo  sandst(jne  on  7  July 
1961.  The  back,  portions  of  the  thoracic  organs, 
and  parts  of  the  neck  and  wings  of  each  had 
been  eaten.  Thev  attributed  the  death  of  the 
two  \oung  to  predation  bv  a  Ringtail  (Bassaris- 


cus  astiitus),  because  of  the  presence  of  fresh 
Ringtail  scats  along  the  ledge  and  because  of  the 
nature  of  the  wounds  on  the  young. 

When  next  \'isited  on  6  Jul)-  1962,  the  adults 
screamed,  using  the  "wailing"  call  described 
by  Hagar  (in  B^ent,  1938).  The  female  then  left 
the  area,  while  the  male  flew  back  and  forth 
but  remained  silent.  The  following  year  both 
adults  were  present,  but  they  remained  perched 
and  made  no  noise.  Only  one  adult  was  seen 
in   May   1964  and  none  in  May  of  1965. 

Later,  White  re-examined  the  Noung  pere- 
grines, which  had  been  preserved  (Univ.  Utah 
collection)  and  could  find  no  chewed  off  feath- 
ers so  characteristic  of  fox-killed  peregrines  and 
other  mammalian  predation  observed  subse- 
quent!) by  him  in  the  Arctic.  Furthermore,  the 
feathers  appear  to  have  been  plucked  from  the 
young  as  though  bv  a  bird,  suggesting  that  their 
death  may  have  been  the  ri'sult  of  predation  by 
the  parent  birds  or  an  avian  predator  rather  than 
a  mammalian  predator.  As  suggested  by  Morlan 
Nelson  (pers.  comm.,  1971),  the  deaths  of  these 
two  \'oung  could  have  been  caused  by  Great 
Homed  Owls  (  BuJ)o  vir^inianus),  or  some  raptor 
other  than  the  adult  peregrines.  (See  Fischer 
1967,  for  a  more  complete  assessment  of  owl 
and  other  avian  predation  on  peregrines. ) 

The  phenomenon  of  egg  breakage  and  egg 
disappearance  ma\  not  be  restricted  to  the  pere- 
grine. A  Prairie  Falcon  e\rie  north  of  the  Bear 
River  marshes  obser\'ed  b\-  R.  D.  Porter,  R.  L. 
Porter,  and  Jack  Hagan  on  6  May  1951  con- 
tained a  single  egg  which  was  slightl)'  cracked 
on  the  small  end.  Tlie  female  was  not  seen  on 
the  nest,  nor  did  she  react  defensively  towards 
her  nest.  Tlic  egg  was  absent  on  our  next  visit 
to  the  nest  on  13  Ma^•.  Moreover,  many  of  the 
Prairie  Falcon  CN'ries  that  were  present  around 
the  Great  Salt  Lake  were  abandoned  during 
the  past  two  decades,  while  those  farther  re- 
moved from  the  marshes,  occupied  by  pairs 
living  mostly  on  rodent  diets,  have  persisted. 

The  pattern  of  reproductive  failure  described 
here  is  similar  to,  and  synchronous  with,  that 
associated  with  the  drastic  declines  which  af- 
flicted the  peregrine  elsewhere  in  the  United 
States,  in  Great  Britain,  and  in  northern  Europe 
(Hickev,  1969)  beginning  early  in  the  1950s. 

The  pattern  of  reproductive  failure  in  Great 
Britain,  where  the  documentation  is  the  most  com- 
plet(\  was  characterized  b\-  a  marked  increase  in 
the  number  of  eggs  that  were  broken  in  the 
nests,  in  the  number  of  eggs  that  disappeared, 
and  in  the  number  of  eggs  eaten  by  the  parent 
birds.  This  pattern  was  followed  by  the  disap- 
pearance of  one  or  both  of  the  adult  birds  and 
finallv    b\-    the    complete    abandonment    of    the 


46 


BKTciHAM  VouNO  Univkhsity  Sciknck  Bulletin 


eyries  (Ratcliffe,  1958,  1963,  1965,  19671),  1969). 
It  was  determined  later  that  the  eggshells  of  the 
peregrine  in  both  Great  Britain  ( Ratcliffe,  1967a, 
1970),  and  in  tlie  United  States  (Hickey  and 
Anderson,  1968)  liad  experienced  a  marked  de- 
crease in  thickness  starting  about  1947.  Ratcliffe 
(1967a,  1970),  who  was  the  first  to  recognize 
and  document  this  phenomenon,  attributed  egg- 
sliell  thinning  to  the  chlorinated  h\drocarbons. 

These  r<>productive  abnormalities  Iiave  been 
duplicated  experimentalK'  in  the  American  Kes- 
trel (Porter  and  Wi<'me\ cr,  1969),  the  Mallard 
(Heath,  Spann,  and  Kreitzer,  1969),  and  Black 
Duck  (Ana.s-  ruhripes)  (Longcore,  Samson,  and 
Whittendale.  1971)  b\'  giving  them  low  dietaiy 
levels  of  organochlorine  pesticides.  The  mode 
of  action  of  these  chemicals  on  avian  reproduc- 
tion has  been  investigated  (Peakall,  1969,  1970, 
1971;  Bitman,  Cecil,  and  Fries,  1970),  and  the 
effects  of  DDT  on  the  structiue  and  chemistry 
of  the  eggshell  are  now  being  studied  ( McFar- 
land,  Garrett,  and  Nowell,  1971;  Longcore  et  al., 
1971). 

Experimental  studies  which  indicate  that 
DDT  dekns  oxidation  in  the  Bengalese  Finch 
(Loncluira  striata)  (Jefferies,  1967)  and  also 
in  American  Kestiels  ( Porter  and  Wiemeyer,  un- 
publ.  data),  suggest  that  this  phenomenon  may 
have  occurred  in  wild  peregrines  as  well.  The 
la\'ing  date  of  th(>  first  egg  in  1952  at  eyrie 
number  7  (Tables  1  and  7)  (29  April)  was  two 
and  one-half  weeks  later  than  in  1948  (approxi- 
mately 11-12  April),  and  a  week  later  than  in 
1947  (about  21-22  April).  However,  this  may  be 
a  reflection  of  the  change  in  females  that  was 
known  to  lunc  taken  place  at  the  e\rie  in  1952, 
or  of  an  adjiistment  to  ;i  change  in  weather, 
rather  than  to  a  pesticide-induced  delav  in  ovu- 
lation. 

Direct  mortalit\  of  adult  birds  due  to  DDE- 
poisoning  cannot  be  discfuuited  as  a  factor  in  the 
decline  of  the  peregrine,  since  Porter  and  Wie- 
mever  (1972)  have  demonstrated  that  dietary 
le\'els  of  onlv  2.S  ppm  (wet  weight  basis)  /;,//- 
DDE  were  letlial  to  S  p(ic(>nt  ol  male  cap- 
tive American  Kestrels  after  one  xcar  on  dosage. 
The  effects  were  most  pionounced  duiing  molt 
and  immediatelv  follow  ing  nesting  seasoTi— a  pe- 
riod when  the  fat  ev'ele  of  the  kestrel  was  at  its 
lowest  point.  Thev  ha\'e  also  shown  (Porter  and 
Wieme\-er,  in  preparation )  that  kestrels  dosed  at 
both  low  (0.28  ppm  dieldrin;  1.4  ppm  DDT) 
and  high  (0.84  ppm  dieldrin;  4.7  ppm  DDT) 
(wet  weight  basis)  dosage  levels  of  DDT  and 
dieldrin  in  combination  are  more  susceptibli-  to 
death  following  stress  of  weather  than  are  non- 
dosed  kestrels. 


Residues  of  Pesticides  in  Peregrine  Prey  Species 
We  will  now  consider  the  quantity  of  or- 
ganochlorin(>  pesticides  in  the  tissues  of  some 
of  the  peregrine's  pre\'  species  in  Utah,  since 
many  of  the  principal  pre\'  of  the  peregrine  are 
known  to  contain  high  levels  of  these  chemicals. 
Cade,  White,  and  Haugh  (1968),  and  Ender- 
son  and  Berger  (1968),  for  instance,  determined 
that  DDT,  DDD,  DDE,  and  dieldrin  were 
present  in  greater  (|uantities  in  the  tissues  of 
migrant  sandpipers  than  in  an\-  other  of  the 
peregrine's  pre\'  species  in  the  .Arctic.  Somc^  con- 
tained DDE  in  their  tissues  in  cjuantities  of  suf- 
ficient magnitude*  to  be  cause  for  concern  (see 
Porter  and  Wiemeyer,  1969.  and  Wiemc\cr  and 
Porter,  1970).         ■ 

DDE  is  considered  to  be  the  most  inimical 
to  avian  reproduction  of  the  metabolites  of  DDT. 
Relatively  high  DDE  residues  were  present  in 
the  eggs  and  in  tissues  of  Short-billed  Dowitch- 
ers  {Limnodromus  griscits),  Killdeer  (Cltarad- 
rius  vociferus),  American  .\\'ocets  and  Rlaek- 
neeked  Stilts  in  California  (Keith  and  Hunt. 
1966).  Surprisingly  liigh  residues  of  /),//-DDE 
( expressed  in  average  and  extreme  ppm.  wet 
weight  basis )  were  found  in  the  eggs  ot  Black- 
necked  Stilts  (4.92,  range  1.0-13.7),  American 
Avoccts  (4.43,  1.5-12.0)',  and  Franklin's  (inlls 
(0.92,  0.5-2  2)  collected  at  the  Bear  River  marsh- 
es in  1968  (unpubl.  data,  Dc>nver  Wildlife  Re- 
search Center).  The  whole  bodv  tissues  ol  two 
Lesser  Yellowlegs  (Totaiius  flavipes)  contained 
(m  the  average  10.95  (range  5.1-16.8)  ppm  /).//- 
DDE  (wet  weight  basis);  four  Long-billed 
Dowitchers  {Liinnodromus  scoloj)a(cus),  13.25 
(0.7-49.20);  one  avoeet,  3.4;  nine  Whit(>-faced 
Ibis  (Plegadis  chihi),  2.55  (0.1-6.5);  and  three 
Marbled  Godwits  (Limosa  fedoa),  6.04  (0.1.5- 
17.8).  Dieldrin  in  the  tissues  of  these  birds 
ranged  from  0.1-0.86  ppm  in  the  ibis,  0.2  ppm 
in  the  Lesser  Yellowlegs,  0.0.5-0.50  ppm  in 
the  godwits,  and  0.6.8  ppm  in  the  avoeet.  Many 
of  the  DDE  values  are  greater  than  the  2.8 
ppm  (wet  basis)  of  l^DE  that  caused  eggshell 
thinning  ( Wiemc^-er  and  Porter,  1970)  and 
adult  mortality  (Porter  and  Wiem(>yer,  1972) 
in  .American  Kestrels.  Residues  of  PCB's  were 
found  in  foui-  of  the  dowitchers  and  two  of  the 
\(41owle^s.  The\  axeraged  3.75  ppin  (1. -5-10.0) 
and  4.5  ppm   (3.0-6.0),  respectively. 

Mosiiuilocidc  I'sagc  in  Vlali 

The  chemical  DDT  was  used  as  a  mos(|uito- 
eide  in  the  marshes  along  the  Great  Salt  Lake 
as  eari\  as  1947  in  Weber  (Ogden  Ba\-  State 
Waterfowl  Managemc-nt  .Area)  (Benge  and 
Fronk.  1970)  and  Box  Elder  eountic-s  ( K.  L. 
Josephson.  pers.  eonnn.,  1971  )  and  on  an  experi- 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Ut^vh 


47 


mental  basis  in  Salt  Lake  County  (Salt  Lake 
City  Mosquito  Abatement  District)  in  1945 
(Graham  and  Rees,  1958).  This  chemical  was 
used  at  Ogden  Bay  until  1961,  at  which  time 
the  use  of  parathion  was  initiated  (Benge  and 
Fronk,  op.  cit. ).  Davis  County  probably  began 
the  use  of  DDT  in  1951  or  1952,  since  mosquito 
control  was  initiated  there  in  1951  (Stewart, 
1954;  Nielson,  1962).  The  quantities  of  DDT 
used  in  the  early  \'ears  probably  were  not  great, 
since  it  was  applied  bv  means  of  foggers  and 
hand-operated  sprayers.  However,  beginning  in 
1949,  DDT  was  applied  to  the  extensive  marshes 
bordering  the  Great  Salt  Lake  by  means  of  air- 
craft (for  additional  history  of  mosquitocide 
usage  in  Utah,  sec  Appendix.  The  utiliza- 
tion of  DDT  increased  with  the  use  of  air- 
planes as  a  vehicle  for  application.  It  is  inter- 
esting to  note  that  reproductive  failure  in  the 
peregrine  was  most  pronounced  in  the  vcars 
coincident  with,  and  immediately  following,  the 
initiation  of  aerial  spraying,  although  this  may 
be  an  unrelated  coincidence. 

Between  1947  and  1961  many  thousands  of 
pounds  of  DDT  were  deposited  on  agricultural 
crops,  and  more  importantly,  directly  on  the 
marshes  and  waters  in  the  Great  Salt  Lake  Valley 
where  nesting  peregrines  obtained  much  of  their 
food.  The  quantities  applied  by  mosquito  abate- 
ment districts  were  greatest  along  the  marshes 
of  the  Great  Salt  Lake,  where  no  peregrine 
eyries  are  known  to  have  been  active  after  1957, 
and  least  in  Utah  County,  where  several  pere- 
grine eyries  apparently  remained  active  until 
the  late  1960s. 

Data  on  the  (juantities  of  organochlorine  in- 
secticides used  for  agricultural  purposes  in  the 
area  surrounding  the  Utah  and  Great  Salt  lakes 
were  unavailable  to  us,  but  chlorinated  hydro- 
carbon pesticides  probably  were  used  in  large 
quantities,  judging  from  a  recent  surv'ey  of 
pesticides  in  Utah  (VVarnick,  1971).  However, 
they  were  applied  to  farm  crops,  farm  animals, 
and  buildings,  and  not  directly  on  the  marshes 
where  the  peregrine  obtained  its  food.  Unfor- 
tunatelw  little  is  known  regarding  the  move- 
ments of  these  chemicals  from  agricultural  lands 
to  the  marshes. 

We  have  no  direct  evidence  linking  these 
chemicals  with  the  sharp  reduction  in  active 
peregrine  e\ries  along  the  Wasatch  Mountains 
during  the  critical  years  between  1945,  when 
the  chemicals  were  first  used,  and  1957,  when 
the  species  was  last  known  to  breed  in  the  area. 
Nor  do  we  know  the  extent  of  the  environmen- 
tal contamination  at  that  time  bv  other  chemicals 
such  as  the  polvchlorinated  biphenyls  (PCBs). 
We  do  not  know  the  effects  of  PCBs  on  raptor 


reproduction,  although  some  PCBs  (1245)  in 
small  dietary  concentrations  do  not  seem  to 
affect  reproduction  in  Mallards,  Pheasants  (Pha- 
siantis  colcliicus)  (Heath  et  al.,  1972),  and  Ring 
Doves  (Streptopelia  risoria)  (Peakall,  1971)  in 
the  same  way  as  does  DDE. 

We  can  only  speculate  regarding  the  resi- 
dues of  chlorinated  hydrocarbons  present  in  the 
tissues  of  either  the  peregrine  or  its  prey  species 
during  the  period  of  its  decline  in  Utah.  Most 
of  the  peregrine's  prey  species  were  migratory  in 
nature.  Thus,  part  of  the  insecticide  residues 
acquired  by  them  were  from  areas  other  than 
Utah  and  the  Great  Salt  Lake  valleys.  We  are 
unable,  therefore,  to  establish  an  absolute  cause 
and  effect  relationship  between  the  quantities  of 
chlorinated  hydrocarbons  used  and  the  decline 
of  the  peregrine  in  Utah,  although  one  is  sug- 
gested by  the  experimental,  ecological,  and  be- 
havioral evidence  which  we  have  presented. 

Disease  Hypothesis  for  Peregrine  Decline 

White  (1963)  referred  to  27  cases  of  botu- 
lism (Clostridium  botuJinum)  in  peregrines  that 
were  found  in  the  Great  Salt  Lake  marshes  be- 
tween 1943  and  1958.  Ralph  B.  Williams  (pers. 
comm.,  1972)  also  found  several  affected  pere- 
grines on  marshes  around  Utah  Lake  in  the 
mid-1940s.  The  disease  was  most  prevalent  be- 
tween late  July  and  early  October,  and  it  ap- 
peared to  affect  adults  more  than  young,  and 
females  more  than  males.  Botulism  undoubted- 
ly has  taken  its  toll  of  peregrines  during  the 
past  several  decades  and  perhaps,  sporadically, 
for  many  hundreds  of  years.  Its  effects,  histori- 
cally, on  the  local  peregrine  population  cannot 
be  assessed  because  the  fluctuations  in  numbers 
of  active  peregrine  eyries  in  Utah  are  not  known. 
We  cannot  evaluate  the  effects  of  botulism  tox- 
ins combined  with  those  of  pesticides,  since 
knowledge  of  the  effects  of  pesticides  on  the 
susceptibilit)'  of  birds  to  various  diseases  and 
the  interactions  of  botulism  toxins  with  the 
chlorinated  hydrocarbons  arc  poorly  understood. 
However,  any  mortality  of  adult  birds  due  to 
disease  during  periods  of  reproductive  failure 
would  tend  to  accelerate  the  decline. 

Human  Activity  Factors  in  the 
Decline  of  the  Peregrine 

A  number  of  human  activities,  besides  the 
agricultural  practices  already  mentioned,  may 
have  adversely  affected  the  peregrine  in  Utah, 
particularly  in  combination  with  the  inimical 
effects  of  organochlorine  pesticides,  botulism 
poisoning,  and  changes  in  the  climate.   (See  an 


48 


Bricham  Young  University  Science  Bulletin 


earlier  analysis  by  White  (1969b)  of  tlit-  effect 
of  human  pressures. ) 

The  impact  of  nest  robbing,  which  started 
earlier  in  the  centurv  with  egg  collecting  and 
later  in  the  centur\-,  starting  about  1939,  with 
the  utilization  of  the  nestlings  for  falconry,  are 
difficult  to  evaluate,  although  there  is  no  evi- 
dence that  these  activities  per  se  were  respon- 
sible for  the  sharp  increase  in  abandoned  eyries 
in  the  state.  Some  peregrine  eyries  in  Europe 
were  robbed  of  their  young  for  many  hundreds 
of  years  without  apparent  harmful  effects  ( Fi- 
scher,  1967;   Ratcliffe,  1969). 

Photography  at  eyrie  sites  also  may  have 
caused  some  birds  to  abandon  their  eyries,  al- 
though to  our  knowledge  onl\'  one  nest  in  Utah 
(Table  1,  site  7)  was  harassed  in  this  way  and 
the  eyrie  site  was  known  to  have  been  active 
subsequently. 

The  reported  collection  of  an  adult  falcon 
from  the  Pelican  Point  eyrie  (Table  1,  site  3) 
in  1935  (Bee  and  Hatchings,  1942)  apparently 
had  little  impact  on  this  eyrie,  since  it  was  still 
occupied  as  late  as  1939  (notes  of  R.  G.  Bee). 
The  removal  of  the  adults  from  evrie  site  4 
(Table  1)  in  1957  or  195S  b\  a  falconer  probably 
hastened  the  abandonment  of  that  eyrie  by  only 
a  few  years,  since  what  seems  to  us  to  have  been 
the  pesticide  syndrome  was  already  in  strong 
evidence  there. 

The  cliff  at  Pelican  Point  (site  3.  Table  1, 
Fig.  6)  became  a  limestone  quarr\'  in  recent 
years  and  the  evrie  site  was  destroyed,  as  was 
an  eyrie  site  in  southwestern  Utah  (site  37, 
Table  1).  Lower  portions  of  the  cliff  near  one 
of  the  most  inaccessible  peregrine  e\ries  in  the 
state  (Table  1,  site  8)  were  blasted  away  dur- 
ing tlie  1960s.  .Some  of  the  earlier  observations 
of  peregrines  in  Utah  were  near  this  site.  A  bird 
was  noted  there  in  1969  ( C.  M.  White),  but  not 
in  1971  (R.  J.  Erwin). 

A  recreation  area,  establislicd  after  196(S,  is 
situated  below  one  eyrie  in  east-central  Utah 
(Table  1,  site  2S).  When  the  e\rie  was  visited 
in  Mav  1971,  several  motore\cle  clubs  were  us- 
ing the  area  as  a  point  of  rendezvous  and  all 
day  and  night  the  roar  of  motorcycles  echoed 
through  the  can\()n.  Although  fresh  excreta 
was  seen  along  a  ledge  nnming  adjacent  to  the 
old  e\rie  site,  no  falcons  were  seen  in  two  da\s 


of  observations.  This  eyrie  had  shown  evidence 
of  the  pesticide  syndrome  as  early  as  1961,  how- 
ever. The  extent  of  the  damage  to  the  above 
site  is  not  known. 

Depredation  oi  the  species  1)\  hunters  is  a 
mortality  factor  which  is  frequently  overlooked. 
Utah's  marshes,  which  in  the  past  were  fre- 
(juented  b\  peregrines  in  the  fall  and  winter, 
have  been  used  by  increasingly  greater  numbers 
of  waterfowl  hunters  in  recent  years.  This  is  es- 
pecialK  true  of  areas  around  the  Great  Salt 
Lake  since  the  establishment  of  state  and  federal 
waterfowl  refuges  between  1930  and  the  early 
1940s.  Often  hunters  kill  raptors  and  other  birds 
indiscriminatelv.  This  could  be  a  contributory 
factor  to  the  peregrine  decline,  since  peregrines 
fre(iuenting  the  marshes  during  hunting  season 
probably  were  from  local  eyries.  However,  the 
significance  of  depredation  by  hunters  is  diffi- 
cult to  assess  since  the  peregrine  is  noted  for 
its  abilitN'  to  withstand  this  type  of  persecution 
and  destructive  treatment  bv  man  (Ferguson- 
Lei's,  1957;  Cadc>,  White,  andHaugh,  196S;  Rat- 
cliffe, 1962,  1969). 

In  the  past  two  decades,  the  construction  of 
human  dwellings  on  the  high  foothills  of  the 
Wasatch  Mountains  below  certain  eyrie  sites 
may  have  had  an  adverse  affect  on  these  eyries 
(sec  White,  1969b),  and  the  effects  of  the  activi- 
ties at  a  nearby  rifle  range  on  one  such  eyrie 
also  ari'  unknown.  Oni'  can  only  spcx'ulate  what 
the  construction  of  homes  near  eyrie  sites  will  do 
to  these  sites,  since  there  is  already  a  precedent 
set  for  peregrines  nesting  above  railroad  tracks, 
on  bridges,  and  in  heavilv  populated  urban 
centers  (Hicke),  1942;  Olivier,  19.5.3).  The  ex- 
tent to  which  some  individuals  of  the  species 
persist,  despite  the  presence  of  human  popula- 
tions near  their  e\ries,  is  illustrated  b\'  the  pere- 
grines at  one  e\  rie  that  tolerati-d  for  o\-er  a 
centurv  the  acti\'ities  of  a  \  illage  of  two  hundred 
peopli'  at  tlie  base  of  the  cliff  th;it  housed  the 
falcon   evrie   (TTiekey.    1942). 

To  sum  up,  pollution,  shooting,  nest  site 
and  hiibitat  destruction,  human  disturbance,  and 
climatic  changes  ha\i'  contributed  singlv  and 
jointK'  to  the  near  demise  of  the  peregrine  in 
Utah.  Of  these,  ]Dollution  ;md  climatic  change 
appear  to  have  played  the  dominant  roles. 


FACTORS  INFLUENCING  PEREGRINE  DISTRIBUTION  AND  ABUNDANCE  IN  UTAH 


To  more  lull\  understand  tlu'  various  fac- 
tors involved  in  I  lie  distribution  of  tin-  peregrine 
in  Utah  prior  to  its  catastrophic  decline,  we  ha\(' 


.ttteniptcd  to  examine  the  impact  on  tlu'  species 
of  \arinus  ecological  factors,  both  past  and 
present. 


Biological  Series,  Vol.  18,  No.  1        Peheghine  F.alcon  in  Ut.\ii 


49 


Water,  Food,  and  Nesting  Sites  as 
Limiting  Factors 

Bond  (1946)  lias  reported  that  in  the  west- 
ern United  States  tlie  peregrine  seldom  nested 
more  than  one  half  mile  (0.8  km)  from 
uater  in  which  to  bathe.  Exceptions  to  Bond's 
( ibid. )  observations  are  icw.  Gabrielson  and 
Jewett  (1940),  for  example,  tell  of  a  pair  that 
nested  in  Oregon  on  an  isolated  rock  far  from 
water  ( 11  mi.;  17.7  km.,  Bond,  1946),  and  Tliom- 
as  Ra\'  (pers.  comm. )  located  an  active  eyrie 
far  from  water  in  arid  western  New  Mexico. 

The  peregrine's  affinit)'  for  free  water  prob- 
ably is  associated  more  uith  its  needs  to  bathe 
and  to  obtain  food  than  \\ith  its  needs  to  drink. 
Bartholomew  and  Cade  (1963)  point  ont  that 
the  larger  predator^'  birds  obtain  adecjuate  quan- 
tities of  water  from  their  food  under  most  cir- 
cumstances. They  cited  instances  of  several  fal- 
cons, including  the  peregrine,  maintaining 
weight  for  man\   months  without  free  uater. 

Beebe  (1960)  concluded  that  because  11 
of  1.3  young  peregrines  taken  from  nests  in  the 
Pacific  Northwest  and  raised  in  Denver  died 
of  deh\  dration,  humidit\'  rather  than  nearness  of 
free  water  was  perhaps  a  critical  factor  in  brood 
success  in  areas  of  the  West  other  than  the 
Northwest  Pacific  coast.  Since  these  nestlings 
died  despite  ha\'ing  been  supplied  with  drink- 
ing water,  Beebe  (ibid.)  Inpothesized  that  pere- 
grines were  more  or  less  restricted  to  nesting 
sites  near  water  because  of  high  humidit\'  rather 
than  the  presence  of  free  water. 

An  important  cjuestion  appears  to  be  whether 
or  not  the  young  mentioned  by  Beebe  were  ac- 
climatized to  tht'  cool,  humid  climate  of  the 
Northwest  before  being  transferred  to  the  arid 
intcmiountain  area.  Nelson  (pers.  comm.,  1971) 
has  suggested  that  these  birds  may  have  died 
of  malnutrition  rather  than  dehydration.  He 
raised  and  trained  one  of  them  and  encountered 
no  difficult\-  uith  deln dration.  Other  nestling 
peregrines  from  British  Columbia  and  the  Aleu- 
tian Islands,  similarly  transferred  to  Utah,  have 
not  been  affected  in  this  manner.  Nestlings 
taken  from  Utah  evries  have  not  appeared  to 
suffer  greatl)'  from  delndration  nor  has  there 
been  any  evidence  of  moisture  loss  among  young 
peregrines  cared  for  in  the  nest  ])\'  their  parents. 

This  affinity  for  high  humidit\-,  if  it  exists, 
mav  be  an  inherited  physiological  characteristic 
of  the  pealei  race,  which  is  less  pronounced  in 
the  peregrine  populations  of  the  arid  Intennoun- 
tain  \\'est  (see  also.  White.  196Sb,  for  further 
documentation  of  this  problem).  Furthemiore, 
other  populations  of  falcons,  such  as  those  of 
the  Shaheen,   exist  and  breed  in  the  deserts  of 


the  Middle  East  under  the  harshest  conditions 
known   (Bartholomew  and  Cade,  1963). 

Food  availability  appears  to  be  a  major  cri- 
terion influencing  the  distribution  and  abun- 
dance of  the  peregrine  in  arid  regions  of  the 
West.  Density  and  distribution  of  peregrine 
populations  in  Utah  appear  to  correlate  best 
with  the  abundance  of  the  food  supply.  Pere- 
grine populations  are  most  dense  in  the  area 
surrounding  the  Utah  and  Great  Salt  lakes 
where  the  preferred  prey  species,  particularly 
shorebirds  and  marshbirds,  are  most  abundant. 
Here,  the  marshes  have  historically  supplied 
food  for  10  to  20  eyries  during  a  single  nesting 
period.  Hunting  areas  for  isolated  pairs  of  pere- 
grines elsewhere  in  the  state  were  supplied  by 
smaller,  less  extensive  marshes  or  by  narrow 
tongues  of  streamside  vegetation.  Usually,  iso- 
lated pairs  survived  and  reproduced  where  ade- 
quate food  was  available. 

Food  availability  apparcnth'  is  an  important 
factor  in  the  distribution  and  abundance  of  the 
peregrine  in  more  humid  and  mesic  regions  as 
well  as  in  arid  regions.  Beebe  (1960)  has  at- 
tributed an  unusually  high  breeding  density  of 
peregrines  in  British  Columbia  to  the  extremely 
high  concentrations  of  four  or  five  species  of 
colonial  seabirds  occurring  there.  These  small 
pelagic  birds  apparcnth'  were  especially  suited 
as  pre\'  species  for  the  peregrine. 

Ratcliffe  (1962)  considered  the  geographic 
variation  of  food  supph'  as  the  most  obvious 
factor  associated  with  population  density  of 
the  peregrine  in  Great  Britain.  He  has  correlated 
size  of  territory  and  density'  of  peregrine  popula- 
tions in  Britain  with  the  nature  of  the  food 
supply. 

The  same  factor  generally  appeared  to  be 
operative  in  Utah,  although  peregrine  density 
in  the  Great  Salt  Lake  Valley  of  Utah  probably 
was  not  limited  by  the  size  of  the  prey  popula- 
tions. However,  the  species  may  be  limited  by 
the  distance  (up  to  17  mi,  27.4  km;  Table  4) 
it  must  fly  to  reach  the  marshes  where  it  obtains 
its  preferred  prey  species. 

Peregrines  ma\-  select  easily  accessible  nest- 
ing sites  in  areas  containing  an  abundance  of 
suitable  prey  species,  as  occurs  in  the  Queen 
Charlotte  Islands  (Beebe,  1960).  Such  sites  are 
seldom  utilized  in  areas  containing  less  favorable 
food  supplies.  This  is  illustrated  in  Utah  by  the 
occurrence  of  the  ground-nesting  peregrines  at 
Ogdcn  Ba\'. 

Hick(>\-  (1942,  1969)  considered  the  cliff  on 
which  per(>grines  nest  as  the  dominant  feature  of 
their  ecological  niche.  He  considered  extremely 
high  cliffs  as  "ecological  magnets"  which  at- 
tract  peregrines    regardless    of   nesting   success. 


50 


Brigham  Young  Univkhsity  Science  Bulletin 


Cade  (1960),  on  the  other  hand,  has  argued 
that  the  ability  of  the  pair  to  breed  effectively 
is  a  result  of  a  strong  pair  bond,  and  that  the 
strength  of  the  bond  is  a  more  important  con- 
sideration than  the  size  of  the  cliff.  He  argued 
that  the  pair  bond  would  be  dissolved  and  that 
the  evrie  would  become  inacti\e  indefinitely  if 
both  the  male  and  female  disappeared  from  the 
eyrie.  Ratcliffe  (Hickey,  1969),  in  support  of 
Hickey  (1942,  1969),  has  cited  examples  of 
several  eyrie  sites  which  were  consistently  reoc- 
cupied  following  the  deaths  of  both  adults.  This 
also  has  been  noted  in  the  Arctic  b\-  White  ( un- 
publ.  data).  (See  Fischer,  1967  for  additional 
documentation. ) 

In  Utah,  selection  of  e\rie  sites  by  pere- 
grines is  associated  with  the  avai]abilit\'  of  suit- 
able sites  near  a  readily  available  supply  of 
preferred  prey  species.  The  preferred  prey  spe- 
cies usually  are  closely  associated  with  a  marsh 
or  stream.  These  two  factors  combined,  then, 
constitute  the  most  important  aspect  of  the  pere- 
grine's nesting  econonn  in  the  state. 

Interspecific  Competition  During 
Nesting  Season 

Cade  (1960)  has  discussed  competition  be- 
tween the  jieregrine  and  the  Cvrfaleon  (Falco 
riisticohis).  White  and  C:ade  (1971)  have  dis- 
cussed competition  among  several  species  of 
raptorial  birds  in  the  Arctic,  and  White  (1968b) 
has  discussed  this  problem  as  concerns  peregrine 
distriliution  and  its  relation  to  large  congeners 
over  broad  distributional  areas.  These  papers 
give  a  valuable  basis  for  the  evaluation  of  the 
competition  between  the  peregrine  and  other 
raptors  whose  range  and  habitat  in  Utah  are 
svmpatrie.  In  our  discussion  of  interspecific 
competition,  we  prefer  the  more  restricted  defi- 
nition of  the  tenn  "interspecific  competition" 
as  given  b\'  Birch  (1957)  and  as  discussed  by 
Cade  (1960).  Tliat  is,  competition  results  when 
more  than  one  species  re(|uires  a  resource  that 
is  in  short  supply. 

Competition  for  food  and/or  nesting  sites 
between  the  peregrine  and  other  species  of  rap- 
tors, particularls'  the  Prairie  Falcon  and  the 
Golden  Eagle,  ma\'  be  factors  contributing  to  the 
relati\'e  paucity  of  peregrines  in  the  arid  Inter- 
mountain  West. 

Where  relati\-el\-  abundant,  the  Colden  EagU- 
ma\'  be  a  eoinpetiti\e  factor  limiting  the  density 
of  the  peregrine  in  the  more  arid  regions  of 
Utah.  Bond  (1946)  has  watched  the  peregrine 
strike  at  Golden  Eagles  and  R.  J.  Erwin  and  J. 
F.  Poonnan  (impubl.  notes)  have  made  a  simi- 
lar observation  in  Utah.  Dixon  (19.37)  tells  of 
one  instance  when   a  pair  nt   Golden   Eagles   in 


California  usurped  a  cliff  that  had  been  occupied 
by  peregrines  for  years.  Tlie  eagles  persistently 
outfought  the  peregrines,  forcing  them  to  leave. 
Cade  ( 1960 )  found  that  the  peregrine  was  quick- 
er and  more  persistent  in  its  attacks  on  Golden 
Eagles  than  on  any  other  raptor  discussed.  Rat- 
cliffe (1962,  196.3)'  reported  that  in  man\-  dis- 
tricts in  Scotland,  where  there  is  a  surplus  of 
suitable  cliffs,  the  densit\'  of  Golden  Eagles  is 
high  while  the  densities  of  the  peregrine  and 
the  Common  Raven  (Corviis  corax)  are  low.  In 
these  situations  apparently  the  eagle  replaced 
the  peregrine  as  the  chief  nesting  predator  in  the 
Scottish  Highlands. 

In  Utah,  peregrines  and  eagles  were  found 
nesting  concurrentK'  on  the  same  set  of  cliffs 
only  once.  The  eagles  nested  one  mile  ( 1.6  km) 
(Morlan  Nelson,  pers.  comm.,  1971)  from  ac- 
tive peregrine  and  Prairie  Falcon  eyries  (see 
Nelson,  1969),  but  on  the  opposite  side  of  the 
mountain  (north).  Tlu-  eagles  apparentK'  foraged 
northwardh ,  while  the  peregrines  foraged  south- 
wardly. No  aggression  was  noted  between  the 
eagles  and  the  falcons  (Nelson,  pers.  comm.).  A 
cliff  formerly  occupied  b\  peregrines  in  Utah 
(site  15,  Table  1)  contained  an  active  Golden 
Eagle's  nest  in  the  spring  of  1971,  and  the  pres- 
ence of  two  old  eagle  nests  ( R.  J.  Erwin)  sug- 
gests a  long  period  of  occupancy  bv  the  eagles. 
The  cliff  also  had  been  occupied  b\'  as  man\-  as 
tliree  pairs  of  Prairie  Falcons  simultaneously 
during  some  oi  the  intervening  \'ears  (Nelson, 
pers.    cdinm.,    1971). 

The  food  habits  of  the  eagle  and  peregrine 
are  sufficicnth'  diverse  in  Utah  so  as  to  negate 
a  strong  competition  for  food.  Additionally,  the 
eagle  seems  to  attain  its  greatest  abundance  in 
the  more  arid  regions  of  the  state,  wIktc  it  more 
liki'K'  would  compete  with  the  Prairie  Falcon 
for  nesting  sites  than  with  the  peregrine,  al- 
though the  abundance  of  eagles  in  the  deserts 
of  Utah  may  be  one  of  the  reasons  whv  the 
piTegriiu'  seldom  occurs  there.  This  latter  postu- 
lation,  liowevi'r,  appears  unlikeK'  because  of  an 
absence  of  the  ft)od  niche  preferred  b\'  the 
peregrine. 

The  Common  HaNcn  lias  lieen  shown  bv 
White  and  C^ade  (1971)  to  compete  rather  ex- 
tensiveh  with  G\  rfaleons  for  nest  sites  in  the 
Arctic,  though  it  seems  to  ha\e  only  limited 
competiti\e  effect  on  Arctic  peregrines  using 
the  same  cliffs.  In  Utah,  where  the  raven  is  com- 
mon, onK  three  cliffs  with  peregrines  were 
known  to  house  ravens.  Like  the  situation  in  the 
.Arctic.  ra\('ns  probably  had  "no"  effect  on  Utah 
peregrines,  although  Porter  observed  peregrines 
at  site  number  4  pursuing  ravens  on  8  .April 
19.51    |{;i\(iis  ina\.  howe\('r.  h.ivc  a  considerable 


Biological  Series,  Vol.  18,  No.  1       Peregrine  Falcon  in  Utah 


51 


modihing  effect  on  Prairie  FaIcon.s,  a.s  wall  be 
discussed  in  a  later  section.  ( See  also  Ratcliffe, 
1962,  for  a  c-onsideration  of  raven-peregrine  in- 
teraction in  Great  Britain. ) 

The  Prairie  Falcon  ( Fig.  .39 ) ,  on  the  other 
hand,  is  more  closeh'  related  plu'logenetically, 
is  more  similar  in  size,  and  is  more  equivalent 
in  ecological  function  to  the  peregrine,  than  is 
cither  the  eagle  or  raven.  Hence,  it  likely  would 
be  a  more  serious  competitor  of  the  peregrine 
and  it  probabK  would  be  a  more  important 
factor  limiting  peregrine  populations  in  areas 
of  sympatr\'. 

The  Prairie  Falcon  is  a  true  desert  falcon. 
It  undoubtedly  evolved  in  the  arid  West,  and 
therefore  is  probabK-  better  adapted  than  is  the 
peregrine  for  Utah's  arid  environment.  The  Pere- 
grine Falcon  is  separated  from  the  Prairie  Falcon 
and  the  Cyrfalcon  at  the  subgeneric  level.  The 
two  species  are  of  similar  size,  although  the 
peregrine  is  somewhat  heavier  than  the  I-'rairie 
Falcon  (Sei'  Table  9  and  Webster,  in  Beebe  and 
Webster,  1964). 

The  peregrine,  which  is  nearh'  cosmopolitan 
in  its  geographic  distribution,  has  a  breeding 
range  which  completely  overlaps  that  of  the 
Prairie  Falcon  geographicallv  but  not  ecologi- 
callv.  The  Prairie  Falcon  breeds  from  central 
British  Columbia,  southern  Alberta,  southern 
.Saskatchewan,  and  North  Dakota,  south  t(j  Baja 
California,  and  northern  Mexico  (Sec  AOU 
Checklist  of  N.  Am.  Birds,  1957).  The  pere- 
grine is  most  abundant  north  of  its  zone  of  svm- 
patry  with  the  Prairie  Falcon. 

According  to  Bond  (1946),  the  Prairie  Fal- 
con ma\'  be  quite  common  up  to  6,000  or  7,000 
feet  (1,829  or  2,1.34  m)  in  suitable  localities  and 
at  elevations  where  trained  Prairie  Falcons,  with 
their  much  greater  surface  to  weight  ratio,  clear- 
ly outflv  trained  peregrines,  which  are  their  su- 
periors at  sea  level.  Morlan  Nelson  (pers.  comm. 
1971),  who  has  tested  Bond's  (1946)  hypothesis 
on  several  occasions  with  captive  falcons,  con- 
siders that  it  is  more  a  matter  of  individual  varia- 
tion  within   both  species  than  it  is  a  factor  of 


elevation. 

Actual  contact  between  the  two  species  oc- 
curs where  their  ecological  niches  overlap.  To 
our  knowledge,  there  is  no  locality  in  Utah 
where  peregrines  nest  which  is  not  also  inhabited 
bv  Prairie  Falcons,  but  not  the  reverse.  The 
peregrine's  proclivity  to  nest  near  water  or 
marshes  where  both  its  food  and  nesting  re- 
quirements are  met  is  not  shared  by  the  more 
euryecious  Prairie  Falcon  which  may  fulfill  these 
requirements  both  near  water  and  in  the  desert 
many  miles  from  water. 

As  discussed  previously,  the  several  pere- 
grine e\ries  found  in  the  deserts  of  Utah  were 
situated  within  easy  access  of  marshes,  desert 
springs,  ponds,  streams,  or  rivers.  Perhaps  this 
reflects  the  differences  in  hunting  methods  and 
food  habits  of  the  two  species,  as  well  as  the 
proclivitv  of  the  peregrine  to  bathe  in  water  as 
discussed  by  Bond  (1946)  and  Cade  (1960). 
Both  species  can  be  dust  bathers  in  captivity 
(Nelson,  pers.  comm.),  although  the  Prairie 
Falcon  is  less  dependent  on  water  than  is  the 
Peregrine  Falcon. 

Some  Factors  Modifying  Competition 
and  Success 

Before  examining  the  kinds  of  competition 
that  may  affect  Utah  peregrines,  a  general  dis- 
cussion is  in  order.  There  are  many  ways  that 
falcons  can  exploit  their  respective  environments. 
Their  success,  that  is,  the  total  number  of 
young  that  become  breeding  adults  in  the  next 
generation,  depends  upon  the  effectiveness  of 
this  exploitation. 

Frequently  ecologists  use  the  terms  "gen- 
eralist"  and  "specialist"  to  describe  a  species  in 
terms  of  the  manner  in  which  it  utilizes  certain 
resources.  Most  frequently  this  pertains  to  the 
manner  in  which  the  food  or  habitat  niche  is 
exploited,  or  to  the  modes  of  hunting  certain 
species  of  prey. 

Although  the  specialist  has  a  narrower  habi- 
tat tolerance,  it  usually  compensates  b\'  being 
more     competitive     (see,    for    example.    Cade, 


Table  9.     Weights  ( in  gram,s )  of  Peregrine  Falcons  and  Prairie  Falcons  from  various  North  American  populations. 


Species 
and 

MALES 

FEMALES 

Population 

n 

X 

range 

n 

X 

range 

PEREGRINE  FALCONS 

(White.  1968a  &  b) 

F.   p.   tundrius' 

F.   p.   anatumr 
PRAIRIE  FALCONS' 

(Enderson,   1964) 

12 
5 

15 

610.9 
678.0 

554.0 

550-647 
67.5-682 

500-635 

19 

5 

31 

952.0 
1,038.0 

863.0 

825-1,094 
870-1,201 

760-975 

'Weights  are  from  adult  birds. 

-From  population  in  western  United  States. 


52 


Bhk;ham  Young  Univebsity  Science  Bulletin 


1960).  When  the  optimal  requirements  for  the 
speciahst  are  present,  it  tends  to  eapitahze  on 
or  "monopoHze"  the  resources  or  conditions 
to  receive  maximum  benefit,  often  to  the  ex- 
clusion of  the  generalist  or  other  specialists.  It 
is  the  existence  of  a  specific  or  optimal  set  of 
conditions  that  allows  the  specialist  to  be  suc- 
cessful. The  generalist  might  also  successfully 
exploit  the  precise  conditions.  However,  because 
of  competition  with  the  specialist,  it  may  alter 
the  manner  in  which  it  uses  the  conditions  by 
partitioning  the  resource,  or  it  mav  be  forced 
into  suboptimal  conditions  because  of  the  domi- 
nance of  the  specialist.  In  the  absence  of  the 
specialist,  the  generalist  obtains  even  greater 
benefit  by  the  use  of  the  specific  combination 
of  resources  or  conditions  that  the  specialist 
would  have  used. 

The  generalist  tends  to  be  more  widespread 
geographicail\'  and  often  more  common  than 
the  specialist.  Moreover,  when  two  closely  re- 
lated species  with  similar  ecological  niches  oc- 
cupy the  same  geographic  area,  one  tends  to 
assume  the  role  of  the  "specialist"  and  the  other 
th(>  role  of  the  "generalist,"  depending  upon 
their  individual  needs.  G\'rfalcons,  for  instance, 
are  specialists  on  the  Arctic  Slope  of  .'\laska, 
where  thev  have  specific  nesting  requirements 
and  where  thev  specialize  on  ptannigan  for  food, 
while  the  sympatric  peregrine  is  the  generalist, 
having  rather  broad  reciuirements  for  nesting 
and  feeding  (White  and  Cade,  1971).  The 
G\  rfaleon  seemingK  has  the  adxantage  and  ap- 
pears to  outcompcte  the  peregrine  for  certain 
resources.  However,  because  the  peregrine  is  a 
generalist,  it  has  less  precise  requirements  and 
therefore  is  able  to  occur  over  a  much  broader 
geographic  range  in  Alaska,  such  as  the  taiga 
regions.  Then,  too,  it  is  probabK  more  numer- 
ous when  considering  its  entire  range. 

Even  though  the  j^eregrine  is  probably  a 
generalist  o\er  much  of  its  cosmopolitan  range, 
it  becomes  a  specialist  in  the  Aleutian  Islands, 
where  it  has  a  narrower  food  niche  consisting 
mostK  of  marine  birds  of  tlie  famih'  Alcididae 
and  of  the  order  Procellariiformes.  Thus,  the 
role  of  the  species  is  modified  In  the  conditions 
in  a  given  localih'. 

Prairie  Falcons  ha\'e  been  thought  of  as  spe- 
cialists liecause  the\'  are  al)le  to  exploit  \('ry 
arid  climates  where  a  limited  number  of  food 
species  are  present.  They  often  occur  where 
other  large  falcons  arc  unable  to  survive.  Be- 
cause they  are  able  to  concentrate  on  the  prey 
species  most  a\ailable,  Prairie  I-'aleons  mav  have 
a  ratlier  highK  specialized  food  niche,  especial- 
ly in  the  more  arid  regions  w^here  a  limited 
number  of  food   species  occur.   Their  abilit\    to 


"specialize"  on  what  is  a\ailable  enables  them 
to  live  successfulh'  in  a  wide  variety  of  eco- 
logical situations. 

If  one  considers  the  Prairie  Falcon's  entire 
geographic  and  ecological  range,  it  is  narrowly 
selective  in  its  exploitation  of  the  climatic  condi- 
tions a\'ailablc  to  it  (i.e.  a  near  obligate  of  xeric 
conditions),  but  it  is  broadh'  selective  in  its  ex- 
ploitation of  food  and  n(-sting  sites.  Additionally, 
where  the  geographic  ranges  of  the  two  species 
o\'i'rlap,  Prairie  Falcons  are  much  more  common 
than  art"  peregrines.  Because  of  the  Prairie  Fal- 
con's seemingly  narrow  climatic  tolerance  dur- 
ing the  breeding  season,  climate  ma\'  be  a  major 
factor  limiting  its  geographic  distribution. 

Peregrines,  imlike  prairies,  are  broadl\-  selec- 
tive in  their  exploitation  of  climatic  conditions 
over  their  entire  geographic  range.  However, 
tlie\'  are  narrowly  selective  in  their  exploitation 
of  food  and  nesting  sites  in  the  arid  West  where 
the\-  must  compete  with  the  s\mpatric  Prairie 
Falcon.  Moreover,  the\'  are  much  less  common 
than  are  Prairie  Falcons,  where  the  ranges  of  the 
two  species  are  svmpatric.  Their  specialized 
food  rcHiuiremi'nts  (generallv  "water-t\  pe  "  birds) 
and  restrictive  methods  of  capturing  pre\  (not 
prone  to  capture  prey  on  the  ground),  are  the 
major  factors  limiting  the  expansion  of  their 
geographic  and  ecological  ranges  in  Utah  and 
probabK   else\\here  in  the  arid  West. 

The  presence  of  surface  water  in  the  arid 
West  ma\'  dramatically  alter  the  environment. 
For  certain  species  it  may  even  act  as  a  limiting 
factor.  Water  creates  a  food  niche  which  ap- 
parenth  is  optimal  for  the  peregrine,  providing 
an  abundance  of  aquatic  birds  in  these  local- 
ized areas.  Hence,  the  peregrine  does  better  in 
the  presence  of  surface  water.  This  is  especially 
evident  at  the  margin  of  the  species'  ecological 
range  in  the  arid  parts  of  Utah.  With  the  pres- 
ence of  these  "oases"  of  acjuatic  habitat  in  an 
otherwise  unexploitable  enxironment,  the  pere- 
grine assumes  the  role  of  specialist:  and,  where 
the  peregrine  and  piairie  occur  together  in  Utah, 
the  prairie  seemingK'  assumes  the  role  of  the 
"generalist."  The  broad  spectnmi  of  food,  habi- 
tat, and  nesting  sites  which  the  prairie  selects 
overlajis  and  surpasses  the  reciuirements  of  the 
peregrine.  The  requirements  of  the  peregrine  are 
more  limited  and  restrictive,  \  I't  it  may  do  bet- 
ter competitiwlv  than  its  congener  when  the 
optimal  conditions  pre\ail. 

(Competition  \\  itli  the  Prairie  I'alcon  for  Food 

Where  the  two  species  occur  together  along 
the  escarpment  of  the  Wasatch  Mountains  and 
adjacent  to  the  Croat  Salt  Lake,  their  food  ap- 


Biological  Series,  Vol.  18,  No.  1       Peheghine  F.\lcon  in  Utah 


53 


pears  to  be  quite  similar  (Table  5),  although 
there  are  some  marked  differences.  In  this  re- 
gion of  joint  occupancy,  the  Prairie  Falcon  uti- 
lizes a  much  wider  \arictA'  of  vertebrate  species 
than  docs  the  peregrine.  As  illustrated  in  Table  5, 
the  Prairie  Falcon  is  more  prone  to  feed  on  ro- 
dents and  on  ground-dwelling  birds,  such  as 
([uail,  pheasants,  meadowlarks,  and  passerine 
l)irds  in  general,  and  is  less  inclined  to  feed  on 
pigeons,  doves,  and  flickers  than  is  the  pere- 
grine (also  see  Bond,  1936a,  b,  and  c). 

Prairie  Falcons  also  feed  on  reptiles.  For  in- 
stance, at  one  Prairie  Falcon  eyrie  in  the  Great 
Basin,  not  far  from  a  peregrine  e)ric,  adults 
were  observed  carrying  large  whiptail  lizards 
( Cnemidophorits  sp. )    to  the  eyrie. 

The  Prairie  Falcon  exploits  a  different  food 
resource  in  thi-  allopatric  parts  of  its  geographic 
range  than  in  those  that  are  sxmpatric  with  the 
peregrine.  A  case  in  point  is  the  high  plateau 
countr\-  of  Utah  NNW  of  the  Uinta  Mountains 
( 6,800'  feet  ele\ation;  2,073  m )  where  only  the 
Prairie  Falcon  occurs,  although  one  would  expect 
peregrines  also  to  occup)'  the  habitat.  Food 
items  taken  from  several  nests  between  1961 
and  1964  in  this  region  of  allopatry  consisted 
of  61  percent  mammals,  about  90  percent  of 
which  was  the  Uintah  Ground  Squirrel  ( CifeUus 
armatus),  although  another  species  of  ground 
squirrel,  a  chipmunk  {Eiitamias  sp. ),  and  a  vole 
(Slicrottis  sp. )  also  occurred.  Birds  made  up 
the  remaining  .39  percent,  with  Mourning  Doves 
being  the  principal  avian  food,  though  the  Brew- 
er's Blackbird  (Euphaniis  aianoccpJwhis).  Flick- 
ers (  Colaptcs  sp. ),  Horned  Larks,  Starling  (Sfi/r- 
ntis  vidp^aris).  and  the  Mountain  Bluebird  {Sialia 
cttrrticoidcs)  also  occurred.  Thus,  about  75  per- 
cent of  the  total  food  uas  made  up  of  t\\'o  spe- 
cies, one  mammal  and  one  bird.  In  this  case,  and 
those  cited  bv  Enderson  (1964),  with  an  ab- 
sence of  peregrines  in  both  localities,  the  Prairie 
Falcon  tended  to  fill  the  role  of  a  "specialist"  in 
food  habits;  and  to  a  large  extent  the  species 
was  mammi\-orous  (mammal-eating).  (See 
Bond,  1936b).  The  avivorous  (bird-eating) 
peregrine,  on  the  other  hand,  consumes  few 
mammals  and  fewer,  if  any,  reptiles. 

Ground-nesting  birds  and  rodents  are  im- 
portant items  in  the  diet  of  the  Prairie  Falcon  in 
areas  other  than  Utah.  For  example,  Enderson 
(1964)  found  remains  of  the  ground-nesting 
Horned  Lark  and  of  the  Richardson's  ground 
sc|uirr(>l  (Cifelhis  richardsonii)  most  often,  and 
sometimi's  exclusi\el\-,  in  the  nests  of  Prairie 
Falcons  in  eastern  W\oming  and  Golorado.  Og- 
den  (1971)  considered  the  Townsend's  ground 
sfiuirrel  (CiteUus  fotcnsei-tdi)  to  be  the  most 
important    food    species,    followed    by    Homed 


Larks,  Meadowlarks,  and  whiptail  lizards  in 
Prairie  Falcon  eyries  along  the  Snake  River  of 
southwestern  Idaho.  The  antelope  ground 
squirrel  (Citcllits  Icucurus)  was  also  present,  but 
in  smaller  numbers. 

The  Horned  Lark  was  also  a  staple  item  in  the 
winter  diet  of  Prairie  Falcons  in  Utah  and  in  the 
prairies  of  Wyoming,  Colorado,  and  New  Mex- 
ico, where  it  influences  the  falcon's  seasonal 
movements  and  distribution   (Enderson,   1964). 

An  overlap  in  the  food  niches  of  the  pere- 
grine and  Prairie  Falcon  is  evident  in  the  area 
along  the  Wasatch  Mountains  (Table  5).  In 
terms  of  biomass,  aquatic  birds  comprised  the 
largest  categoPi'  of  prey  species  in  the  Wasatch 
Mountain  eyries  of  both  species,  but  the\-  were 
much  more  predominant  in  the  eyries  of  the 
peregrine  than  in  those  of  the  Prairie  Falcon. 

The  a\ocet  was  the  major  aquatic  species  in 
the  e\  ries  of  both  falcons  (see  Frontispiece  and 
Fig.  39).  The  importance  of  the  avocet  as  a 
pre\  species  of  the  Prairie  Falcon  was  apparent 
also  at  two  e\ries  in  the  Great  Basin,  northwest 
of  Great  Salt  Lake,  where  the  adult  Prairie 
Falcons  brought  avocets  and  Antelope  Ground 
Squirrels  to  their  young  almost  exclusively  in 
1962  (C.  M.  White,  unpubl.  data)  and  commonly 
in  1969  (P'att,  1971).  This,  however,  was  in  the 
apparent  absence  of  competition  with  the  pere- 
grine. 

The  presence  of  the  avocet  in  the  diets  of 
lioth  species  is  probabK-  a  reflection  of  the  local 
abundance  of  this  shorebird  and  the  ease  with 
uhich  it  may  be  captured.  The  avocet  likely 
did  not  represent  a  resource  in  short  supph'  and 
undoubtedh'  was  an  important  item  in  the  diet 
of  the  peregrine  long  before  the  first  white 
settlers  arrived  in  the  western  United  States. 
In  1S71  Allen  (1872)  found  it  \-ery  abundant 
along  the  shores  of  Great  Salt  Lake,  where  he 
noted  flocks  containing  several  thousand  indi- 
viduals from  1  September  to  8  October,  and  a 
quarter  of  a  century  earlier  (4  April  1850), 
Stansbury  (1852)  observed  innumerable  flocks 
of  long-legged  ]ilo\ers,  many  of  which  probably 
were  avocets,  Willets,  and  stilts.  The  avocet 
predated  uhite  man  in  the  Great  Salt  Lake 
area  1)\  man\'  thousands  of  years,  as  evidenced 
b\'  its  presence  among  the  bird  remains  dating 
l^aek  nearh-  8,500  \ears  B.P.  in  the  early  strata 
of  Hogup  Gave,  just  north  of  the  Great  Salt 
Lake  (Harper  and  Alder,  in  press). 

Tlie  White-faced  Ibis  was  an  additional 
marshbird  upon  which  both  species  of  falcons 
apparenth  preyed.  Wcller  't  al.  (1958)  indi- 
cated that  the  peregrine  killed  White-faced  Ibis 
in    the    Knudson    marshes    near    Brigham    Gity, 


54 


BnicnAM  YouNO  Univfusitv  Science  Bulletin 


and  R.  D.  Porter  (unpuhl.  data)  ohscrvt-d  a 
Prairie  Falcon  feeding  on  an  ibis  at  the  Bear 
River  marshes  on  5  June  1951.  Since  the  ihis 
was  not  found  in  the  evries  of  either  species, 
it  was  prol)ahl\-  too  heavy  for  the  falcons  to 
carry  to  their  eyries.  The  weight  of  an  adult 
female  ibis  as  determined  by  Porter  et  al. 
(unpubl.  ms)  is  517  grams,  whereas  the  weights 
of  two  adult  female  avocets  average  281 
grams. 

In  Prairie  Falcon  eyries  along  the  Wasatch 
Mountains,  shorebirds,  passerines,  rodents,  and 
gallinaceous  birds  were  nearlv  equally  repre- 
sented; whereas  in  the  e\ries  of  the  peregrine, 
shorebirds  predominated  and  gallinaceous  birds 
and  rodents  were  absent  (Table  5).  The  ducks 
present  in  the  eyri(«i  of  the  Prairie  Falcon  (Table 
5)    were  about  half  grown  and  probably  inca- 


pable ot  (light.  Hence,  the\  probabK  were  either 
captured  on  the  water  or  on  the  ground  and 
were  sufficiently  light  in  weight  that  thev  could 
be  carried  hv  the  falcons. 

We  have  no  data  for  comparison  of  the  food 
habits  of  the  peregrines  nesting  in  the  desert 
(Table  6)  with  those  of  desert-nesting  Prairie 
Falcons  in  the  same  region.  A  comparison  of 
this  kind  is  needed  to  fulh'  evaluate  the  compe- 
tition for  food  by  the  two  species.  Cade  (1960) 
found  that  the  overlap  in  food  species  of  the 
peregrine  and  Gvrfalcon  were  least  in  the  areas 
of  contact  and  greatest  in  areas  where  ranges 
were  not  s\mpatric.  A  comparison  of  this  kind 
between  the  peregrine  and  Prairie  Falcon  would 
be  difficult  to  make,  since  in  Utah  the  Prairie 
Falcon  occurs  in  the  same  geographic  area  as 
the  peregrine.    Nevertheless,  one  would  expect 


,« 

^ 


F"ig.  39.     Prairie  Falcon  feeding  its  voung  a  downy  avocct    (peregrine   site   7,    alt.    prairie   site   2,   see   Fig.   26). 
Photo  l>v  W.   1.  Erwin  and' IL  I).  Porter,   1948.' 


liroLoc-.iCAL  Sf.hies,  Vol.  18,  No.  1        Pehegrine  Falcon  in  Utah 


55 


less  latluT  than  more  overlap  in  food  habits  in 
areas  of  allopatry  than  in  areas  of  contact.  The 
isolated  jieregrine's  evrie  in  Oregon,  which  was 
situated  far  from  water  (Gabrielson  and  Jcwett, 
1940),  contained  birds  usually  preyed  upon  by 
Prairie  Falcons,  and  an  adult  peregrine  at  an 
eyrie  in  Zion  Canyon  was  observed  by  Grater  to 
carrv  a  squirrel  into  a  crag  (Woodbury  et  al., 
unpubl.  nis). 

In  Utah,  then,  the  Prairie  Falcon  has  a  wider 
versatility  in  taking  prey  species  than  does  the 
peregrine,  which  would  seem  to  lessen  the  com- 
petition between  the  two  species  for  food. 
Hence  the  role  played  by  the  Prairie  Falcon  in 
Utah  is  similar  to  that  of  the  peregrine  in  the 
.\rctic  (Cade,  I960;  White  and  Cade,  1971),  and 
that  played  bv  the  peregrine  in  Utah  is  similar 
to  that  of  the  Gvrfalcon  in  the  Arctic. 

According  to  White  and  Cade  (1971),  there  is 
no  evidence  to  suggest  that  density  of  breeding 
peregrines  is  influenced  in  anv  way  by  availa- 
bilits-  of  food  in  the  Colville  valley  of  Alaska. 
This  generally  is  not  applicable  to  the  peregrine 
in  Utah,  but  in  the  region  surrounding  the 
Great  Salt  Lake  it  is  difficult  to  surmise  how  the 
density  of  tlic  peregrine  could  have  been  limited 
b\-  availabilit\  of  food,  considering  the  super- 
alDundance  of  prey  species  in  the  Great  Salt  Lake 
marshes.  Nevertheless,  extensive  distances  from 
(•\rie  sites  (Table  4)  to  hunting  sites  in  the 
marsh  mav  have  limited  their  density. 

Competition  with  the  Prairie  Falcon  for 
Eyrie  Sites 

Directional  Exposure  Preferences 

In  Utah  the  peregrine's  preference  for  cliffs 
\\ith  northerh^  or  easterly  exposures  (Fig.  16) 
would  tend  to  lessen  the  competition  for  nest- 
ing sites  between  it  and  the  Prairie  Falcon  if  the 
Prairie  Falcon  had  a  preference  for  south-facing 
cliffs  similar  to  that  reported  for  Colorado  and 
Wyoming  by  Enderson  (1964).  We  investigated 
this  hypothesis  by  examining  the  directional  fac- 
ing of  the  49  evrie  sites  of  the  Prairie  Falcon  in 
Utah  for  which  we  had  available  data.  As  shown 
in  Figure  16,  69.4  percent  of  these  evries  faced 
south  and  west  and  30.6  percent  faced  north  and 
east.  This  relationship  was  statistically  signifi- 
cant at  ;)<0.0I  (X'  test;  calculated  X-  vahu07.37, 
1  df).  Conversely.  70.4  percent  of  27  )ieregrine 
evries  in  Utah  faced  north  and  east  and  29.6  per- 
cent faced  south  and  west,  and  this  relationship 
was  significant  at  /><0.05  (X-  test;  calculated  X' 
value,  4.48;  1  df). 

When  the  two  species  nested  in  close  juxta- 
position on  the  same  set  of  cliffs,  as  at  site  7  in 
the    Wasatch    Mountains,    the    Prairie    Falcon 


seemingly  selected  the  sites  more  exposed  to  the 
afternoon  sun  (west-facing  sites)  than  did  the 
peregrine  (see  Histor)'  of  Nesting  at  a  Wasatch 
Mountain  Evrie,  Table  7  and  Fig.  26).  As  a  gen- 
eral iTilc,  the  Prairie  Falcon  eyries  on  the  escarp- 
ment of  the  Wasatch  Mountains  were  situated 
directly  on  the  west  face,  whereas  those  of  the 
peregrine,  as  discussed  previously,  usually  were 
on  cliffs  in  the  side  canyons  with  northerly  or 
easterly  exposures.  For  example,  three  of  the 
Prairie  Falcon  eyries  were  situated  on  west-fac- 
ing cliffs  (see  Figs.  26  and  39-42).  At  each  of 
these  sites,  peregrines  had  been  seen  in  the  side 
canyons,  although  not  always  concurrently  with 
the  nesting  of  the  Prairie  Falcon  (sites  7,  8,  and 
16,  Table  1).  In  1943,  a  Prairie  Falcon  nested  in 
one  of  the  canyons  (near  peregrine  site  16,  Table 
1),  but  at  a  west-facing  site  in  an  easily  accessi- 
ble Red-tailed  Hawk's  nest. 

Morlan  Nelson  (pers.  comm.,  1971)  noted  a 
similar  orientation  between  the  evries  of  the  two 
species  at  the  Ul  site  in  northern  Utah  (site  11, 
Table  1),  where  he  observed  the  two  species  in 
aerial  combat  (Nelson,  1969).  The  peregrine  eyrie 
was  on  a  ledge  facing  east  and  the  Prairie  Fal- 
con evrie  was  in  a  pothole  (cave-like  recess)  in 
the  side  of  the  wt^st-facing  cliff,  less  than  half  a 
mile  away  (1,320  ft;  402  m;  Nelson,  pers.  comm., 
1971).  Potholes  probably  provide  greater  pro- 
tection from  the  hot  afternoon  ra\s  of  the  sun 
than  do  exposed  ledges. 

These  data  suggest  that  both  species  may  se- 
lect eyrie  sites  on  the  basis  of  directional  expo- 
sure to  the  sun,  and  that  such  a  preference  by 
these  two  species  tends  to  lessen  competition  be- 
tween them  for  eyrie  sites.  Nevertheless,  this 
jihenomenon  needs  further  investigation,  both 
in  Utah  and  elsewhere,  since  some  studies  sug- 
gest that  the  Prairie  Falcon  in  some  parts  of  its 
range  selects  evrie  sites  on  the  basis  of  availabil- 
ity of  suitable  cliffs  rather  than  directional  fac- 
ing. For  example,  Leedy  (1972)  investigated  the 
directional  facing  of  49  Prairie  Falcon  eyries  in 
Montana  during  1970  and  1971  and  compared 
them  u'ith  the  directional  facing  of  the  available 
cliffs.  He  found  that  72  percent  of  the  eyries 
faced  south  (33  percent)  or  east  (39  percent),  8 
percent  faced  north,  and  20  ]iercent  faced  west. 
Of  the  45  available  cliffs  in  Leedy 's  study  area, 
71  percent  faced  south  (31  ]icrcent)  or  east  (40 
percent),  7  percent  faced  north,  and  22  percent 
faced  west— a  near  duplication  of  the  directional 
facing  of  tlu>  eyrie  sites.  Similarly,  Tyler  (1923) 
reported  that  most  Prairii'  Falcon  eyries  exam- 
ined by  him  in  southem  California  had  northern 
exposures  because  in  the  region  where  he  made 
his   observations   the  north   ends   of  the   ridges 


56 


BniGiiAM  Young  University  Science  Bulletin 


broke  off  abniptl\'  into  cliffs  that  faced  north. 
Nevcrtliclcss,  a  few  of  his  e\rics  were  on  west- 
facing  cHffs;  one  was  on  an  cast-facing  cliff;  and 
none   were  on   south-facing  cliffs. 

Height  Preference  for  Cliffs  and  Eyrie  Sites 

The  I'rairie  Falcon  in  Utah  ma\'  use  nesting 
sites  of  a  quality  inferior  to  those  normally  used 
bv  the  peregrine  in  Utah.  Judging  from  Bond's 
(1946)  observations,  this  ina\'  be  typical  of  the 
behavior  of  the  two  species  wherever  their  geo- 
graphic ranges  overlap. 

Three  of  nine  Prairie  Falcon  eyries  found  in 
Utah  bv  Porter  and  Erwin  between  1950  and 
1952  were  at  locations  that  were  easily  accessible 
to  both  humans  and  mammalian  predators.  Two 
were  situated  in  potholes,  one  of  which  was  lo- 
cated onh'  30  inches  (76.2  cm)  from  the  base  of 
a  small  sandstone  cliff  and  the  other  was  onh- 
36  inches  (91.4  cm)  from  the  base  and  48  inches 
(121.9  cm)  from  the  top  of  an  outcropping  of 
limestone.  A  third  e\rie  was  located  in  194.3  by 
R.  L.  Porter  and  J.  F.  Poorman  in  an  old  Red- 
tailed  Hawk's  nest  that  was  situated  on  a  small 
pinnacle  of  rock  which  required  no  climbing  to 
reach.  One  found  in  1958  bv  F.  Welch  and  G.  L. 
Richards  was  on  a  large  rock  about  15  feet  (5  m) 
above  the  ground  and  6  feet  (2  m)  below  the  top 
of  the  rock.  It  probablv  could  have  been  reached 
by  a  good  climber  without  the  aid  of  a  rope.  In 
southwestern  Utah  the  Prairie  Falcon  has  nested 
in  a  stick  nest  in  the  top  of  a  20-foot  (6  m )  juni- 
per tree  (Jtmipcnis  sp.  )  (^^'illiams  and  Matteson, 
1948). 

In  Utah  peregrine  evries  were  a  greater  dis- 
tance from  the  base  of  the  cliffs,  on  the  average, 
than  were  those  of  the  Prairie  Falcon.  They  were 
on  higher  cliffs,  on  the  average,  and  the\'  were 
on  relativelv  more  inaccessible  ledges  than  were 
the  eyries  of  their  congener  (Table  3).  Moreover, 
the  peregrine  evries  averaged  a  greater  distance 
below  the  brink  of  the  cliff  (x=  68.6  ft.  21  m; 
range,  2.5-250  ft,  S-76  ni;  n  =  i;3)  than  did  those 
of  the  Prairie  Falcon  (x=  2.5.3  ft,  7.7  ni;  range, 
4-175  ft,  1-53  m;  n  =  41). 

The  average  height  of  the  Prairie  Falcon  e\- 
ries  in  Utah  (64  ft;  20  ni)  was  grc;iter  than  that 
recorded  by  Enderson  (1964)  in  Colorado  and 
Wyoming  (.34.7  ft;  11.1  m),  and  less  than  that  re- 
ported bv  Leedv  (1972)  in  Montana  (80  ft;  24.4 
m).  The  average  cliff  height  of  101.7  feet  (31  m) 
for  the  Prairie  Falcon  in  Utah  is  nearly  twice 
that  recorded  b\'  Enderson  (1964)  for  this  species 
in  Colorado  and  W\-oining,  and  iibout  25  feet 
(7.6  m)  less  than  that  recorded  In  Leedy  (1972) 
in  Montana.  Table  .3.  which  compares  the  heights 
of  cliffs  and  eyrie  sites  ot  the  Prairie  l-'iileon  \\'ith 


those  of  the  peregrine,  illustrates  the  difference 
in  height  preferences  between  the  two  species. 

The  more  marginal  sites,  including  those  on 
the  smaller  or  more  accessible  cliffs  at  sites  such 
as  1,  3,  11,  and  20  (Table  1),  probablv  were  aban- 
doned b\-  the  peregrine  earlier  in  the  century. 
Both  their  sizes  and  locations  made  them  mar- 
ginal sites.  Several  investigators  (Hickey,  1942; 
Ratcliffe,  1962)  have  indicated  that  the  marginal 
sites  were  the  Hrst  to  become  inactive  following 
the  advent  of  earlv  settlers. 

Eyrie  Type  Preferences 

Till'  Piairie  Falcon  uses  a  wider  variety  of 
nesting  situations  than  does  the  peregrine  (see 
Figs.  .39-45).  For  example,  nearly  half  (45.8  per- 
cent) of  72  Prairie  Falcon  nesting  sites  in  Utah 
were  in  potholes  and  crevices  (Figs.  42-44)  in  the 
face  of  a  cliff,  whereas  onlv  a  third  of  them  (31.9 
percent)  were  on  an  open  ledge  of  a  cliff  (Fig. 
39).  An  additional  third  of  the  e\ries  were  in  the 


Fig.  40.  Tlic  Prairie  Falcon  eyrie  that  was  .situattii  on 
.111  old  Common  Haven'.s  {Corvus  corax)  nest  and 
was  later  leelaiined  by  the  raven.  Note  the  ac- 
cumulation of  fecal  material  and  detritus  suggest- 
ing that  the  e\rie  Ii;ul  been  used  by  the  falcons  for 
a  long  period  of  time  (evrie  site  faces  southwest). 
Photo  bv  W.  D.  Porter,  1951. 


Biological  Series,  Vol.  18,  No.  1        Pehecbine  Falcon  in  Utah 


57 


Fig.  41.     Raven'.s  nest  built  upon  prairie  eyrie   (shown 
in  Fig.  40).  Photo  by  R.  D.  Porter,   1951. 

nests  of  other  species  of  raptors  and  Common 
Ravens,  which  suggests  that  these  species  ma}' 
be  beneficial  to  the  Prairie  Falcon  b\'  providing 
additional  nesting  sites.  Table  10  gives  the  kind 
of  nesting  situations  used  bv  Prairie  Falcons  in 
Utah. 

Sometimes  these  competitors  may  preempt 
their  old  nests  from  the  Prairie    Falcon.  An  oc- 


Table  10.  Percentage  use  of  various  categories  of  eyrie 
sites  bv  Prairie  Falcons  in  Utah  ( see  photos  by 
Wolfe, '1928)' 


Kind 
of 
Site 

Usage 
n 

of  eyrie  types 
Percent 

Potholes= 

26 

36.1 

Open  cliff  ledges 
Crevices 

23 

7 

31.9 
9.7 

Stick   nests 

Red-tailed  Hawk's 
on  cliff  face 

16 

7 

22.2 
9.7 

Common  Raven's 
on  cliff  face' 

Tree  nests 

Golden  Eagle's 
on  cliff  face 

5 
2 

1 

6.9 
2.8 

1.4 

Unknown  species 
of   hawk 
Totals 

1 
72 

1.4 
99.9 

'From  unpuliHshed  data  of  authors,  ficldnotcs  of  R.  G.  Bw.  A 
B,  Boyle,  ana  R.  J.  Envin,  and  from  ornithological  literature  for 
the   stale. 

^Five  or  6,9  percent  of  the  eyries  were  in  old  ravens'  nests  lo 
(ated    witliiii    potholes. 

'IncliidinB  the  five  that  were  in  old  ravens'  nests  within  pot 
holes,   a    total  of    10   or   13.8   percent   were   in   old   ravens'   nests. 


currence  of  this  kind  took  place  at  an  eyrie  in 
Weber  County  observed  by  Porter  and  Erwin. 
The  falcons  were  using  an  old  raven's  nest  which 
apparentlv  had  been  occupied  for  many  vears 
bv  falcons,  since  it  was  almost  entirely  buried 
in  excrement  (Fig.  40).  Without  the  old  raven's 
nest  as  a  base,  a  falcon's  eyrie  would  have  been 
impossible.  When  fir'st  located  on  5  June  1950, 
five  fully  grown  young  were  present  in  the  nest. 
The  following  year  the  eyrie  contained  three. 
fresh  eggs  on  7  April.  When  it  was  next  visited 
on  8  Mav,  a  raven  flushed  from  the  eyrie  site, 
exposing  six  raven  eggs  in  a  newlv  constructed 
stick  nest  over  the  old  prairie  eyrie  (Fig.  41).  The 
whereabouts  of  the  previous  tenants  was  not  de- 
termined. 

Peregrines  apparently  were  more  restrictive 
in  the  selection  of  their  eyrie  sites.  They  used 
prcdominantlv  open  ledges  or  shelves  which  usu- 
alh  were  under  an  overhung  portion  of  the  cliff 
(See  Figs.  26-38).  Only  two  Utah  eyries,  to  our 
knowledge,  were  situated  in  potholes  on  the  sides 
of  cliffs  [sites  4  (alternate)  and  23,  Table  1  (See 
Fig.  44].  We  have  no  evidence  of  a  beneficial 
relationship  between  the  peregrine  and  other 
cliff-nesting  species  similar  to  that  previously 
discussed  for  the  Prairie  Falcon. 

Both  species  of  falcon  apparently  prefer  to 
nest  under  overhangs.  Although  our  data  on  the 


>--■<  V 


^5*^ 


Fig.  42.  Prairie  Falcon  eyrie  in  crevice  on  face  of  west- 
facing  cliff.  Peregrines  nested  up  side  canyon  (site 
8,  Table  1 ) .  Much  of  the  wood  in  the  crevice  was 
carried  there  by  wood  rats  ( Neotoma  sp. ) .  Photo 
bv  R.  D.  Porter,  1951. 


58 


Bhicham  Young  Univehsitv  Scmknt  k  Hi'i.letin 


Fig.  43.  .\  cliff  used  alternately  i)y  I'rairie  Falcons  anil  ravens.  Nesting  site  is  situated  in  a  pothole  similar  to  that 
shown  in  I'igure  4(1  Cliff  is  less  than  2  miles  ( 2.6  km )  from  the  peregrine  eyrie  shown  in  Figure  22,  and 
this  cliff  may  also  have  hecn  used  historically  hy  peregrines.   Photo  hx  l\.  J.  Erwin.  August  1972. 


Prairie  Falcon  arc  incomplete  in  thi.s  regard,  all 
but  one  of  36  Prairie  Falcon  eyries  in  Colorado 
and  Wvoming  reported  1)\'  Ender.son  (1964)  were 
directh'  ovcrhinm  li\   a  |iortioii  of  tiie  clifl. 

Size  Preference  for  Nesting  Area 

The  Prairie  I'"alcon  appears  to  he  less  selec- 
tive than  the  peregrine  in  the  size  of  its  nesting 
or  egg-laying  area.  White  (nnpnbl.  data),  for  in- 
stance, ohserved  a  Prairie  I'alcon  nesting  in  a 
pothole  that  was  appart>ntl\  too  small  for  a  large 
family  of  \()inig  because,  Ix'fore  the  vonng  had 
fledged,  all  but  one  were  forced  from  the  c\rie 
to  an  unlimelv  death  on  the  talus  below  (Figs. 
45-46).  This  nest  was  used  for  fi\e  consccutix'c 
years.  The  female  laid  five  eggs  each  vear  and 
each  vear  onl\  one  \ onng  fledged.  The  e\Tie  was 
then  abandoned.  We  have  also,  however,  seen 
prairies  successfulh'  fledge  large  broods  from 
ledges  e(|ual  to  or  smaller  than  the  site  men- 
tioned above. 

The  aforementioned  Prairie  Falcon  e\rie  in 
Weber  Coimt\    that  was  taken  over  b\'  ravens 


liad  a  total,  nesting  area  of  only  about  310  sq 
inches  (2,000  cm'-)  (measured  from  photographs). 
A  Prairie  Falcon  e\rie  in  Box  Elder  Comity, 
found  bv  Erwin,  was  in  a  crevice  in  the  face  of 
a  cliff  wiiich  was  onlv  20  inches  (51  cm)  wide  at 
the  point  whcr(>  the  eggs  were  laid.  The  crc\'ice 
was  over  80  inches  in  depth  (ca.  200  cm)  and 
nearlx  high  enough  for  a  man  to  stand  in  (mea- 
sured from  a  photograph). 

In  the  Wasatch  Mountains,  peregrines  usual- 
ly laid  their  eggs  on  wider  ledges  with  a  relative- 
Iv  more  spacious  nesting  area  (fref|uentl\'  with 
grass  on  them)  than  did  the  Prairie  I'alcon.  The 
area  and  or  volume  available  for  nesting  on  open 
ledges  and  \\  ithin  potholes  used  as  evrie  sites  in 
Utah  are  gi\en  in  Tables  9  and  11.  The  average 
available  nesting  area  for  peregrine  e\ries  in 
Utah  is  uearK'  tvvice  that  of  prairie  cvries  (Table 
II). 

The  wider  variabilit\'  in  size  and  height  of  the 
Prairie  Falcon's  nesting  siti's  would  appear  to  be 
advantageous  to  the  Piairie  Falcon  in  its  eom|)e- 
tition  with  the  peregrine.  If  the  better  qualit\- 
sites  were  alread\   utilized,  one  of  lesser  qualitv. 


BiOLOcic.\L  Series,  Vol.  18,  No.  1       Peregrine  F.\lcon  in  Utah 


59 


Table  11.     Size  of  area  available  for  nesting  at  Prairie  and  Peregrine  Falcon  eyrie  sites  in  Utah." 


Types  of  sites 
and 

PRAIRIE  FALCONS 

PEREGRINE 

FALCONS 

units  of  measure 

n 

X 

range 

n 

X 

range 

POTHOLE  SITES 

Avail,  nest,  area 

sq  feet 

5 

11.6 

8.0  -18.8 

- 

— 

—     — 

sq  meters 

5 

1.1 

0.74-  1.7 

- 

— 

—     — 

N'olume  of  potholes 

cubic  feet 

4 

20.2 

9.0  -43.7 

- 

— 

—     ■ — 

cubic  meters 

4 

0.6 

0.3  -  1.2 

- 

— 

—     — 

LEDGE  AND  POTHOLE 

SITES,  combined 

sq  feet 
sq  meters 

8= 

16.3 

2.2  -38.8 

7' 

27.8 

10.0-52.0 

8' 

1.5 

0.2  -  3.6 

7' 

2.6 

0.9-  4.8 

kI   R,    J     Envii 


'Data   were  collected  between   1943  and   1972  by  R.   D.    Porter,   C     .M     While 
peregrine  eyrie  site  7. 

^Two  of  the  eyrie  sites  were  alternate  sites  at  site  7   (Table  1);  one  was  used  in  common  with  peregrines. 

^Data    are    from    toiu    different    eyrie    sites,    including    tliree    alternate  eyrie  sites  at   site   7    (Table   1.   figs.   2(i-VI 


r.ilile   8    for   nuiie   detailed    data    on 


and  possibly  not  suitable  for  peregrines,  could 
be  used,  thus  giving  additional  pairs  of  Prairie 
Falcons  the  opportunity  to  nest.  Prairie  Falcons 
nesting  in  the  more  arid  desert  areas  of  Utah 
frequentlv  use  sites  which  probably  would  not 
be  used  b\'  the  peregrine. 

Aggressive  Interactions  between  Peregrines 
and  Prairie  Falcons 

Nelson's  (1969)  reported  decline  in  active 
peregrine  eyries  around  the  Great  Salt  Lake 
probably  involved  the  use  by  Prairie  Falcons  of 
abandoned  peregrine  evries  (Nelson,  pers.  comm., 
1971),  and  as  mentioned  earlier,  the  peregrine 
also  is  known  to  have  occupied  an  eyrie  which 
earlier  in  the  ccntur\  was  used  by  Prairie  Fal- 
cons (see  White,  1969b). 

No  direct  competition  between  the  two  spe- 
cies for  nt>sting  sitt^  was  recorded  during  the 
\ears  that  the  earlier  mentioned  Wasatch  Moun- 
tain evries  (Table  1,  site  7)  were  under  observa- 
tion by  Porter  and  Erwin,  despite  the  fact 
that  the  e\'rie  sites  were  only  about  300  feet  (91 
111)  apart  (Figs.  22  and  23),  and  that  the  pere- 
grines frequenth-  flew  within  100  yards  (91  m) 
or  so  of  the  prairie's  evrie.  Neither  of  the  eyries 
were  visible  from  the  other  (see  Fig.  22).  White 
and  Cade  (1971)  found  peregrines  and  Gyrfal- 
cons  nesting  on  the  same  cliffs  simultancousb 
and  succc>ssfully.  They  postulated  that  perhaps 
peregrines  and  Gvrfalcons  can  coexist  in  close 
ju.xtaposition  if  their  nests  are  not  visible  to  one 
another  and  if  their  schedules  or  routes  of  going 
to  and  from  their  nests  to  hunt  are  different. 

Other  instances  of  amicable  interspecific  co- 
existence between  the  peregrine  and  the  prairie 
have  been  reported.  Bond  (1946),  for  example, 
tells  of  the  two  species  nesting  peaceably  on!\  a 


few  hundred  feet  apart.  Pettingill  and  Whitney 
(1965)  noted  the  nesting  of  a  pair  of  peregrines 
and  prairies  400  yards  (366  m)  apart  in  South 
Dakota  without  apparent  conflict.  French  (1951) 
found  the  tvvo  species  nesting  200  )ards  (183  m) 
apart,  but  not  in  view  of  each  other.  He  watched 
the  peregrines  attack  the  prairies  at  least  three 
times,  but  only  during  one  of  several  visits  to  the 
eyrie.  It  is  possible  that  his  disturbance  of  the 
prairies  at  their  eyrie  helped  provoke  the  attack 
by  the  peregrines.  Lanner  Falcons  {Falco  biara- 


Fig.  44.  Cliff  in  Great  Basin  desert  (site  23,  Table 
1 ) .  Peregrine  eyrie  was  situated  near  the  horse- 
shoe-shaped depression,  "pothole,"  at  the  center  of 
the  cliff  indicated  by  arrow.  Photo  by  R.  J.  Erwin, 
August   1972. 


60 


HiiiGHAM  Young  Univehsitv  Science  Bulletin 


Fig.  45.  Prairie  Falcon  cvrie  in  pothole  on  side  of 
sandstone  cliff.  Photo  hv  Gar\-  D.  Llovd  and  C.  M. 
White,  1958. 

inicus)  and  peiegiint's  in  Sicily  have  been  re- 
ported b\'  Mel).s  (in  Fischer,  1967)  to  nest  only 
50()  meters  apart  w itli  no  apparent  conflict  chn- 
ing  the  nesting  period. 

On  the  other  hand.  Nelson  (1969)  watched  a 
pair  of  Prairie  Falcons  in  aerial  comliat  witli  a 
pair  of  peregrines  in  Utah  near  the  nesting  site 
of  the  latter  (Tal)le  1,  site  11);  the  two  pairs 
nested  about  one-fourth  mile  (402  m)  apart  (Nel- 
son, pers.  conim.,  1971).  In  discussing  the  aerial 
battles  between  the  two  species.  Nelson  (1969), 
indicated  tliat  the  Prairie  Falcons  seemed  to  win 
them.  Later  in  the  paragraph  he  writes,  "The 
battles  were  not  definite  and  alwaws  ended  in 
sort  of  a  draw,  with  observers  deciding  that  the 
Prairie  Falcons  won."  lie  also  noted  that  al- 
though the  Prairie  Falcons  iiad  command  of  tlie 
air,  when  the  two  species  parted  the\'  returned 
to  their  respective  sites.  Hence,  he  did  not  con- 
sider the  aggression  to  result  in  the  abandon- 
ment of  cvrics  b\-  cither  species.  Webster  (in 
Bcebe  and  Webster.  1964)  gives  a  vivid  account 
of  an  aerial  attack  in  Colorado  bv  a  female  I'rai- 
rie  Falcon  on  a  peregrine  presumabb  cariv  ing 
food  to  its  \oimg  in  which  the  Prairie  Falcon 
roblied  tlie  peregrine  of  its  pre\ .  The  Prairie 
Falcon   nested   nearb\ ,   but   the   location   of    the 


Fig.  46.  Young  Prairie  Falcon  in  pothole  eyrie  illus- 
trated in  Fig.  43.  Plioto  bv  Gary  D.  Lloyd  and 
C.  M.  White,  1958. 

peregrine's  e\rie  was  not  ascertained  b\  the  ob- 
si'i^ver. 

Not  all  encounters  between  the  two  species 
are  won  1)\  Prairie  Falcons.  Ogdcn  (1972) 
sighted  an  adult  female  peregrine  along  the 
Snake  River  of  southwestern  Idaho  on  .31  March 
and  6  April  1972.  Although  unmated,  she  forced 
a  pair  of  Prairie  Falcons  to  abandon  their  estab- 
lished territor\  and  clutch  of  eggs  following 
about  two  weeks  of  conflict  between  the  two 
species  (Ogden,  pers.  comm.,  1972).  The  female 
peregrine  remained  and  defended  the  cliff 
through  the  remainder  of  the  nesting  season  and 
on  several  occasions  she  made  reproductive  over- 
tiues  toward  male  Prairie  Falcons  (ibid.).  Richard 
Fvfe  (pers.  comm.,  1972)  made  an  observation 
similar  to  Ogden's  on  11  April  1972  in  Alberta, 
C^anada.  A  pair  of  Prairie  Falcons  was  well  es- 
tablished and  the  female  was  about  to  la\'  eggs 
in  a  "iiothole"  e\rie  on  a  high  dirt  river  bank  at 
the  time  that  the  female  peregrine  arrived  at 
that  cvrie  on  1 1  April.  The  male  pei-egrine  pre- 
ceded her  arrival  b\  a  few  day.s.  Within  a  mat- 
ter of  hours  on  the  da\-  of  her  arrival,  the  pere- 
grines had  dri\-en  the  prairies  awa\'  and  usurped 
the  i)()th()!c. 

Despite  these  obser\ations  of  conflict,  both 
sjiecies  are  able  to  establish  and  hold  an  e\rie 
site  in  close  proximit\'  to  its  congener.  The  near 
e(|Malit\    in  size  and  strength  betweeti   the  two 


Biological  Series,  \'ol.  18,  No.  I        PERECniNE  Falcon  in  Utah 


61 


species  seems  to  recliKv  their  dominance  over 
each  otlier.  This  is  unlike  the  competition  be- 
tween the  peregrine  and  the  Gvrfalcon  in  the 
.Arctic,  \\here  the  larger  and  stronger  Gyrfal- 
eon,  due  to  its  earlier  nesting  and  superioritv 
to  the  peregrine  in  aerial  combat,  is  able  to  es- 
tablish and  hold  the  most  propitious  nesting 
sites  (Cade,  1960). 

Both  peregrines  and  prairies  mav  use  one 
another's  alternate  nesting  sites,  the  availabilitv 
of  which  ma\'  enable  the  two  species  to  nest 
in  closer  pro.\imit\'  to  each  other  than  would 
two  pairs  of  peregrines  or  t\\-o  pairs  of  Prairie 
Falcons.  Mebs  (in  Fischer,  1967)  reported  a 
similar  relationship  between  the  Lanner  Falcon, 
a  near  ecological  i'(|ui\'alent  of  the  Prairie  Fal- 
con, and  the  peregrine  in  Sicih  .  A  nesting  cavity 
(hole)  under  his  observation  for  three  years  was 
occupied  in  1957  b\  lanners  and  in  1958  and 
1959  b\'  peregrines. 

In  some  instances,  tlu'  Prairie  Falcon  ina\' 
occupy  sites  which  otherwise  would  be  used  bv 
additional  pairs  of  peregrines— as  well  as  the 
reverse— thus  possibh'  limiting  each  other's 
breeding  density. 

Each  species  is  known  to  maintain  distances 
between  exries  in  j^arts  of  its  geographic  range 
not  occupied  b\  the  other  species  which  are 
much  less  than  the  distances  between  their 
evries  along  the  Wasatch  escarpment.  Few  of 
the  distances,  however,  averaged  less  than  the 
distance  between  the  alternate  nesting  sites  used 
b\   the  peregrine  and  Prairie  Falcon  at  site  7. 

Hickev  (1942),  for  example,  mentions  that 
two  pairs  of  peri'griius  nested  only  a  half  mile 
(805  m)  apart  in  Canada,  and  Ratcliff  (1962) 
gives  an  instance  in  Great  Britain  of  four  pairs 
breeding  on  a  mile  (1.6  km)  stretch  of  cliff. 
White  and  Cade  (1971)  found  peregrines  nesting 
a  quarter  of  a  mile  (1.40  km)  apart  in  the  Arctic, 
but  this  was  the  exception,  not  the  rule.  Beebe 
(1960)  noted  fi\e  to  eight  pairs  nesting  on  a 
linear  mile  (1.6  km)  of  cliff  in  the  Queen  Char- 
lotte Islands,  the  highest  density  known  for  the 
peregrine. 

The  highest  Prairie  Falcon  densit\",  to  our 
knowledge,  is  along  the  Snake  River  in  south- 
western Idaho,  where  in  1971  Ogden  (1971) 
found  74  acti\e  nest  locations  along  a  53  mile 
(85.3  km)  stretch  of  river,  for  an  average  of  1.4 
occupied  areas  per  linear  mile  (1.6  km).  The 
e\Tie  sites  averaged  less  than  one  mile  (1.6  km) 
apart  (one  pair/3,771    ft;    1,149  m). 

Date  of  Egg  Laying  as  a  Competitive  Factor 

We  have  observed  in  Utah  that  the  Prairie 
Falcon   generalK'  initiates   egg  la\ing  earlier  in 


the  spring  than  does  the  peregrine,  and  Nelson 
(1969)  also  noted  this  relationship  between  the 
two  species.  In  Utah,  peregrines  have  initiated 
egg  laxing  as  earh  as  22  March  and  as  late  as 
the  second  week  in  May.  We  have  records  of 
Prairie  Falcon  clutches  in  the  Great  Salt  Lake 
area  containing  three  eggs  on  7  April,  four 
eggs  on  10  .'^pril  (R.  L.  Porter  and  J.  F. 
Poonnan,  unpubl.  notes),  and  five  eggs  on  22 
April.  Newly  hatched  young  were  present 
on  13  May;  \oung  capable  of  flight  were  pres- 
ent on  10  June.  A  nest  in  extreme  northern 
Utah  found  by  Erwin  in  1969  contained  fully 
fledged  \oung  on  1  June.  Woodbury  et  al. 
(unpubl.  ms)  recorded  51  sets  of  eggs  from 
Tooele,  Salt  Lake,  and  Utah  counties  collected 
from  3  March  to  15  June  1939.  The  average 
date  of  collection  for  16  of  the  clutches,  for 
\\-hich  sufficient  dates  are  available,  was  20 
April  (range:  3  April-22  May).  This  did  not, 
however,  represent  the  dates  of  the  laying  of 
the  first  eggs.  Wolfe  (1928)  records  complete 
clutches  of  Prairie  Falcon  eggs  in  Utah  from 
5  to  20  April.  The  average  nesting  date  for  36 
records  in  I'tah  Count\'  was  18  April  (range: 
3  March-15  June)  (data  from  Bee  and  Hutch- 
ings,  1942). 

An  earlier  nesting  date  would  give  the 
Prairie  Falcon  first  choice  of  eyrie  sites.  We 
have  yer\'  little  precise  information  for  Utah  on 
the  arrival  dates  of  either  species  at  their  eyrie 
sites,  although  White  has  seen  Prairie  Falcons 
at  cliffs  where  e\rie  sites  were  situated  in 
Februarx'  and  earh  March  and  Porter  has  re- 
corded them  at  a  nesting  cliff  in  the  west  desert 
of  Utah  as  early  as  3  Februar\-  (1953)  (Porter, 
Bushman  and  Behle,  unpubl.  ms).  Wolfe  (1928) 
noted  the  first  appearance'  of  Prairie  Falcons  in 
the  Salt  Lake  Valley  about  the  middle  of 
March,  and  earlier  farther  south.  He  indicated 
that  in  some  of  the  warmer  valleys  many  of  the 
falcons  probabh'  remain  during  the  entire  win- 
ter. Morlan  Nelson  (pers.  comm.,  1971)  has 
seen  this  species  at  its  desert  eyries  in  Utah  the 
year  around.  He  believes  that  only  the  young 
leave  the  area  of  the  nesting  site  (ibid.),  although 
Enderson  (1964)  recorded  the  earliest  arrivals  in 
northern  Colorado  on  22  Februar}-  in  1961  and 
observed  that  most  adults  became  associated 
with  the  cliffs  b\-  mid-March. 

Judging  from  the  observation  of  adult  male 
peregrines  at  exries  the  year  around  in  New 
Mexico  (T.  Smylie,  pers.  comm.,  1971),  it  is 
(|uite  possible  that  peregrines  remain  at  or  near 
some  of  the  Utah  e\ries  the  year  around,  [>ar- 
tieularly  the  desert  sites.  Paul  Newey  (pers. 
comm.,  1952)  observed  peregrines  chasing  his 
l^igeons    near    the    Wasatch    Mountains    during 


62 


BiucHAM  Young  Univehsity  Scieni:k  IUu.i.ktin 


the  last  week  in  January  1950  and  again  on  18 
Februar\  1950.  The  falcons  were  probably 
from  a  nearb\-  eyrie.  The  nesting  cliff  was 
climbed  on  25  February  b\'  R.  D.  and  R.  L. 
Porter,  but  no  falcons  were  seen.  Both  pere- 
grines and  Prairie  Falcons,  howe\c'r,  were  seen 
b\'  4  April. 

Re|)roductive  Potential  as  a  Competitive  Factor 

The  Prairie  Falcon  appears  to  have  a  greater 
reproductive  potential  than  does  the  peregrine. 
This,  however,  among  other  things  such  as  food 
availabilit\-  and  winter  niortalit\'  of  \oung,  may 
be  a  reflection  of  the  greater  vulnerability  of 


the  Prairie  Falcon's  eggs  and  \oung  to  predation 
due  to  its  selection  of  evries  at  sites  which  are 
more  easily  accessible  to  predators.  The  average 
clutch  size  for  the  Prairie  Falcon  is  4.5  for  .55 
completed  clutches  in  Wyoming  and  Colorado 
(I'lnderson.  1964),  4..'3  for  20  nests  in  western 
Montana  (Leeds',  1972),  4.25  for  31  eyries  along 
the  middle  Snake  River  in  Idaho  (Ogden,  1971), 
and  4.35  for  the  65  clutches  from  the  Utah 
e\ries  in  the  present  stud\ .  These  are  compared 
with  an  average  clutch  size  of  3.8  for  peregrines 
in  Utah,  3.7  for  peregrines  elsewhere  in  the 
United  States  (Hickey,  1942;  Bond,  1946),  and 
2.9  for  peregrines  in  northern  Alaska  (Cade, 
1960). 


PLEISTOCENE  AND  PREHISTORIC  PEREGRINE  AND 
PRAIRIE  FALCON  DISTRIBUTIONAL  RELATIONSHIPS 


Although  Nelson's  (1969)  climatic  change 
hypothesis  probabh'  is  not  the  complete  answer 
to  the  recent  reduction  in  active  eyries  in  Utah, 
it  has  a  great  deal  of  merit  on  a  long-term  basis. 
Perhaps  the  peregrine's  present  distribution  in 
Utah  can  be  elucidated  best  bv  an  examination 
of  tlu>  possible  distribution  of  the  peregrine  and 
prairie  falcon  during  prehistoric  and  Pleistocene 
times. 

Pleistocene  Distributional  Records 

Botii  tlu'  peregrine  and  tlie  Prairie  Falcon 
are  known  from  late  Pleistocene  deposits  in 
western  North  America  (Howard,  1962b;  Miller, 
1943).  Hence,  both  species  probabh'  were  pres- 
ent in  Utah  during  the  late  Pleistocene.  White 
and  (>ade  (1971)  suggest  that  the  peregrine 
ma\-  have  originated  in  midlatitude  regions  of 
Ein-asia,  then  spread  northward  into  the  Arctic, 
and  from  there  into  North  America  (White 
1968b).  The  Prairie  Falcon  apparently  evolved 
in  situ  in  western  North  America. 

Both  species  were  ]iresent  in  the  Los  Angeles 
area  of  California  conlem]ioraneousl\'  (Howard, 
1962b)  throughout  much  of  the  late  Pleistocene 
period  covered  by  fossils  found  in  the  La  Brea 
Tar  Pits.  The  fossils  in  tlicse  pits  are  believed 
to  range  from  5.()()()  to  10,000  sears  old  (Berger 
and  Libln-,  1966;  Ho,  .Marcus,  and  Berger,  1969; 
and  Downs  and  .Miller,  1971). 

Pit  16  contained  fossils  of  three  each  of 
both  the  peregrine  and  the  Piairic  I-'aleon.  I'ossil 
wood  from  two  depths,  6'/2  and  12  feet  (2-3. 7m), 
in  this  pit  has  been  dated  back  >  40,000  years 
bv  radiocarbon  dating  (Berger  and  Libbw  1966). 


The  occurrence  of  these  two  species  together 
in  this  and  other  pits  (Howard,  1962b)  suggests 
a  long  association  between  the  two  species. 
Since  there  is,  however,  a  considerable  \aria- 
tion  in  the  ages  of  the  fossils  from  the  various 
pits  and  from  the  various  depths  of  each  pit,  and 
since  the  greatest  depths  have  not  alwax's  yield- 
ed the  oldi'st  fossils  (pit  9,  Berger  and  Libb)', 
1966),  the  exact  age  of  the  peregrine  fossils  is 
not  known.  In  addition,  Howard's  (1962b)  pub- 
lished account  of  the  fossils  present  in  the  vari- 
ous pits  does  not  indicate  the  depths  from  which 
the  fossils  were  obtained  nor  if  the  fossils  of 
the  two  species  discussed  here  intermixed  with- 
in the  same  depth.  Therefore,  a  more  definitive 
interpretation  regarding  the  duration  of  a  s\m- 
patric  association  between  the  two  species  and 
the  age  of  their  fossil  remains  must  await  car- 
bon dating  of  the  actual  peregrine  and  Pniirie 
Falcon  fossils. 

Additional  speeiinens  of  tlie  Prairie  Falcon 
from  Pleistocene  deposits  are  known  from  Smith 
Creek  Cave  in  Nevada  (Howard,  1952),  from 
Rock\-  Arro\()  (Wetmore,  1932)  and  Howell's 
Ridge  C;ave  (Howard,  1962a)  in  New  Mexico, 
from  Lubbock  Reservoir  in  Texas  (Brodkorb, 
1964),  and  from  Nuevo  Leon  in  Mexico  (Miller, 
194.3).  Specimens  of  the  peregrine  also  have  been 
found  at  Potter  Creek  Cave  and  at  McKittrick 
in  California  (Miller,  1911  and  1927).  Shelter 
Cave  in  New  Mexico  (Howard  and  Miller.  1933), 
and  at  American  Falls  in  Idaho  (Brodkorb.  1963). 
Vertebrate  fossils  from  the  late  Pleistocene 
American  Falls  bed  B,  wlu're  this  latter  speci- 
men apparently  originated,  have  been  dated  as 
having  an  age  greater  than  29,700  B.  P.  (ibid.). 


Biological  Series,  Vol.  LS,  No.  1        Peregrine  Falcon  in  Utah 


63 


Post-Pleistocene  Distributional  Records 

The  Prairif  Falcon  was  distributed  widely 
durinc;  prehistoric  times.  It  is  known  from  Ore- 
gon (Miller,  1957;  <S,000  B.  P.),  California 
[(Howard,  1929;  ^^l.OOO  B.  P.)  and  (DcMav, 
1942;  ^500  B.  P.)],  Arizona  (Miller,  1932;  1,000 
A.  D.),  and  Utah  [(Harper  and  Alder,  in  press; 
^8,500  B.  P.)  and  (Steward,  1937;  remains  not 
dated,  but  probabh-  very  recent)].  The  pere- 
grine, on  the  other  hand,  has  been  found,  to  our 
knowledge,  only  at  prehistoric  sites  in  California 
(Howard,  1929;'  ==^1,000  B.  P.)  and  Utah  (Stew- 
ard, 19.37;  remains  not  dated,  but  one  of  the  two 
specimens  probably  was  very  recent;  the  other 
may  haye  been  somewhat  older;  one  apparently 
was  within  strata  containing  artifacts  of  the 
Promontor\'  culture). 

These  records  suggest  that  both  species  were 
rather  wideh'  distributed  geographically  during 
the  late  Pleistocene,  and  that  the  peregrine  prob- 
abh' was  more  common  then  than  now;  but  fol- 
lowing the  Pleistocene  period,  the  relative  dis- 
tribution and  abundance  of  the  two  species 
probabh  were  much  the  same  as  the\-  have  been 
historically. 

Lake  Bonneville  and  Peregrine  Distribution 
in  Utah 

Ancient  Lake  Bonneville  was  formed  during 
the  thrusts  of  the  most  recent  Pleistocene  gla- 
ciers some  60,000  to  70,000  \ears  ago  (Black- 
welder,  1948,  and  Autevs,  1948).  At  its  greatest 
height  (the  Bonneville  level),  this  lake  covered 
19,750  sq  miles  (51,153  knv')  of  Utah's  Great 
Basin  (Antevs,  1948)  and  had  a  shoreline  of  2,550 
miles  (4,103  km)  (Fenneman,  1931).  After  stand- 
ing at  the  Bonneville  level  for  a  long  period  of 
time,  it  is  believed  to  have  receded  below  the 
present  level  of  the  Great  Salt  Lake  ( Marsell 
in  Diirrant.  1952).  Then,  some  25,000  \'ears  ago 
during  the  Provo  pluvial  it  rose  to  the  Provo 
level  [Lake  Provo,  13,000  mi=  (.3.3,670  km^ 
area,  Antevs  (1948)].  It  then  receded  (Antevs, 
ibid.;  Marsell,  op.  cit.)  after  which  it  again  filled 
back  up  to  the  Prove  level  (Marsell,  op.  cit.).  In 
the  last  12,000  years  it  receded  to  the  present 
level  (op.  cit.). 

A  warmer  interval  of  some  4,000  years  began 
about  5,550-4,000  years  B.  C.  (Blackwelder, 
1948).  at  which  time  the  lake  receded  to  a  level 
below  that  of  the  Great  Salt  Lake,  with  average 
temperatures  distinctly  higher  than  those  of  the 
present  (Antevs,  1948;  Blackwelder,  1948).  Be- 
ginning about  2, .500  years  ago,  a  reduction  in 
mean  temperatures  and  evaporation  caused  an 


expansion  of  the  lake  to  its  historic  levels  (An- 
tevs, 1948). 

The  present  environmental  conditions  in  the 
Arctic  ina\  be  near  optimal  for  the  pere- 
grine, judging  from  its  recent  distribution  and 
population  density  there.  Climatic  conditions  in 
Utah  during  the  late  Pleistocene  glacial  periods 
probably  were  much  less  arid  than  at  present  and 
consequently  closer  to  those  presently  occurring 
in  the  Arctic.  According  to  Blackwelder  (1948), 
temperatures  in  the  Great  Basin  during  the  cold- 
est ages  probably  were  8-12°  F  below  the  long- 
term  average,  and  the  rate  of  evaporation  was 
much  slower  than  at  present.  The  extent  of  the 
ecological  changes  that  took  place  in  the  south- 
em  part  of  the  Great  Basin  during  the  latest 
glacial  age  are  revealed  in  the  dung  of  extinct 
ground  sloths  found  in  G\  psum  Cave  of  south- 
em  Nevada  (Laudermilk  and  Munz,  193.5).  The 
dung  contained  species  of  plants  which  now  oc- 
cur 3,000  feet  (914  m)  higher  in  the  mountain 
ranges  some  20  miles  (.32.2  km)  awa\'. 

Recent  data  collected  by  Harper  and  Alder 
(in  press)  from  an  anthropological  site  in  north- 
ern Utah,  although  agreeing  in  the  sequence  of 
events,  indicate  that  the  date  of  the  actual  onset 
and  termination  of  these  jieriods  ma\'  be  in  er- 
ror as  might  the  extent  of  temperature  change. 
At  Hogup  Cave,  which  is  located  just  north  of 
the  Great  Salt  Lake,  Harper  and  Alder  (in  press) 
found  that  all  but  one  of  the  plant  species  that 
were  present  in  the  14  feet  of  deposit  dating 
back  8,500  years  presently  occur  within  40 
miles  (64  km)  of  the  cave.  During  this  period, 
the  upland  areas  were  dominated  by  a  xeric 
desert  shrub  community,  although  the  first  500 
years  were  somewhat  more  mesic  in  nature. 
They  (ibid.)  found  that  the  lowlands  had  under- 
gone a  greater  degree  of  change  than  had  the 
uplands,  as  suggested  b\'  both  plant  and  animal 
remains  in  the  deposits.  From  about  7,800  B.  P. 
to  2,500  years  B.  P.  (except  for  a  brief  period 
about  6,000  years  B.  P.),  the  temperature  in- 
creased at  least  1°  C  and  the  open  water  and 
marshlands  decreased.  Then  some  1,500  years 
ago  and  continuing  for  about  a  milleniuin,  there 
was  a  relative  increase  in  grasses  on  the  uplands 
[suggesting  an  increase  in  rainfall].  Haq^er  and 
Alder  (ibid.)  believe  that  the  last  .500  years  were 
more  arid  and  that  the  climate  around  the  cave 
became  as  dry  and  inhospitable  as  at  an\'time 
during  the  past  8,.500  years. 

Historically,  with  the  utilization  for  irrigation 
of  the  river  waters  which  support  the  Great 
Salt  Lake  and  a  general  increase  in  mean  tem- 
peratures and  decrease  in  precipitation  during 
the  past  several  decades,  as  was  discussed  ear- 


64 


Bhigham  Young  Univehsitv  Science  Bulletin 


lier,  the  Groat  Salt  Lake  reached  its  minimum 
level  for  historic  times  in  about  1961.  Since  then 
it  now  has  risen  about  seven  feet  ( 2. 1  m )  above 
its  historic  low. 

The  climate  and  ecological  conditions  pres- 
ent during  the  past  8,500  years  would  not  seem 
to  have  been  sufficienth'  arid  to  have  eliminated 
c()ni]iletelv  the  peregrine  as  a  breeding  bird  in 
the  area  surrounding  the  Great  Salt  Lake.  This 
is  especialK'  so  if  one  considers  the  apparent 
extent  of  the  aridity  during  the  past  500  years 
and  the  persistence  of  the  peregrine  as  a  breed- 
ing bird  in  Utah  despite  the  dr\'  harsh  climate  of 
the  past  half  centur\-. 

The  occurrence  of  the  Prairie  Falcon  at  the 
oldest  level  (at  least  8,350  years  B.  P.).  along 
with  numerous  remains  of  nine  species  of  water 
birds,  at  a  time  when  ecological  conditions 
probabh'  were  more  optimal  for  the  peregrine 
than  at  j^resent,  would  suggest  that  the  region 
surrounding  the  Great  Salt  Lake  was  even  at 
that  time  an  area  of  s\nipatr\"  for  these  two 
species.  The  presence  of  both  species  in  Black 
Rock  Cave,  south  of  Great  Salt  Lake  (Steward, 
1937),  gives  credence  to  this  h\pothesis. 

The  date  of  the  first  occurrence  of  the  pere- 
grine in  the  intermountain  area,  of  course,  is  not 
known,  but  one  can  speculate  that  it  ap]5eared 
during  one  of  the  pluvial  periods  when  the  en- 
vironmental conditions  were  most  propitious 
for  its  sur\ival  and  for  its  competition  with  the 
Prairie  Falcon   tor  food  and  ncstin<r  sites. 

It  is  probable  that  it  \\as  present  in  Utah  dur- 
ing the  late  Pleistocene,  contemporaneoush' 
\\ith  its  occurrence  at  Rancho  La  Brea.  The 
presence  of  this  species  among  fossils  at  the 
.Xmcrican  Falls  bed  B,  dating  back  at  least 
29,7(K)  \t'ars,  tends  to  confirm  this  supposition. 

During  the  Bonneville  and  Provo  pluvials. 
Lakes  Bonneville  and  Provo,  with  their  extensixc 
shorelines  and  numerous  islands,  must  have  pro- 
vided innumerable  nesting  sites,  an  abundance 
of  pre\'  species,  and  a  near  optimal  climate  for 
the  peregrine.  Pleistocene  rivers  and  smaller 
lakes  also  must  have  provided  correlative  con- 
ditions which  ma\'  account  for  e\ries  in  areas 
outside  of  Bonneville  Basin. 

If  the  ])eregrine  was  present  during  the  Bon- 
neville and  Pro\-o  inlerpkn  iais,  it  nia\  have  en- 
countered environmental  conditions  of  even 
greater  aridity  than  at  present.  It  would  be  of 
interest  to  know  if  peregrine  evries  were  main- 
tained during  these  pi-riods  of  extrenie  ariditv  or 
if,  as  suggested  b\-  Nelson  (1969)  for  |iresent 
conditions,  altitudinal  and  latitudinal  adjust- 
ments were  made.  If  the  latter  were  true  then 


the  evries  became  reactivated  when  the  lake 
gradually  increased  again  to  its  maximum  his- 
toric level. 

The  overlap  between  the  breeding  distribu- 
tion of  the  Prairie  Falcon  and  peregrint'  in  the 
intermountain  area  during  the  cooler,  wetter  plu- 
vial period  was  probabh'  dominated  bv  the  pere- 
grine, but  as  the  climate  slowh-  ameliorated, 
populations  of  the  Prairie  Falcon  likely  increased 
in  densit\'  and  gradualK-  extended  northward, 
probably  at  the  expense  of  the  peregrine.  As  the 
environmental  conditions  became  more  arid,  the 
peregrine  eyries  that  were  near  lakes  or  streams 
where  sufficient  food  was  available  ma\'  have 
remained  active.  Those  where  the  water  disap- 
peared probabh'  either  were  taken  over  bv  the 
better  adapted  Prairie  Falcon  or  else  were  de- 
serted. Peregrines  at  the  active  e\ries  may  have 
gradually  adapted  to  the  increasing  aridity,  but 
thev  would  have  been  able  to  compete  with  the 
Prairie  Falcon  onl\-  at  sites  where  water  was 
a\'ailable.  This  hypothesis  seems  to  be  supj^ortcd 
bN'  the  geographical  and  ecological  distribution 
of  the  peregrine  in  Utah  during  historic  times 
(Fig.  1).  For  instance,  of  the  40  known  and 
suspected  e\ries  in  Utah,  26  were  located  in  or 
near  the  Bonneville  Basin.  The  greatest  con- 
cenh'ations  of  breeding  pairs  occurred  near  the 
largest  remaining  bodies  of  water,  jiarticularlv 
in  the  area  surrounding  the  Utah  and  Great  Salt 
lakes. 

The  e\ries  in  the  harsh  en\ironment  of  the 
Great  Salt  Lake  Desert  were  adjacent  to  small 
expanses  of  marsh  (Figs.  20  and  23).  Most 
astounding  is  that  these  evries  existed  at  all, 
considering  the  harsh  nature  of  the  einironment. 
It  is  c\idence  of  the  adaptabilit\  of  the  species 
and  of  tlu'  species'  tenacit\-  at  its  c\ric  sites. 
How  long  these  e\ries  would  have  remained  ac- 
ti\c  in  the  absence  of  human  interference  is  a 
(jucstion  that  ma\'  never  be  answered.  The  te- 
nacit\  of  peregrines  at  their  e\rie  sites  as  dis- 
cuss('(l  hx  Cade  (1960)  and  Hiekey  (1942),  and 
the  t(  lulcncN'  toward  a  genetic  contiinu't\  in  ey- 
rie maintenance  as  proposed  bv  White  (1969a) 
(for  a  nioic  complete  discussion,  see  White, 
196Sb)  woultl  suggest  the  possibilitx  that  some  of 
tlu>  i-\  rie  sites  that  were  acti\c'  during  recent 
times  nia\'  ha\'e  had  long  histories  of  activity 
sonu'  perhaps,  (>ven  extended  back  into  Lak(> 
Honne\ille  tim(>s.  This  possibilitx  seems  especial- 
In'  plausible  when  one  considers  the  relative  re- 
ei'ne\'  of  some  of  the  later  pluvial  periods.  Thus, 
tlie  relationship  between  tlii'  Prairie  Falcon  and 
peregrine  |in)babK  extends  back  maTi\'  thou- 
sands ot  years,  which  ma\  be  a  factor  in  the 
relati\"i-  compatibilitN    of  the  two  species. 


Biological  Sebies,  Vor..  18,  No.  1        Peheghine  Falcxjn  in  Utah 


65 


Data  piivsentcd  pre\iousl\'  regarding  the  coii- 
temporaneit\'  of  the  two  species  at  Rancho  La 
Brea;  tlie  occiirrenci'  of  the  peri'grine  in  a  lossil 
bed  at  American  Falls.  Idalio,  dating  back  to  at 
least  29,700  \ears  B.  P.  (Brodkorb^  1963);  tiie 
presence  of  both  species  at  anthropological  sites 
just  south  of  the  Great  Salt  Lake  (Steward.  1937; 
Black  Hock  C^avc);  and  the  climatic  and  environ- 
mental evidences  from  Hogup  Ca\e  in  northern 
Utah  ( Harper  and  Alder,  in  press )  tend  to  coi- 
roborate  this  supposition.  The  lack  of  aggression 


between   them   also  suggests   a   long  sympatric 
relationship. 

White  and  Cade  (1971)  believe  that  tradi- 
tional use  of  an  eyrie  site  will  in  the  long  run 
reduce  the  total  impact  of  intolerant  behavior 
and  promote  stability  in  the  peregrine  popula- 
tions of  the  Arctic.  If  so,  a  long  history  of  oc- 
cupancN'  at  Utah  evries  probablv  would  have  en- 
hanced the  peregrine's  competitive  position  with 
the  Prairie  Falcon  and  thus  strengthened  the 
peregrine's  hold  on  its  oj^timal  e\rie  sites. 


SUMMARY  AND  CONCLUSIONS 


Utah's  rugged  topograph)'  and  ecological 
variabilitv  is  conducive  to  its  inhabitation  by  a 
wide  varietx'  of  raptorial  species.  This  includes 
the  Peregrine  Falcon,  which  now  has  \irtuallv 
disappeared  as  a  breeding  bird  in  the  state. 

Although  sparselv  distributed  throughout 
Utah,  the  species  apparentlv  found  conditions 
especialh'  suitalile  for  nesting  in  the  environs  of 
the  Great  Salt  Lake  and  Utali  Lake  valle\s, 
where  its  nesting  sites  in  the  adjacent  mountains 
were  within  fhing  distance  of  a  plentitude  of 
preferred  pre\'  species  which  inhabited  the 
marshes  and  shorelines  surroundin<?  the  two 
lakes.  Despite  the  aridity  of  the  environment,  the 
20  eyries  that  occurred  there,  when  and  if  thc\ 
all  were  active  simultaneously,  comprised  a  pop- 
ulation comparable  to  some  populations  else- 
where in  North  America  where  the  environment 
is  considered  to  be  uKjre  congenial  to  the  pere- 
grine. On  the  average,  there  was  one  evrie  site 
for  ever\"  225  stj  miles  (583  km-)  in  an  area  of 
about  4,500  sq  miles  (11,655  km-)  surrounding 
the  Utah  and  Great  Salt  lakes.  The  average  dis- 
tance between  13  evries  along  130  linear  miles 
(209  km)  of  the  Wasatch  Mountains  was  10.0 
miles  (16.1  km)  (range.  2-20  mi;  3.2-32.2  km). 

Elsewhere  in  the  state,  the  species  was  more 
sparseb'  distributed,  and  then  onlv  at  sites  where 
suitable  nesting  cliffs  were  adjacent  to  marshes 
or  rivers.  OnK'  nine  additional  eyries  have  been 
verified  for  the  remainder  of  the  state  [one  pair 
per  7.732  mi-  (20,025  km-)  in  area,  exclusive  of 
the  aforementioned  4,500  mi'},  although  11 
others  are  suggested  bv  the  presence  of  adult 
birds  and /or  voung  during  the  nesting  season. 
If  all  40  known  and  suspected  evries  are  in- 
cluded, there  would  be  about  one  c\  rie  for 
every  2,12.3  s(i  miles  (.'^.499  km  ).  If  1 1  unverifii'd 
evries  are  excluded,  there  woiild  be  about  one 
evrie  for  c\-erv  2.928  s(|  miles  (7.584  km'-')  of  the 
state. 


Peregrines  have  reproduced  successfidh'  in 
the  deserts  of  Utah's  Great  Basin  and  Colorado 
Plateau  under  some  of  the  harshest  climatic 
conditions  to  which  the  species  is  subjected.  All 
evries  in  Utah's  deserts  have  been  situated  near 
marshes,  lakes,  or  rivers.  Peregrine  nesting  sites 
in  the  desert  generallv  were  closer  to  extensive 
marshes  than  were  those  along  the  Wasatch 
escarpment.  The  average  distance  from  evrie  to 
hunting  sites  in  the  marshes  was  onlv  1.3  miles 
(2,1  km)  (range,  0.19-2.8  mi;  0.31-4.5  km)  for 
three  desert  e\ries.  For  the  nesting  sites  in  the 
region  of  the  Utah  and  Great  Salt  lakes,  the  dis- 
tances averaged  3.3  miles  (5.3  km)  (0.19-9.7  mi; 
0.31-15.6  km).  Marshes  used  bv  peregrines  at 
the  desert  e\  rics  usualK  were  less  than  3  sq 
miles  (7,8  km-)  in  extent  (Table  4). 

Although  the  Peregrine  Falcon  has  been 
known  to  occur  in  LUah  since  the  earh'  1870s. 
most  of  our  knowledge  of  its  nesting  distribution 
and  abtmdance  dates  back  onlv  three  or  four 
decades.  The  status  of  the  species  in  Utah  prior 
to  the  late  1930s  is  largely  unknown.  Its  past 
historv  and  present  status  in  LTtah,  therefore, 
has  been  postulated  on  the  basis  of  all  records 
available  to  us.  both  before  and  after  19.39.  Data 
are  too  sketchv  for  a  thorough  understanding  of 
the  kinetics  of  local  populations.  E\ries  that 
siu"\'ived  the  longi'st  arc  those  farthest  from 
areas  of  intensive  agricultural  practices  and  al- 
so dense  human  populations.  Those  at  the  poor- 
est qualit\'  sites  appeared  to  have  been  desert- 
ed first.  Abandonment  of  active  e\ries  first  be- 
came apiiarent  in  the  1940s.  The  known  breed- 
ing ]50]-)ulation  in  Utah  was  reduced  bv  the  late 
1960s  to  less  than  10  percent  of  the  pre-1940 
estimates. 

The  several  factors,  in  order  of  relative  im- 
portance, that  may  have  contributed  to  these 
changes  are  as  follows:  (1)  the  inimical  effects 
of  DDT,  its  metabolites,  and  other  chlorinated 


66 


Bricham  Young  University  Science  Bulletin 


hydrocarboiis  on  percgiiiu'  reproduction;  (2)  a 
drying  up  of  marshes  which  supported  the  pere- 
grine's prey  species,  due  to  a  decline  in  annual 
precipitation;  an  increase  in  the  average  dail\' 
temperatures;  and  the  diverting  of  river  waters 
for  irrigation  purposes;  (3)  the  killing  of  adult 
and  young  falcons  with  firearms;  (4)  the  death 
of  peregrines  due  to  botulism  toxins;  (5)  the 
robbing  of  e\ries  for  their  eggs  or  \oung;  and 
(6)  the  destruction  of  nesting  cliffs  for  mining 
and  construction  operations  and  general  human 
encroachment. 

Reproductive  failure  t\pical  of  the  pesticide 
syndrome  was  recorded  at  three  peregrine  eyries 
and  one  Prairie  Falcon  eyrie  in  Utah  during  the 
period  following  the  extensive  use  of  DDT  to 
control  mosquitoes  and  agricultural  pests  in  Utah 
and  elsewhere.  All  of  these  factors  combined 
probably  have  contributed  to  the  near  extirpa- 
tion of  the  peregrine  in  Utah,  although  the  use 
of  organochlorine  pesticides  probabh'  was  the 
most  important  contributory  factor,  especialh' 
when  combined  with  a  prolonged  drought  which 
occurred  during  the  first  half  of  the  centur\'. 

The  average  clutch  size  at  one  peregrine 
eyrie  site  in  Utah  for  five  \ears  betAveen  1943 
and  1952  was  3.8,  and  an  average  of  2.4  voung 
hatched  during  these  vears;  and  for  seven  vears 
between  1943  and  1953  a  total  of  19  voung  were 
produced  for  an  average  of  2.7  voung  per  vear. 
This  is  in  close  agreement  with  figures  recorded 
at  other  e\rie  sites  in  North  America  at  an 
erjuivalent  latitude.  The  incubation  period  at 
the  aforementioned  e\rie  site  was  estimated  to 
exceed  the  28  to  29  davs  reported  elsewhere  bv 
four  or  fi\-e  da\s.  An  unusualK'  long  incubation 
period  of  about  40  daws  in  1948  was  explained 
on  the  basis  of  rencsting,  if  based  on  a  28-  to 
29-da\   incubation  period. 

Nestling  peregrines  in  Utah  were  given  a 
wide  variety  of  avian  prev  species.  Pairs  nest- 
ing along  the  Wasatch  Mountains  (near  thv 
Great  Salt  Lake)  fed  their  \oung  mosth-  shore- 
aiid  marshbirds,  man\-  of  w  hich  were  obtainable 
onI\'  from  Great  Salt  Lake  marshes  up  to  17 
miles  (27.4  km)  distant.  Avocets  and  Willets  were 
the  species  of  shorebirds  most  used.  Mourning 
Doves,  Rock  Doves,  Red-shafted  Flickers,  and 
Western  Meadowlarks  were  most  used  of  the 
nonatjuatic  prey  species.  Rats,  uhieh  were  the 
only  mammalian  prey  species  present  in  ITtah 
evries,  represented  less  than  one  percent  of  the 
diet.  Passerine  and  gallinaeeous  pre\-  species 
were  of  greater  importance  and  a(|uatic  pre\' 
species  of  lesser  importance  in  the  desert  e\ries. 
The  selection  of  eyrie  sites  hv  peregrines  in  Utah 
appears  to  be  associated  with  the  ;ivailabilitv  of 


suitable  nesting  sites  adjacent  to  a  marsh  or 
stream  where  prey  species  are  available  in  ade- 
(juate  numbers.  Tlie  utilization  of  aijuatic  prey 
species  as  food  for  nestling  peregrines  in  Utah 
undoubtedl)-  is  a  major  factor  in  the  species's 
proclivit)-   for   nesting  sites   near  water. 

The  Golden  Eagle  and  Prairie  Falcon  are  the 
two  species  most  likely  to  compete  with  the 
peregrine  for  food  and  nesting  sites.  Direct  com- 
petition between  the  peregrine  and  Golden 
Eagle  for  food  probablv  is  minimal,  since  mam- 
malian prey  species  contribute  greath'  to  the 
eagle's  diet,  and  no  direct  evidence  of  compe- 
tition between  the  two  species  for  nesting  sites 
has  been  observed  in  Utah. 

The  Prairie  Falcon,  on  the  other  hand,  is  a 
probable  competitor,  which  is  expected  because 
both  species  belong  to  the  same  genus,  both  are 
basically  equivalent  in  ecological  function,  and 
both  are  approximately  ecjual  in  size  and 
strength.  Although  the  habitat  of  the  two  species 
overlaps,  habitat  separations  are  present.  The 
Prairie  Falcon,  for  example,  may  nt>st  in  the  des- 
ert many  miles  from  water.  In  the  zone  of  con- 
tact between  the  two  species,  its  selectivit\'  in 
habitat  and  food  encompasses  and  exceeds  that 
of  the  peregrine.  The  zone  of  contact  between 
the  two  species  appears  to  be  restricted  onl\'  bv 
the  paucit\-  of  suitable  nesting  habitat  adjacent 
to  an  adequate  supply  of  food  for  the  peregrine. 

Where  the\-  occup\-  the  same  habitat  their 
diets  are  somewhat  different,  thus  mitigating 
the  possibility  of  strong  competition  for  food,  al- 
though where  they  nested  side  bv  side  in  the 
Great  Salt  Lake  Valley  their  food  niches  did 
overlap  considerabh-.  Both  species  preved  rather 
extensivcK-  on  the  same  two  |)re\'  species,  the 
avocet  and  Willet,  which  probably  was  a  re- 
sponse to  the  abundance  of  these  two  shorebirds. 
In  general,  the  Prairie  Falcon  was  much  less 
selective  in  its  food  requirements  in  the  area 
surrounding  the  Great  Salt  Lake  than  was  the 
peregrine  in  the  same  area,  and  it  was  more 
prone  to  supph-ment  its  diet  with  rodents, 
ground  nesting  birds,  and  reptiles.  Thus,  in  this 
respect,  it  ap(X'ared  to  have  an  adaptive  ad- 
vantage over  the  peregrine. 

Competition  between  the  two  species  for 
food  did  not  appear  to  ha\e  been  an  important 
factor  in  controlling  their  relative  densities 
along  the  escarpment  of  the  Wasatch  Mountains, 
especialK  when  pojiulations  of  avocets,  Willets, 
and  other  s|X'cies  of  shorebirds  were  sufficiently 
large  to  support  them  both. 

We  have  no  data  regarding  the  food  niches 
of  the  IVairie  Falcon  in  the  zones  of  contact 
between    the    two    species    at    riviT   sites    in    the 


Biological  Series,  Vol.  18,  No.  1        1'ereghine  Falcon  in  Utah 


67 


desert.  However,  we  would  expect  a  greater 
overlap  in  the  avian  prey  of  the  food  niches  of 
the  two  species  in  these  areas  due  to  the  ehmina- 
tion  of  a  great  portion  of  aquatic  birds  from  the 
diet  of  the  peregrine  (see  Gabrielson  and  Jewett, 
1940).  Our  data,  however,  suggest  that  the  ex- 
tensi\'e  utilization  of  rodents,  particulail\'  ground 
squirrels  {Citcllus  sp.),  by  the  Prairie  Fakvn  in 
the  desert  areas  would  tend  to  k'ssen  the  im- 
pact of  the  competition  between  the  two  con- 
geners for  a\ian  pre\   in  those  regions. 

In  regions  of  Utah  where  the  populations  of 
the  peregrine  were  greatest,  pairs  of  Prairie  Fal- 
cons and  peregrines  ne'sted  much  closer  together 
than  did  pairs  of  peregrines  or  pairs  of  prairies. 
Tlie  two  species  sometimes  e\'en  used  one 
another's  alternate  nesting  sites.  When  they  nest- 
ed close  together,  their  nesting  sites  were  not 
known  to  be  visible  from  one  another.  Although 
thev  were  observed  in  aerial  combat,  neither 
species  appeared  to  be  able  to  consistently  dis- 
lodge its  congener  from  its  nesting  site. 

Our  data  suggest  that  both  species  select 
e\Tie  sites  on  the  basis  of  availabilit\',  but  when 
given  a  clioice  thev  seemingly  select  them  on  the 
basis  of  directional  exposure  to  the  sun.  The 
peregrine  shows  a  preference  for  north-  and 
east-facing  cliffs,  and  the  Prairie  Falcon  shows 
a  preference  for  south-  and  west-facing  cliffs. 
This  relationship  between  the  two  species  needs 
additional  investigation  to  further  test  its  valid- 
itv  in  Utah  and  to  test  its  applicability  elsewhere 
in  the  arid  West. 

The  Prairie  Falcon  was  less  selective  than 
was  the  peregrine  in  its  choice  of  nesting  sites, 
sometimes  selecting  sites  which  were  seemingly 
shunned  hv  the  peregrine.  The  former  species, 
for  example,  utili/ed  sites  that  were  located  on 
smaller  ledges  with  a  smaller  total  nesting  area, 
as  well  as  sites  located  on  lower  cliffs  nearer 
the  base  of  the  cliff  or  otherwise  more  easily  ac- 
cessible to  humans  and  to  maniinalian  predators, 
than  did  the  latter  species.  Furthermore,  ravens 
which  are  common  in  Utah,  seemingh'  alter  the 
nesting  habitat  in  a  beneficial  way  for  Prairie 
Falcons  b\  proxiding  additional  nests  that  are 
frequenth"  used  b\'  the  falcons,  whereas  the  pere- 
grine apparently  is  little  affected  by  the  pres- 
ence of  ra\'ens. 

The  Prairie  Falcons  initiated  egg  laying  ear- 
lier in  the  season,  thus  giving  them  first  choice 
of  nesting  sites;  and  on  the  average  they  laid 
larger  clutches  than  did  the  peregrine. 

Tlie  Prairie  Falcon  is  a  true  desert  species.  It 
apparently  evolved  in  the  arid  environment  of 
western  Xortli  .America,  and  as  expected,  in  its 
association  with  the  peregrine  it  appears  to  be 


the  dominant  competitor  in  the  following  ways: 
(1)  it  has  a  greater  reproductive  potential  than 
does  the  peregrine,  based  on  its  larger  clutch 
size;  (2)  it  is  less  selective  than  is  the  peregrine 
in  choice  of  nest  sites  and  thereby  has  more 
nesting  situations  to  choose  from;  (3)  it  lays 
earlier  in  the  season  than  does  the  peregrine; 
thus  it  mav  have  first  choice  of  cliffs  and  evrie 
sites;  (4)  it  shows  less  selectivity  in  its  choice  of 
prey  species  as  food  for  its  young;  consequently 
it  has  a  wider  range  of  species  to  choose  from, 
including  birds,  mammals,  and  reptiles;  and  (5) 
because  of  its  selection  of  prev  species  other 
than  birds,  it  is  not  as  obligate  to  open  water  for 
food,  nor  is  it  as  obligate  to  open  water  for 
liathing,  and  thus  it  may  nest  many  miles  from 
water. 

The  Prairie  Falcon,  then,  would  appear  to 
have  a  marked  adaptive  advantage  over  the 
peregrine,  especially  in  marginal  areas  where 
the  peregrine's  ecological  tolerance  is  restricted 
and  wluTC  the  peregrine's  preferred  food  and/ 
or  nesting  sites  are  in  short  supply.  The  Prairie 
Falcon's  adaptive  advantage  over  the  peregrine 
ma\'  contribute  to  the  restriction  of  the  pere- 
grine to  the  more  optimal  aquatic  habitats  near 
streams  and  marshes  where  food  and  nesting 
sites  are  not  in  short  supply,  and  where  the 
peregrine  competes  successfully  with  its  con- 
gener. 

Some  of  the  reasons  the  peregrine  in  Utah  is 
able  to  compete  successfully  with  the  Prairie 
Falcon  for  food  and  quality  nesting  sites  may  be: 
(1)  the  relative  tolerance  of  the  two  species  for 
each  other  while  nesting  close  together;  (2)  the 
utilization  of  one  another's  alternate  eyries, 
coupled  with  the  inabilitv  of  either  species  to 
consistently  gain  a  dominance  over  the  other  in 
aerial  combat,  although  recent  observations  by 
Ogden  (1972)  and  R.  Fyfe  (pers.  comm.) 
suggest  that  the  peregrine  may  occup\-  the 
most  propitious  sites  because  it  is  capable  of 
forcing  the  Prairie  Falcon  from  them;  (3)  the 
possibk-  partitioning  of  the  mating  cliff  with 
each  species  having  distinct  preferences  for  dif- 
ferent t\|ies  of  nesting  sites  or  a  wide  variability 
in  acceptable  nesting  situations.  There  is,  for  ex- 
ample, tlu'  peregrine's  preference  for  open 
ledges  and  the  Prairie  Falcon's  acceptance  of  a 
wide  range  of  nesting  situations,  illustrated  by 
its  use  of  potholes  in  the  face  of  the  cliff,  open 
ledges,  and  old  stick  nests  of  other  raptorial 
species.  The  pothole  e\'ries  probabK  enhance 
the  survival  prospects  of  voung  reared  on  west- 
facing  cliffs  and  probably  offer  greater  protec- 
tion from  predation  than  do  the  open  ledges;  (5) 
a  variation  between  the  two  species  in  the  size 


68 


Bricham  Young  University  Science  Bulletin 


of  the  nesting  area  and  in  the  height  of  the  chffs 
and  eyrie  sites;  (6)  the  presence,  in  abundance, 
of  the  prey  species  preferred  bv  the  peregrine  in 
areas  of  Utah  wlieri'  tlie  peregrine  was  most 
common,  witli  partial  partitioning  b\'  the  two 
species  of  their  food  niches;  and  (7)  tlie  pere- 
grine's fidehty  to  the  cliff. 

We  have  Inpotlu'si/ed  tliat  the  peregrine 
probably  invaded  the  intennountain  region  dur- 
ing a  pluvial  period  of  the  Pleistocene,  when  the 
environmental  conditions  favored  the  peregrine 
in  its  competition  with  the  Prairie  Falcon.  More- 
over, tlie  iincient  Pleistocene  Lakes  Bonneville 
and  Provo  undoubtedly  presented  the  peregrine 
with  both  an  abundance  of  food  and  a  suffi- 
ciency of  nesting  sites.  Fossil  remains  of  pere- 
grines from  the  La  Brea  Tar  Pits  dating  back 
40,000  \ears  or  more  and  from  American  Falls 
in  Idaho  dating  back  nearly  30,000  years  sup- 
]5ort  this  hvpothesis. 

There  ma\'  have  been  times  during  the  cooler 
pluviiil  periods  when  the  geographic  ranges  of 
the  two  species  were  mutualh'  cxclusi\e,  at  least 
in  some  localities  of  Utah.  During  the  drier  inter- 
pliuials,  the  Prairie  Falcon  probabh'  took  over 
nesting  sites  no  longer  tenable  to  the  peregrine. 
However,  the  peregrine  probabh'  persisted  at 
those  sites  where  the  ecological  conditions  were 
most  propitious  to  its  sur\iyal  and  where  it 
gradually  adapted  to  the  more  arid  condition  of 
the  interpluvial.  as  is  the  present  case.  The  pere- 
grine is  noted  tor  its  fidelit\'  to  certain  cliffs  over 
man\'  generations  of  breeding  birds.  Traditional 
occupanc\'  ma\  not  be  the  rule  with  the  Prairie 
Falcon.  Finally,  one  would  expect  that  the  longer 
the  existence  of  a  svmpatrie  relationship  between 
two  closeh'  related  congeners,  the  more  exten- 
sive would  be  the  partitioning  of  their  resotirces 
and  the  greater  the  reduction  in  the  conflict  be- 
tsveen  them.  The  partitioning  of  the  resources 
between  the  peregrine  and  prairie  seems  to  be 
sufficientK  di'fined  to  suggest  that  this  phe- 
nomenon lias  been  in  operation  for  a  consider- 
able period  of  time.  The  low  level  of  interspecif- 
ic aggressiyeness  as  well  as  the  paleontological 
records  suggest  that  the  relationship  between 
the  two  species  is  probably  of  long  standing. 

Fluctuations  in  |ieregrine  populations  con- 
comitant with  fluetu;itions  in  height  and  length 
of  the  shoreline  of  the  I^leistocene  lakes  prob- 
abh' luive  ])een  of  natural  occurrence  down 
through  the  ages.  Peregrine  populations  possibh' 
have  been  declining  slowh  in  I'tah  o\er  the  past 
several  centuries  eoneurrent  with  a  general 
amelioration  of  climate  and  accompaining  re- 
duction in  suitable  habitat  based  on  climatic 
and   biotic  e\'idenee   from   Tlogup   Cave  dating 


back  8,5(X)  vears,  while  popuhitions  of  the  Prai- 
rie l^'alcon  may  have  slowK  expanded  to  fill  the 
\'oid  as  suggested  by  Nelson  (1969). 

Evidence  that  the  southern  extremit\'  of  the 
peregrine's  geographic  range  historicalh'  shifted 
northward  along  with  an  associated  shift  ;dti- 
tndinalK'  (Nelson,  1969)  has  not  been  demon- 
strated for  Utah.  With  the  drastic  decline  in 
the  species'  breeding  populations  that  is  pres- 
ently taking  place  throughout  North  Amer- 
ic;i,  ;i  Inpothesis  of  this  kind  is  difficult  to  test. 
A  general  cooling  trend  in  Utah  and  elsewhere 
in  the  Northwest  which  started  about  1961,  how- 
ever, should  result  in  more  suitable  ecological 
conditions  for  the  peregrine.  The  extent  to  which 
old  eyrie  sites  are  recolonized  should  be  a  test 
of  the  validitN'  of  Nelson's  (1969)  climatic  change 
liN'pothesis  for  the  peregrine  decline  in  the  west- 
ern United  States. 

The  presence  of  the  peregrine  at  desert  sites 
on  the  peripher^•  of  its  ecological  range  as  late 
as  1959-60  in  the  Great  Basin  (Table  1,  site  23) 
and  the  earl\-  1960s  in  the  Colorado  Plateau 
(Table  1,  site  28)  emphasizes  the  species's  abilit\' 
to  adapt  and  its  tenacity  for  survival. 

The  competitive  roles  of  the  peregrine  and 
the  Prairie  I'alcon  appiu'i'ntK'  change  according 
to  locality,  based  on  a\'ailability  of  food  and 
nesting  sites,  and  on  the  behavior  and  ecology 
of  the  rajitorial  species  with  which  thev  must 
compete.  For  example,  in  the  Arctic  the  Pere- 
grine Falcon  is  a  gi'iieralist,  both  in  terms  of  its 
selection  of  nesting  sites  and  in  regards  to  troph- 
ic relationships  with  its  competitors  (White  and 
Cade,  1971);  there,  this  species  utilizes  a  wide 
variety  of  food,  which  is  not  a  restricti\e  aspect 
of  its  econoniN  in  the  Arctic,  and  a  broad  selec- 
tion of  nesting  sites.  Its  chief  competitors  in  the 
Arctic  are  the  Common  Ra\'en,  the  Cxifalcon. 
and  th(>  Rough-k'gged  Ilauk  (Biitco  Ia<i0j)iis). 
The  C\  ifaleon,  the  peregrines  most  closeK'  re- 
lated competitor,  on  the  other  hand,  is  a  special- 
ist in  tenns  of  nest  site  and  food  selection.  The 
raven  and  C\i-faleon  have  similar  nesting  recjuire- 
ments,  and  since  both  are  earh  nesti'rs  the\ 
have  an  earlier  choice  of  evrie  sites.  Thus,  when 
the  later-nesting  peregrines  and  rough-legs  ar- 
ri\'e.  the  late  anivals  are  more  or  less  limitcxl  to 
the  remaining  sil(>s.  Conse()uentI\'.  the  peregrine 
utili/es  "mar^inid  "  sites  where  it  ma\'  ha\'e  to 
compete  with  the  rough-legs.  Apparenth',  how- 
e\'er.  the  iK^regrine  is  capal)le  of  usurping  the 
I'oiigh-lcgs's  nest.  In  addition,  the  two  species 
ma\'  joint K'  occu|)\'  the  same  cliffs,  thus  lessen- 
ing the  competition  between  them.  White  ;md 
Cade  (1971)  believe  that  .since  ravens  and  pere- 
<j;i'incs    do    not    get    along    well    together,    the 


Biological  Series,  Vol.  18,  No.  1        Pehecuink  F.alcon  in  Utah 


69 


earlier  nesting  raven  max  force  the  peregrine 
into  "marginal"  and  "submarginal"  sites  on  those 
occasions  when  peregrines  tn'  to  nest  too  close 
to  the  ra\ens.  The\  believe  that  the  same  thing 
applies  when  peregrines  attempt  to  settle  too 
close  to  Gyrfalcons  on  the  same  cliff.  The  pere- 
grine, nevertheless,  does  use  "optimal"  sites  in 
the  Arctic  when  thev  are  available. 

In  the  desert,  however,  the  i^eregrine's  role 
is  the  reverse  of  its  role  in  the  Arctic.  Here  the 
peregrine  is  forced  into  the  roll'  of  a  specialist 
because  the  harsh  arid  environment  produces 
few  of  the  pre\'  species  preferred  by  the  pere- 
grine and  because  the  Prairie  Falcon  competes 
more  successfulh'  for  both  the  former's  marginal 
food  niche  and  its  marginal  nesting  niche.  The 
specialization  in  the  peregrine's  food  require- 
ments is  apparent  onh'  when  compared  with  that 
of  the  Prairii-  Falcon  in  the  zones  of  contact  be- 
tween the  two  species.  Here  the  utilization  bv 
the  Prairie  Falcon  of  rodents  (especiallv  ground 
squirrels),  reptiles,  and  birds  (to  a  great  extent 
the  same  jirincipal  shore  birds  used  by  pere- 
grines) makes  it  a  generalist  in  its  food  habits. 
In  areas  of  allopatiy,  as  in  the  deserts,  the  Prai- 
rie Falcon  often  uses  predominantlv  one  or  two 
species  of  rodents  and /or  birds  and,  therefore, 
in  thc^e  regions,  it  is  seemingly  a  specialist. 

In  its  nesting  site  requirements,  the  Prairie 
Falcon  is  a  generalist  when  both  allopatric  and 
svmpatric  with  peregrines.  In  its  selection  of 
nesting  sites,  it  seems  to  prefer  sites  which  we 
would  consider  to  be  marginal  for  the  peregrine. 
This  more  or  less  limits  the  peregrine  to  the 
more  optimal  nesting  sites  and  to  the  role  of  a 
specialist.  Distribution  of  free  water,  and  its 
concomitant  supply  of  suitable  prev  species,  is 
the  most  important  environmental  factor  dictat- 
ing the  distril)uti()n  and  abundance  of  the  Pere- 
grine Falcon  in  the  arid  \\'est.  Con\ersel\-,  lack 
of  free  water  and  its  associated  supph'  of  suit- 
able prev  species  is  a  limiting  factor  in  the  dis- 
tribution and  abundance  of  this  species. 

Climate,  on  the  other  hand,  appears  to  be  a 
major  factor  restricting  the  geographic  distribu- 
tion of  tin-  Prairie  Falcon  as  is  its  strong  pio- 
clivit\'  to  nest  on  cliffs,  thus  nearlv  eliminating 
the  use  of  tree  nests  as  evrie  sites.  In  general, 
however,  the  selection  bv  the  Prairie  Falcon  of 
a  wide  varietv  of  prev  species,  encompassing 
three  classes  of  vertebrates,  its  utilization  of  sev- 
eral different  t\pes  of  nesting  situations,  its  rela- 
tiveh'  high  reproductive  potential,  and  its  abilit\' 
to  exploit  successfulh'  the  arid  environments  of 
western  North  America  points  out  the  extent  to 
which  this  sjiecies  has  become  adapted  to  its  par- 
ticular environment.  With  its  versatilit\'  in  selec- 


tion of  prey  species  and  nesting  sites,  but  more 
especially  the  former,  the  Prairie  Falcon  is 
among  the  better  adapted  and  more  successful 
of  North  American  raptors. 

Because  of  its  extensive  utilization  of  rodents 
for  food,  its  frequent  occurrence  in  areas  many 
miles  from  water  and  man\-  miles  from  civiliza- 
tion, and  its  relatively  nonmigratory  nature,  the 
Prairie  Falcon  is  much  less  likely  to  become  a 
permanent  victim  of  the  indiscriminate  use  of 
the  chlorinated  hydrocarbons  than  is  the  pere- 
grine. 

The  current  precarious  status  of  the  Pere- 
grine Falcon  in  Utah  is  probabh'  a  result  both 
of  a  change  in  climate  and  of  the  inimical  effects 
of  man's  activities.  The  future  of  the  species  in 
Utah,  as  elsewhere,  appears  bleak.  Many  of  the 
factors  responsible  for  its  decline  are  still  in  evi- 
dence. DDT  and  other  harmful  pesticides  are 
still  being  used  in  Utah.  In  1969,  for  example, 
7,593  pounds  (3,440  kg)  of  DDT  were  used  in 
Utah  for  the  control  of  noxious  insects  (in  the 
pesticide  polic\'  statement  of  the  Utah  State  De- 
partment of  Natural  Resources)  and  this  was  in- 
creased to  11,.^8  pounds  (5,140  kg)  in  1970 
(Work  Unit  A,  Pesticides  Applied— State  of  Utah, 
Utah  State  Health  Dept.,  1970;  Stephen  L.  War- 
nick).  The  impact  on  raptors  of  polvchlorinated 
biphen\ls  and  of  the  heav\-  metals,  such  as  mer- 
eurv,  lead,  and  cadmium,  are  still  poorly  un- 
derstood, and  other  chemical  hazards  of  un- 
known kinds  also  ma\'  be  involved. 

Although  man  is  still  encroaching  on  the  ac- 
tivities and  habitat  of  the  peregrine  and  on  its 
environment,  with  the  construction  of  artificial 
lakes  such  as  those  formed  in  Glen  Can\on  and 
in  the  Flaming  Gorge  and  with  a  general  cool- 
ing of  the  climate  which  is  resulting  in  the  re- 
establishment  of  certain  lakes  and  marshes,  nest- 
ing pairs  of  peregrines  mav  vet  be  attracted  in- 
to new  and  old  areas,  hopefully  awa\'  from  the 
harmful  activities  of  man.  Inimical  environmen- 
tal factor's  must  first  be  eliminated.  The  use  of 
management  methods,  such  as  construction  of 
manmade  marshes  near  suitable  nesting  cliffs  or 
manmade  evrie  sites  near  suitable  marshes,  has 
not  vet  been  attempted.  Management  techniques 
have  worked  well  with  other  species,  and  mav 
l^rove  successful  with  the  peregrine. 

The  few  peregrine  eyries  still  remaining  ac- 
tive, as  well  as  the  manv  active  Prairie  Falcon 
evries  in  the  state,  should  be  given  the  strictest 
protection  and  or  management.  All  peregrine 
e\ries  should  be  guarded  zealouslv  that  future 
generations  ma\'  have  the  pleasures  which  have 
been  ours;  that  is,  to  see,  to  stud\'.  and  to  enjoy 
this  magnificent  species  alive  in  its  native  haunts. 


70 


limcaiAM  VouNc  Univehsitv  Science  Bulletin 


AcldeiKlum 
After  the  final  inamiscript  was  in  press,  we 
learned  of  two  more  localities  used  by  pere- 
grines. Ralph  B.  Williams  (pers.  comm.)  told 
us  of  an  eyrie  that  the  late  Charles  Springer  of 
Salt  Lake  City,  an  avid  birder  and  falcon  en- 
thusiast, located  sometime  in  the  late  1930s  and 
early  1940s.  The  eyrie  was  west  of  the  general 
area  of  the  Bear  River  marshes.  From  the  de- 
scription of  the  eyrie  it  appeared  to  be  about 
12  to  15  straight-line  miles  from  eyrie  number 
9    ( Tabic   1 )    and   within   region  A  as  outlined 


on  Figure  1.  It  was  apparently  inactive  after 
the  early  1940s  since  that  area  was  searched 
for  falcons  in  the  mid-1940s.  The  second  locality 
occupied  by  a  pair  of  territorial  peregrines 
would  also  be  included  in  the  area  of  region  A 
but  to  the  cast  of  the  boimdary  lines,  as  shown 
in  Figure  1 .  This  locality  was  adjacent  to  several 
pairs  of  Prairie  Falcons,  but  the  exact  canyon 
in  which  it  was  located  could  not  be  determined 
from  a  map,  as  it  was  located  in  the  lati'  1930s 
and  details  are  vague  (Morlan  Nelson,  pers. 
comm.,  1973). 


ACKNOWLEDGMENTS 


Thanks  and  appreciation  are  extended  to 
Morlan  W.  Nelson  for  his  critical  review  of  an 
early  draft  of  the  manuscript.  His  comments  and 
data  are  distributed  liberalK-  throughout  the 
publication.  Roger  L.  Porter  assisted  in  the  col- 
lection of  data  during  the  earlv  vears  of  the 
study;  Lois  G.  Porter  typed  several  drafts  of  the 
manuscript;  and  Sanford  D.  Porter  made  the 
diagrams  and  offered  helpful  suggestions  at  var- 
ious stages  of  the  writing. 

Van  T.  Harris  and  Thomas  D.  Ray  reviewed 
the  manuscript  prior  to  final  typing,  and  Chand- 
ler Robbins,  Charles  Gish,  and  James  Ruos 
assisted  in  various  wavs  with  the  data  from  the 
Bear  River  Refuge  Christmas  Bird  Counts.  James 
Ruos  critically  reviewed  some  of  the  first  sec- 
tions of  the  manuscript.   Harris,  Robbins,  Gish, 


and  Ruos  are  all  of  the  U.  S.  Bureau  of  Sport 
Fisheries  and  Wildlife;  we  thank  "tliem  for  their 
assistance. 

There  have  been  so  manv  people  that  have 
helped  in  gathering  data  that  it  would  be  diffi- 
cult to  acknowledge  all  of  them  without  missing 
some,  but  they  have  all  been  given  credit  in  the 
bodv  of  the  text.  We  owe  a  special  thanks  to  all 
of  them. 

We  would  like  to  dedicate  this  stud\'  to  the 
late  Gary  D.  Llovd,  who  was  a  constant  com- 
panion to  White  while  working  with  raptors 
tlu-ough  the  1950s  and  earl\-  1960s,  and  who  met 
an  untimcb'  and  premature  death,  along  with 
his  wife,  while  thev  were  working  in  the  falcon 
countrv  of  east-central  LUah. 


APPENDI.X-ADDITIONAL   HISTORY   OF   DDT    USAGE 
AS  A  MOSQUITOCIDE  IN  UTAH 


According  to  Collett  ( 1955),  Salt  Lake  Coun- 
t\-  sprayed  310  acres  (125  ha)  by  aiqjlane  in 
1949  and  in  19.50,  according  to  Smith  (1951),  both 
Weber  and  Salt  Lake  City  Mosquito  Abate- 
ment districts  (MAD)  hired  planes  for  aerial 
spray  work,  and  the  latter  treated  more  than 
1,300  acres  (526  ha).  From  1950  through  1953 
the  Salt  Lake  Cit\'  district  treated  10,680  acres 
(4,322  ha)  by  aircraft  (Collett,  1955)  and  Davis 
(>ounty  sprayed  3,000  acres  (1,214  ha)  by  air- 
craft in  1953  (Stewart,  1954).  Aerial  spraving 
greatlv  increased  in  19.54,  according  to  Graham 
and  Rees  (19.58).  In  that  year  tlie  Salt  Lake 
City  district  (Collett,  1955)  aerialh-  treated 
12,128  acres  (4,908  ha),  of  which  2,286  acrc^ 
(925  ha)  were  in  cooperation  with  the  Davis 
County    MAD.    Insecticides    used    by    the    Salt 


Lake  City  MAD  in  19.54  were  DDT  in  number 
2  fuel  oil,  DDT  and  water  emulsion,  and  hepta- 
chlor  emulsion  in  water;  DDT  was  applied  at 
the  rate  of  two  gals  per  acre  (19  l/ha),  contain- 
ing 0.4  lbs  (181  g)  of  DDT;  heptachlor  was  ap- 
plied at  the  rate  of  0.06  lbs/acre  (67  g/ha)  for 
lai-vae  and  0.08  lbs/acre  (90  g/ha)  for  adults 
(Collett,  ibid.). 

The  Weber  County  MAD  spra\ed  over  10,000 
acres  (4,047  ha)  by  air  in  1952  and  19,825 
acres  (8,023  ha)  in  19.53.  DDT  was  applied  at 
0.2  lbs/acre  (224  g/ha)  for  15,812  acres  (6..399 
ha)  and  at  0.4  lbs/acre  (448  g/ha)  for  1,793 
acres  (726  ha)  in  1953,  for  a  total  of  3,880 
lbs  (1,760  kg)  of  DDT  applied  to  17,605  acres 
(7,124  ha)  of  marsh  and  pasture  lands  (Fronk, 
1954).   In    1954   Weber  County  aerially  treated 


Biological  Series,  Vol.  18,  No.  1        Peregrine  Falcon  in  Utah 


71 


13,300  acres  (5,382  ha)  at  0.1  to  0.4  llxs  of  DDT 
per  acre  (112-448  g/ha)  (Fronk  and  Jenne, 
1955),  while  Box  Elder  Count\'  .similarly  sprayed 
5,000  acres   (2,02,3  ha)    (Josephson,  1955).  ' 

An  abatement  district  was  not  operative  in 
Utah  Count\  nntil  1963,  and  the  chemicals  used 
were  Bavtex,  parathion  (both  in  pastures),  and 
DDT  (where  residues  were  considered  to  be  no 
problem)  (Davis,  1964).  DDT  was  not  used 
b\'  the  South  Salt  Lake  Count\'  district.  Hepta- 
chlor  was  used  in  this  county  starting  with  the 
inception  of  the  MAD  in  1953  (Graham  and 
Rees,  19.58;  Graham  in  letter).  It  was  applied 
at  0.04   lbs  per  acre    (45  g/ha).   Dieldrin   was 


used  extensively  in  this  district  also  at  the  same 
concentrations  as  heptachlor.  Other  districts 
then  began  using  heptachlor,  and  by  1958  it 
became  as  commonly  used  as  DDT  (Graham 
and  Rees,  1958).  Malathion  and  parathion  were 
used  in  1956,  and  parathion  became  the  insecti- 
cide preferred  by  the  Salt  Lake  County  MAD 
in  1957  when  resistance  to  heptachlor  developed 
in  the  mosquitoes  (Graham  and  Rees,  1958). 
B\'  1962  nearly  all  mosquito  abatement  districts 
in  Utah  had  abandoned  the  use  of  DDT  because 
pastures,  milk,  and  food  were  becoming  polluted 
with  residues,  and  by  1970,  only  Box  Elder 
Count)'  was  still  using  DDT. 


LITERATURE  CITED 


Allen,  J.  A.  1872.  Notes  on  an  ornithological  recon- 
naissance of  portions  of  Kansas,  Colorado,  Wyoming, 
and  Utah.    Bull.   Mus.  Comp.  Zool.,  3(6):113-183. 

Antevs,  E.  1948.  The  Great  Basin  with  emphasis  on 
glacial  and  postglacial  times.  III.  Climatic  changes 
and  prewhite  man.  Bull.  Univ.  Utah  38(20),  Biol. 
Ser.   10(7):167-191. 

A.O.U.  Checklist  of  North  American  Birds.  1957. 
5th  ed.,  (Amer.  Ornith.  Union)  The  Lord  Balti- 
more Press.  Inc.,  Baltimore,  Md. 

Baird,  S.  F.  18.52.  Birds,  pp.  314-335.  In  H.  Stans- 
buPv',  An  expedition  to  the  valley  of  the  Great  Salt 
Lake  of  Utah.   Lippincott,  Grambo  and  Co.,  Phila. 

Bartholomew,  G.  A.,  and  T.  J.  Cade.  1963.  The 
water  economv  of  land  birds.    Auk  80(4 ) :504-539. 

Bee,  R.  G.  Unpubl.  Field  notes,  deposited  with  De- 
partment of  Zoology  and  Entomology.  Brigham 
Y'oung  University. 

Bee,  R.  G.,  and  J.  Hutchings.  1942.  Breeding  rec- 
ords of  Utah  birds.  Great  Basin  Nat.  3(3-4)  :61-85. 

Beebe,  F.  L.  1960.  The  marine  peregrines  of  the 
Northwe.st  Pacific  coast.    Condor  62(3) :  145-189. 

Beebe,  F.  L..  and  H.  M.  Webster.  1964.  North 
American  falconry  and  hunting  hawks.  Publ.  Priv., 
N.  Am.  Falconr)-  and  Hunting  Hawks,  Box  1484, 
Denver,  Colorado.  315  p. 

Behle,  W.  H.  19.58.  The  bird  life  of  Great  Salt  Lake. 
Univ.  Utah  Press,  Salt  Lake  City,  Utah.  XIII  + 
203  p. 

.      1960.     The  birds  of  southeastern  Utah.    Univ. 

Utah  Biol.  Ser.  12(l):l-.56. 

Behle,  W.  H.,  J.  B.  Bushman,  and  C.  M.  Greenhalgh. 
1958.  Birds  of  the  Kanab  area  and  adjacent  high 
plateaus  of  southern  L'tah.  Univ.  Utah  Biol.  Ser. 
ll(7):l-92. 

Benge,  M.  K.,  and  L.  E.  Fronk.  1970.  Effects  of 
pesticides  on  nontarget  aquatic  organisms  on  the 
Ogden  Bay  Waterfowl  Management  Area,  Utah. 
Utah  Mosq.  Abate.  Assoc.  Proc.  23:34-40. 
Bent,  A.  C.  19.38.  Life  histories  of  North  American 
birds  of  prey  (pt.  2).  U.S.  Natl.  Mus.  Bull.  170: 
VIII  +  482  p. 
Berger,  D.  D.  and  H.  C.  Mueller.  1969.  Nesting 
Peregrine  Falcons  in  Wisconsin  and  adjacent  areas, 
pp.  115-122.  In  J.  J.  Hickey,  [ed.].  Peregrine  Fal- 
con populations,  their  biology  and  decline.  Univ. 
Wisconsin  Press,  Madison.  XX'l  1  +  596  p. 


Berger,    R.,    and   W.    F.    Libby.     1966.     University   of 
California    at    Los    Angeles    radiocarbon    dates    V. 
Radiocarbon  8:467-497. 
Birch,    L.    C.      1957.     The    meanings    of    competition. 

Amer.   Nat.  91:5-18. 
Bitman,  J.,  H.  C.  Cecil,  S.  J.  Harris,  and  G.  F.  Fries. 
1969.     DDT  induces  a  decrease  in  eggshell  calcium. 
Nature  224  ( 5214 ):  44-46. 
Bitman,    ].,    H.    C.    Cecil,    and    G.    F.    Fries.     1970. 
DDT-induced   inhibition   of  avian   shell   gland   car- 
bonic  anhydrase:    a  mechanism   for  thin   eggshells. 
Science  168(  .3931 )  :594-596. 
Blackwelder,    E.      1948.     The   Great   Basin,   with   em- 
phasis   on    glacial    and    postglacial    times.     I.     The 
geological   background.     Bull.    Univ.    Utah   38(20), 
Biol.  Ser.   10(7):3-16. 
BoLEN,    E.    G.      1964.     Plant     ecology     of     spring-fed 
marshes  in  western  Utah.  Ecol.  Monog.  .34:143-166. 
Bond,    R.    M.      1936a.     Eating    habits    of    falcons    with 
special  reference  to  pellet  analysis.  Condor  38(2): 
72-76. 

.      1936b.     Some  observations  on  the  food  of  the 

Prairie   Falcon.   Condor  .38(4)  :169-170. 

.      1936c.     Observations  on  the  food  of  the  Duck 

Hawk.   Condor  38(5)  :217-218. 

.      1946.     The    peregrine   population    of    western 

North  America.   Condo'r  48(  3)  ;101-116. 
Brodkorb,  p.      1963.     Pleistocene  birds  from  American 
Falls,  Idaho.    Quart.  Jour.  Florida  Acad.  Sci.  26(3): 
280. 

.      1964.     Catalogue   of   fossil   birds:    Pt.   2   (An- 

seriformes     through     Galliformes).      Bull.     Florida 
State  Mus.  Biol.  Sci.  8(3) :  196-326. 
Brown,    L.,    and    D.    Amadon.      1968.     Eagles,    hawks, 
and    falcons    of    the    world.    Vol.    2.    McGraw-Hill 
Book  Co.,  New  York.    (Hamlyn  Publ.  Group,  Ltd.. 
Middlesex,  England).    945  p. 
Cade,  T.  |.      1960.     Ecology  of  the  peregrine  and  Gyr- 
falcon    populations    in    Alaska.     Univ.    Calif.    Pub. 
Zool.  63(3):  151-290. 
Cade,   T.   J.,   C.   M.   White,   and  ].   R.   Hauch.      1968. 
Peregrines  and  pesticides  in  Alaska.    Condor  70(2): 
170-178. 
Collett,  G.  C.      1955.     Airplane  operations  in  the  Salt 
Lake     City     Mosquito    Abatement     District.      Utah 
Mosq.  Abate.  Assoc.,  Abstr.  and  Proc.  8:15-16. 


72 


Bric.ham  Young  University  Science  Bulletin 


Craighead,    J.    J.,    and    F.    C.    Chaigiie.m),    |u.     1956. 
Hawks,   owls,    and   wildlife.    Stackpolc,    Harrishurg, 
Pa.  .\lX  +  443  p. 
Davis,    T.      1964.     Mostiuito    control    in    Utah    Connty. 

Utah  Mosq.  Abate.  Assoc.  Proc.  17:21. 
De  .May,  I.  S.  1942.  An  avifanna  from  Iiuhan  kitchen 
middens  at  Bnena  Vista  Lake,  California.  Condor 
44(5):228-2;5(). 
Dementiev,  G.  p.  1951.  [The  Peregrine  Falcon  in  the 
USSR],  pp.  87-105.  In  G.  P.  Dementiev  and  N.  A. 
Ghidkov  [ed.].  Birds  of  the  Soviet  Union,  [in 
Russian].  Vol.  1.  645  pp.  (Translated  1966  by 
Israel  Program  for  Scientific  Translations,  Jerusa- 
lem; U.S.  Dept.  Comm.  Clearinghouse  for  Fed. 
Sci.  and  Tech.  Inf. ) 

.      1957.     On     the     Shaheen     Faico     pcrcnrinus 

hahiilonicuK.   Ibis  99(3)  :477-482. 
Dixon,  ].   B.      1937.     The  Golden  Eagle  in  San   Diego 

County,    California.    Condor    39(2):49-56. 
Downs,  T..   and  G.  J.   Miller.      1971.     Asphalt  ceme- 
tery of  the  ice  age,  pp.  52-63.  In   1972  Britannica 
Yearbook  of  Science  and  the  Future.    Encyclopedia 
Britannica,  Inc.,  Chicago,  448  p. 
DuBRANT,     S.     D.      1952.    Mammals    of     Utah.      Univ. 

Kansas  Publ.  Mus.  Nat.  Hist.  6:1-549. 
Enderson,  J.  H.      1964.     A  study  of  the  Prairie  Falcon 
in  the  central  Rocky  Mountain  region.  Auk  81(3): 
332-352. 

.      1965.     A    breeding    and    migration    survey    of 

the  Peregrine  Falcon.  Wilson  Bull.  77(4)  :327-339. 
Enderson,   J.   H.,   and   D.   D.    Bebcer.      1968.     Chlori- 
nated hydrocarbon  residues  in  peregrines  and  their 
prey  species  from  northern  Canada.    Condor  70(2): 
149-153. 
Fenneman,     N.     M.      1931.     Physiography    of    western 
United   States.     McGraw-Hill    Book   Co.,   Inc.,   New- 
York,  .XIII -1-534  p. 
Ferguson-Lees,  I.  ].      1951.     The  peregrine  poiiiilation 
of  Britain.  Bird  Notes  24:200-205.  309-314  [original 
not  seen;  quoted  by  Ferguson-Lees,   19.57  and  Rat- 
cliff  e,   1969]. 

.      1957.      [The  rarer  birds  of  pre\';  their  present 

status   in   tlie   British   Isles.]    Peregrine   (FaIco  perc- 
griiii/.v).  British  Birds  ,50(4  ):  149-155. 
Fischer,    \V.      1967.     Der   Wanderfalk    [The    Peregrine 
Falcon]  (Fiilco  percgrinus  und  Falco  pdcgrinoklcs). 
(A.   Ziemsen  Verlag.   Wittenberg   Lutherstadt;   Ber- 
lin Zoological  Park,  Book  No.  13);   1.50  pp   (Trans- 
lated  1972  for  U.S.  Dept.  Interior,  Bureau  of  Sport 
Fisheries    and    Wildlife    and    the    National    Science 
Foundation.    Washington,   D.C.   by   the   Indian   Na- 
tional    Scientific     Documentation     Center,     Hillside 
Road,  New  Delhi,  India. ) 
Fremont,  J.  C.      1845.      Report  of  the  exploring  expe- 
dition  to   the   Roekv   Mountains   in   the   year   1842, 
and   to   Oregon   and   North   California  in   the  \ears 
1843-44.      Blair    and     Rives    Printers,    Washington. 
693  p. 
French,    N.    R.      1951.     Duck   Hawks   nesting   in   Colo- 
rado. Condor  53(I):54. 
Fronk,   L.   E.      1954.     U.se   of   the   iiirplane   in   the   ap- 
plication  of   insecticides   in  mosquito   control.   Utah 
Moscj.    .iVbate.    .\ssoc.,    Abstr.    and    Proc.    (Mimeo) 
7:24-26. 
Fronk,  L.  E.,  and  E.  A.  Jenne.     19.55.     Highlights  of 
the  Weber  County  Moscpiito  Abatement  District  for 
the   year    1954.     Utah   Mosc).   Abate.   Assoc,    .Vbstr 
and  Proc.  8:20-21. 
Gaukielson,  1.  N..  and  S.  (;.  Jewett.      1940.      Birds  of 
Oregon.    Oregon  St;itc  Monogr.,  Studies  in  Zool.  2., 


Oregon    State    College,    Corvallis,    Oregon,    XXX-j- 

6.50  p. 
(iiiAHAM,  ].  E.,  AND  D.  M.  Rees.  1958.  chemical 
control  of  mosquitoes  in  Utah.  Proc.  ;uid  Papers. 
26th  Ann.  Conf.,  Calif.  Mosq.  Contr.  Assoc,  pp. 
16-19. 
Grater,  R.  K.  1947.  Birds  of  Zion,  Bryce,  and  Cedar 
Breaks.  Zion-Bryce  Mus.  Bull.  5.  Zion  Nat.  Park. 
93  p.  ' 

Haines,    A.    L.      1955.     Osborne    Russell's   journal   of   a 
trapper.    Lhiiv.    Nebra.ska    Press,    Lincoln,    XVIII -f- 
191   p. 
Hall,  E.  R.      1946.     Mammals  of  Nevada.    Univ.  Calif. 

Press,  Berkeley,  XI-|-710  p. 
Hall,    G.    H.      1955.     Great    moments    in    action,    the 
story    of    the    Sun    Life    Falcons.    Mercury    Press, 
Montreal,  Canada   (reprinted   1970.  Canadian  Field 
Nat.  84(3):2Il-230). 
HAiu't:n,    K.    T.    and    G.    M.    Alder.     The    macroscopic 
plant    remains    of    the    deposits    of    Hogup    Cave, 
Utah,    and    their    paleoclimatic    implications.    L'niv. 
Ut;ih  Anthro.  Papers,  in  press. 
Harris,   W.   R.     1909.     The  Catholic  Church  in   Utah. 
Salt     Lake     City;     Intermountain     Catholic     Press. 
Heath,  R.  G.,  J.  W.  Spann,  and  ].  F.  Kreitzeb.      1969. 
Marked  DI!)E   impairment  of  Midlard  reproduction 
in    controlled    studies.     Nature   224(5214)  :47-48. 
Heath,   R.   G.,  J.   W.   Spann,  J.   F.   Kreitzeb,  and  C. 
Vance.      1972.       Effects  of  polychlorinated  biphe- 
nyls  on  birds.  Proc.  .\V  Internat.  Omithol.  Congr., 
E.  ].  Brill,  Leiden,  pp  475-485. 
Henshaw.  H.  W.      1874.     An  annotated  list  of  the  birds 
of    llt.ih,    .Annals    New    York    Lyceum    Nat.    Hist. 
11:1-14, 
.      1875.     Report   upon   the  ornithological   collec- 
tions made  in  portions  of  Nevada,  Utah,  California, 
Colorado,    New    Mexico,    and    Arizona,    during    the 
years    1871,    1872,    1873,    and    1874,    pp.    13U507, 
977-989.    In   Cleorge   M.  Wheeler.   Rept.  Geog.  and 
Geol.  Expl.  and  Sur\-.  West  lOOth  Meridian,  Vol.  5. 
Herrert,    R.   A.,   AND   K.   C.    S.    Hebhebt.      1965.     Be- 
havior of  Peregrine  Falcons  in  the  New  York  Citv 
region.    Auk  S2(l):62-94. 
HicKEY,    |.    |.      1942.     Fasten)   population   cjf   the   Duck 

Hawk.  Auk  .59(2) :  176-204. 
.  1969.  Peregrine  Falcon  populations,  their  bi- 
ology and  decline.  J.  ].  Hickey  [ed.],  Univ.  Wis- 
consin Press,  Madison,  X.XII 4-596  p. 
Hickey,  J.  ].,  and  D.  W.  Andebson.  1968.  Chlori- 
nated liNdrocarbons  and  eggshell  changes  in  rap- 
torial  and   fish-eating  birds.     Science    162:271-273. 

.      1969.     The  Peregrine  Falcon:  life  history  :md 

|)opulation  literature,  pp.  3-42.  In  ].  J.  Hickey 
[ed.].  Peregrine  Falcon  populations,  their  biology 
and  decline.  Uni\'.  Wisconsin  Press,  Madison.  XXU 
-f  .596  p. 
Ho.  T.  Y,,  L,  F.  Marcus,  and  R.  Bergeh.  UXiO.  Radio- 
e;ul)on  dating  of  petroleum-impregnated  bone  from 
t;ir  pits  at  Rancho  La  Brea,  California.  Science 
164:1051-10.52. 
Howard,  H  1929.  The  avifauna  of  Emeryx  ille  shell- 
mound.     Univ.  Calif.  Publ.  Zool.  .32(2):301-.394. 

.      1952.     The     prehistoric     avifauna     of     Smith 

Creek  C:i\c.  Nevada,  with  a  description  of  a  new 
gigantic  raptor.  Bull.  So.  Calif.  .'\cad.  Sci.  51,  pt. 
2:'50-.54. 

.      1962;i.      Bird      remains      from      ;i      prehistoric 

c:i\-e  deposit  in  Grant  Countx',  New  Mexico.  Condor 
64(3):241-242. 


Biological  Series,  Vol.  18,  No.  1        PEnEcniNE  Falcon  in  Utah 


73 


.      1962b.     A    comparison    of    avian    assemblages 

from  inclividnal  pits  at  Rancho  La  Broa,  California. 
Los  Angeles  County  Mus.  Contr.  Sci.  .58:1-24. 
Howard,  H.,  and  A.  H.  Miller.      1933.     Bird  remains 
from  cave  deposits  in  New  Mexico.    Condor  35(  1 ) : 
15-18. 
[efferies,    D.    ].      1967.     The   delav    in   ovulation   pro- 
duced  bv    p,p'-DDT   and    its    possible    significance 
in  the  field.    Ibis  109:266-272. 
Johnson,  H.  C.     1899.     A  successful  dav  \\ith  the  Duck 

Hawks.  Condor  l{3):45-46. 
josEPHSON,   K.   L.      1955.     Mosquito  activities  for   1954 
of  the  Box  Elder  Mosquito  and  Fly  Abatement  dis- 
trict.    Utah   Mosq.   Abate.   Assoc.,   Abstr.  and   Proc. 
8:18-19. 
Keith,   J.   O.,   and  E.   C.   Hunt.      1966.     Levels  of  in- 
secticide residues  in  fish  and  wildlife  in  California. 
N.  Am.  Wildl.  Conf.  31:150-177. 
KoBNS,  J.  R.      1951.     West  from  Fort  Bridger;  the  pio- 
neering of  the  immigrant  trails   across   Utah   1846- 
1850.    Utah  State  Hist.  Soc.  Salt  Lake  City.  296  p. 
Laudermilk,    J.    D..    AND    P.    A.    MuNZ.      1935.     Plants 
in  the  dung  of  Nothrotherium  from  Gypsum  Cave, 
Nevada.    Carnegie  Inst.  Wash.,  Publ.  4.53:29-37. 
Leedy,   R.   R.      1972.     The  status  of  the  Prairie  Falcon 
in  Western   Montana:   special  emphasis  on  possible 
effects  of  chlorinated  hydrocarbon  insecticides.  M.S. 
Thesis,   Univ.   Montana,   unpublished. 
Lincoln,   F.   C.      1933.     A   decade  of   bird  banding  in 
America:  A  review.  Ann.  Rpt.  Smithsonian  Inst,  for 
year  ending  June  30,    1932.   Publ.   3185:    327-351. 
Linsdale,    ].M.      1937.     The    natural    history    of    mag- 
pies.  Pacific  Coast  Avifauna  25:1-234. 
Lonccore,  J.  R.,  F.  B.  Samson,  and  T.  W.  Whitten- 
DALE,  Jr.      1971.     DDE  thins  eggshells  and  lowers 
reproductive  success  of  captive  Black  Ducks.   Bull. 
Envir.   Contam.   and  Toxicol.   6(6)  :485-490. 
Lonccore,   ].   R..    F.   B.   Samson,  ].   F.   Kreitzer,  and 
J.  W.   Spann.      1971.     Changes  in  mineral  compo- 
sition of  eggshells  from  Black  Ducks  and  Mallards 
fed    DDE    in    the   diet.     Bull.    Envir.    Contam.    and 
Toxicol.  6(4):34.5-3.50. 
Low,   ].    B.      1966.     Waterfowl   interests   in   relation   to 
vector  control  programs.   Utah  Mosq.  Abate.  Assoc. 
Proc.    19:25-30. 
McFarland,  L.  Z.,  R.  L.  Garrett,  and  J.  A.  Nowell. 
1971.     Normal  eggshelLs  and  thin  eggshells  caused 
by  organochlorine  insecticides  viewed  by  the  scan- 
ning     electron      microscope.      Scanning      Electron 
Microscopy   (pt.   1),  Proc.  4th  Ann.  Scanning  Elec- 
tron   Microscope    Symposium.     IIT    Research    Inst. 
Chicago,  111.  pp.  377-384. 
McGahan,    ].      1968.     Ecology    of    the    Golden    Eagle. 

Auk  85(1):1-12. 
Mees,  F.      1949.     Waamemingen  over  het  vangen  van 
Meermuizen  door  Roofvogels  op  West-Java.    Ardea 
.37:17.3-175. 
Miller,  A.  H.      19.32.     Bird  remains  from  Indian  dwell- 
ings in  Arizona.  Condor  .34(3)  :138-1.39. 
Miller,    L.      1911.     Avifauna   of   the    Pleistocene    cave 
deposits  of  California.   Univ.  Calif.  Publ.  Bull.  Dept. 
Gaol.  6(16): 38.5-400. 
.      1927.     The  falcons  of  the  McKittrick  Pleisto- 
cene. Condor  29(3):  150-152. 

.      1943.     The   Pleistocene   birds   of   San   Josecito 

cavern,    Mexico.    Univ.    Calif.    Publ.    Zool.    47(5): 
143-168. 
.      19.57.     Bird   remains   from   an   Oregon    Indian 


Nelson,  M.  W.  1969.  The  status  of  the  Peregrine 
Falcon  in  the  Northwest,  pp.  61-72.  In  J.  J.  Hickey 
[ed.],  Peregrine  Falcon  populations,  their  biology 
and  decline.  Univ.  Wisconsin  Press,  Madison,  Wise. 
XXlI-t-596  p. 

Nelson,  N.  F.  1954.  Factors  in  the  development  and 
restoration  of  waterfowl  habitat  at  Ogden  Bay 
Refuge,  Weber  County,  Utah.  Utah  State  Dept. 
Fish  and  Game  Publ.  No.  6:1-87. 

.      1966.     Waterfowl     hunting     in     Utah.     Utah 

State  Fish  and  Game  Publ.  No.  66-10:1-100. 

Nelson,  R.  W.  1972.  The  incubation  period  in  Peak's 
Falcons.  Raptor  Research  6(1):11-15. 

Nice,  M.  M.  1954.  Problems  of  incubation  periods  in 
North  American  birds.    Condor  56(4  )  :173-197. 

Nielson,  L.  T.  1962.  The  Utah  Mosquito  Abatement 
Association — a  brief  history  of  mosquito  control  in 
Utah.    Utah    Mosq.    Abate.    Assoc.    Proc.    15:12-15. 

OnuM,  E.  P.  1959.  Fundamentals  of  ecology,  2nd  ed. 
W.  B.  Saunders  Co..  Phila..  XVIl-t-546  p. 

Ogden,  V.  1971.  A  nesting  study  of  the  Prairie  Falcon. 
Quarterly  Report,  Idaho  Cooperative  Wildl.  Res. 
Unit  24(2  and  3):18-20,  16-17. 

.  1972.  Nesting  density  and  reproductive  suc- 
cess of  Prairie  Falcons  (Faico  mcxicanus)  in  south- 
western Idaho.  Ouarterly  Report,  Idaho  Coopera- 
tive  Wildl.    Res.    Unit   25(1    and   2):13,    13. 

Olivier,  G.  1953.  Nidification  du  faucon  pelerin  sur 
les  edifices.  L'Oiseau  et  la  Revue  Franc.  d'Ornithol. 
23(2):109-124. 

Peakall,  D.  B.  1969.  Effect  of  DDT  on  calcium 
uptake  and  Vitamin  D  metabolism  in  birds.  Nature 
224(5225):  1219-1220. 

.  1970.  p,p'-DDT:  Effect  on  calcium  metab- 
olism and  concentration  of  estradiol  in  the  blood. 
Science  168(  3931 )  :.592-.594. 

1971.     Effect     of     polychlorinated     biphenyls 


(PCB's)    on    the    eggshells    of    Ring    Doves.    Bull. 

Envir.   Contam.  and  Toxicol.   6(2)  :100-101. 
Pettingill,  O.  S.,  Jr.,  and  N.  R.  Whitney,  Jr.     1965. 

Birds    of   the    Black    Hills.     Cornell   Lab.    Omithol. 

Spec.  Publ.  No.  1:VII+1.39. 
Phillips,    A.,    J.    Marshall,    and    G.    Monson.      1964. 

The  birds  of  Arizona.  Univ.  Arizona  Press,  Tucson. 

212  p. 
Platt,  J.  B.      1971.     A  survey  of  nesting  hawks,  eagles, 

falcons,   and   owls   in   Curlew   Valley.    Utah.     Great 

Basin  Nat.  31(2)  :51-65. 
Porter,    R.    D.,   J.    B.    Bushman,    and   W.    H.    Behle. 

Birds  of  the  Great  Salt  Lake  Desert.    Unpubl.  Ms. 

(in  preparation). 
Porter,  R.  D.,  and  S.  N.  Wiemeyer.      1969.     Dieldrin 

and  DDT:   Effects  on  Sparrow  Hawk  eggshells  and 

reproduction.    Science.   165:199-200. 
.      1972.     Reproductive      patterns       in       captive 

American    Kestrels    (Sparrow    Hawks).    Condor   74 

(l):46-53. 

1972.     DDE   at   low  dietary   levels  kills   cap- 


midden.   Condor  59(1) :59-63. 


live   American    Kestrels.    Bull.   Envir.   Contam.   and 

Toxicol.  8(4):  193-199. 
Powell,  J.  W.      1879.     Report  on  the  lands  of  the  arid 

region  of   the   United   States,  with  a  more  detailed 

account    of    the   lands    of    Utah.    (2nd    Ed.),    U.S. 

Gov.  Print.  Office,  Washington. 
Ratcliffe,    D.    a.      19.58.     Broken    eggs    in    peregrine 

eyries.    British  Birds  51:2.3-26. 
'-.      1962.     Breeding     density     in     the     peregrine 

Falco  pcre'^rimis  and  raven  Corvits  corax.    Ibis  104: 

1 3-39. 


74 


Bnir.HAM  Young  University  Science  Bulletin 


.      1963.     The   status   of   the   peregrine  in   Great 

Britain.    Bird  Stiuly  !()(  2  )  :.56-90. 

.  1965.  The  peregrine  situation  in  (ire^it  Brit- 
ain 1963-64.   Bird  Stxidy  12(2):66-82. 

.  1967a.  Decrease  in  eggshell  weight  in  cer- 
tain birds  of  prey.    Nature  215(  5097)  :208-210. 

.  1967b.  The  peregrine  situation  in  Great  Brit- 
ain  1965-66.    Bird  Study  14(4) :238-246. 

.  1969.  Population  trends  of  the  Peregrine  Fal- 
con in  Great  Britain,  pp.  239-269.  In  J.  J.  Hickey 
[ed.].  Peregrine  Falcon  populations,  their  biology 
and  decline.  Univ.  Wisconsin  Press,  Madison.  XXII 
-f  596  p. 

1970.     Ghanges    attributable    to    pesticides    in 


egg  breakage  frequencv  and  eggshell  thickness  in 
.some  British  birds.  J.  Appl.  Ecol.  7(I):fi7-115. 
Remy,  J.,  and  J.  Brenchley.  1861.  A  journev  to 
Great  Salt  Lake  Citv.  Vols.  I  and  II.  W.  Jeffs, 
London  .501  &  605  p. ' 
RiiXiWAY,  R.  1874.  Notes  on  the  bird  fauna  of  the 
Salt  Lake  Valles  and  adjacent  portions  of  the 
Wahsatch  Mountains.  Bull.  Essex  Institute  5:  168- 
173. 

.      1877.     Ornithology,    pp.    303-669.    In    "orni- 

thologv    and    paleontology,"    Glarence    King.     U.S. 

Geol.  Expl.  40th  Parallel.  Vol.  4,  Pt.  3.  pp.  303-669. 

Smith,  D.  A.      1961.     Participation  in  mosquito  control 

by  the  Department  of  Fish  and  Game.    Utah  Mosq. 

Abate.  Assoc.  Proc.  14;4-5. 

Smith,    ].    V.      1951.     Progress  of   mosquito    abatement 

in  Utah.    Proc.  and  Papers,  19th  Ann.  Gonf.,  Galif. 

Mosq.  Gontr.  Assoc,  pp.  42-43. 

Stager,    K.    E.     1941.     A    group    of    bat-eating    Duck 

Hawks.  Gondor  43(3) :  137-139. 
•Stansdury,   H.      18.52.     An  expedition   to   the  valley  of 
the  Great  Salt  Lake  of  Utah,  including  a  reconnais- 
sance  of   a    new   route   through   the    Rocky   Moun- 
tains.   U.S.    Senate;    Lippincott.    Grambo    and    Go.. 
Phila.  487  p. 
Steward,  J.  H.      1937.     Ancient  caves  of  the  Great  Salt 
Lake  region.  Smithsonian  Inst.  Bureau  of  American 
Ethology,   Bull.   116:1-131. 
Stewart,    G.    W.      19.54.     Davis    Gounty.    ( In    Reports 
from   Mosquito   Abatement   Districts),    Utah    Most]. 
Abate.  As.soc,  Ab.str.  and  Proc.   ( Mimeo. )   7:.34-35. 
TiNBERCEN,   L.      1946.     Der  Sper\ver  al   roofvijand   van 
Zangvogels.     Ardea    34:1-213     [original    not    seen, 
(|uoted  bv  F.   and  J.   Graighead    (19.56)   and  Gade 
I960)]. 
Two.MEY',    \.    G.      19.36.     Glimographic    studies    of   cer- 
tain   introduced    and    minrator\-   birds.     Ecologv    17 
(1):122-132. 

.      1942.     Birds  of  the   Uinta  Basin,   Utah.    Ann. 

Carnegie  Mus.  28,  Art.  17:.341-490. 
Tyler,  J.  G.      1923.     Observations  on  the  haliits  of  tlic 

Prairie    Falcon.    Gondor    25(3):90-97. 
U.S.  Department  of  Gommerce.      1965.     Glimatogra- 
phy  of  the  United  States  86-37;   Decennial  census 
of  the  Unit<'d   States  clim;itc;   Glimatie  summary  of 
the    United    States,    Supplement    for    1951    through 
1960,  Utah. 
Vaubie,  G.      1961.     Sxstematic  notes  on  I'alciiretic  birds. 
No.  44  Falconidae:  The  genus  fairo  (Part  1,  Falro 
peregrinus    and    Falco    pelcgrinoidcs) .    Am.    Mus. 
Novitates  No.  2035,  pp.  1-19. 
Warnick,  S.  L.     1971.     The  Utah  community  pesticide 

study.    Utah  Science,  Agr.  E.\p.  Sta.  .32(2)  :.5.3-,5,5. 
Wauer,    R.    H.,    and   D.    L.   Garter.      1965.     Birds   of 
Zion    National    Park   and   vicinity.     Zion    Nat.    Hist. 
Assoc..  Zion  Nation;il  Park  92  p. 


VVelleh,  M.  W.,  B.  H.  Wingfield,  and  ].  B.  Low. 
1958.  Effects  of  habitat  deterioration  on  bird  pop- 
ulations of  a  small  Utah  marsh.  Gondor  60(4): 
220-226. 

VVetmore,  a.  1915.  Mortality  among  waterfowl 
around  Great  Salt  Lake,  Utah.  Bull.  U.S.  Dept. 
Agr.  No.  217:1-10. 

.      1918.     The  duck  sickness  in  Utah.    U.S.  Dept. 

Agr.  Bull.  No.  672:1-25. 

1932.     Additional  records   of  birds  from  cav- 


ern deposits  in  New  Mexico.    Gondor  34(3)  :141-142. 
1933.     The  eagle,  king  of  birds,  and  his  kin. 


Nat.  Geogr.  Mag.  64(l):43-95. 

White,  G.  M.  1963.  Botulism  and  myiasis  as  mor- 
tality factors  in  falcons.    Condor  65(  5)  :442-443. 

.      1968a.     Diagnosis     and     relationships    of    the 

North    American    tundra-inhabiting    Peregrine    Fal- 
cons.   Auk  85(2):179-191. 

.      1968b.     Biosystematics     of     North     American 

Peregrine     Falcons.     Ph.D     dissertation,     Univ.     of 
Utah,  unpublished.   195  p. 

.  1969a.  Is  there  a  genetic  continuity  con- 
cerned in  eyrie  maintenance?  pp.  391-397.  In  J.  ]. 
Hickey  [ed.].  Peregrine  Falcon  populations,  their  bi- 
ology and  decline.  Univ.  Wisccmsin  Press,  Madison, 
XXli  +  596  p. 

1969b.     Population    trends    in    Utah    raptors. 


pp.  359-362.  In  J.  J.  Hickey  fed.").  Peregrine  Falcon 
populations,  their  biology  and  decline.  Univ.  Wis- 
consin Press,  Madison,  XXII +  596  p. 

White,  C.  M.,  W.  B.  Emison,  and  F.  S.  L.  William- 
son. 1971.  Dynamics  of  raptor  populations  on 
Amchitka  Island,  Alaska.  BioScience  21(12):623- 
627. 

.      1973.     DDE    in    a    resident    Aleutian    Island 

peregrine  population.    Gondor   (in  press). 

White,  G.  M.,  and  G.  D.  Lloyd.  1962.  Predation  on 
peregrines  bv  ringtails.    Auk  79(2):277. 

White,  G.  M.,  and  T.  J.  Cade.  1971.  Cliff-nesting 
raptors  and  ravens  along  the  Golville  River  in  arc- 
tic Alaska.  The  Living  Bird.  Laboratory  of  Orni- 
thology, Cornell  Univ..  Ithaca,  N.  Y.  10th  annual: 
107-150. 

Wiemeyer,  S.  N.,  and  R.  D.  Porter.  1970.  DDE 
thins  eggshells  of  captive  American  Kestrels.  Nature 
227  (.52.59):  737 -738. 

Williams,  R.  B.,  and  G.  P.  Matteson,  Jr.  1948. 
Wyoming  hawks.  Wyoming  Game  and  Fish  Dept., 
Bull.  No.  5,  Cheyenne,  Wyoming,  84  p. 

WiTiiERHY,  H.  F..  C.  R.  Jourdain,  N.  F.  Ticehurst, 
AND  B.  W.  Tucker.'  19.39.  The  handbook  of 
British  birds.  Vol.  3,  H.  F.  and  G.  Witherby. 
London,  399  p. 

Wolfe,  L.  R.  1928.  The  breeding  Accipitres  of  Utah. 
Oologists"  Record  8(4):90-102. 

.     1929.    Collecting  rent  from  falcons  and  ravens. 

Oologist,  whole  no.  .501.  4fi(2):16-20. 

WooDiuHV,  A.  M.,  AND  H.  N.  Russell,  Jr.  1945. 
Birds  of  the  Navajo  country.  Bull.  Univ.  Utah. 
.35(14),  Biol.  Ser.  9(1):  1-160. 

Woodhuhv,  a.  M.,  C.  Gottam,  and  J.  W.  Suoden. 
1949.  Annotated  checklist  of  the  birds  of  Utah. 
Bull.   Univ.   Utah  .39(16),   Biol.   Ser.    ll(2):l-40. 

.  The  birds  of  Utah.  Unpublished  Ms.  (de- 
posited with  Lynn  Hayward.  Brigham  Young  Uni- 
versity ) . 

Wf)oi)HURY.  A.  M..  AND  G.  Gottam.  1962.  Ecological 
studies  of  birds  in  Utah.  Univ.  Utah  Biol.  Ser. 
12(7):V  +  28  p. 


^./l//4  -  'f'f^ro^o^ 


Brigham  Young  University 

Mus.  coMP.  zoou        Science  Bulletin 


NOV    51973 

u'OTicOLOGICAL  SURVEY  OF  THE 

ALGAE  OF 
HUNTINGTON  CANYON,  UTAH 


by 

Lorin  E.  Squires 

Samuel  R.  Rushforth 

Carol  J.  Endsley 


BIOLOGICAL  SERIES  —  VOLUME  XVIII,  NUMBER  2 
JUNE  1973/ISSN   0068-1024 


BRIGHAM  YOUNG   UNIVERSITY   SCIENCE  BULLETIN 
BIOLOGICAL  SERIES 

Editor:   Stanley  L.  Welsh,  Department  of  Botany, 

Brigham  Young  University,  Provo,  Utah 

Acting  Editor:  Vernon  J.  Tipton,  Zoofogy 

Members  of  the  Editorial  Board: 

Ferron  L.  Andersen,  Zoology 
Joseph  R.  Murdock,  Botany 
WiLMER  W.  Tanner,  Zoology 

Ex  officio  Members: 

A.  Lester  Allen,  Dean,  College  of  Biological  and  Agricultural 
Sciences 

Ernest  L.  Olson,  Director,  Brigham  Yoimg  University  Press 

The  Brigham  Young  University  Science  Bulletin,  Biological  Series,  publishes 
acceptable  papers,  particularly  large  manuscripts,  on  all  phases  of  biology. 

Separate  numbers  and  back  volumes  can  be  purchased  from  University  Press 
Marketing,  Brigham  Young  University,  Provo,  Utah  84602.  All  remittances  should 
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Orders  and  materials  for  Ubrary  exchange  should  be  directed  to  the  Division 
of  Gifts  and  Exchange,  Brigham  Young  University  Library,  Provo,  Utah  84602. 


Brigham  Young  University 
Science  Bulletin 


AN  ECOLOGICAL  SURVEY  OF  THE 

ALGAE  OF 
HUNTINGTON  CANYON,  UTAH 


by 

Lorin  E.  Squires 

Samuel  R.  Rushforth 

Carol  J.  Endsley 


BIOLOGICAL  SERIES  — VOLUME  XVIII,  NUMBER  2 
JUNE  1973/ISSN   0068-1024 


TABLE  OF  CONTENTS 

ABSTRACT    1 

INTRODUCTION  1 

REVIEW  OF  SELECTED  ALGAL  STUDIES  IN  UTAH    S 

DESCRIPTION  OF  THE  HUNTINGTON  CANYON  DRAINAGE   6 

GEOLOGY  6 

CLIMATE  AND  VEGETATION  ZONES  12 

DESCRIPTION  AND  USES  OF  HUNTINGTON  CREEK    15 

DESCRIPTION  OF  SAMPLING  SITES  17 

LAWRENCE    ( SITE   1 )    17 

HIGHWAY  10  BRIDGE  (SITE  2)  17 

PLANT  SITE   ( SITE  3 )   17 

BEAR-RILDA  CAMPGROUND   (SITE  4)    19 

TIE  FORK  POND  (SITE  5)   20 

STUART  FIRE  STATION  (SITE  6)  20 

BEAR  CANYON   ( SITE  7 )    20 

METHODS    22 

PHYSICAL  AND  CHEMICAL  MEASUREMENTS   22 

Temperature   22 

Turbidity  22 

Water  Chemistry  22 

PHYTOPLANKTON   22 

Net  Plankton  22 

Naimoplankton   24 

PERIPHYTON  24 

VISIBLE   BENTHIC  ALGAE   26 

FLORISTIC  SAMPLING  26 

RESULTS  AND  DISCUSSION  26 

LAWRENCE  ( SITE  1 )  26 

HIGHWAY  10  BRIDGE  (SITE  2)  31 

PLANT  SITE   ( SITE  3 )   33 

BEAR-RILDA  CAMPGROUND  (SITE  4)  39 

STUART  FIRE   STATION    (SITE   6)    44 

BEAR  CANYON    ( SITE  7 )    50 

TIE  FORK  POND  (SITE  5)  51 

ALGAL  FLORA  OF  HUNTINGTON  CANYON  55 

ACKNOWLEDGMENTS     57 

APPENDIX  I— NET  PLANKTON,  NANNOPLANKTON,  PERIPHYTON,  AND  VISIBLE  BENTHIC  ALGAL 
TABLES   57 

APPENDIX  II— ALGAE  COLLECTED  FROM  HUNTINGTON  CANYON  OCTOBER  1970— MARCH  1972  ....  84 

LITERATURE    CITED   86 


AN   ECOLOGICAL  SURVEY   OF  THE  ALGAE  OF 
HUNTINGTON   CANYON,   UTAH 

by 
Lorin  E.  Squires/  Samuel  R.  Rushforth/  and  Carol  J.  Endsley' 


ABSTRACT 


A  quantitative  and  ecological  study  of  the 
algae  of  Huntington  Canyon,  Emery  County, 
Utah,  was  conducted  from  March  1971  to  April 
1972.  Net  plankton,  nannoplankton,  periphyton, 
and  visible  attached  algae  were  studied.  Cer- 
tain physical  and  chemical  parameters  in  the 
waters  of  Huntington  Creek  and  a  small  pond 
along  its  course  were  also  measured. 

Huntington  Creek  contains  a  wide  diversity 
of  genera  and  species  of  algae.  Diatoms  are  the 
main  constituent  of  the  flora  of  this  stream 
throughout  the  year.  Hydrurus  foetidus  is  preva- 


lent in  Huntington  Creek  from  late  winter  to 
early  summer,  and  filamentous  blue  green  algae 
abound  in  the  summer  and  fall.  Cladophora 
glomerata,  Oedogonitim  sp.,  and  Cham  vulgaris 
are  abundant  in  the  creek  beyond  the  mouth 
of  the  canyon.  Most  plankton  in  Huntington 
Creek  originate  on  the  substrate  and  in  reser- 
voirs on  the  left  fork. 

Huntington  Creek  is  a  cold,  fast-flowing, 
hard-water  mountain  stream,  and  the  algal 
flora  of  this  creek  is  typical  of  such  a  habitat. 


INTRODUCTION 


In  October  1970  a  study  of  the  algae  of 
Huntington  Canyon,  Emery  County,  Utah,  was 
initiated  ( Fig.  1 ) .  The  need  for  this  study  stems 
from  the  construction  of  a  coal-fired  power- 
generating  station  and  a  30,000  acre-foot  reser- 
voir by  Utah  Power  and  Light  Company.  The 
generating  station  is  located  in  lower  Hunting- 
ton Canyon  approximately  12  miles  northwest 
of  Huntington,  Utah,  on  land  formerly  owned 
by  the  Utah  State  Division  of  Wildlife  Re- 
sources and  the  Bureau  of  Land  Management 
(Fig.  2).  The  Peabodv  Coal  Company  will  sup- 
ply coal  for  the  generating  station  from  a  mine 
2.5  miles  southwest  of  the  station,  and  the  elec- 
tricity will  be  transmitted  south  to  the  Four 
Comers  area  and  north  to  Camp  Williams 
(Draft  Environmental  Statement,  1971).  When 
completed,  the  station  will  consist  of  four  gen- 
erating units.  The  first  unit  will  generate  430 
megawatts  of  electricity  and  will  be  operational 
in  1974.  Thereafter,  one  unit  will  be  completed 
during  each  of  three  four-year  periods.  Upon 
completion,  the  station  will  be  capable  of  gen- 
erating 2,000  megawatts  of  electricity. 

The  four  generators  will  be  cooled  with 
water  taken  from  Huntington  Creek.  To  insure 


Fig.    1.      Index    map 
area. 


of   the   Huntington   Canyon   study 


^Department  of  Botany  and   Range  Science.   Brigliain  YounK   University,   Provo.   t'l.ili   ^f4(l02 


Bricham  Young  University  Science  Bulletin 


Fig.  2     Mouth  of  Huntington  Canyon  on  tlio  eastern  edge  of   tlie  Wasatch   Plateau.  The  Utah  Power  and  Light 
Company  Generating  Station  is  located  at  the  right  center.  Photographed  Feb.  7,  1972. 


that  a  continuous  supply  of  water  will  be  avail- 
able, a  new  reservoir,  called  E'ectric  Lake,  will 
be  constructed  on  the  right  fork  of  Huntington 
Creek  approximately  20  miles  upstream  from 
the  generating  station  near  the  mouth  of  Bear 
Canyon,  Emery  County,  Utah  (Fig.  3).  The 
reservoir  will  be  approximatelv  4.5  miles  long 
and  215  feet  deep  at  the  dam  (Fig.  4).  It  will 


store  water  from  the  spring  nmoff,  which  will 
be  released  as  needed  during  the  summer  and 
fall  months.  A  paved  road  will  allow  access  to 
the  reser%oir,  and  public  recreational  facilities 
will  be  provided. 

Initial  impact  of  this  project  on  the  environ- 
ment of  Huntington  Canyon  will  result  from 
the  following  four  factors :   ( 1 )  the  construction 


Biological  Sehies,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


Fig.   3.     Locality  of  the  dam  for  Electric  Lake  on  the  Right    Fork    of    Huntington    Creek    below    Bear    Canyon. 
Photographed  Nov.  16,  1970. 


Bricham  Young  University  Science  Bulletin 


Fig.   4.     Upper   drainage   of   the  Right   Fork   ol   Huntjiigtoii  Creek.   Flat  Canyon  is  at  the  lower  right  and  James 
Canyon  is  at  the  left  center.  Photographed  Nov.  16,  1970. 


of  the  generating  station  itself,  which  neces- 
.sitates  extensive  excavation  and  will  infringe  on 
the  winter  deer  range;  (2)  the  scarring  of  the 
mountainside  during  the  construction  of  the 
dam  and  the  relocation  of  approximately  15 
miles  of  road  through  heavily  forested  regions; 
(3)  the  flooding  of  approximately  4.5  miles  of 


prime  fishing  stream  on  the  right  fork  of  Hun- 
tington Creek,  which  currently  serves  as  spawn- 
ing grounds  for  brown  and  cuttliroat  trout;  and 
(4)  the  destruction  of  watersheds  along  the 
patli  of  the  power  lines. 

Other  less  obvious  effects  may  occur,  espe- 
cially in  the  aquatic  environment,  which  often 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


becomes  a  repository  for  chemical  and  physical 
pollutants  entering  via  effluents,  drainage  from 
surrounding  lands,  and  directly  by  rain  and 
snow.  The  silt  load  in  the  creek  is  an  important 
factor,  especially  during  construction  periods, 
causing  abrasion  and  erosion  which  can  be 
detrimental  to  the  stream  ecosystem.  Also,  the 
release  of  reservoir  water  into  Huntington  Creek 
may  cause  temporary  or  permanent  temperature, 
chemical,  and/ or  nutrient  changes  which  will 
affect  the  ecological  balance  of  the  biota  of  tlie 
stream. 

Because  of  the  possible  environmental  effects 
of  this  project,  the  Center  for  Health  and  En- 
vironmental Studies  at  Brigham  Young  Univer- 
sity, with  primary  funding  from  Utah  Power 
and  Light  Company,  undertook  a  comprehensive 
study  of  the  aquatic  environment  of  the  Hun- 
tington Canyon  region  in  September  1970.  The 
initial  goal  of  this  study  was  to  gather  data  on 
physical,  chemical,  and  biological  parameters, 
which  may  be  used  to  determine  future  changes 
in  this  ecosystem. 

Algae  are  important  in  such  an  environmen- 
tal impact  study  inasmuch  as  they  are  extremely 
responsive  to  changes  in  the  environment  and 
thus  indicate  changes  and  fluctuations  that  may 
occur.  For  instance,  Blum  (1957)  found  a 
marked  change  in  the  benthic  algal  flora  as 
pollution  outfalls  entered  the  Sahne  River,  Mich- 
igan. Foerster  and  Corrin  ( 1970 )  observed  that 
the  presence  or  absence  of  certain  algae  enable 
one  to  determine  the  condition  of  the  water  in 
which  they  are  normally  found.  Palmer  ( 1961 ) 
stated  that  a  knowledge  of  the  algal  population 
of  rivers  both  quantitatively  and  qualitatively 
is  important  if  one  is  to  assess  their  true  value  in 


the  ecosystem.  Pahner  ( 1961)  fmther  stated  that 
"...  it  can  be  important  to  know  the  algal 
population  of  a  river  before  any  major  change  is 
made  in  the  use  of  the  stream.  Also,  we  need 
to  know  the  algal  population  of  rivers  through- 
out the  year  and  not  merely  for  the  simimer 
months." 

This  paper  reports  the  initial  algal  studies 
of  Huntington  Creek.  Future  comparative  studies 
will  be  made  during  and  after  construction  and 
operation  of  the  power  plant-reservoir  complex. 

The  initial  goal  of  this  study  was  to  obtain 
an  overall  picture  of  the  entire  aquatic  algal 
flora  rather  than  one  specific  part.  Therefore, 
sampling  included  water  chemistry,  quantitative 
analysis  of  phytoplankton  and  attached  algae, 
and  a  floristic  survey. 

Plankton  are  interpreted  in  this  study  as  all 
organisms  found  in  the  open  water  (Kofoid, 
1^)8),  and  only  chlorophyll-bearing  phytoplank- 
ton (Welch,  1935)  are  considered  in  this  paper. 
Phytoplankton  are  divided  into  net  plankton 
(those  forms  large  enough  to  be  retained  by  a 
67-//,m  mesh  plankton  net)  and  nannoplankton 
(those  forms  which  can  pass  through  the  net). 
Nannoplankton  are  of  primary  importance  in  this 
study,  since  diatoms,  the  dominant  algae  in  most 
rivers  (Rice,  1938),  are  included  in  this  group. 

Sampling  of  the  attached  algae  included  bo£h 
microscopic  periphyton,  defined  by  Young 
(1945)  as  that  assemblage  of  microscopic  or- 
ganisms growing  upon  free  surfaces  of  sub- 
merged objects  in  water,  and  the  visible  at- 
tached algae. 

Floristic  sampling  was  done  to  determine 
the  composition  and  distribution  of  the  algae  of 
the  canyon. 


REVIEW  OF  SELECTED  ALGAL  STUDIES  IN  UTAH 


Aquatic  research  in  Utah  has  not  been  ex- 
tensive, although  it  has  included  several  ecologi- 
cal and  pollution  studies.  One  significant  con- 
tribution was  made  by  Clark  (1958),  who  stud- 
ied the  phytoplankton  of  the  Logan  River  in 
the  Bear  River  Range  of  the  Wasatch  Moun- 
tains. Clark's  results  were  valuable  for  com- 
parison with  those  of  the  present  study,  since 
the  two  streams  are  similar  in  size  and  certain 
other  characteristics.  A  companion  study  to  that 
conducted  by  Clark  was  completed  by  McCon- 
nell  (1959),  who  estimated  the  algal  productiv- 
ity of  the  Logan  River  from  chlorophyll  extracts 
of  the  algae  growing  on  the  river  bed. 

Samuelson  ( 1950)  completed  a  study  which 
illustrated  man's  influence  on  the  algal  floras 
in  two  mountain  streams  in  the  Wasatch  Moun- 


tain Range  east  of  Salt  Lake  Valley,  Utah.  He 
observed  that  hvestock  grazing  and  recreation 
severely  damaged  the  aquatic  ecosystem  in 
Emigration  Canyon  as  compared  to  that  of  Red 
Butte  Canyon. 

Another  pollution  study  (Quinn,  1958)  dem- 
onstrated that  organic  wastes  from  the  effluent 
of  a  sugar  beet  factory  were  detrimental  to  the 
algal  flora  of  the  Jordan  River  in  Salt  Lake 
County,  Utah. 

Currently,  an  algal  floristic  and  ecological 
investigation  is  being  conducted  along  the  en- 
tire length  of  the  Provo  River  (Lawson,  pers. 
comm. ) .  This  study  will  establish  the  algal  com- 
munities in  the  river  and  their  responses  to 
man's  use  of  the  drainage  area. 

More    investigations    have    been    conducted 


Bricham  Young  University  Science  Bulletin 


on  insects  than  on  algae  in  Utah  streams.  These 
studies  are  valuable,  since  they  often  include 
information  on  the  algae  in  the  ecosystem  being 
studied  and  give  general  information  concerning 
biological  responses  to  environmental  stresses. 
One  such  study  was  conducted  by  Smith  ( 1959 ) , 
who  included  algal  samples  in  his  macroinverte- 
brate  study  of  the  Weber  River  in  north  central 
Utah.  His  results  showed  that  siltation  from 
watershed  misuse,  habitat  destruction  from 
dredging,  and  stream  bottom  exposure  resulting 
from  irrigation  diversion  were  more  destructive 
to  the  aquatic  biota  than  organic  pollution. 

An  earlier  study  by  Dustans  ( 1951 )  on  the 
Provo  River  also  discussed  the  effects  of  dredg- 
ing on  aquatic  life.  He  mentioned  reduced 
photosynthesis,  loss  of  marginal  vegetation,  and 
the  loss  of  diatoms,  desmids,  and  filamentous  al- 
gae as  primary  contributing  causes  to  the  re- 
duction of  insect  benthos  in  dredged  stream 
channels. 

A  pollution  studv  was  conducted  in  central 
Utah  on  the  Price' River  (Miller,  1959).  Al- 
though this  river,  like  Huntington  Creek,  drains 
the  Wasatch  Plateau,  it  is  of  little  value  for  com- 
parison with  the  present  study,  since  the  ex- 
treme silt  load  in  the  Price  River  and  organic 
pollution  contributed  by  towns  through  which 
it  passes  severely  restrict  biological  life.  Mil- 
ler found  only  rare  and  limited  amounts  of 
Cladophora  sp.  and  Chaetophora  elegans  in  the 
river  and  a  noteworthy  absence  of  aquatic  vas- 
cular plants. 

Work  has  also  been  done  on  the  plankton 


of  ponds,  reservoirs,  and  lakes  of  Utah.  These 
studies  include  the  following:  Piranian's  (1937) 
report  on  the  plankton  of  the  Bear  River  Migra- 
tory Waterfowl  Refuge;  Chatwin's  (1956)  study 
of  the  vertical  distribution  of  phytoplankton  in 
Deer  Creek  Reservoir,  Wasatch  County,  Utah; 
Pratt's  ( 1957 )  investigation  of  plankton  periodi- 
city in  Salem  Lake,  Salem,  Utah;  and  Longley's 
( 1969)  discussion  of  the  phytoplankton  associa- 
tions in  Flaming  Gorge  Reservoir.  The  infor- 
mation provided  by  these  and  similar  studies 
is  valuable  in  understanding  stream  environ- 
ments and  communities,  since  lentic  environ- 
ments normally  exert  a  definite  strong  influence 
on  the  streams  that  drain  them.  Since  several 
reservoirs  presently  occur  on  the  Huntington 
Creek  drainage,  and  a  new  one  (Electric  Lake) 
is  under  construction  as  of  1972,  their  manage- 
ment and  algal  populations  need  to  be  con- 
sidered as  factors  affecting  the  physical  and  bio- 
logical parameters  of  Huntington  Creek  itself. 
Mention  should  also  be  made  of  some  im- 
portant taxonomic  references  concerning  Utah 
algae.  The  most  significant  contribution  in  this 
regard  was  made  by  Dr.  Seville  Flowers  who 
published  mimeographed  keys  to  the  common 
algae  of  Utah  (n.d.,  a)  and  to  the  blue  green 
algae  of  Utah,  (n.d.,  b).  Flowers  has  also  re- 
ported on  the  nonvascular  plants  of  various  re- 
gions of  the  state  ( 1959,  1960 ) .  Two  other  taxo- 
nomic studies  are  those  by  Norrington  (1925) 
and  Coombs  (1964)  of  the  Wasatch  and  Uinta 
Mountains,  and  the  Western  Uinta  Mountains, 
respectively. 


DESCRIPTION  OF  THE  HUNTINGTON  CANYON  DRAINAGE 


Geology 
Huntington  Creek  is  one  of  many  streams 
that  drain  the  Wasatch  Plateau  of  central  Utah. 
This  plateau  is  the  northernmost  of  the  plateaus 
of  Utah  and  is  situated  in  the  central  part  of  the 
state  between  30  and  40  degrees  north  latitude 
and  111  and  112  degrees  west  longitude.  It 
merges  northward  with  the  higher  land  of  the 
Uinta  Basin  and  is  separated  from  the  Fish 
Lake  Plateau  to  the  south  by  a  20-mile-vvide 
erosional  depression.  The  Wasatch  Plateau, 
which  rises  to  elevations  of  11,000  feet  above 
sea  level  and  5,000  to  6,000  feet  above  Castle 
Valley  on  the  east  and  Sanpete  Valley  on  the 
west  (Spieker  and  Reeside,  1925),  is  essentially 
a  tableland  90  mik^  long  and  20  to  30  miles 
wide  (Figs.  5-6).  Strata  in  the  plateau  are 
mostly  Late  Cretaceous  and  Early  Tertiary  in 
age  and  lie  flat  or  dip  at  moderate  angles.  Re- 


sistant rocks  alternate  with  those  less  resistant, 
giving  cliff,  bench,  and  slope  profiles  much  like 
those  of  the  Colorado  Plateau  (Spieker  and 
Billings,  1940).  Castle  Vallev  on  the  east  is  of 
erosional  origin.  The  western  edge  of  this  valley 
exhibits  a  sharp  profile,  since  the  eastern  edge 
of  the  Wasatch  Plateau  drops  abruptly  through 
horizontal  strata  from  one  formation  to  another 
( Fig.  2 ) .  Sanpete  and  Sevier  Valleys,  west  of 
the  plateau,  arose  from  down  folding  and  fault- 
ing, with  the  western  front  of  the  plateau  itself 
being  a  great  monoclinal  flexure.  Otlu^  faults 
nnming  through  the  plateau  have  created  ir- 
regularities in  stratigraphy,  and  erosion  has 
carved  canyon,  cliffs,  and  gullies  throughout  the 
area  (Dutton,  1880). 

The  eastern  slopes  of  the  Wasatch  Plateau 
are  dissected  bv  deep,  rock\'  gorgt»s  with  fast- 
flowing    streams    similar    to    lower    Huntington 


Biological  Series,  Vol.  18.  No.  2       Algae  ok  Huntington  Canyon,  Utah 


Fie  5  North  central  portion  of  the  Wasatch  Plateau  sliowing  the  Huntington  Creek  drainage.  Left  Fork  of 
Huntington  Creek  is  at  A,  Right  Fork  of  Huntington  Creek  is  at  B,  Nuck  Woodward  Canyon  is  at  C, 
North  Hughes  Canyon  is  at  D  and  Candland  Mountain  is  at  E.  Photographed  i-eb.  7,  197Z. 

Creek    The  eastern  face  of  the  plateau  consists  of  the  eastern  slopes  of  the  plateau.  The  San 

of  sharp  cUffs  of  Starpoint  sandstone  and  rough  Rafael  River  drains  into  the  Green  River,  which 

erosion    of    the    uppermost    layers    of    Mancos  in   turn  feeds  the   Colorado   River.   Streams  of 

shale.  From  the  mouth  of  Huntington  Canyon,  the  western  slope  of  the  Wasatch  Plateau  dram 

Castle  Vallev  extends  eastward  toward  the  San  into  the  San  Pitch  and  Sevier  rivers. 
Rafael  River  (Fig.  7),  which  collects  the  waters  Spieker   and   Billings    (1940)    described   the 

of  Huntington  Creek  and  other  drainage  waters  stratigraphy    and   thickness    of   each   formation 


Bricham  Young  Univehsity  Science  Bulletin 


> 


Fig.  6.  Eastern  edge  of  the  Wasatch  Plateau  and  Lower  Huntington  Canyon  looking  eastward  toward  the  San 
Rafael  Swell.  The  Left  Fork  of  Huntington  Creek  is  at  the  lower  right,  the  right  fork  is  at  the  lower  left 
and  Tie  Fork  Canyon  is  at  A.  Photographed  Feb.  7,   1972. 


of  the  Huntington  Canyon  section  of  the  Wa- 
.satch  Plateau  as  follows: 

Paleocene 

Flagstaff  limestone.  Gray,  tan,  white 

limestone,  with  minor  amounts  of  shale 

and   sandstone;   lacustrine   300-500' 

Upper  Cretaceous  and  Paleocene 

North  Horn  formation.  Buff,  gray,  red 
sandstone,  gray  to  variegated  shale, 
conglomerate,  some  limestone;  flood- 
plain   and   lacu,strine  in  origin  


Upper  Cretaceous 

Price  River  formation. 

Upper  member:  Gray  sandstone  and 
conglomerate  with  minor  amounts  of 
shale    


2000' 


600' 


Castlegate  sandstone  member:  Massive, 
cliff-forming  gray  sandstone,  coarse 
grained  to  conglomeratic   300' 

Blackhawk  formation.  Medium-tcnfine- 
grained  buff  and  gray  sandstone,  gray 
shale,   coal    1500' 

Starpoint  sandstone.  Massive,  cliff- 
forming  buff  sandstone,  medium-to- 
fine  grained;  marine  450' 

Mancos  shale.  Gray  marine  shale  (only 
uppermost  pat^  exposed  in  area 
described)    4000'  -\- 

The  upper  portion  of  the  Huntington  Creek 
drainage  (Fig.  8)  is  mostly  North  Horn  sand- 
stone and  shale  with  glaciated  cirques,  moraines, 
and  widened  valleys  with  outwash  deposits  of 


Biological  Series,  Vol,  18,  No,  2       Alcae  of  Huntington  Canyon,  I'taii 


Fig,  7,     Mouth  of  Huntington  Canyon  looking  across  Castle    Valley    toward    the    San    Rafael   Swell,    Photographed 
Feb,  7,   1972, 


Pleistocene  age  (Spieker  and  Billings,  1940). 
Most  cirques  occur  in  Joe's  Valley  Graben,  a 
vertically  displaced  fault  block  in  the  central 
part  of  the  plateau.  This  graben  averages  2.5 
miles  wide  and  extends  south  for  60  miles  from 
the  north  central  part  of  the  plateau  (Spieker 
and  Billings,  1940).  Most  glaciers  issued  east- 
ward from  the  western  edge  of  the  plateau 
into  the  graben  valk'\-,  often  coalescing  to  form 
large  sheetlike  moraines.  Stream  notches  in  many 
of  these  moraines  have  been  dammed  in  recent 
years  to  foma  storage  reservoirs,  such  as  Cleve- 
land and  Huntington  reservoirs. 

The  left  fork  of  Huntington  Oeek  drains  the 
northern  part  of  tliis  graben  and  the  slopes  that 
rise  from  it.  The  headwaters  gather  from  Spring, 


Lake,  Rolfson,  and  Staker  canyons,  flow  across 
the  graben  valle\ ,  and  descend  through  a  rocky 
gorge  approximatel)'  3,000  feet  deep  (Spieker 
and  Billings,  IMO).' 

The  headwaters  of  the  right  fork  of  Hun- 
tington Creek  arise  north  of  the  termination  of 
Joe's  Valley  Graben,  which  ends  at  Cleveland 
Reservoir.  The  right  fork  origmates  in  narrow 
rocky  canyons  in  the  Price  River  sandstone  but 
flows  early  into  Blackhawk  sediments  where 
the  stream  channel  widens  into  a  broad  U- 
shaped  valley  (Fig.  9).  This  valley  remains 
prominent  to  Bear  Canyon,  where  it  narrows 
again  to  a  V-shaped  mountain  gorge  (Fig.  10). 
This  flat-bottomed  valley  was  created  by  lateral 
erosive  cutting  by  glaciers  in  this  canyon. 


10 


Bricham  Young  University  Science  Bulletin 


"Xfea. 


Fig.  8.     Geologic  map  of  part  of  the  Wasatcli  Plateau,  Utah  (after  Spieker  and  Billings,  1940). 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


11 


Fig.   9.     Glacier  cut  U-shaped  valley  in  the  upper  drainage   of   the    Right   Fork   of   Huntington   Creek.    Northern 
end  of  Joe's  Valley  Graben  is  at  the  upper  right.  Photographed  Nov.  19,  1970. 


12 


Bricham  Young  University'  Science  Bulletin 


Fig.   10.     Deep  gorges  of  Huntington  Canyon.  Pole  Canyon   (A),  Left  Fork   (B),  Horse  Creek  Canyon   (C),  Tie 
I^ork  Canyon   (D).  Photographed  Feb.   7,   1972. 


Climate  and  Vegetation  Zones 

Tlie  upper  part  of  the  drainage  of  Hunting- 
ton Creek  exists  under  semihumid  montane  con- 
ditions, with  30  to  40  inches  of  precipitation 
annually  (Draft  of  Environmental  Statement, 
1971).  A  large  snowpack  accumulates  in  this 
region  in  the  winter,  creating  a  high  spring 
runoff  supphing  ground  water  which  feeds 
local  springs  throughout  the  year.  Aspen-snow- 
berr\-  ( Populus  tremttloides-Stjinphoricarpos  vac- 
cinoides)  associations  are  scattered  throughout 
this  upper  drainage  with  populations  of  sub- 
alpine  spruce  ( Picea  engelmannii )  on  the  north- 
other  slopes  and  in  the  open  valleys  (Figs.  11- 


12).  Wet  meadows  and  willows  are  common 
along  gendy  flowing  streams  and  in  pockets 
formed  from  Pleistocene  glaciation. 

Lower  Huntington  Canyon  exhibits  a  semi- 
arid  climate  with  approximately  12  inches  of 
precipitation  amuially.  Pinyon-juniper  [Pinus 
monopJiyUa-Junipcrus  osteosperma)  and  sage 
{Artemesia  tridentata)  communities  are  the 
dominant  vegetation  types  here,  with  cotton- 
woods  (Populus  angustifolia)  often  hning  the 
streams  in  the  canyon  bottoms  (Fig.  2). 
em  slopi^  and  sagebrusli-grass  communities  on 

Castle  Valley   is   flat  and  arid  with  a  few 
scattered  small  towns.  It  provides  some  pasture 


Biological  Series,  \'ol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


13 


Fig.  11 .     North  Hughes  Canyon  looking  northeast  from  the  Right  Fork  of  Huntington  Creek  toward  the  Book  Cliffs 
(in    the    background)     showing    spruce-aspen    forest  cover.  Photographed  Nov.  16,  1970. 


14 


Bricham  Young  University  ScitNCE  Bulletin 


<t 


■'h 


^3 


Fig.   12.     Right  Fork  of  Huntington  Creek  at  James  Canyon.  Photographed  Nov.  16,  1970. 


Biological  Series,  Vol.  18.  No.  2       Alc.\e  of  Huntington  Canyon,  Utah 


15 


land  and  crop  land  for  alfalfa,  com,  and  other 
grains,  utilizing  irrigation  water  supplied  from 
streams  draining  the  eastern  slopes  of  the  Wa- 
satch Plateau.  Much  of  the  lower  slopes  of  the 
eastern  face  of  the  Wasatch  Plateau  and 
the  Castle  Vallev  floor  are  composed  of  Man- 
cos  shale  deposits.  Since  these  rocks  are  rich  in 
carbonates  and  other  easily  dissolved  mineral 
salts,  the  streams  passing  through  them  are 
greatly  influenced  and  become  less  desirable  for 
agricultural  uses.  Because  of  this,  much  of  the 
irrigation  water  used  in  Castle  Valley  is  obtained 
via  canals  from  storage  reservoirs  and  streams 
further  up  the  canyon  where  the  water  is  of 
higher  quality. 

Description  and  Uses  of  Huntington  Creek 

The  present  study  is  mainly  concerned  with 
the  right  fork  of  Hunrington  Creek  and  its  main 
course  below  the  junction  of  the  two  forks,  since 
these  will  be  influenced  directly  by  the  Utah 
Power  and  Light  Company  project.  As  men- 
tioned, the  upper  reaches  of  the  right  fork  are 
gentle  and  smooth  flowing,  becoming  torrential 
upon  descent  through  deep  canyon  gorges.  From 
the  headwaters  of  the  right  fork  until  it  joins 
the  San  Rafael  River,  Huntington  Creek  is  ap- 
proximately 50  miles  long  and  drains  approxi- 
mately 320  square  miles.  The  lengtii  of  the  creek 
sampled  during  this  study  extended  from  the 
mouth  of  Bear  Canyon  downstream  approxi- 
mately 35  miles  to  the  town  of  Lawrence  on  the 
western  edge  of  the  San  Rafael  Swell. 

The  Huntington-Fairview  Forest  Highway 
follows  Huntington  Creek  and  its  right  fork 
rather  closely  and  is  paved  from  its  junction 
with  Utah  Highway  10  at  Huntington  to  two 
miles  above  the  junction  of  the  right  and  left 
forks.  Plans  for  the  future  in  this  area  include 
an  all-weather  road  across  the  summit,  linking 
Huntington  and  Fairview  (Draft  of  Environ- 
mental Statement,  1971).  Many  campgrounds 
and  picnic  areas  presently  occur  along  the  creek, 
and  these  facilities  are  well  used,  especially  on 
summer  and  fall  weekends.  The  stream  and 
neighboring  reservoirs  are  stocked  and  managed 
by  the  Utah  State  Division  of  Wildlife  Re- 
sources and  provide  some  of  the  best  fishing  in 
eastern  Utah.  The  upper  reaches  of  the  right 
fork  provide  excellent  spawning  grounds  for 
German  brown  and  cutthroat  trout,  and  the 
natural  channel  of  the  creek  provides  good  hab- 
itat for  aquatic  insects,  which  contribute  to  a 
productive  environment  for  fish.  The  upper  val- 
le\s  are  also  used  for  summer  grazing  of  cattle 
and  sheep. 

Cleveland,   Miller's   Flat,   Rolfson,  and  Him- 


tington  Reservoirs  on  the  left  fork  of  Hunting- 
ton Creek  are  maintained  and  managed  by  the 
Huntington-Cleveland  Irrigation  Company  to 
supply  water  to  the  communities  and  farms  of 
Castle  Valley.  These  reservoirs  achieve  some 
control  of  the  spring  runoff  and  allow  a  con- 
stant flow  to  Castle  Valley  through  the  summer 
and  fall  dry  period.  Most  of  the  water  released 
by  these  reservoirs,  as  well  as  water  from  Hun- 
tington Creek  proper,  is  diverted  from  the  creek 
into  a  canal  by  a  diversion  dam  located  four 
miles  northwest  of  Huntington.  This  canal  emp- 
ties into  North  Huntington  Reservoir  northeast 
of  the  town  of  Huntington.  The  water  stored 
there  is  used  for  agricultural  purposes  in  Castle 
Valley.  Below  this  diversion  dam  the  stream 
flow  is  greatly  reduced  but  increases  slightly  as 
it  gathers  drainage  waters  from  the  surrounding 
land  and  springs  along  its  course.  The  water 
in  this  lower  portion  of  Huntington  Creek  is 
greatly  affected  bv  this  drainage  water  and  is 
generally  of  low  qualit\-. 

Water  discharge  in  Huntington  Creek  fluc- 
tuates greatly  with  the  seasons.  Discharge  mea- 
surements have  been  made  at  two  localities 
along  the  creek.  Utah  Power  and  Light  Com- 
pany took  readings  at  the  site  for  Electric  Lake 
on  the  right  fork  just  below  the  mouth  of  Bear 
Canyon.  Tlie  U.S.  Geological  Survey  took  read- 
ings at  Station  9-318,  located  seven  miles  north- 
west from  the  town  of  Huntington  and  one 
mile  upstream  from  Fish  Creek.  The  average 
yearly  flow  for  the  Electric  Lake  locality  was 
30.3  cubic  feet  per  second  for  the  period  1968 
to  1971.  The  average  monthly  mean  reached  a 
high  over  this  same  time  period  of  159.7  cfs  at 
spring  flood  in  May  and  a  low  of  7.8  cfs  in 
January.  Water  flow  near  the  mouth  of  the  can- 
yon (U.S.G.S.  Station  9-318)  showed  a  yearly 
average  of  100  cfs  for  the  years  1966  to'  1971, 
with  the  monthly  mean  being  high  in  May  at 
309  cfs  and  low  in  January  and  February  at 
27  cfs.  The  six-\'ear  high  was  in  May  1969,  when 
the  discharge  was  552  cfs.  The  six-year  low  was 
in  Februan-  1966,  when  the  water  level  dropped 
to  18  cfs. 

Observations  of  the  creek  throughout  the 
1971-72  study  period  supported  the  water  flow 
data.  Heav)-  spring  runoff  began  in  early  April 
1971,  and  reached  a  peak  during  May  and  early 
June.  A  significant  drop  in  water  flow  was 
noted  on  Juno  29,  1971,  followed  by  a  gradual 
decline  during  the  summer  and  fall  to  winter 
lows  in  Januarv-  and  February  1972.  The  summer 
decline  in  the  main  creek  was  less  severe  than 
that  of  the  right  fork  because  the  natural  drain- 
age of  the  main  fork  was  supplemented  with 


16 


BiucHAM  YouNC  University  Science  Bulletin 


Fig.   13.     Index  map  of  Huntington  Canyon  drainage. 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


17 


water  from  the  reservoirs  on  the  left  fork.  The     but  an  early  thaw  opened  a  major  part  of  the 
river  was  completely  frozen  by  December  1971,      creek  channel  in  February  1972. 


DESCRIPTION  OF  SAMPLING  SITES 


Sampling  sites  were  chosen  to  represent  a 
variet)-  of  different  ecological  niches  along  the 
drainage.  Seven  sites  were  estabhshed  for  quan- 
titative study,  which  were  numbered  beginning 
downstream  at  Lawrence  and  proceeding  up 
Huntington  Canyon  to  the  mouth  of  Bear  Can- 
yon (Fig.  13).  Tliis  was  also  the  general  order 
followed  during  sampling. 

Lawrence  (Site  1) 

This  site  is  located  on  Huntington  Creek  4.7 
miles  southeast  of  Huntington,  Emery  County, 
Utah,  and  1.5  miles  east  of  Lawrence,  Emery 
Countv',  Utah.  It  is  approximately  nine  miles 
below  the  main  diversion  dam  on  Huntington 
Creek  and  was  established  to  monitor  effects  of 
agricultural  drainage  and  increased  dissolved 
minerals  on  the  algal  flora.  The  actual  sampling 
site  was  located  in  a  pasture  through  which  the 
creek  meandered  near  the  intersection  of  Hun- 
tington Creek  and  a  road  leading  to  the  San 
Rafael  Swell  (Fig.  14).  The  average  width  of 
the  creek  at  this  locahty  was  22  feet  during  the 
spring  flood  and  15  feet  during  low  water 
periods.  Average  water  depths  during  the  same 
periods  were  22  and  13  inches,  respectively. 
This  site  included  slow-flowing  deep  water  and 


lli-1 


A-r 


^;.A.wJ*Jft 


Fig  14.  Huntington  Creek  47  niileb,  southeast  of  Hun- 
tington. I'tah.  Locality  of  collecting  site  1.  Photo- 
graphed April  28.   1972. 


swifter-flowing  shallow  riffles,  providing  varied 
algal  habitats.  A  sharp,  eroded  bank  character- 
ized the  west  side  of  the  stream,  whereas  the 
east  bank  sloped  gradually  into  a  pasture.  Popu- 
lus  angustifolia,  Tamarix  pentandra,  Chrijsotham- 
nus  tmuseosus,  and  Artemesia  tridentata  oc- 
curred along  the  banks  throughout  this  area. 
The  stream  bed  here  consisted  mostly  of  silt  and 
sand,  with  small  stones  in  the  riffles,  and  the 
water  was  generally  of  low  quality.  In  talking 
with  the  rancher  who  owns  the  land  at  this 
locality,  he  mentioned  that  over  the  last  few 
years  his  cattle  will  no  longer  drink  the  water 
from  the  creek  unless  they  have  no  other  source. 
This  is  probably  due  to  the  diversion  of  the  bet- 
ter quality  water  upstream,  and  perhaps  to  the 
addition  of  organic  pollutants  by  Huntington 
City. 

Highway  10  Bridge  (Site  2) 

Tliis  site  is  located  four  miles  upstream 
from  Lawrence  and  is  0.3  mile  northeast  of  Hun- 
tington on  Utah  Highway  10  at  the  crossing  of 
the  creek  by  the  road.  Samphng  at  this  site  in- 
cluded water  chemistry,  visible  attached  algae, 
and  floristics.  It  was  established  to  augment  the 
data  collected  at  site  1  and  was  similar  to  it  in 
most  respects.  The  bottom  was  silty  in  the  slow 
areas  and  rocky  in  tlie  faster  water.  The  aver- 
age width  was  35  feet  in  the  spring  and  16  feet 
in  the  summer  and  winter,  and  the  average 
depth  was  12  to  18  inches  and  5  to  7  inches,  re- 
spectively, during  the  same  periods.  Streamside 
vegetation  was  similar  to  that  of  site  1  except 
that  a  large  grove  of  cottonwoods  created  some 
shading  effect  at  this  site. 

Plant  Site  (Site  3) 

This  site  is  located  approximately  three  miles 
above  the  North  Huntington  Reservoir  diversion 
dam  about  three-fourtlis  of  a  mile  downstream 
from  the  Utah  Power  and  Light  generating  sta- 
tion, at  an  altitude  of  6,.300  feet  above  sea  level. 
It  is  approximately  0.3  mile  below  the  entry 
of  Deer  Creek,  which  drains  the  mountains  west 
of  the  generating  station  (Fig.  15).  The  river 
at  this  location  was  basically  deep  and  fast  flow- 
ing, although  some  swift  riffles  were  present. 
The  average  depth  of  the  creek  at  this  site  was 
three  feet  during  the  spring  flood  when  it  was 
25  or  more  feet  wide.  In  the  low  flow  period. 


18 


Bitir.iiAM  Yni'Nr:  I'niversitv  Scikncf.  But.LETiN 


Fig.   15.     Utah  Power  and  Light  Company  Generating  Stntioii.    Deer   Creek    (A),    transmission   lines    (B),    collect- 
ing site  3  (C).  Photographed  Feb.  7,  1972. 


Bioi.oGicAi.  Series,  Vol.  18,  No.  2       Alg.\e  or  Huntincion  Canyon,  Utah 


19 


it  was  usually  less  than  1.5  feet  deep  and  about 
20  feet  wide.  The  bottom  was  strewn  with  large 
and  small  stones,  and  many  large  boulders  pro- 
truded from  the  water.  This  site  often  showed 
siltation  resulting  from  construction,  and  pollu- 
tion from  Deer  Creek,  which  carried  coal  dust 
and  other  pollutants  originating  from  mines 
above  the  generating  station.  The  water  here 
was  often  turbid  with  suspended  sediments,  and 
the  bottom  generally  showed  coal  dust  deposits. 
Terrain  surrounding  this  site  included  steep 
banks  on  the  west  side  of  the  stream  with  a 
more  gentle  incline  on  the  east.  Terrestrial  vege- 
tation here  was  dominated  by  Pinus  monophyUa, 
Juniperus  osteospermum,   Arteinesia   tridentata. 


with  Poptihis  angustifolia  abundant  along  the 
stream  channel.  This  site  was  established  to 
monitor  the  effects  of  construction  and  opera- 
tion of  the  generating  station  on  the  algal  flora 
of  the  creek. 

Bear-Rilda  Campground  (Site  4) 

This  site  is  located  approximately  two  miles 
above  the  generating  station  between  Bear 
Creek  and  Rilda  Canyons  at  an  elevation  of 
6,600  feet  above  sea  level  (Fig.  16). 

The  creek  at  this  campground  was  character- 
ized by  a  deep-flowing  chamiel,  a  shallow  rif- 
fle, and  a  deep  pool,  thus  providing  a  variety  of 


Fig    16      Huntington  Canvon  above  Bear  Creek  Canyon   (A)   showing  collecting  site  4   (B).  Photographed  Feb.  7, 
1972. 


20 


habitats.  Tlio  stream  here  was  bordered  by  a 
broad  flood  plain  and  averaged  about  2  feet 
deep  and  55  feet  wide  at  spring  flood.  During 
low  water  the  riffle  area  became  exposed  when 
the  current  was  limited  to  a  narrow  channel. 
The  average  width  during  this  period  was  11 
feet  and  the  depth  1  foot.  The  pool  at  this  site 
collected  sediment  and  exliibited  a  deep  accumu- 
lation of  silt.  The  bottom  over  much  of  the  rest 
of  the  stream,  especially  in  the  riffle,  was  cov- 
ered with  small  stones.  Willows  ( Salix  sp. )  and 
cottonwoods  ( Populus  angtistijolia )  were  abun- 
dant on  the  banks,  and  a  large  thicket  of  Rus- 
sian Olive  (Eleagnus  angiistifolia)  was  present 
( Fig.  17 ) .  Leaves  from  these  trees  contributed 
to  the  detritus  in  the  stream  during  the  fall 
months,  and  the  trees  were  responsible  for  some 
shading  throughout  the  year,  particularly  in  the 
spring  and  summer. 

Tie  Fork  Pond  (Site  5) 

This  site  is  a  small  shallow  pond  located  at 
the  mouth  of  Tie  Fork  Canyon  at  7,300  feet  ele- 
vation, six  miles  upstream  from  the  generating 
station  (Fig.  18).  Tliis  pond  is  fed  by  drainage  and 
seepage  from  the  surrounding  hillsides  and  in 
turn  drains  into  Huntington  Creek  via  a  culvert. 
This  site  was  established  to  provide  infonnation 
concerning  the  composition  and  seasonal  fluctua- 
tions of  algal  populations  characteristic  of  some 
of  the  ponds  and  backwaters  occurring  along 
the  creek  drainage.  Heavy  growths  of  Potomo- 
geten,  Cham,  and  filamentous  algae  dominated 
the  vegetation  in  this  pond  during  the  summer 


Bbicham  Young  University  .Science  Bulletin 


Fig.   17.     Huntington  Creek  at  collecting  site  4.   Photo- 
graphed Feb.  7,   1972. 


Fig.   18.     Tie  Fork  Pond  just  west  of  the  mouth  of  Tie 
Fork  Canyon.  Photographed  April  28,  1972. 

months,  and  a  thick  accumulation  of  organic 
mud  from  decomposition  lined  its  bottom.  The 
water  level  here  was  high  in  the  spring,  became 
quite  low  during  the  summer,  and  rose  again 
in  the  fall.  It  was  completely  frozen  from  No- 
vember 1971  to  March  1972. 

Stuart  Fire  Station  (Site  6) 

This  site  is  located  on  the  right  fork  of  Hun- 
tington Creek  1.5  miles  below  Stuart  Fire  Sta- 
tion at  an  elevation  of  7,700  feet  (Fig.  19).  The 
creek  meandered  through  this  portion  of  the 
canyon  and  was  less  turbulent  than  downstream 
(Fig.  20).  The  site  included  a  riffle  with  small 
stones  and  a  deep-flowing  channel  with  larger 
rocks  providing  good  habitat  for  the  attachment 
of  visible  bcnthic  algae  and  diatoms.  The  right 
fork  at  this  site  averaged  25  to  .30  feet  in  width 
and  about  1  foot  in  depth  throughout  most  of 
the  year.  A  steep  mountain  slope  covered  with 
sage,  grasses,  and  spruce  rose  from  the  south- 
west bank,  whereas  the  northeast  bank  was 
lined  with  willows  and  gently  rose  a  few  feet  to 
the  canyon  floor.  This  was  the  highest  eleva- 
tion in  the  canyon  that  could  be  reached  during 
winter  months. 

Bear  Canyon  (Site  7) 

This  site  is  located  on  the  right  fork  near 
the  mouth  of  Bear  Canyon  at  the  present  junc- 
tion of  the  Huntington-Fairview  Forest  High- 
way with  the  Miller's  Flat  road  (Fig.  21).  The 
elevation  here  is  S,4(X)  feet.  This  portion  of  the 


Biological  Series,  Vol.  18,  No.  2       .^lcae  of  Huntington  Canyon,  Utah 


'■*«-#^?»igfe._^. 


21 


<^ 


^' 


■X 


■**-—.«. 


'■J^-'^''  •'■''■  ijN-i    '     ■ 


Jfe'^^?" 


'•-'''V!^^'.  ,  y-«^^;.-'i-'^^<. 


^«V'  „,*'? 


Fig.    19.     Right  Fork   of  Huntington   Creek.   Nuck   Woodward   Canyon   is   at   the   right   center  of   the   photograph, 
Stuart  Fire  Station  is  at  A  and  collecting  locality  6  is  at  B    Photographed  Nov.  16,  1970. 


22 


Bricham  Young  UNrvERSiTv  Science  Bulletin 


creek  averaged  20  feet  wide  and  less  than  2 
feet  deep  throughout  the  study.  The  bottom 
was  sandy  in  slow  areas  and  covered  with  small 
stones  in  the  riffles.  A  clay  shelf  along  part  of 
the  channel  supported  growths  of  benthic  Chlo- 
rophyta  during  much  of  the  growing  season. 
Stream  banks  at  this  site  were  vertical  and  un- 
dercut, rising  approximately  10  feet  above  the 
stream  channel.  The  creek  valley    here  is  wide 


with  grass-covered  low  hills  rising  gently  to 
the  mountains.  This  site  is  located  at  the  tran- 
sition zone  between  the  broad  U-shaped  valleys 
of  the  upper  drainage  and  the  deep  gorges  of 
the  lower  canyons.  It  was  added  to  the  previous 
six  sites  in  June  1971  to  sample  the  flora  of  the 
upper  drainage  and  for  comparison  with  site  6. 
From  December  to  June,  this  site  was  inacces- 
sible due  to  snow  pack. 


METHODS 


Physical  and  Chemical  Measurements 

Physical  and  chemical  sampling  was  initiated 
on  June  8,  1971,  at  sites  1,  3,  4,  5,  and  6;  and  sites 
2  and  7  on  August  20,  1971.  Measurements  were 
taken  during  each  collecting  trip  until  the  study 
was  terminated  in  March  1972.  However,  site  7 
became  inaccessible  after  November  1971;  and 
site  5  was  frozen  from  November  to  March  of 
the  study  period. 

Temperature.  Water  temperature  was  recorded 
at  each  sampling  station  in  degrees  centigrade. 

Turbidity.  Turbidity  was  measured  using  the 
colorimeter  in  a  Hach  model  DR-EL  portable 
water  engineer's  laboratory.  Turbidity  was  ex- 
pressed in  Jackson  turbidity  units  (JTU)  as  a 
measure  of  the  intensity  of  light  scattered  by 
particles  suspended  in  the  water. 

Water  Chemistry.  The  pH  was  tested  using  a 
Sargent-Welch   pH    meter.    All   other   chemical 


Fig.  20.  View  down  the  Right  Fork  of  Huntington 
Creek  from  collecting  site  6.  Photographed  April 
28,   1972. 


tests  were  run  following  standard  methods 
(Amer.  Public  Health  Assoc,  1971)  using  a 
Hach  Model  DR-EL  portable  water  engineer's 
laboratory.  Tests  were  run  for  the  levels  of  dis- 
solved oxygen,  carbon  dioxide,  nitrate,  ortho  and 
meta  phosphate,  silica,  calcium  and  magnesium 
hardness,  alkalinity,  and  sulfate. 

The  amount  of  oxygen  dissolved  in  the 
water  was  tested  in  the  field,  since  biochemical 
and  chemical  oxygen  demand  can  alter  the  dis- 
solved oxygen  content  of  a  stored  sample.  All 
other  tests  were  completed  in  the  laboratory 
upon  returning  from  the  field. 

Phytoplankton 

Phytoplankton  studies  were  divided  into  net 
plankton  and  nannoplankton.  Traditionally  this 
division  is  determined  by  the  ability  of  nanno- 
plankton to  pass  through  the  meshes  of  bolting 
cloth  No.  25,  which  has  meshes  measuring  0.04 
to  0.05-mm  square  (Ward  and  Whipple,  1918). 
This  classification  will  be  altered  here  so  that 
nannoplankton  will  include  all  diatoms  regard- 
less of  size,  and  other  algal  forms  too  small  to  be 
adequately  sampled  with  a  0.067-mm  mesh 
plankton  net. 

Net  Plankton.  Net  plankton  were  collected  by 
filtering  40  liters  of  water  through  a  67-/im  mesh 
plankton  net.  Tlie  4()-liter  sample  was  collected 
by  scooping  an  8-liter  bucket  of  river  water 
from  five  randomh'  chosen  sections  at  each 
sampling  site.  Tlie  concentrated  sample  was 
collected  in  a  .30-ml  vial  attached  to  the  net. 
Care  was  taken  to  wash  the  net  witli  filtered 
water  to  remove  anv  organisms  that  might  cling 
to  it.  The  vials  were  transported  to  the  labora- 
tory where  net  plankton  were  examined  and 
enumerated.  Since  it  was  possible  to  count  net 
plankton  soon  after  returning  to  the  laboratory, 
preservatives  were  not  used  on  these  algae. 

Tlie  40-liter  quantitative  sample  (Clark, 
1958)  is  similar  to  the  plankton  pump  method 
described  by  Ward  and  Whipple  (1918).  This 
method   is   superior  to  plankton  net  tows   used 


BiOLOCiCAi,  Series,  Vol.  18.  No.  2       Algae  of  Huntington  Canyon,  Uiaii 


23 


Fig.    21.     Right    Fork   of   Huntington    Canyon   at   junction  with   Bear  Canyon    (A).   Collecting  site  7  is  at  B,  the 
dam   of  Electric   Lake  is  at  C   and  North  Hughes  Canyon  is  at  D.  Photographed  Nov.  16,  1970. 


24 


Brigham  Young  University  Science  Bulletin 


by  Kofoid  (1908),  Allen  (1920),  and  others, 
since  a  known  volume  of  water  is  filtered  and 
the  chance  of  error  from  an  uncertain  amount 
of  water  passing  through  the  plankton  net  is 
eliminated. 

Enumeration  of  net  plankton  was  done  using 
a  Sedgwick-Rafter  counting  cell.  This  counting 
cell  is  commonly  used  for  plankton  studies  (Ko- 
foid, 1908;  Allen,  1920),  and  many  different 
counting  procedures  have  been  adapted  to  it. 
The  counting  method  used  for  this  study  was 
adapted  from  Weber  ( 1970 ) .  After  thoroughly 
mixing  the  30-ml  vial  of  concentrated  river 
water,  a  1-ml  aliquot  was  pipetted  into  the 
Sedgwick-Rafter  cell.  The  sample  was  counted 
at  100  magnifications  under  the  microscope.  An 
ocular  micrometer  was  used  to  measure  a  width 
of  1  mm  on  the  slide,  and  two  or  more  longi- 
tudinal transects  across  the  slide  were  made. 
Algae  encountered  during  these  transects  were 
identified,  and  the  number  of  occurrences  of 
each  genus  or  species  was  recorded.  From  the 
total,  an  average  number  of  organisms  per  single 
50-mm  transect  was  calculated,  and  from  this, 
the  number  of  organisms  per  liter  of  river  water 
was  determined. 

Occasionally,  it  was  necessary-  to  modifv 
these  procedures  slightly.  During  the  summer 
months  the  density  of  net  plankton  at  site  5 
(Tie  Fork  Pond)  required  dilution  of  the  30-ml 
concentrate.  In  September  and  October  the 
sample  size  at  Tie  Fork  Pond  was  reduced  from 
40  liters  to  24  liters  in  order  to  reduce  algal  den- 
sity in  the  sample.  Because  of  low  frequency  and 
low  total  number  of  organisms,  samples  taken 
during  the  winter  months  were  concentrated  by 
centrifugation  to  5  or  10  ml  to  increase  sensi- 
tivity during  counting. 

Nannoplankton.  Nannoplankton  were  collected 
by  obtaining  1  liter  of  river  water  from  each  of 
four  randomly  chosen  sections  at  each  site.  This 
sample  was  placed  in  a  gallon  container  and  re- 
turned to  the  laboratoiy.  Two  liters  of  this 
sample  were  then  suction  filtered  through  a 
membrane  filter  with  a  pore  size  of  1.2-,"m.  This 
filtering  process  removed  all  phvtoplankton  and 
much  (>xtrancous  suspended  matter  from  the 
water.  The  filters  were  cleaned  using  distilled 
water,  and  the  resulting  suspension  centrifuged. 
The  excess  water  was  carefully  decanted,  and 
the  pellet  was  resuspended  in  5  ml  of  standard 
formalin-alcohol-acetic  acid  (FAA)  to  preserve 
it  or  in  5  ml  of  distilled  water,  if  counting  was 
done  immediately. 

Nannoplankton  were  counted  using  a  Pal- 
mer nannoplankton  counting  slide  (Palmer  and 
Maloney,  1954).  This  slide  is  designed  for  use 
with  high  power  dr\'  microscope  objectives  and 


allows  for  higher  magnification  and  resolution 
necessary  to  identify  and  count  nannoplankton 
genera.  All  nannoplankton  observations  and 
counts  were  made  at  400x.  An  ocular  micrometer 
was  used  to  measure  a  0.25-mm  width  on  the 
Palmer  slide,  and  the  algae  encountered  in  four 
transects  of  this  width  were  counted  across  the 
diameter  of  the  slide.  From  the  four  counts,  an 
average  count  per  transect  was  then  computed. 
In  most  cases  a  new  aliquot  was  used  for  each 
count,  and  the  samples  were  always  thoroughly 
mixed  before  the  alicjuot  was  taken  to  maximize 
the  chances  for  uniform  distribution  of  the  sus- 
pended organisms. 

Furthermore,  averaging  the  number  of  algae 
c^ncounterc^d  in  four  transects  increased  the 
probability  of  obtaining  an  accurate  representa- 
tion of  algae  actually  found  in  the  river  and 
reduced  abnormal  values  due  to  clumping.  The 
number  of  algae  encountered  in  each  transect 
was  tallic^d  separately  as  a  check  on  the  preci- 
sion of  the  counts,  and,  in  most  cases,  relatively 
little  variation  occurred  between  the  four  counts. 

As  mentioned  previoush'.  all  diatoms  were  in- 
cluded in  these  nannoplankton  investigations, 
as  well  as  algal  forms  too  small  to  be  adequately 
retained  in  the  plankton  net.  Since  the  original 
sample  was  taken  directly  from  the  river,  net 
plankton  forms  were  encountered  during  nanno- 
plankton enumeration.  These  were  not  included 
in  the  nannoplankton  computations,  although 
they  did  provide  a  check  on  net  plankton  studies. 

Turbidity  was  a  noteworthy  problem  during 
nannoplankton  investigations  since  most  sus- 
pended particles  were  retained  by  the  filters. 
Silt  and  sand  particles,  which  were  especially 
prevalent  during  the  spring  lainoff,  often  ob- 
scured the  algal  specimens  and  made  it  neces- 
sary to  dilute  samples  to  10  ml,  15  ml,  or  20  ml. 
In  rare  eases,  higher  dilutions  were  necessar)'. 

Pemianc^nt  diatom  slides  were  made  from  the 
nannoplankton  samples  from  September  1971  to 
March  1972  so  that  a  permanent  record  of  the 
plankton  flora  would  be  available.  Methods 
have  been  described  by  Weber  (1970)  and 
Patrick  et  al.  (1954)  to  count  diatoms  and  char- 
acterize diatom  floras  from  prepared  slides.  Such 
studies  may  be  undertaken  at  a  future  date,  and 
the  slides  are  also  valuable  to  compare  with 
future  collections.  All  diatoms  were  mounted  in 
Pleurax  (Hanna,  1949).  This  mounting  medium 
has  a  very  high  index  of  refraction  (1.770)  and 
greatly  facilitates  resolution. 

Periphyton 

Sampling  of  the  periphxton  community  has 
received  the  attention  of  many  workers  in  recent 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


25 


years,  and  many  variations  in  sampling  methods 
have  been  attempted.  Sladeckova  (1962)  sum- 
marized techniques  ajid  materials  developed  in 
periphyton  work.  Recent  trends  have  been  to 
submerge  artificial  substrates  at  study  sites  to 
obtain  both  a  qualitative  and  quantitative  con- 
cept of  periphyton  communities  from  studying 
the  algae  that  become  attached  to  these  sub- 
strates. Materials  such  as  wood,  slate,  concrete, 
asbestos,  asbestos  cement,  various  sheet  metals, 
plastics,  celluloid,  st\'rofoam,  and  glass  have 
been  used.  However,  smooth  glass  is  most  wide- 
ly used  and  has  given  accurate  results.  Patrick 
et  al.  (1954)  found  that  by  using  glass  slides 
for  sampling  periphyton  they  were  able  to 
sample  75%  to  85%  of  all  species  obtained  by 
other  collections,  and  95%  of  those  species  with 
more  than  eight  individuals  per  sample.  Dor 
( 1970 )  compared  glass  slides  with  basalt  and 
limestone  substrates  in  Lake  Tiberia  in  Israel 
and  found  that  production  on  slides  was  73% 
of  that  produced  on  natural  substrates.  Odum 
(1957)  found  that  succession  of  algae  on  glass 
slides  was  similar  to  that  on  Sagittaria  plants. 
In  general,  Whitf ord  and  Schumacher  ( 1963 ) 
found  that  colonization  on  glass  slides  was  simi- 
lar to  that  of  rock  substrates,  although  it  was 
somewhat  different  from  colonization  observed 
on  hving  plants. 

Under  certain  conditions,  glass  may  be  sur- 
passed by  styrofoam  as  a  colonization  substrate 
for  periphvton,  especiallv  diatoms.  Holm  and 
Hellerman'(1963)  found  that  at  16°  and  25°C, 
both  substrates  gave  reprcsentarive  colonies;  but 
at  3°C,  diatom  species  diversity  on  the  glass  was 
reduced  as  much  as  40%  while  the  sts'rofoam 
continued  to  support  a  representative  flora. 
However,  Dillard  (1966)  reported  glass  to  have 
higher  diatom  populations  at  both  high  and  low 
temperatures. 

The  means  of  attaching  slides  to  the  sub- 
strate has  also  resulted  in  the  development  of 
many  devices.  Butcher  (1932),  who  did  a  pio- 
neer river  study  using  glass  slides  to  sample 
periphvton,  used  a  frame  attached  to  tlie  river 
bed  to  support  his  slides.  Patrick  ct  al.  (1954) 
developed  a  special  apparatus  for  holding  slides 
in  the  water  which  they  called  the  Catherwood 
diatometer.  This  apparatus  consists  of  a  plastic 
rack  with  attached  floats  so  that  it  can  be  sus- 
pended at  desired  depths  in  the  water.  Slides 
are  placed  vertically  in  the  rack,  which  allows 
diatoms  to  colonize  the  slides  and  concurrently 
reduces  silt  deposition.  Weber  and  Raschke 
(1970)  described  a  similar  apparatiis  with  styro- 
foam floats  as  a  standard  periphyton  sampler 
for  pollution  surveillance.  In  Huntington  Creek 
the    current    is    extremely    swift    during    runoff 


and  quite  low  in  tlie  summer  and  fall.  In 
addition,  the  stream  and  canyon  are  heavily 
used  by  campers,  picnickers,  and  fishermen;  and 
a  periphyton  sampling  device  such  as  described 
above  is  impractical. 

Consideration  has  also  been  given  to  the 
length  of  time  the  slides  should  be  left  in  the 
water.  Patrick  et  al.  (1954)  found  two  weeks  to 
be  optimum,  since  by  that  time  diatom  diver- 
sity had  been  established  and  longer  periods 
had  been  allowed  for  excessive  silt  and  debris 
deposition.  Newcombe  (1949),  on  the  other 
hand,  suggested  25  days  to  be  the  optimum 
time  period.  Patrick  et  al.  (1954)  found  that 
the  accumulation  of  debris  and  other  organisms 
on  the  slides  over  a  long  time  period  made  them 
less  favorable  for  diatom  growth,  and  the  more 
adapted  species  actually  crowded  others  out. 
However,  a  longer  time  period  allows  dominant 
species  to  become  well  established  on  tlie  slides, 
and  this  may  actually  be  an  advantage  in  aid- 
ing an  understanding  of  relationships  between 
periphyton  and  the  periphyton-influenced  plank- 
ton assemblages. 

Newcombe  (1949)  discussed  the  advantages 
of  vertical  placement  of  the  slides  versus  hori- 
zontal placement,  claiming  the  latter  to  be  best 
since  production  was  higher  and  the  results 
were  more  reproducible.  However,  Hohn  and 
Hellerman  ( 1963 )  reported  no  appreciable  dif- 
ference due  to  slide  placement,  and  since  silt 
accumulation  on  horizontal  slides  presents  a 
problem,  vertical  placement  is  often  used.  Peri- 
phvton slides  in  the  present  study  were  oriented 
both  horizontally  and  vertically,  and  no  appre- 
ciable difference  in  silt  accumulation  or  diatom 
populations  was  observed. 

Periphyton  sampling  techniques  used  in  the 
present  studv  were  similar  to  those  used  by 
Whitford  and  Schumacher  (1963).  Clean  1"  x 
3"  microscope  slides  were  fastened  to  a  length 
of  copper  or  stainless  steel  wire  by  means  of 
electrician's  tape.  The  slides  were  then  secured 
in  the  river  bv  fastening  the  wire  to  submerged 
sticks,  large  stones,  or  other  convenient  objects. 
Generally,  the  slides  were  allowed  to  drift  free- 
Iv  in  the  current.  Four  slides  were  placed  in  the 
water  at  each  site  monthly  and  retrieved  the  fol- 
lowing month.  Both  sides  of  the  slides  were 
cleaned  with  distilled  water  in  the  laboratory, 
and  the  attached  algae  were  preserved  in  10  ml 
of  FFA  until  counting  could  be  done.  Samples 
were  counted  using  a  Palmer  counting  slide,  and 
procedures  similar  to  those  used  in  counting 
nannoplankton  were  followed,  except  that  all 
algal  forms  encountered  were  identified  and  re- 
corded. 


26 


Bricham  Young  University  Science  Bulletin 


In  computing  the  algal  totals,  an  average 
number  of  individuals  per  transect  across  the 
Palmer  slide  was  made  from  four  individual 
counts.  Periphyton  were  computed  in  number 
per  cm-.  This  counting  method  was  used  because 
it  is  the  most  precise  commonly  used  method 
(Sladeckova,  1962)  and  it  correlated  with  the 
nannoplankton  procedures,  thus  allowing  the 
establishment  of  accurate  relationships  between 
periphyton  and  plankton  assemblages. 

Difficult)'  was  often  encountered  due  to  ex- 
cessive silt  deposition  on  the  slide,  which  ap- 
parently was  entrapped  by  mucilage  secreted  by 
the  algae.  Dilutions  beyond  10  ml  were  often 
necessary  for  accurate  counting,  although  dilu- 
tions were  kept  as  low  as  possible. 

Data  presented  from  periphyton  studies  were 
obtained  from  counts  on  slides  taken  as  much 
as  possible  from  one  specific  location  at  each 
site.  These  data  characterize  the  general  peri- 
phyton flora  of  the  area  but  certainly  are  not 
representative  of  every  available  ecological  con- 
dition. Slides  submerged  at  site  1  were  sus- 
pended in  slow,  evenly  flowing  water.  Those  at 
site  3  were  in  deep  fast-flowing  water.  Shdes 
from  site  4  were  in  a  deep  hole  where  the  water 
was  quiet  and  in  a  shallow  riffle.  Slides  from 
site  6  were  in  a  shallow  riffle,  and  slides  from 
the  pond  (site  5)  were  submerged  just  below 
the  water  surface  in  still  water. 

Visible  Benthic  Algae 

Visible  benthic  algae,  including  such  forms 
as  Cladophora,  Chara,  and  Hydrurus  were 
sampled  following  the  methods  of  Blum  (1957) 
and  Dillard  (1966),  combining  quadrat  and 
line  transect  methods  for  studying  plant  com- 
munities. Transects  were  chosen  across  the 
stream  at  right  angles  to  the  current  flow  in 
areas  displaying  average  growth  conditions.  The 
percent  coverage  of  the  substrate  by  each  genus 
encountered  was  estimated  in  alternating  10-cm 
by  25-cm  plots  along  this  transect.  Macroscopic 
benthic  algae  were  always  most  abundant  in 
riffles,  and  so  one  or  more  representative  tran- 


sects of  a  riffle  were  taken  at  each  study  site. 
At  sites  1  and  2  slow  water  also  supported  sig- 
nificant algal  growths.  Transects  were  run  in 
these  slow  water  areas  as  well  as  in  riffles  at 
these  sites,  and  the  results  were  averaged  to 
give  a  figure  representative  of  the  site  as  a 
whole. 

From  data  gathered  it  was  possible  to  calcu- 
late cover,  composition,  and  frequency  of  each 
genus  on  the  stream  substrate.  The  frequency 
percent  for  each  genus  was  obtained  by  dividing 
the  total  number  of  quadrats  in  the  transect  into 
those  quadrats  in  which  each  genus  occurred. 
The  cover  percent  for  each  genus  was  deter- 
mined by  assigning  coverage  classes  (Dauben- 
mire,  1968)  to  the  estimation  of  each  genus  re- 
corded in  the  field  and  then  averaging  the  mid- 
points of  these  coverage  classes.  From  the  cover 
percentage,  the  percent  composition  of  the  total 
communitv  represented  bv  each  genus  was  de- 
termined bv  dividing  the  total  cover  into  the 
cover  of  each  genus  and  multiplying  by  100. 

This  method  of  estimating  cover  in  each 
quadrat  gave  more  accurate  information  than 
Blum's  (1957)  method  of  onlv  recording  the 
presence  or  absence  of  a  species  beneath  the 
plots. 

Where  the  water  was  deep  and  swift,  this 
sampling  method  was  not  applicable.  Turbid 
waters  also  hindered  its  use,  altliough  a  glass  jar 
submerged  in  the  water  enhanced  visibility. 

Floristic  Sampling 

Samples  were  taken  from  rocks,  twigs,  sand, 
and  macroscopic  vegetation  at  fourteen  sites 
along  the  creek.  Seven  of  these  sites  corresponded 
with  the  seven  quantitative  sites;  and  the  other 
sites  represented  ponds,  backwaters  and  other 
areas  where  algae  were  found  growing.  Floristic 
sampling  began  in  October  1970  and  continued 
throughout  the  study.  Tlie  algae  in  these  samples 
were  identified  to  species  in  the  laborator)-. 
Samples  of  man\-  filamentous  algae  were  pre- 
served in  FAA  solution,  and  pennanent  diatom 
slides  were  made. 


RESULTS  AND  DISCUSSION 


Each  site  in  this  study  was  chosen  to  repre- 
sent a  unique  ecological  habitat.  Consequently, 
each  site  was  studied  with  the  view  in  mind  to 
characterize  the  complete  alga!  communitv'  and 
ecological  parameters  found  under  each  set  of 
conditions.  The  following  discussion  therefore 
treats  the  algolog\'  and  ecology'  of  each  site  of 
the  studv  area. 


Lawrence  (Site  1) 
The  algal  flora  at  Lawrence  is  dominated  by 
macroscopic  species  including  Cladophora 
glomerata,  Oedogonhim  sp.  and  Chara  vulgaris 
and  bv  many  diatom  genera.  Cladophora  glom- 
erata was  first  recorded  from  floristic  samples 
in  April  1971.  B\-  Ma\-  it  was  prevalent  among 
the  rocks  on  the  stream  bottom  (Fig.  22).  The 


BioLocicAi.  Series,  Vol.  18,  No.  2       Alg.^e  of  Huntington  Canyon,  Utai 


27 


iignnl 


Fig.  22.  Cladophora  glomerata  attached  to  a  stone  at 
site  2.  This  photograph  was  taken  in  the  spring 
when  Cladophora  began  to  be  prominent  in  the  flora, 
and  the  alga  is  approximately  one  half  as  long  as 
it  is   at  maturity.   Photographed  April   28,    1972. 

first  quantitative  sample  in  June  showed  this 
alga  to  cover  35%  of  the  stream  bottom  in  riffle 
areas.  The  second  sample  in  June  showed  a  peak 
development  of  C.  glomerata  when  it  covered 
43%  of  the  riffle  substrate  occurring  as  long  deep 
green  streamers  from  the  stones. 

C.  glomerata  declined  sharply  through  July 
and  hx  the  end  of  the  month  was  represented 
mostly  by  stubb)-  basal  portions  of  the  plant. 
These  fragments  have  the  ability  to  regenerate 
(Fritsch,  1906),  and  many  began  to  do  so  in 
September,  causing  this  species  to  reappear  sig- 
nificantly in  the  flora.  However,  the  fall  growth 
consisted  only  of  heavily  encrusted  compact 
mats  which  lacked  the  long  luxuriant  streamers 
charactt'ristic  of  spring  growth. 

Tliis  cycle  of  Cladophora  glomerata  develop- 
ment at  Lawrence  supports  the  assumption  of 
Blum  (1956)  that  this  alga  is  sensitive  to 
temperatures  approaching  25°C  and  does  very 
poorl\-  at  higher  temperatures.  The  water  tem- 
perature at  this  site  on  June  29,  1971  was  15°C 
in  earl\-  morning  and  approached  25°C  by  late 
afternoon.  Temperatures  through  July,  August 
and  early  September  likewise  approached  25°C 
for  at  least  portions  of  the  day. 

Cladophora  glomerata  beds  at  Lawrence 
provided  excellent  habitat  for  development  of 
other  organisms.  Consequently,  they  were  often 
full  of  insects  and  epiphytic  algae.  The  peak  of 
biological  activity  of  the  stream  could  thus  al- 


most be  said  to  parallel  the  peak  of  Cladophora 
development. 

Mats  of  Oedogonium  sp.  also  formed  long 
green  streamers  intermingled  with  Cladophora 
glomerata.  This  alga  could  be  recognized  since 
the  mats  were  generally  formed  nearer  the  water 
surface  and  their  color  was  yellow  green  as  op- 
posed to  the  deep  green  of  Cladophora.  The 
pattern  of  development  of  this  genus  at  Lav^'- 
rence  was  similar  to  that  of  C.  glomerata.  Oedo- 
gonium sp.  appeared  in  April  and  reached  a 
peak  of  development  in  June.  By  July  Oedo- 
gonium sp.  was  not  evident  as  a  visible  alga  al- 
though small  filaments  were  found  to  colonize 
glass  slides  throughout  the  year  and  were  found 
in  the  net  plankton  until  November. 

Mats  of  Chara  vulgaris  began  developing  in 
(\arly  summer  when  the  water  level  declined 
and  the  water  temperature  rose.  By  October  C. 
vulgaris  dominated  the  aquatic  vegetation  cover- 
ing 64%  of  the  total  substrate.  C.  vulgaris  oc- 
curred in  greatest  abundance  in  slow-flowing 
water,  where  it  reached  85%  cover  in  October. 
Riffles  averaged  only  54%  Chara  cover  at  the 
same  time.  The  water  level  was  extremely  low 
during  this  period,  and  C.  vulgaris  mats  literally 
filled  much  of  the  creek  channel.  By  November 
the  plants  forming  these  large  mats  had  begun 
to  die  and  decompose,  and  walking  through 
them  stirred  up  a  black  organic  ooze  and  large 
amounts  of  entrapped  silt.  Visible  films  of  epi- 
ph\'tic  diatoms  covered  the  upper  filaments  of 
C.  vulgaris.  These  diatoms  consisted  mostly  of 
Achnanthes  minutissima  and  Sijnedra  ulna.  Simi- 
lar to  the  Cladophora  glomerata  mats,  Chara 
vulgaris  beds  were  the  site  of  a  great  deal  of 
biological  activity. 

In  December  and  January  extensive  decom- 
position of  C.  vulgaris  occurred  under  the  ice 
cover  and  the  stream  bed  became  very  murky 
with  silt  and  decomposition  products.  The  water 
was  significantly  influenced  by  decomposition 
during  this  period.  Due  to  high  biological  oxygen 
demand,  dissolved  oxygen  levels  during  Novem- 
ber, December  and  January  fell  to  6,  3  and  8 
ppm,  respectively,  from  the  usual  average  of 
9-10  ppm.  Carbon  dioxide  levels  rose  concur- 
rently from  averages  of  2-4  ppm  to  6,  24,  and 
16  ppm  for  the  same  three  months.  The  higher 
CO2  levels  also  lowered  the  pH  slightly  through 
this  period.  It  is  interesting  that  a  significant 
amount  of  Chara  vulgaris  remained  viable 
through  the  winter  months,  indicating  that  suf- 
ficient light  penetrated  the  ice  and  snow  to  al- 
low photosynthesis  and  also  indicating  that  C. 
vulgaris  is  quite  resistant  to  low  temperatures. 

The  ice  broke  in  February  1972  due  to  an 
early  thaw,  and  the  large  mats  of  Chara  had 


28 


Brigham  Young  Univehsity  Science  Bulletin 


entrapped  large  amounts  of  silt.  The  bottom 
was  black  and  murky,  and  the  water  was  ex- 
tremely turbid  from  silt  stirred  up  from  the 
substrate.  With  the  rise  of  the  spring  flood  in 
March,  turbidity  became  so  intense  that  visibility 
through  the  water  was  reduced  to  zero  as  higher 
and  faster  water  began  scouring  the  stream 
channel  and  washing  silt  deposits  downstream. 
During  late  summer  and  early  fall,  a  pros- 
trate, often  encrusted  alga  became  quite  evi- 
dent on  smaller  stones  of  the  stream  bottom. 
This  alga  was  very  difficult  to  identify  accu- 
rately due  to  its  growth  form,  but  was  suspected 
to  be  Trotoderma  viride  since  this  alga  was  prev- 
alent on  periphyton  slides  collected  in  Septem- 
ber. P.  viride  appears  to  prefer  wann  water, 
since  it  first  appeared  in  the  summer  then  dis- 
appeared as  the  waters  cooled  in  the  fall. 

The  vascular  plant,  Potomogeton  sp.  was  in- 
cluded in  the  sampling  at  Lawrence  since  it 
was  an  important  aquatic  plant  throughout 
much  of  the  growing  season.  Interestingly,  few 
epiphytic  diatoms  were  found  growing  on  living 
Potomogeton  sp.  plants  as  contrasted  to  Oedo- 
goniurn  sp.  and  CladopJiora  glomerata  which 
supported  large  popularions  of  attached  diatoms. 
Hynes  (1970)  indicated  that  some  species  of 
aquatic  plants  such  as  Potomogeton  pectinattis 
support  a  poorlv  developed  periphyton  assem- 
blage while  living,  and  apparently  this  holds 
true  for  the  Potomogeton  at  Lawrence. 

Potomogeton  sp.  first  appeared  in  early  July 
and  bv  late  July  constituted  an  important  part 
of  the  total  flora.  Small  amounts  remained  pres- 
ent throughout  the  winter  and  were  still  present 
when  the  ice  broke  in  February.  Most  Potomo- 
geton plants  lasting  through  the  winter  were  re- 
moved by  scouring  during  spring  high  water. 

Net  plankton  pulses  showed  a  definite  cor- 
relation with  the  appearance  and  development 
of  Oedogonium  sp.  and  Cladophora  glomerata 
(Fig.  2.3).  C.  glomerata  fragments  were  a  major 
component  of  net  plankton  samples  during  late 
spring  and  early  summer  but  disappeared  in 
Julv  and  August.  Oedogonium  sp.  appeared  in 
the  net  samples  in  Mav,  reached  a  peak  in  June 
when  it  was  also  most  abundant  as  a  visible 
benthic  form,  and  fell  off  shaq^ly  in  July.  Total 
net  plankton  occurrence  followed  much  the  same 
curve  as  Cladopliora  glomerata  and  Oedogo- 
nium sp.,  being  highest  in  the  spring  and  ver)' 
low  throughout  the  summer  and  fall.  Net  plank- 
ton at  Lawrence  increased  significantly  in  Feb- 
ruary and  March  1972  because  of  the  growth 
of  Vlothrix  tenerrima  on  the  substrate  during 
winter  months.  Periphyton  slides  retrieved  in 
December  and  March  likewise  had  populations 
of  U.  tenerrima  growing  on  them.  Blum  (1957) 


noted  a  similar  winter  growth  of  Ulothrix 
through  tlie  late  winter  months  in  the  Saline 
River  ,  Michigan. 

Although  the  Lawrence  site  is  located  low 
on  the  creek  drainage,  few  true  planktonic  al- 
gae were  collected.  Clark  ( 1958 )  likewise  found 
the  lower  Logan  River,  Utah,  to  be  low  in 
true  phytoplankton.  Kofoid  (1903)  and  Whit- 
ford  and  Schumacher  (1963)  discussed  the  de- 
velopment of  euplankton  in  rivers  and  con- 
cluded that  the  water  in  a  stream  must  be  sev- 
eral weeks  old  before  a  true  river  plankton  will 
develop.  Thus,  the  water  in  Huntington  Creek 
probably  takes  much  less  time  than  this  to  pass 
from  its  origin  into  the  San  Rafael  River. 

Infonnarion  on  diatom  populations  in  this 
study  came  from  periphyton  and  nannoplankton 
investigarions.  A  strong  vernal  increase  in  peri- 
phyton was  evident  in  April  and  early  May  fol- 
lowed by  a  summer  low  and  a  general  increase 
from  September  through  December.  Winter  lows 
occurred  from  January  to  March  and  fewer 
total  organisms  were  present  during  this  time 
than  in  the  summer.  This  yearly  trend  was  basi- 
cally fomied  by  the  genera  Navicula,  Sijnedra, 
Diatoma,  Cymbella  and  Surirella  (Fig  24). 
Gomphonema  likewise  followed  this  general 
trend  except  for  a  significant  increase  in  Sep- 
tember and  October.  This  September-October 
Gomphonema  pulse  was  caused  by  rapid  in- 
crease of  G.  gracile.  G.  olivaceum,  on  the  other 
hand,  was  more  important  in  the  fall  and  espe- 
cially in  the  winter. 

Nitzscliia  (mostly  N.  palea)  was  an  impor- 
tant component  of  the  periphyton  in  early  June 
(30%  of  the  total  periphyton).  It  decreased 
through  the  summer  until  October,  when  a  sig- 
nificant pulse  occurred.  It  then  declined  again 
through  the  winter  months.  Whitford  and  Schu- 
macher ( 1963 )  classified  periphyton  into  late 
spring-early  fall  species  and  early  spring-late  fall 
species.  This  classification  followed  their  obser- 
vation that  diatoms  appearing  in  late  spring 
usually  also  showed  a  high  colonization  rate  in 
early  fall  and,  likewise,  early  spring  diatoms 
also  were  present  in  large  numbers  in  the  late 
fall.  The  data  on  Nitzschia  palea  from  Lawrence 
indicate  that  this  taxon  is  a  late  spring-early  fall 
form. 

Se\eral  diatoms  reached  theii'  peak  of  de- 
velopment during  summer  months.  Tliese  in- 
cluded Cocconeis  (mostly  C.  pediculus  in  June 
and  C.  placentula  in  August),  Achnanthcs  ininu- 
tissima,  Ct/cloteUa  meneghiniana  and  Pleurosig- 
ma  delicatulum.  Cocconeis  constituted  approxi- 
mately 22'/(  of  tlic  periphyton  from  June  to  Au- 
gust. Cocconeis  placentida  was  an  especially 
important  epiph\'te  throughout  most  of  the  sum- 


BiOL<;ciCAi,  Series,  Vol.  18.  No.  2       Alo.-ve  of  Huntington  Canyon,  Utah 


29 


Total   Net  Plankton:   1  =  50  algae    I 


Selected  Genera 
1  =  25  algae    I 


Nov.         Jan.         Mar. 


Cladophora 


Oedogonium 


Oscillatoria 


Ulothrix 


Fig.   23.     Seasonal  distribution  of  selected   net  plankton  at  Lawrence  (site  1). 


30 


BmciiAM  Ydi'Mc  University  Science  Bulletin 


Total    Periphyton:    1  =  10  algae 


m 


Selected  Genera:   1=5  algae  ml 
May         June        Aug.       Oct.        Dec. 


Navlcula 


Nitzschla 


Coccone/s 


Fig.    24.     Seasonal    distribution    of    selected    periphvtoii  at  I.jiwrenre  (site  1). 


Biological  Series,  Vol.  18.  No.  2       Alg.ae  of  Huntington  Canyon,  Utah 


31 


mer,  and  it  was  not  uncommon  to  collect  a  fila- 
mentous green  alga  covered  with  hundreds  of 
specimens  of  this  species.  Pleurosigma  delicatu- 
lum  was  most  prevalent  in  July- 

During  the  August-October  period,  Achnan- 
thes  minutissinui  comprised  about  36%  of  the 
periphyton.  However,  this  species  was  absent 
from  the  periphyton  in  October,  indicating  that 
colonization  decreased  sharply  during  that 
period. 

Cyclotella  meneghiniana  was  the  only  cen- 
tric diatom  prevalent  in  Huntington  Creek.  It 
showed  a  peak  of  development  in  the  summer 
from  July  to  September  with  a  maximum  in 
August. 

Nannoplankton  in  Huntington  Creek  at  Law- 
rence were  high  throughout  most  of  the  year. 
The  higher  nutrient  levels  in  the  creek  here,  and 
the  availability  of  filamentous  green  algae  as  a 
substrate  for  diatom  growth  contributed  to  the 
continuously  high  levels.  Some  diatom  genera, 
such  as  Gyrosigma,  Cocconeis,  Cyclotella,  and 
Achnanthes  appeared  in  high  numbers  in  the 
nannoplankton  beginning  in  July  1971  when 
spring  and  fall  genera  such  as  Navicula,  SuTirel- 
la,  and  Synedra  became  quite  low  ( Fig.  25 ) . 
These  latter  genera  increased  again  greatly  in 
late  fall  when  most  of  the  dominant  summer 
genera  declined  in  numbers.  A  low  point  for  the 
season  in  total  nannoplankton  was  reached  in 
October.  However,  a  large  pulse  occurred  in 
November  composed  mostly  of  Synedra  ulna, 
which  comprised  41?  of  the  total  nannoplankton. 
Synedra  also  actively  colonized  glass  slides  dur- 
ing this  month,  and  it  grew  so  profusely  on 
d\ing  Chara  vulgaris  mats  that  a  brown  film 
was  visible  on  each  Chara  plant. 

From  Januarv  to  March  1972  a  scouring  of 
the  stream  channel  occurred  as  the  early  run- 
off waters  riled  the  silt  and  decomposition  prod- 
ucts built  up  during  the  fall  and  earlv  winter 
season.  This  scouring  process  also  scoured  many 
of  the  prevalent  winter  and  spring  diatoms  from 
the  substrate  and  from  among  accumulated 
plant  material,  causing  extremelv  high  numbers 
of  these  diatoms  to  occur  in  the  nannoplankton. 
Thus,  nannoplankton  in  Februars  and  March 
exceeded  2  million  cells  per  liter.  Important 
genera  during  this  period  included  Synedra, 
Cymhella,  Surirella  and  Navicula.  Nannoplank- 
ton levels  were  also  high  in  April  and  May  1971, 
which  was  probably  caused  by  renewed  coloni- 
zation following  spring  scouring. 

The  flora  at  LawTcnce  differed  significantly 
from  that  of  the  sites  in  Huntington  Canyon,  es- 
pecially in  the  growth  of  Oedogonium  sp.,  Cla- 
dophora  glomerata.  and  Chara  vulgaris,  and  the 
absence  of  Hydrurtis  foetidus  on  the  stream  bed. 


The  general  plankton  pattern  at  this  site  was 
similar  to  that  of  other  sites  consisting  mostly  of 
diatoms.  However,  the  diatom  communities  here 
were  much  different  in  structure  from  those 
of  other  sites  since  Cocconeis  ( mostly  C.  placen- 
tula),  Cyclotella  meneghiniana,  Pleurosigma  deli- 
catulum,  and  Gyrosigma  spencerii  were  present 
in  much  greater  numbers,  while  Cymbella  spp. 
were  greatly  reduced. 

To  summarize  seasonal  community  variations 
at  Lawrence,  Cladophora  glomerata  and  Oedo- 
gonium sp.  dominated  the  flora  in  late  spring 
and  early  summer,  with  diatoms  such  as  Navi- 
cula, Cymbella,  Synedra,  and  Surirella  occurring 
in  high  numbers  on  stones  and  macroscopic  al- 
gae. Chara  vulgaris  dominated  the  stream  bot- 
tom from  summer  through  fall  and  occurred 
with  Protoderma  viride,  Cocconeis  spp.,  Achruin- 
thes  minutissima,  and  Cyclotella  meneghiniana. 
Late  summer  and  early  fall  allowed  maximum 
development  of  Gomphonema  gracile  and  Nitzs- 
chia  (mostly  N.  palea),  while  the  late  fall  en- 
vironment stimulated  another  general  diatom 
pulse.  Net  and  nannoplankton  assemblages 
were  derived  largely  from  cells  and  filament 
fragments  released  from  the  substrate,  and  true 
planktonic  algae  were  rare  in  the  flora. 

Highway  10  Bridge  (Site  2) 

Water  chemistry  and  visible  attached  algal 
data  from  this  site  correlated  closely  with  that 
from  Lawrence  and  consequently  differed  from 
data  collected  upstream  in  the  canyon.  The 
water  at  sites  1  and  2  had  significantly  higher 
levels  of  nitrates,  phosphates,  alkalinity,  and  es- 
pecially hardness,  silica,  and  sulfate  than  the 
water  at  site  3,  which  is  the  first  site  located  in 
Huntington  Canyon  (Table  1). 

The  same  table  illustrates  that  the  levels  of 
these  chemicals  in  the  water  at  Lawrence  are 
generally  higher  than  at  Highway  10.  This  is 
because  as  the  creek  leaves  the  canyon  it  passes 
through  strata  and  soils  which  are  extremely 
rich  in  carbonates.  In  addition,  the  creek  here 
drains  both  fanning  and  grazing  lands  which  are 
responsible  for  the  addition  of  nitrates  and  phos- 
phates, and  passes  near  Huntington  City  which 

Table    1 .     Chemical    Data    for    Huntington    Creek,    De- 
cember 17,   1971. 


Site  1 

Site  2 

Site  3 

Nitrate  nig/1 

0.6 

0.33 

0.3 

Pbosphatc  nig/I 

0.16 

0.06 

0.08 

Alkalinity  mg/l 

410 

370 

240 

Total  harHness  mg/I 

2000 

1300 

250 

( 

CaCO, 

■Silica  mg/l  SiO' 

16 

18 

2.7 

.Sulfate  mg/l 

2700 

1300 

28 

Brioiiam  Young  University  Science  Bulletin 


Total    Nannoplankton:   1=100  olgoe  ml 


Selected  Genero:   l:=25  olgae  ml 


Apr.       June        July        Sept.         Nov.  Jon. 


Nitzschla 


'Occoneis 


Fip.     i'l,      Seasoiml     distrihutiim     of     •^^lp(to<l     iiHiuinplniik ton    at    T.awrenrp    (site    1). 


Biological  Series,  Vol.  18.  No.  2       Algae  of  Huntington  Canyon,  Utah 


33 


likely  also  adds  nutrients.  Due  to  the  removal 
of  water  for  irrigation  and  storage  above  these 
tsvo  localities,  the  creek  is  generally  low  at 
sites  1  and  2  and  thus  the  addition  of  these 
nutrients  has  a  profound  effect  on  water  quahty. 

The  algal  community  at  site  2  was  very  simi- 
lar to  that  of  site  1  in  many  aspects,  and  both 
resemble  that  reported  by  Blum  ( 1957 )  for  the 
Saline  River,  Michigan,  and  appear  to  be  typi- 
cal of  highly  calcareous  streams  in  general. 
CladopJwra  glotiwrata  at  Highway  10  demon- 
strated a  late  spring-early  summer  development. 
This  species  was  prevalent  here  throughout  May 
and  June  1971,  covering  25%  of  the  riffle  sub- 
strate in  early  June  and  57%  by  late  June.  By 
July,  C.  glomerata  had  apparently  stopped 
growing,  but  mats  of  it  were  still  evident  at- 
tached to  stones  and  streaming  in  the  current. 

Chara  vulgaris  appeared  in  July  1971  and 
became  prevalent  in  August.  This  alga  was 
found  mostly  in  slower  water  rather  than  in 
riffles,  indicating  that  the  replacement  of  Clado- 
phora by  Chara  in  the  flora  was  not  a  result  of 
direct  competition  but  rather  represented  sea- 
sonal change.  Transects  to  measure  visible  ben- 
thic  algae  were  run  in  both  riffles  and  slow 
water  at  this  site,  and  the  results  were  aver- 
aged to  characterize  overall  trends.  However, 
a  comparison  of  the  data  summarized  from  each 
area  (Table  2)  illustrates  some  interesting  habi- 
tat preferences  for  these  two  species.  Cladophora 
glomerata  prefers  riffles  with  fast  water  and  a 
ston\'  substrate,  whereas  Chara  vulgaris  prefers 
slow  water  and  a  silty  substrate. 

Chara  persisted  through  the  fall  and  into 
the  winter  under  the  ice  cover.  However,  it  did 
not  form  the  extensive  mats  which  were  present 
at  Lawrence  since  the  creek  channel  was  much 
shallower  here  and  the  water  faster.  As  the 
water  level  fell  late  in  the  season,  much  of  the 
Chara  on  the  creek  margins  dried  from  t^xpo- 
sure.  When  the  ice  melted  in  February  1972, 
Chara  was  completely  gone  from  the  riffles  but 
still  covered  13%  of  the  stream  bed  in  slower 
areas.  However,  during  the  high  runoff  in  March 

Table  2.  July-November  1971  averages  of  the  fre- 
quency, percent  cover  and  percent  composition  for 
Cladophora  and  Chara  in  a  riffle  and  in  a  slow 
water   area   at   Highway   10    (Site  2). 


Riffle 

Slow  water 

Cladophora  glomerata 
Frequency 
Cover 
Composition 

Chara  vulgaris 
Frequency 
Cover 
Composition 

76.3 

7.3 

62.5 

25.3 

4.4 

36.5 

42.4 

3.7 

15.1 

86.4 
42.0 
84.1 

most  of  it  was  displaced  and  washed  down- 
stream by  high  turbulent  water. 

From  floristic  sampling  at  Highway  10  sev- 
eral trends  in  population  became  apparent.  In 
early  June  and  again  in  October  1971,  Vaucheria 
gemiiiata  was  found  intermingled  among  Clado- 
phora filaments  and  was  covered  with  epiphytic 
diatoms.  Diatoms  most  abundant  in  the  creek  in 
May  and  June  were  Ct/mbella  parva,  Amphi- 
pleura  pellucida,  Diatoma  vulgare,  Diatoma 
tenue  and  Stjnedra  ulna.  In  late  June  Nitzschia 
spp.  and  Cocconeis  placentula  entered  the  flora 
in  significant  numbers.  Diatoms  decreased  gener- 
ally during  the  summer  months,  and  the  stones 
became  covered  with  an  encrusting  cyanophyte 
and  Protoderma  viride.  This  crust  disappeared  in 
October.  In  September  1971  large  amounts  of 
Spirogtjra  sp.  were  found  here  as  well  as  species 
of  Oscillatoria  and  Ltjngbya.  In  October  Amphi- 
pleura  pellucida  showed  an  increase  which  was 
followed  in  November  by  an  increase  in  Sijned- 
ra  ulna  and  Achnanthes  minutissima.  The  Janu- 
ar\'  sample  showed  these  three  diatoms  to  still 
be  important  in  the  flora. 

Although  floristic  trends  at  this  site  were 
similar  to  those  at  Lawrence,  the  total  abun- 
dance of  algae  at  Highway  10  was  considerably 
lower.  This  likelv  resulted  from  the  influence  of 
faster  and  shallower  water  here,  fewer  nutrients 
present  in  the  water  and  the  shade  of  the  bridge 
and  nearby  cottonwood  trees  reducing  the 
amount  of  sunlight  available  for  photosynthesis. 

Plant  Site  (Site  3) 

The  plant  site  was  the  first  site  located  on 
Huntington  Creek  in  Huntington  Canyon  prop- 
er, and  its  algal  flora  was  similar  in  many  re- 
spects to  that  of  other  creek  sites  in  the  canyon. 
The  dominant  genera  at  this  localit)'  were  Hyd- 
rurus,  Oscillatoria,  other  Oscillatoriaceae,  Navi- 
cula,  Gomphonema,  CijmheUo,  Synedra,  Nitzs- 
chia and  Achnanthes. 

Immediately  after  the  ice  broke  in  Febru- 
ary 1972,  Hy drums  foetidus  covered  24%  of  the 
stony  substrates  of  this  site.  It  consisted  of  light 
brown  filaments  on  stones  with  scattered  patches 
becoming  dark  brown.  However,  it  lacked  the 
luxuriant  growth  evident  for  this  species  further 
upstream.  By  March  1972  all  H.  foetidus  had 
disappeared  except  for  a  few  isolated  clumps. 
However,  in  May  and  early  June  of  the  previous 
year  during  the  high  point  of  the  spring  flood, 
some  specimens  of  this  species  were  observed 
growing  on  large  rocks  close  to  the  water  sur- 
face or  partly  exposed. 

Net  plankton  totals  for  //.  foetidus  at  the 
plant  site  showed  that  this  May-June  period  was 


34 


BmcHAM  Young  University  Science  Bulletin 


the  peak  of  production  for  this  species  in  Hun- 
tington Creek  upstream  from  the  plant  site 
(Fig.  26).  Most  specimens  observed  in  the  net 
plankton  were  damaged,  indicating  that  they 
undoubtedly  originated  some  distance  upstream 
from  where  they  were  collected.  H.  foetidus 
showed  a  definite  downward  trend  in  produc- 
tivity as  the  water  temperature  increased  to- 
ward 12°C  which  Zhadin  (1961)  indicated  as 
the  critical  temperature  for  this  alga. 

Filamentous  blue  green  algae  were  also  espe- 
cially important  in  the  net  plankton  from  the 
spring  through  the  summer  and  into  the  fall. 
These  algae  in  Huntington  Creek  consisted  of 
Schizothrix  JTagUe,  OsciUatoria  spp.  and  other 
genera  of  the  family  Oscillatoriaceae.  They  usu- 
ally occurred  mixed  with  diatoms,  silt  and  debris 
as  encrustations  on  stones  and  other  solid  sub- 
strate on  tlie  creek  bottom.  Single  filaments  or 
clumps  of  filaments  were  released  into  the 
creek  current  and  were  second  only  to  diatoms 
as  a  contributor  to  the  total  plankton  of  lower 
Huntington  Creek  in  the  spring  and  summer. 

Periphyton  data  indicate  that  blue  green  al- 
gae were  most  active  in  colonizing  the  substrate 
from  late  June  to  October.  Floristic  samples 
taken  each  month  revealed  that  the  greatest 
abundance  and  diversity  of  filamentous  blue 
green  algae  occurred  in  the  summer  and  early 
fall.  By  September  a  considerable  accumulation 
of  blue  green  algae,  diatoms  and  sediment  had 
accumulated  on  the  stony  substrate  of  the  creek. 
In  October  1971  a  definite  resistant  blue  green 
algal  encrustation  had  developed  beneath  this 
accumulation,  and  in  November  it  was  easily 
scraped  free.  Periphyton  data  indicate  that  no 
cyanophyte  colonization  occurred  during  No- 
vember, which  suggests  that  the  onset  of  winter 
made  conditions  unsuitable  for  these  algae. 

Net  plankton  data  for  the  fall  months  cor- 
relate very  well  with  periphyton  results.  In 
September  small  clumps  of  blue  green  algae 
began  appearing  in  the  net  plankton  in  signifi- 
cant numbers  and  by  November  they  comprised 
70f  of  all  net  plankton  indicating  that  these  al- 
gae were  being  readily  released  from  the  sub- 
strate. Colonization  began  again  during  the 
January-March  1971  period  when  an  active 
growth  of  OsciUatoria  amphibia  and  O.  agardhii 
was  noted  both  under  the  ice  and  in  open  water 
after  the  thaw.  Tliis  recolonization  trend  was 
mostly  determined  from  floristic  samples  taken 
one  to  two  mik^  above  and  Ix-low  the  plant 
site  where  OsciUatoria  spp.  were  especially  abim- 
dant. 

Green  algae  occurred  onl\-  sporadically  on 
periphyton  sampling  slides  at  the  plant  site. 
However,   net  plankton  data  and  visual   obser- 


vation indicated  that  some  species  of  Chloro- 
phyta  were  present  on  the  stream  bottom.  Ulo- 
thrix  tenuissima  was  most  significant  in  June 
1971  and  again  in  March  1972.  Oedogonium  sp. 
occurred  throughout  most  of  the  summer,  and 
Cladophora  glomerata  appeared  in  early  sum- 
mer and  again  in  early  fall.  This  suggests  that 
the  approximate  temperature  preferences  for 
these  algae  are:  Ulotlirix  tenuissima  around 
10°C;  Cladophora  glomerata  close  to  15°C;  and 
Oedogonium  sp.  15°C  and  higher. 

Spirogijra  sp.,  Zijgnema  sp.,  and  Mougeotia 
sp.,  filaments  occurred  in  the  net  plankton  in 
low  amounts  in  the  summer  and  early  fall.  These 
filaments  probably  originated  from  quiet  side 
waters  or  ponds  upstream  from  the  plant  site. 

A  few  true  planktonic  algae  were  noted  in 
the  net  plankton  during  the  summer  months. 
The  most  significant  of  these  were  Pandorina 
morum  which  occurred  from  late  June  to  Oc- 
tober and  Ceratiiim  hirundinella  which  was  col- 
lected from  August  to  November  ( Fig.  26 ) .  The 
source  of  these  algae  was  likely  from  lentic  en- 
vironments which  drain  into  Huntington  Creek 
above  the  plant  site.  Cleveland,  Miller's  Flat, 
Rolfson,  and  Huntington  reservoirs  on  the  up- 
per drainage  of  the  left  fork  of  Huntington 
Creek  were  the  probable  sources  of  these  eu- 
plankters.  In  addition,  these  algae  may  have 
originated  in  part  from  pools,  ponds  and  quiet 
waters  along  the  creek.  The  cycle  of  develop- 
ment of  Pandorina  morum  in  Tie  Fork  Pond 
substantiates  this  assumption  since  this  alga  was 
prevalent  in  the  pond  from  July  to  October, 
reaching  a  peak  in  number  in  September.  This 
trend  correlated  with  the  highest  number  in  the 
river,  both  at  the  plant  site  and  upstream  at 
site  4.  Floristic  samples  taken  from  Cleveland 
and  Miller's  Flat  reservoirs  in  Julv  showed  Pan- 
dorina morum  to  be  present  there  also,  but  the 
presence  of  this  alga  in  right  fork  plankton 
samples  discourages  the  conclusion  that  these 
reservoirs  are  its  only  source  into  the  creek. 

Ceratium  hirundinella  is  suspected  to  origi- 
nate almost  entirely  in  the  reservoirs  on  the  left 
fork  of  Huntington  Creek.  Tliis  species  has  been 
reported  as  a  dominant  summer  plankter  from 
other  reservoirs  in  Utah  (Chatwin,  1956;  Long- 
lev,  1969)  with  large  pulses  generally  occurring 
in  August  and  September,  which  were  the 
months  of  maximum  Ceratium  hirundinella 
abundance  in  Huntington  Creek.  These  were 
also  the  months  of  m;iximum  water  release  from 
the  storage  reservoirs  on  the  left  fork  to  provide 
irrigation  water  for  Castle  Valley.  Many  C.  hir- 
undinella cells  in  the  plankton  were  broken, 
suggesting  that  they  had  been  transported 
downstream  from  the  reservoirs. 


l^KM.iicirM,  Skhiks,  \'()i..   18.  \'().  2       Ai.cak  ok  Hunting  ii-n'  C)\n\()N,  Uiaii 

Total    Net   Plonkton:    1  =  100  olgae 


35 


Selected   Genera:    1=50  algae    I 
Apr.       June         July  Sept.  Nov.  Jan.       Mar. 


Hydrurus 


Osclllatoria 


Fig.   26.      Seasonal   distribution   of   selected    net   plankton  at  the  plant  site  (site  3). 


36 


Bricham  Young  University  Science  Bulletin 


Nannoplankton  samples  taken  during  the 
summer  of  1971  contained  three  other  true 
planktonic  algae,  Dinobrijon  cijlindricum  and  the 
diatoms  Asterionella  formosa  and  Fragihria  cro- 
tonensis.  These  algae  were  likely  also  released 
into  the  creek  from  the  storage  reservoirs.  Long- 
ley  ( 1969 )  reported  Dinobryon  to  be  the  domi- 
nant phytoplankter  in  Flaming  Gorge  Reservoir, 
Utah,  during  June  and  July.  Daily  ( 1938 )  in- 
dicated that  Dinobryon  was  present  in  Lake 
Michigan  during  most  months  of  the  year  but 
that  it  demonstrated  a  strong  peak  of  develop- 
ment in  July  and  a  lesser  peak  in  November. 
Pratt  ( 1957 )  likewise  found  a  similar  cycle  in 
Salem  Lake,  Utah  County,  Utah,  where  Dino- 
bryon showed  a  summer  pulse  from  late  June 
to  mid  September  and  another  pulse  from  mid- 
October  to  mid-November.  Dinobryon  cyUndri- 
cum  was  present  in  Huntington  Creek  from 
early  June  through  November,  with  July  and 
October  being  peak  months.  Maximum  develop- 
ment of  this  alga  in  Huntington  Creek  corre- 
lated with  water  release  from  the  left  fork  reser- 


voirs. 


Asterionella  formosa  appears  to  prefer  colder 
water  conditions  thim  Dinobryon.  Longley 
( 1969 )  indicated  this  species  to  be  important  in 
Flaming  Gorge  Reservoir  from  September  to 
May,  and  Pratt  ( 1957 )  found  very  high  amounts 
in  November  and  December.  Pratt  also  reported 
a  small  pulse  in  August  only  on  the  bottom  of 
the  pond  where  the  temperature  was  approxi- 
mately 14°C.  The  cycle  of  Asterionella  formosa 
in  Huntington  Creek  was  intimately  associated 
with  the  management  of  waters  of  the  left  fork 
reservoirs.  These  reservoirs  are  either  complete- 
ly drained  or  kept  at  very  low  levels  during 
late  fall  and  early  winter  months  and  are  sub- 
sequently filled  with  runoff  waters  during  the 
late  winter  and  early  spring.  Consequently,  no 
opportunity  exists  for  the  release  of  euplank- 
ton  from  these  reservoirs  during  this  period,  ex- 
plaining why  very  few  euplanktonic  species, 
especially  A.  formosa,  were  found  in  the  creek 
during  these  months.  When  these  reservoirs  are 
filled  in  the  spring,  the  overflow  enters  Hun- 
tington Creek  carrying  with  it  any  plankton 
which  may  have  developed  in  tlie  reservoir  over 
the  winter.  This  was  the  probable  source  of  A. 
formosa  in  the  plankton  of  Huntington  Creek, 
since  this  diatom  was  highest  in  the  creek  in  June 
1971  (59,490  coloni(>s  per  liter  on  June  8,  and 
30,250  colonies  per  liter  on  June  29).  It  declined 
gradually  through  the  summer  and  then  in- 
creased slightly  in  October.  Tliis  trend  was  un- 
doubtedly directly  txirrelated  with  the  tempera- 
ture curve  in  the  reservoirs. 

Clark  (pers.  comm. )  studied  a  similar  situa- 


tion in  Idaho  where  Henry's  Lake  drains  into 
the  north  fork  of  the  Snake  River.  Blooms  of 
Asterionella  formosa  occurred  in  Henry's  Lake 
in  June  and  October  1971,  and  this  alga  was 
found  in  the  river  plankton  for  35  miles  below 
this  lake  during  the  time  of  the  bloom.  A.  for- 
mosa density  was  815,200  colonies  per  liter  at 
the  Lake's  outlet  and  decreased  to  32,600  colo- 
nies per  liter  35  miles  downstream  from  the  lake 
due  to  the  effects  of  the  river  current. 

A  similar  reduction  in  colony  number  would 
be  expected  in  Huntington  Creek  from  the  reser- 
voirs on  the  left  fork  downstream  to  the  plant 
site,  which  represents  a  distance  of  approxi- 
mately 18  miles.  Onlv  moderate  currents  are  suf- 
ficient to  cause  such  a  reduction  (Allen,  1920) 
and  turbulent  cunents  can  often  cause  extreme 
reduction  in  euplankton.  For  instance,  Galstoff 
( 1924 )  reported  a  40%  reduction  in  plankton 
during  an  eight-hour  passage  of  the  water  of 
tlie  Mississippi  River  through  the  Rock  Island 
Rapids. 

Many  of  the  Asterionelln  formosa  colonies 
collected  in  the  plankton  at  the  plant  site  were 
fragmented,  which  Brinley  (1950)  cited  as  an 
evidence  that  they  originated  in  a  lentic  environ- 
ment and  were  not  natural  stream  inhabitors. 

Fragilaria  crotonensis  was  another  euplank- 
tonic diatom  present  in  the  nannoplankton  at 
site  3.  Clark  (per.  comm.)  mentioned  that  Fra- 
gilaria crotonensis  was  abundant  in  Island  Park 
Reservoir,  Idaho,  in  October  1971.  Likewise, 
Daily  (1938)  indicated  this  species  as  a  domi- 
nant fonn  from  October  to  December  in  Lake 
Michigan,  and  Longley  (1969)  observed  the 
same  trend  in  Flaming  Gorge,  Utah.  Fragilaria 
crotonensis  was  prevalent  at  the  plant  site 
from  September  to  November,  with  a  large  peak 
in  October  when  its  density  reached  80,620 
colonies  per  liter.  The  source  of  these  algae  was 
likely  the  reservoirs  on  the  left  fork. 

Other  diatoms  in  the  creek  were  produced 
largely  on  the  substrate  and  subsequently  re- 
leased into  the  current.  Thus,  understanding 
trends  in  periphyton  is  essential  to  understand- 
ing algal  trends  in  the  stream  as  a  whole.  Peri- 
phyton data  demonstrated  a  rather  smooth 
seasonal  colonization  curve  of  diatom  develop- 
ment on  the  substrate.  A  gradual  increase  in 
colonization  rate  occurred  through  the  spring 
and  earl\  summer  until  July,  after  which  a  de- 
cline occurred  until  December.  Dominant  genera 
included  Navicttla,  Ct/mbella.  Gomphonema, 
Synedra,  Nitzschia,  and  Achnanthes. 

As  shown  by  Table  3,  the  importance  of 
these  genera  on  the  substrate  correlated  rather 
closely  with  their  importance  in  the  nannoplank- 
ton. 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


37 


Table  3.     Percent  occurrence  of  selected  genera  of  periphyton  and  nannoplankton  at  plant  site  (Site  3). 


5/13 
1971 


6/29 
1971 


7/30 
1971 


8/20 
1971 


10/8 
1971 


11/15 
1971 


12/17 
1971 


2/19 
1972 


Navicula 

Periphyton 

Nanno 
Cymbella 

Periphyton 

Nanno 
Gomphonema 

Periphyton 

Nanno 
Synedra 

Periphyton 

Nanno 
Nitzschia 

Periphyton 

Nanno 
Achnanthes 

Periph3rton 

Nanno 
Hannaea 

Periphyton 

Nanno 
Diatoma 

Periphyton 

Nanno 
Other  Diatoms 

Periphyton 

Nanno 
Nondiatoms 

Periphyton 

Nanno 


26.4 
14.7 

11.2 
17.3 

18.0 
22.4 

26.8 

22.7 

26.6 
14.1 

14.0 
20.7 

15.9 
13.3 

9.9 
13.9 

30.5 
19.9 

44.2 
36.1 

10.9 
26.2 

15.9 
24.3 

13.1 
15.4 

19.5 
18.7 

30.4 
17.7 

26.0 
24.6 

22.0 
32.2 

11.7 
6.2 

3.1 
8.7 

2.6 
10.1 

2.7 
5.0 

7.3 
6.7 

9.1 
3.1 

36.2 
20.8 

14.0 
8.9 

5.2 
3.1 

1.5 
1.2 

3.5 
1.9 

4.5 
8.5 

11.8 
7.6 

8.4 
7.7 

7.5 
8.2 

16.5 

6.9 
14.3 

6.2 
18.6 

32.7 
20.3 

36.9 
26.4 

28.7 
38.7 

20.3 
25.3 

10.5 
16.7 

5.0 
2.8 

11.7 
6.2 

57.1 
12.3 

13.7 
12.6 

6.2 
5.8 

5.0 

2.2 

4.1 

7.2 

3.9 

4.4 

.6 
.5 

2.0 
4.1 

.3 
.3 

.1 

1.1 

.3 
1.1 

1.9 

.5 
1.1 

.4 
2.1 

1.1 
1.7 

1.4 

2.5 

8.0 
1.1 

5.1 
22.1 

5.7 
9.6 

1.1 
3.2 

4.1 
12.0 

.8 
8.0 

1.4 
6.3 

3.3 
22.2 

4.5 
4.4 

.8 
3.9 

.9 

.3 

2.7 

2.0 

2.1 

6.0 

5.8 

A  comparison  of  the  total  number  of  algae 
colonizing  periphyton  sampling  slides  with  the 
total  nannoplankton  at  the  plant  site  for  the 
studv  period  is  illuminating  (Fig.  27).  General- 
ly speaking,  the  nannoplankton  were  dependent 
upon  the  periphyton  and  the  peaks  and  lows  for 
the  two  corresponded.  However,  through  the 
summer,  especially  in  July,  the  production  of 
periphyton  was  high  due  to  a  heavy  colonization 


of  Achnanthes  (mostly  A.  minutissima)  and 
Navicula  spp.  This  summer  periphyton  increase 
was  followed  by  an  early  fall  nannoplankton  in- 
crease. Tliis  nannoplankton  pulse  was  caused 
by  such  genera  as  Navicula,  Cymbella,  Gompho- 
nema, Synedra,  Nitzschia,  and  Achnanthes  (Fig. 
28).  Tliese  genera  had  developed  on  the  creek 
bottom  throughout  the  spring  and  early  summer 
and  apparently  were  released  into  the  stream  in 


O 
O 

o 


lOOO 


750 


§  500 


i 

z 
< 

a. 

o 

z 
z 
< 
z 


250 


PERIPHYTON 
NANNOPLANKTON 


I60 


I20 


80 


40 


O 
O 
O 


5 
z 

z 

O 

t— 
>- 
I 


APRIL  JUNE  JULY  SEPT  NOV  JAN  MAR 

Fig.  27.     Density  and  seasonal  distribution  of  nannoplankton  and  periphyton  at  the  plant  site   (site  3). 


38 


Brigham  Young  University  Science  Bulletin 


Total   Nannoplankton:   1  =  100  algae  ml 


Selected  Genera:   1  =  50  algae  ml 
Apr.         June        July         Sept.       Nov.         Jan. 


Mar. 


Navicula 


Cymbella 


Gomphonema 


Nitzschia 


Fig.     28.      Seasonal     distnbiition    of    splortpcf     niiiiiiopl;iiiktoti   at   the   plant    sito    (site  i). 


Biological  Series,  Vol.  18.  No.  2       Alg.-\e  of  Huntington  Canyon.  Utah 


39 


the  late  summer  due  to  certain  enviromnental 
stimuli.  This  conclusion  is  supported  by  de- 
creased colonization  rates  during  the  nanno- 
plankton  pulse. 

Nitzschia  spp.  (especially  N.  palea)  were  im- 
portant in  the  nannoplankton  throughout  the 
study  period  but  demonstrated  a  peak  of  occur- 
rence from  August  to  October.  The  yearly  high 
occurred  in  August,  one  month  later  than  the 
Nitzschia  high  at  Lawrence  and  one  month  ear- 
lier than  the  Nitzschia  peak  from  localities  fur- 
ther up  the  canyon. 

Cocconeis  placentula  and  Achnanthes  minu- 
tissima  were  predominately  summer  diatoms  at 
site  3,  and  Hannaea  arcus  was  a  late  spring- 
early  summer  species.  Diatoma  vulgare  and 
Gomphonema  olivaceum  have  been  reported  by 
Blum  ( 1957 )  to  be  important  winter  colonizers 
of  bare  areas.  He  found  Diatoma  vulgare  most 
abundant  in  early  winter  in  the  SaUne  River, 
Michigan,  and  Gomphonema  olivaceum  most 
abundant  in  late  winter  and  early  spring.  Peri- 
phyton  data  from  the  plant  site  show  Diatoma 
vulgare  to  have  been  most  active  in  colonization 
in  November  1971.  D.  vulgare  also  occurred  in 
high  numbers  in  the  plankton  during  the  fall 
and  winter  months.  Gomphonema  olivaceum  be- 
came most  important  in  the  periphyton  in  Janu- 
ary-March 1972.  The  cells  and  mucilaginous 
stalks  on  which  they  grow  formed  an  extensive 
diatom  "ooze"  on  the  entire  creek  substrate  dur- 
ing these  months.  Nannoplankton  data  from  the 
spring  of  1971  and  the  winter  of  1972  indicate 
that  Gomphonema  spp.  were  important  in  the 
flora  throughout  the  winter  and  spring. 

In  summary,  the  algal  flora  at  site  3  was 
predominately  composed  of  Htjdrurus  foetidus 
in  the  spring,  filamentous  blue  green  algae  in 
the  summer  and  diatoms  throughout  the  entire 
year.  Filamentous  algae  contributed  to  the  net 
plankton  of  the  river  and  diatoms  comprised 
nearly  the  entire  nannoplankton.  The  plankton 
at  site  3  was  also  influenced  by  blooms  occur- 
ring in  Miller's  Flat  and  Cleveland  Reservoir 
on  the  headwaters  of  the  left  fork  of  Huntington 
Creek.  Planktonic  algae  originating  from  these 
reservoirs  included  Panclorina  morum,  Asterio- 
nella  jormosa  and  Dinohrijon  cijlindricum  in  the 
late  spring  and  summer  and  Ceratium  hirundi- 
nclla  and  Fragilaria  crotonensis  in  the  fall. 

Bear-Rilda  Campground  (Site  4) 

The  campground  locality  is  located  three 
miles  upstream  from  site  3  and  exhibited  a  simi- 
lar flora.  However,  certain  noteworthy  variations 
between  the  two  floras  occurred.  These  differ- 
ences are  attributed  to  different  ecological  con- 


ditions at  site  4  and  the  effects  of  construction 
and  pollution  from  Deer  Creek  on  site  3. 

The  creek  at  site  4  was  high  from  April 
to  early  June  1971  with  a  definite  dechne  in 
water  level  in  late  June.  Hydrtis  foetidus  ap- 
peared here  in  May  on  stones  in  a  broad  shallow 
riffle  and  increased  to  cover  25%  of  the  sub- 
strate in  early  June.  By  June  29,  1971,  this  spe- 
cies had  disappeared  from  the  visible  benthic 
algae  at  site  4,  but  was  still  prevalent  in  the  net 
plankton  indicating  that  it  was  carried  down- 
stream from  higher  elevations  where  it  persisted 
later  in  the  season.  A  light  film  of  H.  foetidus 
appeared  on  the  substrate  in  February  but  dis- 
appeared in  March  1972.  High  water  and  prob- 
able abrasion  from  ice  breakup  upstream  con- 
tributed to  the  disappearance  of  this  alga  at 
sites  3  and  4  during  this  period. 

The  summer  and  early  fall  diatom  ooze  and 
blue  green  algal  encrustation  noted  at  the  plant 
site  were  even  more  apparent  at  site  4  where 
the  water  was  shallower,  creating  more  exten- 
sive riffles.  Algal  and  sediment  buildup  began 
in  July  and  continued  through  October,  when  an 
extensive  blue  green  algal  crust  was  evident 
under  the  diatom  ooze.  In  November  this  crust 
began  flaking  off. 

It  is  possible  that  Protoderma  viride  or  an- 
other encrusting  green  alga  was  a  member  of 
this  community.  However,  filamentous  blue 
green  algae  were  definitely  the  predominant 
constituents  since  large  amounts  of  blue  green 
algae  were  found  in  the  net  plankton  when  the 
crust  began  to  break  up  (Fig.  29).  Also  floristic 
samples  from  the  campground  and  further  up- 
stream at  the  junction  of  the  two  forks  of  Hun- 
tington Creek  showed  large  amounts  of  Schizo- 
thrix  fragile  and  other  filamentous  Cyanophyta. 
The  presence  of  these  algae  in  Huntington 
Creek  correlates  with  the  findings  of  Clark 
( 1958 )  in  the  Logan  River,  Utah,  where  a  blue 
green  encrusting  mat  was  also  found  on  the 
substrate  under  the  diatom  ooze.  A  new  build- 
up on  the  substrate  was  noted  in  January  and 
February  1972,  but  it  consisted  mostly  of  di- 
atoms. Filamentous  blue  green  algae  were  pres- 
ent at  that  time  but  not  in  sufficient  quantities 
to  create  an  encrusted  mat.  During  spring  flood, 
the  high  water  and  abrasion  from  its  increased 
silt  load  usually  scoured  the  stones  of  much  of 
their  periphyton. 

By  July,  turbulence  in  the  riffle  had  de- 
creased significantly  and  many  scattered  mats 
of  Oscillatoria  cf.  tenuis,  together  with  trapped 
sediments,  occurred  on  the  stream  bottom. 
These  were  small  mats  covering  only  6.4%  of  the 
substrate   in   shallow   water  although  they   oc- 


40 


Brigham  Young  University  Science  Bulletin 


Total   Net  Plankton:   1=100  algae    I 


Selected  Genera: 
Apr.        June       July         Sept. 


=50  algae   I 
Nov.  Jan. 


Mar. 


Ulothrix 


Fig.    29.     Season<il    di.stribntion   of   selected    net    plankton   at    the   rampground    (site   4). 


Biological  Series,  Vol.  18.  No.  2       Alc.ae  of  Huntington  Canyon,  Utah 


41 


curred  in  77%  of  the  plots  observed  in  transects 
across  the  creek.  The  mats  were  gone  in  August 
but  were  evident  to  a  lesser  extent  again  in  Sep- 
tember. 

Similar  to  other  sites  along  the  creek,  net 
plankton  assemblages  at  site  4  were  directly 
influenced  by  the  benthic  algae.  Oscillatoria  cf. 
agardhi  filaments  were  most  abundant  in  the 
net  plankton  in  the  spring,  although  they  oc- 
curred throughout  the  year.  In  September  and 
November  many  small  clumps  of  filamentous 
Cyanophyta  were  collected  in  the  net  plankton 
because  of  the  aforementioned  breakup  of  the 
blue  green  algal  encrustation.  Ulothrix  sp.  oc- 
curred mostly  in  May  and  June,  Cladophora 
glomerata  from  June  through  August,  and  Oedo- 
gonium  sp.  from  May  through  October.  Spiro- 
gijra  sp.,  Mougeotia  sp.,  and  Zi/gnerna  sp.  oc- 
curred through  the  summer  months,  and  Stigeo- 
clonium   stagnatile   appeared   in   the  fall. 

The  same  true  planktonic  algae  occurred  in 
tlie  creek  at  the  campground  localitv  as  at  the 
plant  site  (Fig.  .30).  Tliese  included  Ceratium 
hirundinella  in  August  and  September  1971, 
Pandorina  morum  in  June  through  October, 
Dinobrt/on  cylindricum  from  June  to  November, 
Asterionella  formosa  from  June  to  December, 
with  highest  numbers  in  June,  and  FragiJaria 
CTotonensis  from  October  to  December,  with 
highest  occurrence  in  November.  Tliese  trends 
were  similar  to  those  at  the  plant  site. 

Periphyton  colonization  trends  were  similar 
to  those  of  the  plant  site.  A  general  increase  in 
periph>'ton  was  noted  through  the  spring  of  1971 
until  Jul\',  followed  by  a  decline  to  November 
1971.  Periphyton  data  were  compiled  from  slides 
placed  both  in  a  pool  and  in  riffles  in  order 
to  compare  colonization  in  the  two  habitats. 
Both  areas  showed  a  general  decrease  in  most 
genera  collected  on  slides  on  June  29,  1971,  al- 
though Achnanthes  mimttissima  increased  great- 
ly. This  species  increased  from  2,928  cells  per 
cm-  on  June  8,  to  2.3,.532  cells  per  cm-  on  June 
29,  for  slides  in  the  riffle,  and  from  27,298  cells 
per  cm*  on  June  8,  to  12.3,650  cells  per  cm-  on 
June  29,  for  slides  in  the  pool  (Table  4).  From 
late  June  to  August.  Achnanthes  (mostly  A. 
minutissima)  was  the  highest  contributor  to  the 


Table  4.  Percent  composition  of  Achnanthes  on  glass 
slides  at  the  campground,  .lune  8-September  16, 
1971. 


6/8       6/29       7/30       8/20 


9/15 


Slides  in  riffle  3.2        28.1         54.6        43.2  (NS)* 

Slides  in  pool  12.8         75.8         75.3         14.9  16.0 

*NS — No  slide    was    collected    from    the  riffle    in 
September. 


benthic  diatom  flora  in  terms  of  number  of  cells 
produced. 

Most  other  diatoms  in  the  periphyton  fol- 
lowed the  general  trend  of  the  total  for  this 
site  discussed  above.  The  most  important  genera 
were  Navicula,  CAjmbella,  Gomphonema,  Nitzs- 
chia,  and  Sijnedra.  Stjnedra  (mostly  S.  ulna)  dif- 
fered somewhat  by  nearly  disappearing  during 
the  wanner  months.  Diatoma  vulgare  showed 
good  growth  in  November  as  it  did  at  the  plant 
site,  but  Gomphonema  olivaceum  did  not  show 
the  expected  late  winter  increase.  However, 
nannoplankton  data  for  G.  olivaceum  showed 
this  species  to  increase  in  February  and  May, 
which  correlated  with  the  conclusion  drawn  from 
site  3  that  this  genus  is  a  late  winter  and  early 
spring  form. 

Hannaea  arcus  was  definitely  a  late  spring 
diatom,  and  Cocconeis  placentula  a  summer  di- 
atom, as  indicated  by  the  periphyton  and  sub- 
stantiated by  nannoplankton  data.  Certain  true 
plankters  were  occasionally  found  on  the  peri- 
phyton sampling  slides.  These  algae  became 
entrapped  there  as  they  floated  downstream 
and  fell  out  of  the  water  column. 

A  comparison  of  data  from  slides  placed  in 
the  pool  and  the  riffle  reveals  certain  differen- 
ces in  colonization  in  the  two  habitats.  The  total 
number  of  periphyton  and  the  number  of  indi- 
viduals of  most  genera  were  much  higher  in  the 
pool.  The  only  exception  to  this  was  Cocconeis 
placentula,  which  showed  a  comparable  colon- 
ization rate  in  the  riffle  to  that  in  the  pool.  The 
reason  for  the  high  colonization  rate  in  the  pool 
was  undoubtedly  due  to  reduced  removal  of 
periphyton  by  the  stream  current  while  concur- 
rently allowing  sufficient  water  flow  for  ade- 
quate nutrient  and  gas  exchange  for  rapid  algal 
metabolism. 

Periphvton  composition  percentages  for  the 
period  May  through  August  1971  show  certain 
significant  differences  between  the  diatoms  of 
the  pool  and  the  diatoms  of  the  faster  water. 
The  riffle  had  a  higher  composition  percentage 
of  Gomphonema  (mostlv  G.  olivaceum) ,  Sijnedra 
(mostly  S.  ulna),  Ctjinhella  spp.,  Nitzschia 
(mostly  N.  palea).  Cocconeis  (mostly  C.  pla- 
centula), Ulothrix  sp.,  and  Hijdrurus  foetidus 
than  the  pool.  Converselv,  the  pool  had  a  higher 
percentage  of  Navicula  spp.,  Achnanthes  minu- 
tissima, Diatoma  vulgare  and  Surirella  (mostly 
S.  ovata). 

From  comparing  periphyton  data  with  nan- 
noplankton data  at  site  4  ( Fig.  31 ) ,  it  is  evident 
that  high  periphyton  production  in  June  1971 
caused  the  high  nannoplankton  levels  of  the 
same  period  and  slightly  later.  The  turbulence 
of    high    water    during    this    period    probably 


42 


Bait;ii\M  Yoi'Nt:  I'Nniusnv  Sciknck  Bvi.i.ktin 


Total   Nonnoplonkton:   1=100  algae  ml 


Selected   Genera:   1=50  algae  ml 
Apr.         June        July        Sept.  Nov.  Jan. 


Mar. 


Fragllaria 


Cymbella 


Asterlonella 


Ceratoneis 


Fig.     ^0.     Sccison.il     ilistiilnitian    itf    sclcrtrd     niinnopl.iiiklnn    ill    tho    cnnipgrniintl     fsito    4). 


Biological  Series,  \'ol.  18.  No.  2       Alc.-ve  of  Huntington  Canyon,  Utah 


43 


lOOO 


o 
o 
o 


s 

Z3 

Z 

z 
o 


z 
< 

a. 

o 
z 
z 
< 

z 


750 


500 


250 


PERIPHYTON 
NANNOPLANKTON 


APRIL  JUNE  JULY  SEPT  NOV 

Fig.   31.     Densitj'  of  nannoplankton  and  periphyton  at  the  campground   (site  4). 


300 


O 

225     8 


5 


150     iJ 
to 

5 
z 


75 


X 


JAN 


MAR 


scoured  many  diatoms  from  the  substrate  into 
the  current.  Periph\ton  production  continued 
to  rise  in  Julv  1971,  when  nannoplankton  levels 
dropped,  probably  because  fewer  diatoms  were 
removed  from  the  substrate  by  the  current  dur- 
ing this  period.  Tliese  periphytic  diatoms  were 
subsequently  released  into  the  current  during 
earh"  fall  when  plankton  levels  increased  again. 
The  November  nannoplankton  increase  and  sub- 
sequent relativeh'  high  winter  levels  were  prob- 
ably due  to  new  colonization,  since  periphyton 
levels  also  rose  during  this  period. 


The  nannoplankton  cycle  for  site  4  basically 
followed  the  trend  described  for  site  3.  High 
diatom  levels  were  evident  from  April  to  late 
June,  followed  by  a  summer  low,  and  a  high 
pulse  in  September  (Fig.  32).  The  decline  in 
plankton  in  October  and  subsequent  rise  in  No- 
vember followed  a  trend  similar  to  that  observed 
at  Lawrence,  Stuart  Station,  and  Bear  Canyon, 
although  the  plant  site  did  not  exhibit  the  No- 
vember increase.  The  plant  site  also  had  much 
lower  plankton  levels  on  June  29,  1971,  than  the 
campground.    Turbidity    in    Huntington    Creek 


lOOO 


750 


O 


z 
o 

z 
< 

I 

a. 

o 
z 
z 
<. 

z 


-J     CO 


500 


250 


PLANT    SITE 
CAMPGROUND 


APRIL  JUNE  JULY  SEPT  NOV  JAN 

Fig.  32.     Seasonal  densities  of  nannoplankton  at  the  plant  site  (site  3)  and  the  campground  (site  4). 


MAR 


44 


BrICHAM    IfoUNG    UNrvERSITY    SCIENCE   BULLETIN 


at  the  plant  site  was  40  JTU  on  June  29  com- 
pared to  15  JTU  at  site  4.  Likewise,  on  July  5, 
1971  turbidity  was  25  JTU  for  site  3  and  11  JTU 
for  site  4  ( Wingett,  per.  com. ) .  The  higher  tur- 
bidity levels  were  attributed  to  excavation  at 
the  generating  station  approximately  one  mile 
upstream  from  site  3.  Abrasion  caused  by  the 
extra  silt  load  in  the  water  may  have  depleted 
the  source  of  nannoplankton  at  this  site  by  re- 
ducing periphyton  populations  prior  to  the  June 
29  collection,  thus  accounting  for  the  lower 
nannoplankton  levels  here  during  this  period. 

The  lower  nannoplankton  levels  in  Novem- 
ber 1971  are  attributed  to  pollution  from  Deer 
Creek.  This  creek  flows  east  from  a  coal  mine 
across  the  Utah  Power  and  Light  Co.  generating 
station  to  Huntington  Creek.  During  much  of 
the  year  its  flow  was  restricted,  but  during  cer- 
tain periods  it  flowed  freely,  carrj'ing  an  ex- 
tremely heavy  load  of  coal  dust  and  mining 
wastes.  In  October  and  November  the  black, 
soupy  water  from  Deer  Creek  clouded  the  clear 
waters  of  Huntington  Creek  and  caused  heavy 
coal  dust  sedimentation  on  the  creek  bottom. 
The  effect  of  this  water  was  probably  the  main 
reason  for  the  low  November  counts  here. 

In  summary,  the  flora  at  site  4  was  similar  to 
the  flora  at  site  3  in  containing  large  numbers  of 
diatoms  both  on  the  substrate  and  in  the  nanno- 
plankton. High  periphyton  production  in  late 
spring  contributed  to  corresponding  high  nanno- 
plankton levels.  Production  decreased  during 
late  summer  and  increased  again  in  winter. 
Nannoplankton  levels  at  site  4  fluctuated  greatly 
and  differed  somewhat  from  those  of  site  3. 
These  differences  were  apparently  caused  by  ex- 
cavation above  site  3,  and  pollution  from  Deer 
Creek.  Encrustations  of  filamentous  Cyanophyta 
were  more  abundant  at  site  4  than  site  3  in  late 
summer  and  visible  mats  of  Oscillatoria  sp.  oc- 
curred at  the  campground.  Hydrunts  foetidns 
grew  more  profusely  at  the  campgroimd  in  the 
spring  and  greatly  influenced  the  net  plankton 
during  this  period.  Both  sites  were  influenced 
by  euplankton  from  reservoirs  on  the  upper 
drainage  of  the  left  fork. 

Stuart  Fire  Station  (Site  6) 

The  Stuart  Fire  Station  locality'  is  located 
on  the  right  fork  of  Huntington  Creek  approxi- 
mately 8  miles  below  the  proposed  site  for  the 
dam  creating  Electric  Lake.  Tliis  site  had  con- 
siderably less  water  volume  and  lacked  the  in- 
fluence of  reservoirs  and  artificial  flow  regu- 
lation noted  for  the  left  and  main  Forks  of  Hun- 
tington Creek.  However,  physical  and  chemical 
conditions  of  the  water  at  site  6  were  similar 


to    conditions    downstream    except   for   slightly 
higher  silica  and  alkalinity  levels. 

Seasonal  fluctuations  in  the  algal  flora  at 
Stuart  Station  differed  in  many  respects  from 
those  at  other  sites.  This  was  probably  due  in 
large  part  to  the  higher  altitude  and  consequent 
lower  temperature  and  shorter  growing  season 
and  to  the  shading  effect  from  the  steep  walls 
in  this  part  of  the  canyon. 

Hijdrurus  foetidus  was  much  more  prevalent 
at  Stuart  Station  than  lower  in  the  canyon.  It 
was  abundant  here  as  early  as  March  in  1971, 
although  the  creek  was  mostly  frozen  over.  It 
remained  present  throughout  the  spring  and  by 
June  it  reached  a  peak  of  development  forming 
a  prevalent  dark  covering  on  most  of  the  stones 
and  rocks  of  the  stream  bottom.  The  quadrat 
method  for  estimation  of  cover  and  frequency 
showed  this  alga  to  cover  30%  of  the  total  sub- 
strate and  be  present  in  100%  of  the  plots  on 
June  8,  1971.  Visual  estimation  on  the  same  date 
of  several  sites  further  up  the  canyon  showed  H. 
foetidus  to  be  even  more  abundant  there  than  at 
Stuart  Station.  By  June  29,  this  species  had  de- 
clined significantly  and  soon  after  disappeared. 
H.  foetidus  reappeared  in  December  1971  and 
became  abundant  in  Februar)'  1972  after  the  ice 
had  melted.  This  alga  usually  exhibited  more 
luxuriant  growth  on  larger  rocks  than  on  small 
stones,  and  it  was  common  to  find  rich  brown 
filaments  trailing  in  profusion  from  these  rocks. 
The  spring  net  plankton  here  was  greatly  influ- 
enced bv  broken  Hi/drums  filaments,  and  the 
peak  in  net  plankton  occurred  in  early  June 
concurrent  to  the  peak  of  Hi/drurus  production 
on  the  substrate  (Fig.  33). 

Filamentous  blue  green  algae  formed  an  im- 
portant part  of  the  algal  communitA'  at  Stuart 
Station.  They  occurred  in  all  floristic  samples 
and  net  plankton  samples  from  this  site,  often 
occurring  in  abundance.  Maximum  development 
of  these  algae  occurred  on  the  substrate  from 
July  to  October  1971,  when  filaments  of  Lyng- 
hija  spp.,  Pliormidium  spp.,  Oscillatoria  spp., 
and  Schizothrix  fragile  formed  extensive  en- 
cnisting  mats.  These  filaments  were  dense  and 
intertwined,  and  heavily  laden  with  silt  par- 
ticles, diatom  mucilage  and  frustules,  and  thick 
deposits  of  calcium  carbonate,  which  made  the 
exact  characterization  of  this  communit)'  diffi- 
cult. However,  Oscillatoria  agardfiii  was  abun- 
dant in  August  and  Schizothrix  fragile  and 
Li/nghi/a  acniginco-cocrulea  were  abundant  in 
October.  Fragments  of  these  blue  green  algae 
appeared  in  high  numbers  in  the  net  plankton 
from  October  to  November  (Fig.  33)  similar  to 
sites  3  and  4.  Oscillatoria  cf.  tenuis  also  ap- 
peared in  October  as  bright  blue  green  filamen- 


1^1(11  cK.KM-  Si  Mils,  \()i  .  US.  \i).  2       Aix;\K  oi'  Huntincion  Canyon,  I'taii 


45 


Total   Net   Plankton:   1  =  50  algae    I 


Selected   Genera:   1=25  algae    I 
Apr.        June         July         Sept.  Nov.         Jan.         Mar. 


Oscillatoriaceae 


Mougeotia 


Splrogyra 


Hydrurus 


Fig.      55.     Soasiirinl     rlistrilnition     of     sclfcti'ci     net     plankton    at    Stuart    Station     (site    6). 


46 


BniGHAM  Young  UwivEnsiTi'  Science  Bulletin 


tous  entanglements  similar  to  those  observed  at 
the  campground  in  July. 

O.  agardhii  was  also  abundant  in  the  flora 
during  the  winter  months.  It  was  prevalent  on 
periphyton  slides  in  November  and  February 
and  from  floristic  data  it  appeared  to  be  wide- 
spread on  the  substrate  throughout  the  Novem- 
ber-Feb  ruar)'  period.  The  high  levels  of  Os- 
cillatoria  spp.  in  the  1971  spring  net  plankton 
were  probably  the  result  of  a  similar  coloniza- 
tion during  the  winter  of  1970-71. 

Although  this  blue  green  algal  community  at 
Stuart  Station  was  ver>'  important  on  the  sub- 
strate, it  was  of  little  significance  on  the  peri- 
phyton slides  placed  in  the  creek  to  monitor 
substrate  colonization.  Blum  ( 1957 )  reported  a 
similar  situation  in  the  Saline  River,  Michigan, 
where  a  cnistose  Schizothrix-Phormidium  com- 
munity occurred  on  the  river  bottom.  He  found 
that  even  after  a  year's  period,  sterile  rocks 
placed  in  the  river  failed  to  develop  a  commu- 
nits'  stnicturt^  comparable  to  the  mature  Schizo- 
thrix-Phormidium crust  evident  in  the  river.  He 
concluded  that  a  mature  crust  required  a  year 
or  more  to  develop,  and  that  the  Schizothrix- 
Phormidium  communit\'  was  a  permanent  mem- 
ber of  the  algal  flora  in  tlie  Saline  River.  A  simi- 
lar situation  occurs  in  Huntington  Creek.  The 
basic  blue  green  algal  community  persists  at 
Stuart  Station  throughout  the  year  and  develops 
extensively  during  summer  and  fall  months. 

Cladophora  pjomerata  likewise  chd  not  ac- 
tive^lv  colonize  microscope  slides  at  Stuart  Sta- 
tion, although  it  occurred  abundantly  on  the  sub- 
strate and  significantK'  influenced  the  net  plank- 
ton in  the  spring  and  fall.  This  species  covered 
6f  of  the  substrate  in  September  and  10.5%  of 
the  substrate  in  October  1971.  It  occurred  more 
on  large  rocks  than  on  small  stones  and  was 
covered  with  epiphvtic  Cocconeis  placentula, 
Gomphonema  olivaceum,  and  other  diatoms.  It 
was  much  reduced  in  November,  exhibiting  a 
stubby  growth  form,  but  existed  through  the 
winter  and  became  heavilv  encrusted  with  cal- 
cium carbonate  and  sediment. 

In  December  C.  glomerata  was  intertwined 
with  many  filaments  of  UlotJirix  zonata  and  V. 
aequalis.  lUothrix  was  otherwise  most  evident  in 
Mav  and  Jun(>  at  this  localit\'. 

Oedogonium  sp.  was  rare  at  Stuart  Station, 
although  it  occurred  throughout  the  summer. 
Stiaeoclonium  attenuatum  and  S.  stagnatile  oc- 
cuiTcd  here  inostK'  in  the  fall  months.  Mougeo- 
tia  sp..  Spirogijra  sp.,  and  Zijgnema  sp.  were  of 
unique  importance  in  the  summer  net  plankton 
at  Stuart  Station  and  were  the  algae  responsible 
for  the  steadv,  relatively  high  net  plankton  rates 
through  this  period  as  contrasted  to  the  lower 


summer  rates  at  other  sites  on  Huntington  Creek. 
These  species  occurred  mostly  from  late  June  to 
October,  but  Spirogtjra  sp.  was  found  from  early 
June  to  Februar\'.  Mougeotia  sp.  showed  a  signif- 
icant increase  in  July  when  it  comprised  62%  of 
the  net  plank-ton,  and  was  the  main  contributor 
to  the  general  increase  in  net  plankton  during 
that  month  (Fig.  33).  The  creek  upstream  from 
Stuart  Station  contains  many  regions  with  slow 
water  and  meandering  stream  channels,  as  well 
as  springs,  pools,  and  quiet  backwaters.  These 
areas  supported  luxuriant  growths  of  conjugate 
algae  and  were  undoubtedly  the  source  of  these 
algae  in  the  net  plankton  at  Stuart  Station.  Al- 
gae in  these  ponds  and  backwaters  probably 
only  entered  the  creek  during  runoff  from  late 
summer  rain  storms,  but  those  growing  in  pools 
and  side  waters  of  the  creek  itself  were  con- 
stantly released  into  the  channel. 

Diatom  colonization  of  the  creek  substrate 
at  Stuart  Station  showed  peak  development  in 
May  and  November  1971.  with  lesser  peaks  in 
late  June  1971  and  Febmar\'  1972.  The  Novem- 
ber-March diatom  density  was  much  greater  at 
Stuart  Station  than  that  of  any  period  at  sites 
3  and  4  (Fig.  34),  suggesting  that  the  aquatic 
habitat  here  was  more  conducive  to  diatom 
production  than  lower  in  the  canyon.  The  low 
colonization  rate  in  early  June  was  likely  in 
part  a  result  of  the  extensive  Hydrurus  foetidus 
development  during  that  period.  Summer  diatom 
production  was  low  here  as  it  was  at  sites  3  and 
4,  although  the  summer  low  began  in  July. 

Many  diatom  genera  on  the  substrate  con- 
tributed to  the  total  periphvton  trends  for  the 
study  period  (Fig.  .3.5).  Certain  genera  such  as 
CijmheUa  (mostly  C.  ventricosa  and  C.  parva), 
Synedra  (mosth'  S.  uJrtc),  and  Diatoma  (mostly 
D.  vulgare)  demonstrated  high  numbers  on  the 
slides  collected  on  June  29,  1971.  These  genera 
were  responsible  in  large  part  for  the  general 
periphyton  increase  of  that  period.  CymheUa 
spp.  were  especially  abundant  in  June.  Floristic 
samples  taken  on  June  15,  at  Stuart  Station  and 
select(>d  sites  downstream  demonstrated  extreme- 
Iv  high  numbers  of  CymheUa.  Diatoma  vulgare 
was  also  an  important  colonizer  during  this 
period. 

The  fall  and  winter  Diatoma  vulgare-Gom- 
phomnna  olivaceum  increase  was  much  the  same 
at  Stuart  Station  as  at  sites  3  and  4  down  can- 
v(m.  However,  increased  D.  vulgare  colonization 
began  in  October  rather  than  in  November,  and 
G.  olivaceum  colonization  began  increasing  in 
November  rather  than  later  in  the  winter.  D. 
vulgare  began  forming  long  prominent  zigzag 
colonies  in  October  which  became  a  dominant 
part  of  the  periphvton  flora  in  November  and 


Biological  Series,  Vol.  18,  No.  2 
400 


300 


Algae  of  Huntington  Canyon,  Utah 


47 


O 

o  o 

h 


o 


200 


lOO 


stuart  station 
Campground 


APRIL 


JUNE 


JULY 


SEPT 


NOV 


JAN 


MAR 


Fig.    34.     Density   of   periphj-ton   at   the   campground    (site  4)  and  Stuart  Station  (site  6). 


continued  dominant  through  the  winter  until 
February  1972.  G.  olivaceum  demonstrated  a 
high  colonization  rate  throughout  the  November- 
early  May  period. 

Nitzschia,  as  a  whole,  demonstrated  spring 
and  fall  highs  and  a  simimer  low,  thus  following 
the  general  diatom  trend.  However,  N.  acicularis 
occurred  mostly  in  the  summer  and  early  fall, 
when  it  was  found  in  both  the  periphyton  and 
nannoplanlcton  from  late  June  to  November. 
Cocconeis  placenttila  also  occurred  in  greater 
abundance   during   the   summer   and   early   fall 


months.  It  began  colonizing  in  July  and  reached 
a  peak  in  August  and  September,  after  which 
it  decreased  significantly. 

Butcher  (1932)  described  an  Ulvella-Coc- 
coneis  community  which  was  abimdant  in  En- 
glish calcareous  rivers  during  summer  months. 
An  alga  similar  to  Ulvella,  but  identified  as 
Protoderma  viride  (after  Prescott,  1962)  was 
found  colonizing  glass  slides  at  Stuart  Station 
on  September  15,  1971.  Protoderma  is  a  green 
alga  exhibiting  a  prostate,  often  encrusted 
growth  habit.  In  Huntington  Canyon  it  becomes 


400 


O 

O 
O 


300 


:^ 


^   200 


z 
o 


<    lOO 


O 

z 
z 
< 

z 


.      .    .      ..     PFRIPHYTON 

NANNOPLANKTON 

\ 

\  \/       \    / '-    / 

\ 

\     \'                ^        /     \       '/ 

.      \ 

\     1    \            /      \                      '               ^        1 

\  '   \      /     \         \  '           \    // 

1            \        /                   \                     i                              *    '/ 
\       /                      \                                                    * '/ 

\      \ 
\      \ 
\      \ 
\      \ 
\      \ 

\  /                   \                                       V 

\ 

400 


O 
300  O 

o 


200\ 


s. 
z 

lOOg 

t— 

>- 
I 


APRIL 


JUNE 


JULY 


SEPT 


NOV 


JAN 


MAR 


Fig.  35.     Density  of  nannoplankton  and  periph>'ton  at  Stuart  Station  (site  6). 


48 


BiuGHAM  Young  University  Science  Bulletin 


crusted  with  calcium  carbonate  and  silt  parti- 
cles, making  it  difficult  to  identify  except  when 
on  periphyton  slides.  This  same  species  was 
found  abundantly  on  shdes  at  Lawrence  in  Sep- 
tember and  October  1971  and  was  an  important 
alga  in  the  benthic  community  there.  It  was 
likely  also  an  important  constituent  of  the  crusts 
evident  at  sites  3  and  4  during  this  same  early 
fall  period,  although  accurate  identification  was 
difficult  and  Protoderma  was  absent  on  glass 
slides  at  these  sites. 

Four  periphyton  slides  were  retrieved  from 
site  6  in  September,  and  Protoderma  viride  was 
prevalent  in  three  of  the  four,  covering  an  esti- 
mated 10%  to  2D%  of  the  surface  of  each  slide. 
In  October  P.  viride  was  found  on  only  one  of 
three  slides  and  had  decreased  in  importance 
on  that  slide.  Tliis  alga  therefore  exhibited  a 
short  colonization  period  here  and  was  probably 
not  as  effective  in  colonizing  bare  surfaces 
rapidly  as  some  diatoms,  such  as  Cocconeis  and 
Achnanthes. 

Visual  observation  of  the  stream  bottom 
throughout  the  summer  indicated  that  Proto- 
derma viride  was  more  prevalent  than  our  data 
suggest.  Such  prostate,  often  encrusted  forms 
are  rare  in  the  plankton  (Butcher,  1932),  thus 
eliminating  plankton  data  as  a  means  of  moni- 
toring their  production  on  the  stream  bed. 
Hence.  Protoderma  viride  did  not  appear  in 
nannoplankton  counts  from  Stuart  Station.  This 
represents  a  weakness  in  subsampling  and  illus- 
trates that  total  numbers  of  individuals  in  a 
flora  as  determined  onlv  by  one  sampling  method 
may  not  always  convey  a  true  picture  of  the 
flora  as  a  whole.  Protoderma  viride  mats  were 
few  in  number  on  the  periphyton  slides  although 
each  covered  a  considerable  area,  making  it 
important  in  terms  of  total  cover  although  in- 
significant in  total  number  of  cells  when  com- 
pared to  diatoms  on  the  same  slide. 

Achnanthes  minutissima  and  Cocconeis  pla- 
centuhi  illustrate  a  similar  problem  of  sampling. 
Table  5  compares  the  total  number  of  Achnan- 
thes minutissima  and  Cocconeis  phirentula 
cells  per  cm=  and  their  relative  abundance  on 
periphyton  slides  for  the  summer  and  early  fall 
of  1971. 


Table  5.  Density  in  cells/cm^  and  relative  abundance 
of  Achnanthes  and  Cocconeis  in  the  periphyton  of 
Site  6  July-October  1971. 


GENUS 

7/30 

8/20 

9/15 

8/10 

Achnanthes 

Density 

Composition 
Cocconeis 

Density 

Composition 

29,500 
61.2% 

2,750 

5% 

37,290 
5.3.1% 

7,900 
11.2% 

32,989 
61.2% 

3,851 
7.1% 

5,1+8 
8.0% 

762 
1.2% 

These  data  show  both  of  these  genera  to  be 
abundant  in  the  summer  flora  at  Stuart  Station, 
although  Achnanthes  minutissima  appears  to  be 
much  more  important.  However,  cells  of  this  spe- 
cies are  small  and  occur  on  branched  mucilagi- 
nous stalks,  often  with  many  cells  appressed 
together.  Cocconeis  placenttila,  on  the  other 
hand,  is  larger  and  grows  adnate  to  the  sub- 
strate. The  microscope  slides  from  this  site  in 
September  were  visually  examined  prior  to  clean- 
ing, and  C.  placentula  appeared  as  one  continu- 
ous sheet  of  cells  covering  tlie  substrate.  It  thus 
appeared  to  be  more  important  as  a  substrate 
cover  than  A.  minutissima,  which  was  present 
in  higher  numbers.  Therefore,  care  must  be  used 
in  sampling,  and,  whenever  possible,  subjective 
description  should  accompany  numerical  charac- 
terization describing  a  total  flora  as  it  occurs  in 
place. 

Nannoplankton  at  Stuart  Station  were  rela- 
tively constant  throughout  the  year  except  for 
lows  in  Mav,  August,  and  October  1971,  and 
March  1972  (Fig.  .36).  The  high  winter  and 
spring  nannoplankton  levels  here  were  supported 
by  similar  high  production  on  the  substrate.  As 
periphvton  production  declined  in  July  and  Au- 
gust, the  number  of  nannoplankton  also  dropped. 
In  September  a  large  number  of  Nitzschia  spp. 
and  Navicula  spp.  released  from  the  substrate 
caused  an  increase  in  the  number  of  nanno- 
plankton. An  October  low  occurred  at  site  6 
as  it  did  at  site  4. 

Generally  speaking,  nannoplankton  levels 
showed  much  less  fluctuation  at  Stuart  Station 
than  at  sites  3  and  4  (Fig.  37),  whereas  peri- 
phvton levels  fluctuated  more  (Fig.  .34).  Nanno- 
plankton levels  were  also  generalh'  lower  at  site 
6  than  at  sites  3  and  4  (Fig.  37).  Tliis  was  due 
to  the  collection  of  diatoms  in  the  plankton  as 
the  current  carried  them  downstream,  thus  giv- 
ing higher  levels  lower  in  the  drainage.  How- 
ever, many  fluctuations  and  occasional  lack  of 
correspondence  between  nannoplankton  and 
peripln  ton  data  suggest  that  manv  factors  along 
the  stream  affect  these  levels.  For  instance,  many 
algae,  especially  nondiatom  species,  are  de- 
stroyed as  they  travel  dowoistream.  The  abun- 
dance of  filamentous  conjugales  at  Stuart  Sta- 
tion and  their  paucitv  at  sites  3  and  4  illustrate 
this  fact.  Likewise,  localized  habitat  differences 
are  also  extremely  important  in  creating  differ- 
ences between  floras  of  different  parts  of  the 
stream.  Ilannaea  arcus,  for  instance,  was  im- 
portant at  the  plant  site  and  campground,  but 
was  almost  nonexistent  at  site  6.  A  noteworthy 
lack  of  euplankton  was  also  evident  at  Stuart 
Station. 

Successive  collections  of  nannoplankton  from 


Biological  Series,  Vol.  IS    Nd.  2       Aicvk.  of  HuNTiN't;TON  Canyon,  Uiam 


49 


Total   Nannoplankton:   1  =  50  algae  m 


Selected   Genera:   1  =  25  algae  ml 
Apr.        June       July        Sept.        Nov.  Jan.  Mar. 


Diatoma 


Fig.     .36.     Seasonal     dislriliulioii    of    selertpd     iiaiiMiipl.inktoii    at     Stiiail    Station     Csite    6). 


50 


Brigham  Young  University  Science  Bulletin 


900 


6  75 


450 


225 


STUART    STATION 
CAMPGROUND 


APRIL 


JUNE 


JULY 


SEPT 


NOV 


JAN 


MAR 


Fig.  37.     Density  of  narmoplankton  at  the  campground   (site  4)  and  Stuart  Station  (site  6) 


Stuart  Station  were  made  on  February  19  and 
23,  1971.  The  results  of  tliese  two  samples  are 
summarized  in  Table  6.  Tlie  close  correlation  of 
these  two  counts  supports  the  reliability  of  the 
sampling  techniques  used  and  also  indicates  rela- 
tively stable  conditions  in  the  creek  during  this 
four-day  period. 

In  summary,  the  flora  at  Stuart  Station  dem- 
onstrated many  species  of  diatoms  on  the  sub- 
strate throughout  the  year  with  an  Achiianthes- 
Cocconeis-Protoderma  community  prevalent  in 
summer  and  early  fall.  Filamentous  blue  green 
algae  were  important  here  throughout  the  year, 


Table    6.     Nannoplaiiltton    totals    for    February    19    and 
February   23,    1972,   from   Stuart   Station. 

February  19,   1972  February-  23,  1972 

No.  Percent  No.          Percent 

Per  Compo-  Per          Compo- 

Liter           sition  Liter  sition 


Navicula 

capitata 

14,595 

4.5 

8,340 

2.3 

Navicula 

Iripunclala 

13,900 

4.3 

18,070 

5.0 

Other 

Navicula 

37,530 

11.3 

56,990 

15.7 

Cymbella 

115,370 

35.2 

125,100 

34.4 

Gomphonema 

33,350 

10.2 

38,225 

10.5 

Synedra 

23,630 

7.2 

22,935 

6.3 

Nitzschia 

47,955 

14.7 

47,260 

13.0 

Achnanthes 

24,325 

7.1 

21,545 

6.5 

Diatoma 

yulgare 

4,170 

1.3 

9,730 

2.7 

Diatoma 

hiemale 

1,390 

.4 

1,390 

.4 

Gyrosigma 

695 

.2 

695 

.2 

Surirella 

2,085 

.6 

4,170 

1.1 

Cocconeis 

4,170 

1.3 

3,475 

1.0 

Other 

diatoms 

4,170 

1.3 

5,500 

1.5 

especially  in  the  summer-fall  period.  Hi/drurus 
foetidus  was  abundant  in  spring  and  CAadoplwra 
glomerata  was  quite  prevalent  in  fall.  The  dom- 
inant diatoms  were  Navicula,  Cymbella,  Gom- 
phonema, Nitzschia,  Achnanthes,  Stjnedra,  Coc- 
coneis, Diatoma  and  Surirella. 

Bear  Canyon  (Site  7) 

Sampling  at  Bear  Canyon  was  conducted 
from  July  to  November  1971.  The  stream  gradi- 
ent at  this  site  was  not  steep  and  the  stream  ran 
clear,  usuallv  with  lower  water  flow  than  at 
Stuart  Station  9  miles  downstream.  Creen  and 
blue  green  algae  were  significant  in  the  flora  at 
Bear  Canyon.  Ulothrix  tenuissima  was  highest 
in  the  net  plankton  in  June,  indicating  that  it 
was  an  active  stream  bottom  colonizer  during 
late  spring.  Oedogonium  sp.  and  Cladophora 
glomerata  were  prevalent  throughout  the  sum- 
mer in  the  plankton,  and  Oedogonium  sp.  was 
also  abundant  on  tlie  substrate.  Long  streamers 
of  this  alga  were  found  on  stones  and  a  sub- 
merged clay  shelf  in  September  and  October. 
In  September  Oedogonium  sp.  covered  12.3*  of 
the  substrate  and  occurred  with  79%  frequency, 
and  in  October  it  covered  7.2%  of  the  substrate 
and  occurred  in  86%  of  the  plots  studied.  In  Oc- 
tober Spirogijra  sp.  filaments  were  intermingled 
with  the  Oedogonium  sp.  strands.  In  November 
the  decrease  in  abundance  of  Oedogonium  sp. 
was  accompanied  by  the  initiation  of  growth  of 
Hijdrurus  foetidus  on  the  substrate.  Much  of  the 
creek  bottom  at  Bear  Canyon  and  upstream 
was  sandy  and  provided  little  habitat  for  the  at- 
tachment  of  benthic   algae,   and   consequently. 


Biological  Series,  Vol.  18,  No. 


Algae  of  Huntington  Canyon,  Utah 


51 


the  total  amount  of  attached  algae  was  low  in 
these  areas. 

The  seasonal  cycle  of  Htjdrurtis  foetidtis  at 
Bear  Canyon  probably  was  much  the  same  as 
at  Stuart  Station.  It  appeared  in  the  late  fall 
and  was  Ukelv  present  throughout  the  winter, 
since  it  was  prevalent  in  the  early  spring  when 
the  ice  broke.  Because  of  the  high  altitude  and 
consequent  lower  temperature  of  the  water  here, 
H.  foetidus  persisted  longer  into  the  summer 
than  at  sites  lower  in  the  drainage.  Thus,  this 
species  was  abundant  in  tlie  net  plankton  as  late 
as  June  29,  and  still  present  in  the  July  30,  1971, 
sample. 

Growth  of  CladopJiora  glomerata  was  not  ex- 
tensive at  Bear  Canyon,  and  when  found,  it 
was  covered  with  numerous  epiphytic  diatoms 
such  as  Cocconeis  placentula  and  Gomphonema 
olivaceum.  Filaments  of  several  conjugate  algae 
were  retrieved  in  net  samples  during  the  sum- 
mer and  early  fall  months.  These  algae  largely 
originated  in  protected  environments  upstream 
from  Bear  Canyon  where  luxuriant  mats  of 
Spirogi/ra  sp.  were  observed  in  October.  Spiro- 
gijra  sp.  was  more  prevalent  in  these  samples 
in  the  fall  while  Moiigeotia  sp.  and  Ztjgnema 
sp.   occurred   mostly   during   the  summer. 

Closterium  spp.  (mostly  C.  moniJiferum)  were 
important  in  the  creek  at  Bear  Canyon.  In  July 
their  density  in  the  net  plankton  was  67.5  cells 
per  liter  and  in  August  thev  were  present  at  42 
cells  per  liter.  CAostcrium  production  in  the 
creek  occurred  in  the  substrate  in  protected 
areas,  among  mats  of  filamentous  algae  and  in 
partially  submerged  streamside  vegetation.  These 
same  habitats  were  also  the  site  of  production 
for  Trachelomonas  robusta,  which  appeared  in 
the  creek  in  August,  September,  and  November. 

Nannoplankton  samples  were  taken  during 
the  August-November  period.  Tlie  total  numbers 
varied  somewhat  from  the  figures  obtained  at 
Stuart  Station  and  in  general  were  more  stable 
and  quite  consistently  high  (Table  7). 

One  reason  for  the  stability  in  nannoplank- 
ton levels  at  Bear  Canyon  was  a  large  occur- 
rence of  Nitzschia  palea  and  Gomplwnema  oli- 
vaceum in  September,  even  though  most  other 
genera  decreased  in  numbers  during  this  period. 
A  similar  Nitzschia  sp.  pulse  contributed  to  the 
Stuart  Station  nannoplankton  in  September,  but 
the  numbers  of  most  other  genera  increased  as 

Table  7.  Nannoplankton  totals  in  cells  per  liter  for 
Stiiart  Station  and  Bear  Canyon  for  August-No- 
vember 1971. 


Aug. 


Sept. 


Oct. 


Nov. 


Stuart    Station 
Bear  Canyon 


116,741 
215,576 


310,271 
218,223 


66,435 

112,295 


282,768 
265,056 


well,  thus  producing  a  large  pulse.  This  Sep- 
tember increase  at  Stuart  Station  was  followed 
by  a  yearly  low  in  October,  which  also  occurred 
at  sites  1,  4,  and  Bear  Canyon.  A  November 
nannoplankton  pulse  was  noted  at  Bear  Canyon 
as  well  as  at  other  sites,  caused  by  a  general  in- 
crease in  the  numbers  of  most  diatom  genera. 

A  second  reason  for  the  plankton  stability 
in  the  upper  drainage  of  Huntington  Creek  is 
attributed  to  the  terrestrial  environment.  The 
terrain  upstream  from  Bear  Canyon  consists  of 
large  grassy  valleys  and  rolhng  mountains.  Con- 
sequently, late  summer  storms  have  less  effect 
on  the  right  fork  here  than  in  the  canyon  im- 
mediately above  Stuart  Station  where  the  moun- 
tain sides  are  steep  and  easily  eroded  during 
storms,  thus  raising  the  water  level  rapidly  and 
increasing  the  silt  load  in  the  creek.  This  in- 
creased silt  load  and  high  water  is  Hkely  respon- 
sible for  scouring  diatoms  from  the  substrate 
and   thereby   altering   nannoplankton   counts. 

Tie  Fork  Pond  (Site  5) 

The  lentic  environment  of  Tie  Fork  Pond 
provided  a  habitat  uniquely  different  from  that 
of  the  swift  flowing  Huntington  Creek,  and  thus 
the  flora  here  contained  many  algae  which  did 
not  occur  in  the  creek.  In  addition,  the  cycles 
of  occurrence  of  some  genera  common  to  both 
environments  were  very  different. 

Physical  and  chemical  properties  of  the 
water  in  Tie  Fork  Pond  differed  in  several  im- 
portant aspects  from  that  of  the  neighboring  por- 
tion of  Huntington  Creek.  Silica  fluctuated  from 
levels  below  to  levels  above  those  found  in  the 
creek  waters.  Hardness  was  usually  greater  in 
the  pond,  with  magnesium  hardness  being  much 
higher  and  calcium  hardness  being  somewhat 
lower  than  in  the  creek.  Total  alkalinity  in  the 
pond  was  higher  and  carbonate  alkalinity  was 
usually  present  along  with  bicarbonate  alkalinity. 
Turbidity  was  also  higher  in  the  pond  because 
of  abundant  planktonic  algal  growth,  and  water 
temperature  was  usually  5-I0°C  higher  since 
the  small  pond  was  easily  and  rapidly  warmed 
by  the  sun. 

The  pond  was  completely  frozen  during  the 
winter.  On  March  11,  1972,  it  had  begun  to 
thaw,  but  neither  visible  benthic  algae  nor 
plankton  were  evident.  A  nannoplankton  sample 
taken  from  the  pond  yielded  only  a  few  diatom 
fnistules  which  appeared  to  be  left  from  the 
previous  year. 

In  April  1971,  the  pond  was  completely 
thawed,  and  the  remains  of  the  previous  year's 
Chara  mat  were  evident  on  the  bottom.  Fila- 
mentous algae  such  as  Oedogonium  sp.,  Spiro- 


52 


Bricham  Young  University  Science  Bulletin 


gtjra  sp.,  and  Microspora  sp.  were  already  float- 
ing on  the  surface  of  the  pond,  indicating  that 
spring  colonization  is  rapid.  The  plankton  dur- 
ing this  month  were  predominately  diatoms  in- 
cluding Navicula,  Cijmhella,  Gomphonema, 
Sijnedra,  Nitzschia,  Achnanthes  and  Cocconeis. 

Filamentous  algae  developed  throughout  the 
summer  ( Fig.  38 ) .  By  June  a  new  growth  of 
Chara  vulgaris  was  evident  on  the  bottom  and 
Spirogyra  spp.  filaments  were  abundant  through- 
out the  pond.  Mougeotia  spp.  and  Zt/gnetna  sp. 
mats  were  abundant  near  the  south  shore  of  the 
pond  wh(>re  a  culvert  drained  under  the  high- 
way into  the  creek.  In  July  Potomogeton  sp.  was 
abundant  in  the  pond  and  the  Potomogeton- 
Cfiara  association  completely  covered  the  bot- 
tom. Mougeotia  (mostly  M.  gemiflexa)  develop- 
ment reached  a  climax  during  this  month  and 
thoroughly  saturated  the  water  when  it  fonned 
bright  green  fluffy  "clouds"  throughout  the  pond. 
Tliis  summer  development  of  Mougeotia  corre- 
lated closely  with  its  appearance  in  the  net 
plankton  of  the  creek  throughout  the  canyon, 
indicating  that  the  same  developmental  cycle 
occurred  in  other  habitats  supporting  Mougeotia 
growth.  Spirogi/ra  spp.  development  occurred 
mostlv  in  late  summer  and  early  fall  in  the  pond, 
similar  to  other  locahties. 

By  August  the  water  level  in  Tie  Fork  Pond 
had  fallen  considerably  and  very  little  free 
water  above  the  Chara-Potomogeton  cover  was 
present.  Consequently,  the  filamentous  green  al- 
gae declined  considerably  and  generally  became 
restricted  to  narrow  channels  near  the  culvert. 
Conditions  in  September  were  much  the  same 
except  that  a  new  bloom  of  Mougeotia  (mostly 
M.  gentiflexa)  and  Spirogt/ra  sp.  occurred  in  the 
limited  free  water  in  the  pond.  The  late  summer 
environment  of  August  and  September  allowed 
the  rapid  development  of  Oscillatoria  limosa  and 
O.  tenuis  and,  to  a  lesser  extent,  Lynghtja  major 
and  L.  aerugineo-coerulea. 

The  water  level  rose  again  in  October  and 
by  November,  a  1-inch  layer  of  ice  covered  the 
pond.  Extensive  decomposition  of  the  summer 
acjuatic  vegetation  began  beneath  the  ice,  mak- 
ing the  water  black  and  putrid. 

Tie  Fork  Pond  supported  a  large  population 
of  diatoms  throughout  the  studv,  although  sev- 
eral genera,  such  as  Gomphonema.  Si/nedra, 
Achnanthes,  and  Cymhella,  declined  in  the  sum- 
mer months.  Other  genera,  such  as  Nitzschia 
(including  N.  palea,  N.  sigmoiclea,  and  N.  linea- 
ris), Epithemia  (mostly  E.  gihha),  Fragilaria 
crotonensis,  and  F.  virescens,  were  ver\'  abun- 
dant in  the  summer  (Fig.  39).  Nitzschia  spp. 
fluctuated  throughout  the  study  period  from 
.\pril  to  October.  Epithemia  (including  E.  gihha. 


E.  turgida,  and  E.  argus)  showed  a  maximum  of 
159,750  cells  per  liter  occurring  in  July. 

Fragilaria  crotonensis  and  F.  virescens  oc- 
curred throughout  the  summer.  F.  crotonensis 
occurred  in   highest  numbers   in  late  June  and 

F.  virescens  in  July.  The  bloom  of  F.  crotonen- 
sis was  apparently  much  earlier  here  than  in 
the  reservoirs  on  the  left  fork  of  Huntington 
Creek,  where  the  bloom  occurred  in  October. 

Tlie  many  nondiatom  species  present  in  the 
nannoplankton  and  the  large  number  of  net 
plankton  during  the  summer  in  Tie  Fork  Pond 
are  characteristic  of  fresh  water  lentic  environ- 
ments. True  plankters  in  the  nannoplankton  here 
included:  Trachelomonas  robusta,  which  in- 
creased in  density  throughout  the  summer  to  a 
peak  in  October;  Scenedesmus  (mostly  S.  bi- 
juga),  which  was  most  abundant  in  July  ( 113,125 
colonies  per  liter)  but  persisted  in  the  flora  un- 
til October;  N ephrocijtium  hinatum,  which  ap- 
peared in  high  numbers  in  July,  declined  in 
August  and  September,  and  was  essentially  gone 
by  October;  the  desmid  Sphaerozosma  sp.,  which 
composed  25%  of  the  flora  in  August  and  Sep- 
tember, appearing  mostly  as  single  cells  rather 
than  in  its  typical  colonial  form;  Cosmarium  sp., 
which  occurred  throughout  the  season  and 
pulsed  slightly  in  July  and  August;  and  Stauras- 
trum  sp.,  which  occurred  from  June  29  to  Oc- 
tober 8,  being  highest  in  July  and  August.  These 
last  two  genera  were  of  minor  importance  in 
relation  to  the  entire  flora,  never  comprising 
more  than  37c  of  the  total  nannoplankton. 

True  plankters  in  the  net  plankton  included: 
Pandorina  morum.  which  increased  from  July  to 
a  maximum  densitA'  in  September  of  400  colonies 
per  liter;  Euglerui  spp.,  which  were  prevalent 
throughout  the  season,  occurring  in  greatest 
numbers  in  August  and  September  when  they 
reached  2,750  cells  per  liter;  Chisterium  (mostly 
C.  monilifcntm),  which  appeared  occasionally 
after  May;  planktonic  Chroococcales  (Cyano- 
phyta)  which  occurred  from  July  to  October; 
and  species  in  Pyrrhoph\ta  (mostly  Peridinium 
cinctum).  which  appeared  in  low  numbers  in 
July,  August,  and  October.  Most  of  these  algae 
were  not  significant  in  numbers.  Desmids,  for 
instance,  were  generally  rare  in  Tie  Fork  Pond 
and  throughout  the  drainage  since  they  are 
more  adapted  to  softwater  and  acid  habitats 
(Prescott,  1962)  than  to  calcareous  waters  such 
as  those  of  Huntington  Canyon. 

Many  euplanktonic  algae  were  also  found  on 
periphvton  slides.  Most  of  these  probabU'  settled 
out  of  the  water  onto  the  slides  and  became  a 
part  of  the  community  developing  there.  For  in- 
stance, Scenedesmus  was  quite  prevalent  on  the 
slides   throughout  the  summer.   Butcher   (1932) 


Bi(M/^o:r\L  Series.  \<>i     IS.  No.  2       Ai.caf,  ok  Huntinoion  C\nv(in,  Utah 


53 


Total    Net   Plankton 
1=2500  algae    I 


Selected   Genera 

1  =  2000  algae    I 

Apr.      June       July  Sept. 


Euglena 


Mougeotia 


Qscillatoria 


Splrogyra 


Fig.     38.      Seasonal     ilistribulioii     of     selerteil     not     plankton     at    Tic    Fork     Pond     (site    5). 


54 


BniGiiAM  VouNC.  Univehsitv  Science  Bulletin 


Total    Nannoplonkton 
1  =  100  olgae  ml 


Selected  Genera 

1=25  algae  ml 

Apr.        June        July         Sept. 


E  pit  he  mi  a 


Scenedesmus 


Fragilaria 


Fifj.      ^t.      Sensorial     distiibutioii     of    solciti-d     iiiiiiiiopl.nikloii    ^it    Tii-    Fork    I'micl     I  site    5). 


Biological  Series,  Vol,  18,  No,  2       Alcae  of  Huntington  Canyon,  Utah 


55 


discussed  Scenedesmus  and  other  algae  such  as 
Pediastrum  and  Ctjclotella  that  are  cosmopohtan 
in  distribution  and  usually  found  on  the  bottom 
of  ponds,  ditches,  and  slovv-flovving  streams 
where  they  live  and  reproduce  until  they  are 
disturbed  and  become  a  part  of  the  plankton. 

Production  of  diatoms  on  glass  shdes  in  Tie 
Fork  Pond  was  generally  less  than  in  Hunting- 
ton Creek,  but  since  no  current  continually 
washed  the  diatoms  downstream,  numbers  in  the 
plankton  of  the  two  habitats  were  comparable. 

Trends  similar  to  those  observed  in  Tie  Fork 
Pond  occurred  in  other  ponds  throughout  the 
Huntington  Canyon  drainage.  One  such  pond  is 
located  adjacent  to  site  2.  This  pond  maintained 
an  extensive  mat  of  Cham  vulgaris  throughout 
the  year,  with  continual  production  and  decom- 
position adding  to  the  2  feet  of  black  organic 
mud  on  the  bottom. 

A  pond  located  about  2  miles  east  of  the 
plant  site  was  filled  with  moss  rather  than  Chara. 
In  May  this  pond  contained  Microspora  sp. 
much  as  Tie  Fork  Pond  and  a  bloom  of  Fragil- 
aria  virescens  which  continued  through  early 
June.  Microspora  sp.,  Mougeotia  sp.  and  Spiro- 
gyra  sp.  were  abundant  here  in  the  early  spring, 
and  Oscillatoria  limosa  and  O.  tenuis  became 
abundant  in  late  June.  Epithemia  gibba  was 
present  from  May  to  July  and  Navicula  sp.  and 
Nitzschia  sp.  were  abundant  in  early  summer. 
Green  algae  declined  generally  through  the  sum- 
mer, while  filamentous  blue  green  algae,  es- 
pecially  Oscillatoria   tenuis  and  O.   limosa,   in- 


Fig.  40.  Shallow  pond  adjacent  to  the  Right  Fork  of 
Huntington  Creek,  These  small  ponds  represent  one 
source  of  euplanktonic  algae  in  the  flora  of  Hun- 
tington  Creek,   Photographed   April   28,   1972, 


creased  greatly.  Desmids  were  more  abundant 
in  this  pond  than  in  any  other  habitat  sampled 
in  Huntington  Canyon.  The  dominant  desmid 
was  Closterium  rnoniliferum,  common  from  July 
to  October. 

A  similar  mossy  pond  is  located  one  mile 
above  Stuart  Station  (Fig.  40).  The  spring  flora 
of  this  pond  included  Vaucheria  geminata,  Mou- 
geotia parvula,  and  Ulothrix  tenuissima.  In  June, 
Spirogyra  dubia  occurred  and  Vaucheria  gemiw- 
ata  disappeared.  Draparnaldia  plumosa  was  abun- 
dant in  June,  as  were  Chlamydomonas  sp.,  Clos- 
terium moniliferum,  C.  erhenbergii,  and  C.  ros- 
tratum.  Tliese  desmids,  along  with  Cosmarium 
sp.,  were  also  collected  throughout  the  summer 
in  floristic  samples.  Mougeotia  genuflexa 
bloomed  in  July  and  Spirogyra  dubia  and  Oedo- 
gonium  sp.  bloomed  in  August.  Euglena  (includ- 
ing E.  acus)  was  often  present  in  the  Spirogyra 
mats.  Epithemia  sp.  (mostly  E.  gibba)  was  pres- 
ent throughout  the  season  in  this  pond  and  was 
most  prevalent  in  August.  Filamentous  algae 
became  rare  by  October  except  for  Oedogonium 
sp.  Spirogyra  dubia  became  prevalent  again  in 
November  and  was  accompanied  by  a  bloom  of 
Synedra  (mostly  S,  ulna). 

The  third  pond  is  adjacent  to  the  Bear  Can- 
yon sampling  site.  Its  flora  consisted  of  Spiro- 
gyra sp.,  abundant  throughout  most  of  the  sea- 
son except  for  July,  Nitzschia  sp.  and  Cymbella 
sp.  in  June,  and  Zygnema  sp.  in  July  and  Au- 
gust. Epithemia  gibba  was  also  abundant  in  Au- 
gust, as  were  several  species  that  were  also 
found  in  Tie  Fork  Pond,  including  Oscillatoria 
limosa,  O.  tenuis,  and  desmids.  Staurastrum 
eustephanum,  especially,  was  common  here  in 
July-September. 

In  September  and  October  Amphipleura  pel- 
lucida  appeared  abundantly  in  this  pond,  and 
Epithemia  gibba  continued  abundant.  Early  fall 
filamentous  algae  included  Spirogyra  sp.,  Zyg- 
nema sp..  Mougeotia  sp.,  and  Vaucheria  gemi- 
nata. Tolypothrix  larmta  was  prevalent  in  Sep- 
tember and  Oscillatoria  tenuis  became  abundant 
in  October.  Chara  vulgaris  was  present  in  this 
pond  during  the  summer  and  fall  season  but  did 
not  form  the  extensive  mats  found  in  Tie  Fork 
Pond. 

Algal  Flora  of  Huntington  Canyon 

Huntington  Creek  is  a  cold,  clear,  fast-flow- 
ing, calcareous  stream,  which  supports  a  diverse 
algal  flora  adapted  to  these  conditions.  Diatoms 
are  the  most  abundant  algae  present,  occiuring 
throughout  the  year  on  the  substrate  and  in  the 
plankton.  Tlie  dominant  genera  are  Navicula, 
Ci/mbella,  Gomphonema,  Nitzschia,  Synedra, 
Achnanthes,  and  Diatoma.  Diatoms  show  maxi- 


56 


BniGHAM  Young  University  Science  Bulletin 


mum  production  on  the  substrate  in  late  spring 
and  early  summer  and  in  late  fall  and  early 
winter. 

Benthic  diatoms  are  the  main  contributors 
to  the  nannoplankton,  and  the  composition  and 
seasonal  fluctuations  of  the  nannoplankton  are 
largely  determined  by  similar  fluctuations  on 
the  substrate.  Water  level  fluctuations,  water 
temperature  changes,  and  mechanical  distur- 
bances also  appear  to  be  factors  influencing 
nannoplankton  levels. 

Pcriphyton  colonization  is  higher  in  the  right 
fork  of  Huntington  Creek  than  lower  in  the  can- 
yon, and  nannoplankton  amounts  increase  as 
the  water  moves  downstream.  However,  the  in- 
crease is  not  entirely  cumulative  since  destruc- 
tion of  cells  occurs  in  the  turbulent  water. 

True  planktonic  algae,  including  Asterionella 
formosa.  Frapilana  crotonensis,  Dinohnjon  cijl- 
inclricum,  Pandorina  morum,  and  Cerathim  hir- 
undinella  occur  in  the  plankton  of  Huntington 
Creek.  These  algae  are  thought  to  originate  in 
reservoirs  on  the  upper  drainage  of  the  left  fork 
of  Huntington  Creek,  and  their  occurrence  in 
the  creek  basically  correlates  with  algal  cycles 
in  these  reservoirs. 

Filamentous  algae  are  also  important  con- 
stituents of  the  Huntington  Creek  algal  flora. 
Hydrurus  foetidus  grows  profusely  from  late 
winter  to  early  summer,  especially  in  the  upper 
reaches  of  the  canyon,  forming  thick  mucilagi- 
neous  growths  on  stones  and  rocks  on  the  stream 
bed.  Blue  green  algae  are  present  on  the  creek 
substrate  throughout  the  year,  but  show  high- 
est production  during  summer  and  fall  when 
encrusted  communities  form  on  the  stony  sub- 
strate. Other  filamentous  algae  present  in  the 
canyon  include  Ulothrix  tenuissima,  U.  zonata, 
and  Stigeoclonium  stagnatile,  which  occur  most- 
ly in  the  spring,  and  Mougeotia  spp.,  Spirogyra 
spp.,  Zt/gnerna  spp.,  and  Vaucheria  geminata, 
which  grow  in  backwaters,  pools,  and  ponds 
along  the  creek  through  the  summer  and  fall. 

Fragments  from  these  filamentous  algae  are 
an  important  source  of  net  plankton.  Hydrurus 
foetidus  fragments  are  prevalent  in  the  plankton 
in  the  spring,  and  filaments  of  blue  green  algae 
occur  in  large  quantities  during  October  and 
November.  Most  filamentous  green  algae  occur 
during  the  summer  months,  and  they  are  most 
prevalent  in  the  right  fork  where  protected  areas 
along  the  stream   channel   allow   for  their  de- 


velopment (Fig.  41).  Most  of  these  filamentous 
algae  are  quickly  destroyed  as  they  are  carried 
downstream  by  the  current. 

Cladophora  glomerata  and  Oedogonium  sp. 
also  occur  in  significant  numbers  in  Huntington 
Creek.  C.  glomerata  is  most  abundant  in  the 
lower  reaches  of  the  right  fork  during  the  fall, 
and  Oedogonium  sp.  is  most  abundant  in  the 
upper  right  fork  during  the  same  period.  These 
genera  are  likewise  prevalent  in  tlie  lower  Hun- 
tington Creek  as  it  flows  through  Castle  Valley, 
where  they  form  long  streamers  from  the  stones 
during  late  spring  and  early  summer. 

Chara  vulgaris  occurs  in  lower  Huntington 
Creek  from  July  to  December,  forming  large 
mats  and  sometimes  filling  large  sections  of  the 
stream  channel. 

Diatoms  important  in  the  flora  of  the  lower 
Huntington  Creek  include  Navicula,  Nitzschia, 
Diatoina,  Gomphonema,  Synedra,  Surirella, 
Cymhella,  Cocconeis,  Achnanthes,  and  Cyclo- 
tella. 

Ponds  in  the  drainage  support  abundant  sum- 
mer algal  floras.  Filamentous  algae,  desmids, 
and  such  motile  genera  as  Chlamydomoixas,  Eu- 
glena,  and  Trachelomonas  are  common  constitu- 
ents of  these  floras. 


Fig.  41.  A  small  tributary  of  Huntington  Creek  (A) 
with  profuse  growths  of  Microspora  willeana  and 
Cladophora  glnmrrata.  Photograj)he<i  April  28.  1972. 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 

ACKNOWLEDGMENTS 


57 


This  investigation  was  supported  in  part  by 
Biomedieal  Sciences  Support  Grant  FR-5  505 
RR0711-03  from  the  General  Research  Support 
Branch,  Division  of  Research  Resources,  Bureau 
of  Health  Professions  Education  and  Manpower 
Training,  National  Institutes  of  Health.  Support 
was  also  received  from  a  Brigham  Young  Uni- 


versity research  grant,  from  a  grant  by  Utah 
Power  and  Light  Company  to  the  Brigham 
Young  University  Center  for  Health  and  En- 
vironmental Studies,  and  from  National  Science 
Foundation  Undergraduate  Research  Participa- 
tion Grant  GY-9052. 


APPENDIX  I 


NET  PLANKTON,  NANOPLANKTON,  PERIPHYTON,  AND 

N'ISIBLE  BENTHIC  ALGAL  TABLES 

Table  8.   Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  Lawrence  (Site  1) 


Algae 

4/15 

.5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Chroococcales 





18.5 





3.8 

2.9 

— 

— 

— 

_ 

— 

— 

— 

— 

12.1% 

— 

— 

5.9'^ 

14.1% 

— 

— 

— 

— 

— 

— 

Oscilhltoria 

23.0 



3.9 

7.5 

— 

— 

1.9 

— 

_ 

4.5 

4.1 

3.8 

1.5.0 

59.71 

— 

2.5% 

1.4% 

— 

— 

9.2"^ 

— 

— 

59.2<? 

16.3% 

2.9% 

3.2% 

Oth.T  Oscillii- 







— 

— 

— 

3.0 

1.9 

20.0 

.6 

.5 

2.5 

— 

toriaceat^ 

— 

— 

— 

— 

— 

— 

14.8", 

2.3.6T 

87.3% 

7.8% 

2.07,. 

1.9% 

— 

Chlamydomonas 

— 

— 

4.3.0 

— 

— 

— 

1.9 

— 

— 

— 

- 

- 

- 

— 

— 

28.1% 

— 

— 

— 

9.2% 

— 

— 

— 

— 

— 

— 

Pandoriuu 

— 

— 

— 

55.5 

— 

— 

.6 

— 

— 

— 

— 

— 

— 

morum 

— 

— 

— 

10.5'/-; 

— 

— 

3.0% 

— 

— 

— 

— 

— 

— 

Pcdiwitrum 

— 

— 

_ 

1.5.0 

— 

_ 

— 

— 

— 

— 

— 

— 

— 

— 

_ 

_ 

2.8% 

— 

— 

— 

— 

— 

— 

— 

— 

— 

Ulothrix 

_ 



7,7 







— 

— 

— 

_ 

14.4 

109.7 

246.0 

— 

— 

5.0% 

— 

— 

— 

— 

— 

— 

— 

■57.4% 

84.7% 

51.7% 

Sti^t'ociuuium 

— 

— 

— 

— 

_ 

— 

— 

— 

— 

.6 

— 

— 

— 

— 

— 

_ 

_ 

— 

— 

— 

— 

— 

7.8'v 

— 

— 

— 

OfUo^iitiium 



7.7 

49.0 

423.0 

25.5 

22.5 

2.5 

.6 

— 

1.9 

4.1 

5.0 

.36.0 

— 

5.8% 

32.0% 

80.3% 

69.4% 

35.3%, 

12.3% 

7.8% 

— 

25.0% 

16.3%. 

3.9% 

7.6% 

('tuditjtfiora 

15.5 

86.0 

18.5 

18.0 

3.8 

— 

— 

1.7 

— 

— 

— 

5.5 

36.0 

^hnnnata 

40.3'-; 

64.9';i: 

12.1% 

3.4<f„ 

10.2% 

— 

— 

21.5% 

— 

— 

— 

4.2% 

7.6% 

Spirii^yra 

_ 

_ 

_ 

_ 

_ 



.6 



— 

— 

3.0 

15.0 

— 

— 

— 

— 

— 

— 

— 

7.8% 

— 

- 

— 

2.3':! 

3.2% 

Xy^nctna 











^ 

— 

_ 

_ 

— 

1.5 

— 

— 

— 

— 

_ 

_ 

— 

— 

— 

— 

— 

— 

6.0% 

— 

— 

C.lostcrium 



7.7 



3.8 

3.8 

— 

— 

— 

— 

— 

— 

— 

— 

— 

5.8'7< 

— 

.7% 

10.2% 

— 

— 

— 

— 

— 

— 

— 

— 

Cositiariurii 

— 

_ 

— 

— 

— 

7.5 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

11.7% 

— 

— 

— 

— 

— 

— 

— 

Stiiurii^tntnt 







— 

— 

_ 

.6 

1.3 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

3.1% 

15.8% 

— 

— 

— 

— 

— 

I'lilirotatiiiiitit 



— 

— 

— 

_ 

— 

— 

.6 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

7.8% 

— 

— 

— 

— 

— 

Eufflejia 



31.0 

12.4 

3.8 

.3.8 

_ 

— 

.6 

1.7 

— 

.5 

— 

— 

— 

2.3.4% 

8.1% 

.7% 

10.2% 

— 

— 

7.8% 

7.4% 

— 

2.0% 

— 

— 

riutcus 





— 

— 

— 

— 

— 

— 

1.3 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

5.4% 

— 

— 

— 

— 

Ceratium 

— 

_ 

_ 

— 

— 

.30.0 

6.7 

— 

— 

— 

— 

— 

— 

hirundinetta 





— 

— 

_ 

47.1% 

3.3.0% 

— 

— 

— 

— 

— 

— 

Vaurhrria 









— 

— 

_ 

.6 

— 

— 

— 

— 

22.5 







— 

— 

_ 

— 

7.8% 

— 

— 

— 

— 

4.7% 

Hydrurus 

_ 









— 

— 

_ 

— 

— 

— 

— 

105.0 

fnftidus 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

22.0% 

Total  .Mgae 

.38.5 

1.32.4 

153.0 

526.5 

36.8 

6.3.8 

20.1 

7.9 

23.0 

7.6 

2.5.1 

129.5 

475.5 

58  BiiicHAM  YouNO  Univkhsity  Science  Bulletin 

Table  9.  Number  of  organisms  per  liter  and  relative  abundance  of  nannoplankton  at  Lawrence  (Site  1) 


Algae 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Cyctotella 





1.042 

4,180 

46.200 

79,250 

25,716 

15,567 

11,620 

5,560 

22,240 

48,6.50 

27,800 

— 

— 

.4% 

2.9% 

11.8% 

36.4%, 

13.9% 

18.6% 

2.97„ 

2.0% 

2.8% 

2.5% 

1.2%, 

Diatiyma 

4,010 

4,170 

4.170 

1,042 

— 

— 

_ 

— 

— 

— 

— 

58,380 

69,500 

tenui' 

1.1% 

1.3% 

1.6% 

.7% 

— 

— 

— 

— 

— 

— 

— 

2.9% 

3.0% 

Diatoma 

1,390 

8,060 

5,550 

696 

— 

— 

— 

— 

— 

695 

11,120 

— 

13,900 

vulnare 

A% 

2.4%, 

2.1% 

.5% 

— 

— 

— 

— 

— 

.2% 

1.4% 

— 

.6% 

Fratiilaria 

798 

.2% 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

Sftridion 

798 

.2% 
6.344 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

Sytiedra  cf. 

12,2.30 

9,720 

5.560 









6,670 









pulchella 

I.77o 

3.7% 

3.7%, 

3.9% 

— 

— 

— 

— 

1.6% 

— 

— 

— 

— 

Synedra  cf. 

30,126 

20,570 

9,312 

11.120 

4,180 

348 

1,668 

20,961 

160,015 

41,700 

278,000 

497,000 

291,900 

ulna 

8.3% 

6.1% 

3.6%, 

7.9% 

1.1% 

.2% 

.9% 

25.1% 

41.2% 

14.8% 

35.2% 

24.5% 

12.7% 

Achruinthes 

6,344 

_ 

1,390 

696 

8,360 

35,500 

44,.500 

13,900 

29,190 

20,850 

48,920 

136,220 

97.300 

1.7% 

— 

.5%, 

.5% 

2.1% 

16.  ,3% 

24.0%, 

16.6% 

7.2% 

7.4% 

6.2% 

6.7%. 

4.2% 

Cncconeis 

798 

— 

— 

4,338 

5,560 

52,500 

9,035 

5,837 

23,240 

11,676 

44,480 

136,220 

194.600 

.2% 

— 

— 

3.1% 

1.4%, 

24.1% 

4.9% 

7.0% 

5.7% 

4.1% 

5.6% 

6.7% 

S.4% 

RhdicosphtTiia 

_ 

1,390 

— 

— 

— 

— 

— 

— 

— 

1,390 

5,560 

_ 

— 

— 

.4% 

— 

— 

— 

— 

— 

— 

— 

.5% 

.7% 

— 

— 

Amphtprora 

_ 

_ 

348 

696 

348 

_ 

— 

696 

2,780 

695 

— 

— 

— 

— 

— 

.1% 

.5% 

.1% 

— 

— 

.S% 

.7% 

.2% 

— 

— 

— 

C'.yrosinma- 

1,.589 

2,780 

4,448 

4.448 

89,250 

4,170 

1,.390 

2,780 

7,505 

4,726 

11,120 

29,19U 

13.900 

Phxirosi^ma 

.4% 

.8% 

1.7%, 

3.1% 

22.8%, 

1.9% 

.8% 

.3..3% 

1.9% 

1.7% 

1.4% 

1.4%,, 

.6% 

Navicula  cf. 

1.5,888 

11,120 

3,0.57 

1,042 

10,700 

2,085 

— 

— 

— 

— 

— 

— 

83,400 

tripunctata 

4.4% 

3.3% 

1.2% 

.7%, 

2.7'7„ 

1.0% 

— 

— 

— 

— 

— 

— 

3.6% 

Other 

88,959139,000 

97,300 

36,488 

40,387 

15,919 

12,075 

6,5.50 

50.040 

65,886 

111,200 

369,740 

333,600 

Naviclua 

24.3% 

41.7% 

37.1% 

25.8% 

10.4%, 

7.3% 

6.5% 

7.8% 

12.4% 

2.3.3% 

14.1% 

18.3% 

14.5% 

Piuuularia 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

9,730 

.5% 
77,840 

— 

CioniphotnTna 













68,805 

7,060 

26,062 

7,.506 

I 

27,800 

gracil  e 

— 

— 

— 

— 

— 

— 

.37.1% 

8.3% 

6.4% 

2.7% 

— 

3.8% 

1.2%r 

Gomphonema 

23,543 

6,670 

1,390 

3,480 

11,275 

1,668 

4,865 

2,780 

348 

7,.505 

71,160 

194,600 

542,100 

olivaceum 

6..5% 

2.0%, 

.5%, 

2.5% 

2.9% 

.8% 

2.6%, 

3.3% 

.1% 

2.7% 

9.0%, 

9.6% 

23.5% 

Cymbt'lla 

109,611 

1,.390 

2,367 

2,088 

8,360 

3,750 

1,668 

— 

3,335 

2,085 

33,360 

68,180 

180,700 

30.0% 

.4% 

1.0% 

1..5% 

2.1%, 

1.7% 

.9% 

— 

.8%, 

.7% 

4.2%, 

3.4% 

7.8%, 

Epithrmia 

— 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

— 

13,900 

.6%, 

S'itzschia 





2,780 

6,950 

3,480 

696 

1,390 

1,668 

2,085 

I 

z 

I 

acicularis 

— 

— 

1.1% 

4.9%, 

.9% 

.3% 

.8% 

2.0% 

.5% 

— 

— 

— 

— 

Nitzschia 

— 

— 

— 

— 

— 

1,042 

1,168 

1,042 

4,170 

— 

— 

_ 

55,600 

deriticula 

— 

— 

— 

— 

— 

.5%, 

.6% 

1.2%„ 

1.0% 

— 

— 

— 

2.4% 

Other 

46,760 

94,.520 

104.2.50 

41,800 

163,000 

18,632 

10, .508 

2,780 

65,330 

92,296 

115,640 

291,900 

305,800 

Nitzschia 

12.8%. 

28.3%, 

40.9% 

29.5% 

41.7% 

8.6% 

5.7% 

3.4% 

16.2% 

32.7% 

14.6% 

14.4% 

13.3%, 

Surirrtla 

22,874 

31,690 

13,900 

3,480 

_ 

_ 

1,390 

348 

12,510 

20,015 

37,800 

107,030 

55,600 

6.3% 

9.5% 

5.3% 

2.5<!t 

— 

— 

.8% 

.4%. 

3.1% 

7.1'v 

4.8% 

5.3% 

2.4% 

Other 

4,168 

— 

— 

11,120 



















Pen  n  ales 

1.2% 

— 

— 

7.8% 

— 

— 

— 

— 

— 

— 

— 

— 

— 

Scenedcsmus 

- 

- 

- 

- 

- 

.348 

.2% 

215,908 

- 

- 

- 

- 

- 

- 

- 

Tot.il    \Iv:,M 

364,000  333,590 

261,024 

139.224 

391,100 

184,178 

81,969 

404,900 

282,586 

790,600  2024,680 

2307,400 

Bioi.oGicAi.  Sehies,  Vol.  18.  No.  2       Algae  of  Huntington  Canyon,  Utah 


59 


Table  10.   Number  of  organisms  per  cm^  and  relative  abundance  of  periphyton  on  glass  slides  at  Lawrence  (Site  1) 


Algae 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

CyclotcUa 

810 

— 

304 

2,045 

20,900 

6,075 

6,281 

1,523 

2,574 

304 

288 

.3% 

— 

.7% 

10.0%, 

21.67c 

5.77c 

3.2%, 

1.2% 

.6%, 

3.7% 

1.17c 

Diatoma 

9,320 

204 

102 

— 

1,020 

52 

206 

1,235 

48,392 



536 

1.9<t 

.7% 

.2% 

— 

1.17c 

.1% 

.1% 

.9% 

11.07c 

— 

2.1% 

Frafiilaria 

404 

_ 

206 

309 

.1% 

— 

— 

— 

— 

.27c 

.1% 

— 

— 

— 

— 

Sytiedra  ct. 

29.3,211 

7,1.57 

10,000 

— 

_ 

_ 

— 

— 







pulchclla 

60.9'-f 

24. 9-^^ 

21.8% 

— 

— 

— 

— 

— 

— 

— 

— 

Synedra  cf. 

18,800 

1,132 

849 

479 

1.624 

2,368 

7,619 

49,999 

115,833 

2,317 

4,5.30 

ulna 

3.9T^ 

3.9% 

1.97,, 

2.4% 

1.77c 

2.27c 

3.8% 

38.27 

26.37c 

27.8%. 

17.67c 

Achruinthes 

19,411 

204 

3,090 

68 

26,000 

51,996 

— 

27,594 

62,292 

309 

412 

4.0'7f 

."% 

6.7%, 

.3% 

26.97c 

49.0%, 

— 

21.17c 

14.17o 

13.0% 

1.6% 

Cocconeis 

— 

— 

10.400 

3,889 

22,100 

5,910 

5,354 

2,183 

5,150 

1,081 

535 

— 

— 

22.7% 

19.0% 

22.9% 

5.6% 

2.6% 

1.7% 

1.27c 

3.77c 

2.17c 

Amphiprora 

2,030 

— 

102 

— 

— 

— 

103 

— 

2,059 

— 

— 

.4% 

— 

.2% 

— 

— 

— 

.17c 

— 

.5% 

— 

— 

Gyrosigma- 

38,822 

808 

204 

4,727 

_ 

_ 

618 

288 

515 

— 

700 

Pleurosigma 

8.1<J 

2.9'^r 

.47c 

23.0% 

— 

— 

.37c 

.2% 

.1% 

— 

2.7% 

Savirula 

69,610 

6,152 

3,218 

5,309 

8,108 

4,223 

16,268 

17,009 

56,115 

927 

6,177 

U.-S'^J 

21.47, 

7.0%, 

26.0% 

8.4% 

4.0% 

8.27c 

13.0% 

12.7%, 

11.1% 

24.07c 

Gontpfwnt^ia 

— 

— 

_ 

_ 

_ 

— 

17,297 

— 

— 

309 

— 

gracih' 

— 

— 

— 

— 

— 

— 

8.7% 

— 

— 

3.77c 

— 

Com  phonttna 

4,040 

1,886 

1,320 

34 

2,1.30 

25,6.38 

2,368 

10,996 

41,185 

1.236 

5,231 

olivaceum 

.87c 

6.6'^c 

2.9% 

.27c 

2.2%, 

24.0% 

1.2% 

8.47. 

9.3% 

15.37c 

20.47c 

CymbeUa 

810 

2,216 

2,150 

625 

— 

247 

1,441 

1,.3.59 

2,574 

309 

1,770 

.2'v, 

7.7% 

4.7% 

3.0%, 

— 

.27c 

.7% 

1.07c 

.6% 

3.77c 

6.97c 

Sitz-schia 

_ 

8,186 

4,422 

2,238 

4,060 

4,716 

133,851 

15,650 

80,311 

1,081 

3,583 

— 

28..5<-f 

9.6'5 

11.0% 

4.2%, 

4.57, 

67.4% 

12.07c 

18.2% 

13.07c 

13.97c 

Surirdla 

14,127 

486 

304 

34 

— 

_ 

_ 

2,347 

14,930 

463 

1,2.35 

2.9% 

1.8% 

.7% 

.2% 

— 

— 

— 

1.8% 

3.4% 

5.6% 

4.87c 

Other 

1,210 

304 

2,250 

138 

— 

— 

— 

— 

— 

— 

124 

Pennales 

.3% 

1.17c 

4.9% 

.7% 

— 

— 

— 

— 

— 

— 

.5% 

Chroococcales 

4,860 

_ 

_ 

— 

408 

— 

— 

— 

— 

_ 

— 

1.0<5 

— 

— 

— 

.4% 

— 

— 

— 

— 

— 

— 

Oscillatoria 

3,240 

— 

812 

410 

_ 

_ 

_ 

124 

515 

_ 

288 

.7% 

— 

1.87o 

2.0% 

— 

— 

— 

.1% 

.1% 

— 

1.17c 

Other  Oscillator- 

— 

— 

— 

— 

9,  .300 

— 

— 

— 

— 

— 

— 

iaceae 

— 

— 

— 

— 

9.6% 

— 

— 

— 

— 

— 

— 

Ulothnx 

- 

- 

- 

- 

- 

- 

- 

- 

3,604 

.8% 

- 

288 
1.17c 

Proloderma 







I 

I 

3,192 

3,706 





— 

— 

— 

— 

— 

3.07, 

1.9% 

— 

— 

— 

— 

Stigeocloniuvi 

- 

- 

- 

- 

- 

- 

- 

- 

3,089 

.7% 

1,544 

- 

— 

Oedogonium 





2,040 

150 

812 

1,071 

2,.578 

412 

— 

— 

— 

— 

4.4% 

.77c 

.8% 

1.0% 

1.3% 

.3% 

.3% 

— 

— 

Cladophora 

— 

— 

849 

— 

204 

_ 

618 

— 

515 

— 

— 

— 

— 

1.9% 

— 

.2% 

— 

.37 

— 

.1% 

— 

— 

Other  Filamen- 

— 

— 

2,040 

_ 

1,220 

— 

— 

— 

— 

— 

— 

tous  Chlorophyta    — 

— 

4.4% 

— 

1..3% 

— 

— 

— 

— 

— 

— 

C:lostrrium 

— 

— 

612 

.50 

— 

— 

— 

— 

— 

— 

— 

— 

— 

1.4%, 

.2% 

— 

— 

— 

— 

— 

— 

— 

Cosmarium 

- 

- 

- 

- 

- 

52 
.1% 

— 

— 

— 

— 

— 

Euglena 

1,210 



406 

175 



— 

— 

_ 

_ 

— 

.3% 

— 

.97 

.97 

— 

— 

— 

— 

— 

— 

— 

Total  Algae 

481,915 

28,735 

4.5,474 

20,372 

97,886 

105,746 

198,617 

1.30,719 

441,197 

8,341 

25,697 

60  BRir.iiAM  YouNC  University  Science  Bulletin 

Table  11.  Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  plant  site  (Site  3) 


Algae 

4/15 
1971 

5/13 
1971 

6/8 
1971 

6/29 
1971 

7/30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

11/15 
1971 

12/17 
1971 

1/20 
1972 

2/19 
1972 

3/11 
1972 

Chroococcales 

- 

15.5 
3.0% 

3.9 
1.0% 

— 

11.2 

4.2% 

165.0 
17.6% 

3.5 
1.0% 

2.3 
1.5% 

— 

— 

— 

— 

— 

Oscitlatoria 

Other  Oscilla- 
toriaceae 

69.5 

40.7% 

233.0 
45.4% 

- 

3.8 

1.4% 

45.0 
18.8% 

18.2 

1.9% 
11.2 

1.2% 

15.8 

4.4% 
64.7 
17.9% 

10.5 

6.9%. 
47.0 
30.7% 

120.0 

22.9% 
367.0 
70.0% 

3.1 
20.7% 

5.7 
38.0% 

5.2 
14.0%, 

7.6 
20.5%, 

5.5 

7.1% 

4.3 

5.5% 

17.5 
8.2% 
9.8 
4.6% 

Anabaena 

- 

- 

- 

- 

- 

- 

— 

1.8 

1  l%i 

— 

— 

— 

— 

— 

Chlamyd(ym(>nas 

- 

- 

- 

- 

- 

- 

1.8 

.5%, 
78.7 
21.7% 

1.8 

1.1%. 
10.5 
6.9% 

- 

- 

- 

- 

- 

Pandorina 
moTum 

- 

- 

- 

15.0 

5.6% 

67.5 

28.0% 

78.0 

8.3% 

- 

- 

- 

- 

- 

Other  Volvo- 

— 

— 

— 

— 

— 

3.8 

— 

— 

— 

— 

— 

— 

— 

caceae 

— 

— 

— 

— 

— 

.4% 

— 

— 

— 

— 

— 

— 

— 

Ulothrix 

— 

— 

96.0 

25.3%. 

30.0 

11.3%. 

3.8 
1.6% 

7.5 

.8% 

— 

3.5 
2.3% 

— 

— 

1.5 

4.0% 

3.8 

4.8% 

11.0 

5.2% 

StigeocUinium             ________  22.5  —  2.6            _  1.3 

________  4.3%  _  7.07o        —  .6% 

Oedogonium              —            —              3.9          .37.5           _  3.8  54.2  28.0  _  _  1.0              .6  2.5 

_            —              1.0%       14.1%         —  .4%  15.0%,  18.3%  —  _  2.7%           .8%,  1.2% 

Cladophora                —            —             7.7          44.9          1.5.0  18.0  _              9.3  7.5  .6  —              1.3  1.3 

Rlomerala                —             —               2.0%       16.9%          6.3%  1.9%,  —               6.1%  1.4%,  4.0%  _               1.6%  .6% 

M(mgeotia                   —             —               —               —               7.5  —  —               1.8  —  —  —               —  — 

_             _               _               _               3.1%  —  —                1.1%  _____ 

Spirogyra                   _____  11.2  7.0  11.0  3.8  3.1  _                .6  2.5 

_            —              —              —              —  1.2%  1.9%         7.2%  .7%  20.7%  —                .8%,  1.2% 

Zygnema                    _            _              _              _            15.0  _  _              3.0  —  1.9              .5           —  — 

—  —              —              —              6.3%  _  —              2.0%  _  12.7%,  1.3%        _  — 
Other  Filamen-        23.2        15.5          11.6            —              —  3.8  7.0            _  —  .6  6.1            —  — 

tousChloro-          13.6%,        3.0%,         3.1%         _              _  .4%  1.9%  _  _  4.0%  16.4%,         _  _ 
phyta 

ClosteHum                 _            _              _              _            22.5  3.8  1.8            1.8  —  —              1.0              .6  1.3 

—  —              —              —              9.4%,  .4%  .5%         1.1%  —  —  2.7%           .8%  .6% 
Cosmarium                  —             —               —               —               3.8  —  —               —  —  —  —               —  — 

Staurastrum                _             _               7.7            —             22.5  93.7  —               1.8  —  —  —              —  — 

—  —              2.0%         —              9.4%  9.9%  —              1.170  —  _  —              —  — 
Euglena                      _____  3.8  _              1.8  _  _  _              _  _ 

—  —               —               —               —  .4%,  _               1.1%,  _____ 
Ceratium  hir-              _____  17.4  127.7             7.0  7.5  —  —               —  — 

undindla               _____  5.0%  35.3%,         4.6%,  1.4%,  _  _              _  _ 

Other  Pyrrho-              —             _               3.9            _               _  _  _               8.7  _  _  _               _  _ 

phyta                        _             _               1.0%         _               _  _  _               5g<5[,  _  _               _ 

Hydmms                  78.0      248.0       244.0        135.0          25.5  _  —              _  _  _  11.6  62.0  165.0 

foetidus                45.7%,     48.4%       64.0'"^       .50.7%       10.7%,  _____  31.3%  80.1%  77.5% 

Total  Algae            170.7      512.0       378.8       266.2       239.3  939.2  362.2  151.6  528.3  15.0  37.1  78.7  212.2 


BiOLOGiCAi,  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah  61 

Table  12.   Number  of  organisms  per  liter  and  relative  abundance  of  nannoplankton  at  plant  site  (Site  3) 


Algae 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Cyclotella 





2,780 

— 

3,127 

2,780 

— 

— 

— 

695 

_ 

_ 

— 

— 

— 

.4% 

— 

.9% 

.5% 

— 

— 

— 

.8% 

— 

— 

— 

AsttTionella 

— 

— 

59,490 

30,250 

13,344 

6,115 

3,335 

6,096 

— 

— 

— 

— 

— 

— 

— 

8.7% 

9.6% 

3.9% 

1.0% 

.4% 

1.2% 

— 

— 

— 

— 

— 

Hannaea 



1,390 

47,260 

13,066 

1.042 

— 

— 

695 

— 

_ 

1,668 

2,780 

3,892 

arms 

— 

.5% 

6.9% 

4.1%. 

.3%- 

— 

— 

.1% 

— 

— 

1.2%, 

1.1%, 

1.3% 

Diatoma 

— 

1,390 

2,780 

695 

— 

— 

— 

— 

— 

— 

— 

— 

973 

hifmalf 

— 

.5% 

.4% 

.2% 

— 

— 

— 

— 

— 

— 

— 

— 

.3% 

Diatoma 





— 

— 

— 

— 

— 

— 

_ 

18.348 

6,960 

21,545 

8,757 

tillUC 

— 

— 

— 

— 

— 

— 

— 

— 

— 

20. 27^ 

4.9% 

8.5%. 

2.970 

Diatoma 

3,475 

4,170 

2,780 

3,475 

7.086 

10,286 

11,120 

13,100 

1,737 

1.668 

4,450 

2,780 

1,946 

vul^are 

.5% 

1.4% 

.4% 

.9% 

2.1% 

1.7% 

1.2% 

2.5% 

1.1% 

1.8%, 

3.2% 

1.17c 

.6% 

Fra^ilaria 







1,390 

— 

1,390 

2,780 

80,620 

3,474 

1.390 

1,042 

695 

973 

— 

— 

— 

.5% 

— 

.2% 

.3% 

15.4% 

2.2%. 

1.5% 

.7% 

..3% 

.3% 

Mi^ndioti 

— 

_ 

— 

695 

1,042 

1,390 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

.2% 

.3%. 

.2% 

— 

— 

— 

— 

— 

— 

— 

Synedra 

90,350 

26,130 

28,910 

9,730 

4,170 

11,125 

25,020 

44,480 

11,812 

6.950 

1.5,985 

20,850 

25,298 

14.1% 

8.9% 

4.27^ 

3.1% 

1.2% 

1.9% 

2.8% 

8.5% 

7.6% 

7.77- 

11.37- 

8.2% 

8.3%, 

Achtuinthes 

3,475 

8,340 

19,460 

19,460 

42,600 

75,500 

29,745 

30,580 

3,474 

6,533 

6,255 

11,120 

18,487 

.5% 

2.8% 

2.7% 

6.2% 

12.3% 

12.69fc 

3.2% 

5.8% 

2.2%, 

7.2% 

4.47c 

4.4% 

6.1% 

Cocconeis 

— 

2,780 

— 

— 

5,004 

14,400 

2,780 

4,170 

1,737 

695 

1,042 

695 

1,946 

— 

.9% 

— 

— 

1.4% 

2.4% 

.3% 

.8% 

1.1% 

.8% 

.77c 

.37c 

.6%, 

Amphipleura 

— 

— 

— 

_ 

— 

— 

695 

2,085 

— 

347 

— 

— 

973 

— 

— 

— 

— 

— 

— 

.1%, 

.4% 

— 

.4%, 

— 

— 

.37., 

Navirula  cf. 



1,390 

1,390 

695 

— 

— 

_ 

— 

— 

_ 

4,4,50 

1,390 

973 

capitata 

— 

.5%. 

.5% 

.2% 

— 

— 

— 

— 

— 

— 

3.2% 

.57c 

.37c 

Navicuta  cf. 

— 

— 

— 

695 

4,170 

10,286 

44,505 

15,290 

1,737 

— 

— 

— 

— 

rhyncocephala 

— 

— 

— 

.2% 

1.2% 

1.7%, 

4.9%. 

2.9% 

1.1% 

— 

— 

— 

— 

Navicuta  cf. 

— 

_ 

— 

18,070 

13,344 

32,500 

43,085 

13,900 

15,287 

— 

5.560 

13,205 

18,487 

tripunctata 

— 

— 

— 

5.7% 

3.9%. 

5.4% 

4.7% 

2.5% 

9.8%. 

— 

3.97- 

5.2% 

6.1% 

Other 

104,250 

41,700 

115,650 

35,305 

59,826 

93,144 

120,930 

45,035 

15,287 

12,093 

1.5.568 

20,8.50 

35,028 

.Voficii/a 

16.2% 

14.2% 

15.8% 

11.2%. 

17.3% 

15.6% 

13.47o 

8.7% 

9.8% 

1.3.3%, 

11.17c 

8.27c 

11.57c 

StauToneis 











— 

— 

— 

— 

— 

348 

695 

_ 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

.3% 

.37c 

— 

GomphoniTna 

139,000 

94,520 

116.760 

19,460 

.30,024 

60,500 

65,330 

26,400 

10.425 

2,780 

15.985 

.52,820 

75,894 

21.6% 

32.2% 

17.0% 

6.2% 

8.7% 

10.1% 

7.2% 

5.0% 

6.7% 

3.1% 

11.. 3% 

20.8% 

24.87c 

Cymbclta 

205.520 

58,380 

150.120 

113,980 

90,375 

145,500 

216,505 

80,620 

29.187 

15,985 

25.993 

62,5.50 

6.5,191 

32.0% 

19.9% 

21.9% 

36.1% 

26.2% 

24.3% 

23.8% 

15.4% 

18.7% 

17.7% 

18.4% 

24.6% 

21.3% 

Nitzschia 

— 

— 

— 

695 

5,004 

2,084 

2,362 

2,362 

— 

— 

— 

— 

— 

acicularis 

— 

— 

_ 

.2% 

1.4%. 

.4%. 

.3% 

.4% 

— 

— 

— 

— 

— 

Other 

86,175 

46,980 

129,550 

44,420 

.59.175 

119,416 

328,038 

136,220 

60.462 

22,935 

34,333 

42,395 

44,758 

Nitzschia 

13.4% 

16.5% 

18.9% 

14.1% 

17.2%. 

19.9% 

36.1% 

26.0 

38.7% 

25.3% 

24.37c 

16.77c 

14.67c 

SurircUa 

10.425 

4,170 

1,.390 

695 

1,042 

2,780 

9,7.30 

3,335 

1.737 

347 

696 

— 

1,946 

1.6% 

1.4% 

.2% 

.2% 

.3% 

.5% 

1.0% 

.6% 

1.1% 

.4% 

.57c 

— 

.6% 

Other 

— 

1,390 

7,230 

3,335 

1,042 

— 

695 

— 

— 

— 

696 

695 

— 

Pennales 

— 

.9% 

1.1% 

1.1%> 

.3% 

— 

.1% 

— 

— 

— 

.5% 

.6% 

— 

Dinnbrynn 

— 

— 

1,390 

1,390 

3,127 

8,900 

695 

20,016 

— 

— 

— 

— 

— 

— 

— 

.2% 

.4% 

.9% 

1.5%, 

.1% 

3.8% 

— 

— 

— 

— 

— 

Total  Algae 

642,670  292,730 

686,940 

317,501 

344,544 

598,096 

907,350 

52.5,004 

1.56.356 

90,766 

141,031 

255,065 

305,522 

62 


BmcHAM  Young  University  Science  Bulletin 


Table  13.    Number  of  organisms  per  cm^  and  relative  abundance  of  periphyton  on  glass  slides  at  plant  site  (Site  3) 


Algae 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

Cyclotetla 

- 

- 

- 

- 

204 

.2% 

- 

62 

.2%,, 

— 

— 

- 

- 

Asterionella 

~_ 

445 

850 

202 

612 



62 









— 

.5% 

1.0% 

.1% 

.6% 

— 

.2%c 

— 

— 

— 

— 

Hannaea 

154 

445 

1.740 

496 

_ 

_ 

— 

371 

— 

154 

309 

arcus 

.6% 

.5% 

2.0%, 

.3%, 

— 

— 

— 

1.1% 

— 

.3% 

1.6% 

Diatoma  hitinale 

- 

51 
.1% 

- 

- 

204 

.2% 

- 

- 

— 

— 

— 

— 

Diatoma  tiiiue 

z 

I 











2,625 

1,081 

— 

— 

— 

— 

— 

— 

— 

— 

— 

5.1%, 

5.7% 

Diatoma  vulgare 

_ 

51 

406 

598 

847 

1,544 

474 

2,.595 

407 

309 

154 

— 

.1% 

.5% 

.4%, 

.9% 

3.2% 

1.4% 

8.0% 

5.1% 

.6%, 

.8% 

Fratiilnria 

— 

— 

— 

— 

— 

— 

350 

247 

— 

_ 

154 

CTotujicnsis 

— 

— 

— 

— 

— 

— 

1.1% 

.7% 

— 

— 

.8%, 

Meridian 

— 

51 

.1% 
2.062 

- 

— 

— 

— 

- 

- 

- 

- 

- 

Synedra 

3,855 

4.530 

2,393 

3,420 

762 

1,503 

3,830 

678 

3,861 

1.081 

14.0% 

2.5% 

5.2%, 

1.5% 

3.5%, 

1.6%, 

4.5% 

11.8%, 

8.4%, 

7.5%, 

5.7%, 

Achnanthcs 

1,.390 

3.960 

10.300 

94,100 

13,340 

15,589 

2,060 

1,606 

325 

2.008 

618 

5.07o 

4.8%, 

11.7%, 

57.1%, 

13.7% 

32.3%, 

6.29t 

5.0%. 

4.1%, 

3.9% 

3.3% 

Cocconeis 

103 

— 

— 

596 

305 

1,174 

144 

— 

— 

— 

— 

.4% 

— 

— 

.4%, 

.3%. 

2.4% 

.4%. 

— 

— 

— 

— 

Amphipleura 

— 

— 





64 

52 

206 

864 





154 

— 

— 

— 

— 

.1%. 

.1% 

.6% 

2.7%. 

— 

— 

.8%, 

Navicula  cf. 

— 

1,167 

4,530 

.5,335 

6,997 

556 

2,471 

1.831 

407 

1,390 

463 

tripunctata 

— 

2.0% 

5.2%, 

3.2%. 

7.2% 

1.2% 

7.5% 

5.7% 

5.1% 

2.7%. 

2.4%c 

Other  Savicula 

7.258 

5,255 

5,136 

24,265 

18.973 

.3,913 

6,322 

2.707 

868 

3,707 

772 

26.4<7< 

6.4%, 

5.9%r 

14.8%. 

19.6%^ 

8.1% 

19.1% 

8..3% 

10.8% 

7.2% 

4.1%,, 

Gomphonema 

6,067 

14.415 

10,300 

5,050 

2.501 

3,027 

885 

2.348 

732 

18.688 

7.877 

22.0% 

17.5%, 

11.7% 

3.1%. 

2.6% 

6.3%, 

2.7% 

7.. 3%, 

9.1% 

36.2^ 

41.5%, 

Cymbctia 

8,408 

35,382 

38,755 

18,000 

15.400 

8,175 

4,324 

6.301 

2.441 

13.437 

2.317 

30.5%. 

43.0%c 

44.2% 

10.9%t. 

15.9% 

17.0% 

13.1% 

19.5%, 

30.4%o 

26.0% 

12.2%o 

Nitzschia 

— 

_ 

_ 

920 

406 

206 

— 

— 







acicularis 

— 

— 

— 

.6% 

.4% 

.4% 

— 

— 

— 

— 

— 

Other  Nilzschia 

— 

17,649 

6,062 

9,240 

32.094 

12,397 

12,335 

9.267 

1.627 

5.406 

3.861 

— 

21.4%, 

6.9%, 

6.2% 

32.7%. 

25.7% 

36.9%. 

28.7% 

20.3%, 

10.5%b 

20.3%,, 

Surirclla 

201 

303 

536 

503 

204 

154 

144 

371 

68 





.7% 

.4% 

.67o 

.3% 

.2%, 

.3% 

.4% 

1.1% 

.8% 

— 

— 

Other  I'ennales 

— 

294 

2.183 

_ 

_ 

52 

62 

— 

— 

— 

— 

— 

.3% 

2.5% 

— 

— 

.1% 

.2% 

— 

— 

_ 

— 

Dinohryoii 

— 

203 

_ 

— 

— 

— 

62 









— 

.2% 

— 

— 

— 

— 

.2% 

— 

— 

_ 

_ 

Osciltatoria 

— 

— 

2.040 

1.056 

_ 

412 

— 

— 

203 



154 

— 

— 

2.3% 

.6% 

— 

.2% 

— 

— 

2.5% 

— 

.8% 

Other 

93 

— 

_ 

1.151 

1,877 

103 

1,853 

— 

203 





Oscillatortaceae 

.3% 

— 

— 

.7% 

1.9% 

.9% 

5.67o 

— 

2.5% 

— 

— 

Anabacna 

— 

_ 

_ 

95 

64 

— 











— 

— 

— 

.17o 

.1% 

— 

— 

_ 

_ 

_ 

_ 

Ulothnx 

_ 

_ 

— 

95 



103 











— 

— 

— 

.1% 

— 

.2% 

— 

— 

— 

— 

— 

Stigeoclonium 

— 

— 

— 

— 

— 

_ 

_ 

— 

68 

— 

— 

— 

— 

— 

— 

— 

— 

— 

_ 

.8%, 

— 

_ 

Oedogonium 

— 

— 

— 

— 

— 

52 

— 

— 

_ 

_ 

_ 

— 

— 

— 

— 

— 

.1% 

— 

— 

— 

— 

— 

Other  Filamentous 







738 

_ 

_ 

144 

_ 

Chlorophyta 

— 

— 

— 

.4% 

— 

— 

.4%, 

_ 

_ 

— 

— 

Ctostmum 

— 

— 

85 

— 

64 









_ 



— 

— 

.1%, 

— 

.1% 













EugltTia 

- 

51 

1% 

— 

- 

- 

- 

- 

- 

- 

- 

- 

HydntrlM  foetidus 



51 

247 

95 

z 

— 

.1% 

.3% 

.1%C 

— 

— 

— 

— 

— 

— 

— 

Total  Algae 

27.529 

82.285 

87.700 

164.928 

97,576 

48,271 

33,463 

32.338 

8,027 

51..585 

18.995 

Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


63 


Table  14.   Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  campground  (Site  4) 


Algae 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Chroococcales 

— 

— 

— 

— 



97.5 

22.5 

8.7 











— 

— 

— 

— 

— 

13.5% 

1.2% 

10.8% 

— 

— 

— 

— 

— 

Oscillatoria 

93.0 

123 

3.9 

7.5 

3.8 

15.0 

30.0 

7.7 

33.7 

4.5 

3.1 

2.5 

7.5 

60.0% 

21.2% 

.8% 

2.4%, 

2.9%, 

2.1% 

1.6% 

9.6% 

5.8% 

14.6%, 

9.5%, 

4.4% 

14.5% 

Other  Oscilla- 

7.7 

54.0 

_ 

_ 

_ 

30.0 

385.0 

5.2 

502.5 

21.9 

10.3 

1.9 

3.8 

toriaceae 

5.0% 

9.3% 

— 

— 

— 

4.1%, 

19.9% 

6.5% 

87.0% 

69.9%, 

31.4% 

3.3% 

7.2% 

Anabaeria 

— 

7.7 
1.3% 

— 

— 

— 

— 

— 

— 

— 

— 

- 

- 

- 

Chlamydomonas 





I 

15.0 

I 

I 

1.8 

I 

I 

~ 

I 

I 

— 

— 

— 

— 

11.5%, 

— 

— 

2.2% 

— 

— 

— 

— 

— 

Pandorina 

— 

— 

— 

— 

11.4 

45.0 

232.5 

3.5 











morum 

— 

— 

— 

— 

8.6% 

6.2% 

11.9% 

4.4%, 

— 

— 

— 

— 

— 

Other  \'olvo- 

— 

— 

— 

— 

— 

3.8 

— 

3.5 

— 

_ 

_ 

— 

_ 

caceae 

— 

— 

— 

— 

— 

.5% 

— 

4.4%, 

— 

— 

— 

— 

— 

Ulothrix 

— 

46.5 

161.0 

7.5 

7.5 

3.8 

_ 

2.6 

3.8 

— 

1.0 

2.5 

— 

— 

8.0% 

32.0%. 

4.0% 

5.8% 

.5% 

— 

3.2% 

.6% 

— 

3.1% 

4.4% 

— 

Stigeoctonium 

— 

— 

— 

— 

_ 

— 

_ 

_ 

22.5 

3.9 

1.5 

— 

2.5 

— 

— 

— 

— 

— 

— 

— 

— 

3.9% 

12.6% 

4.6% 

— 

4.8% 

Oedogonium 

— 

15.5 

3.9 

11.2 

3.8 

— 

127.5 

20.3 

— 

— 

.5 

— 

— 

— 

2.7% 

.8% 

6.0% 

2.9% 

— 

6.5%, 

25.3% 

— 

— 

1.5% 

— 

— 

CtadophoTQ 

— 

— 

11.6 

15.0 

15.0 

15.0 

_ 

4.4 

_ 

.6 

1.0 

.6 

_ 

glomerata 

— 

— 

2.3% 

8.0% 

11.5% 

2.1% 

— 

5.4% 

— 

1.9% 

.3.1% 

1.1% 

— 

Mougeotia 

— 

— 

— 

— 

— 

7.5 

— 

.9 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

1.0% 

— 

1.1% 

— 

— 

— 

— 

— 

Spirogyra 

— 

— 

7.7% 

— 

— 

— 

— 

7.7 

_ 

_ 

— 

.6 

— 

— 

— 

1.5%> 

— 

— 

— 

— 

9.6%, 

— 

— 

— 

1.1% 

— 

Zygnema 

— 

_ 

_ 

— 

33.0 

3.8 

— 

.9 



— 

1.0 





— 

— 

— 

— 

25.3%, 

.5% 

— 

1.1% 

— 

— 

.3.1% 

— 

— 

Other  Filamen- 

7.7 

— 

3.9 

_ 

— 

— 

— 

— 

— 

— 

2.0 

.6 

— 

tous  Chlorophyt 

:a   5.0% 

— 

.8% 

— 

— 

— 

— 

— 

— 

— 

6.1% 

1.170 

— 

Closterium 

— 

23.0 

— 

— 

26.2 

3.8 

7.5 

2.6 

3.8 

— 

— 

.6 

.6 

— 

4.0% 

— 

— 

20.2% 

.5% 

.4% 

3.2% 

.64% 

— 

— 

1.1% 

1.2% 

Staurastrum 

— 

_ 

— 

— 

— 

72.0 

7.5 

— 

3.8 







— 

— 

— 

— 

— 

— 

9.9% 

.4% 

— 

.64% 

— 

— 

— 

— 

Euglena 

- 

— 

— 

- 

- 

3.8 
.5% 
423.0 

- 

.9 
1.1% 
7.0 

- 

- 

- 

- 

- 

Ceratium  hir- 

I 

I 

I 

I 

I 

1110.0 

7.5 

I 

I 

undinella 

— 

— 

— 

— 

— 

.58.4% 

57.6%, 

8.7% 

1.3% 

— 

— 

— 

— 

Other 

— 











7.5 













Pyrrophyta 

— 

— 

— 

— 

— 

— 

.4% 

— 

— 

— 

— 

— 

— 

Hydrurus 

46.5 

310.0 

309.0 

146.8 

15.0 











12.4 

48.0 

37.5 

foetidus 

30.0% 

53.5%, 

62.0% 

78.. 3% 

11.5% 

— 

— 

— 

— 

— 

.37.8% 

84.7%, 

72.37o 

Vaucheria 

- 

- 

- 

- 

- 

- 

- 

2.6 
3.2% 
80.3 

- 

- 

- 

- 

- 

Total  Algae 

154.9 

579.7 

501.0 

188.0 

130.7 

724.0 

1930.0 

578.2 

30.9 

32.8 

57.3 

51.9 

64  Bbicham  Young  University  Science  Bulletin 

Table  15.  Number  of  organisms  per  liter  and  relative  abundance  of  nannoplankton  at  campground  (Site  4) 


Algae 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Cyclolella 







4,170 

— 

1,668 

— 

— 

_ 

1,042 

— 

— 

— 

_ 

_ 

— 

.5% 

— 

.7% 

— 

— 

— 

.4% 

— 

— 

— 

Asterionella 

— 

— 

46,425 

88,9,50 

13,200 

2,357 

1,390 

2,085 

2,085 

1,042 

— 

— 

— 

— 

— 

9.0% 

11.6% 

6.1%. 

1.0% 

.2%. 

.8% 

.4% 

.4% 

— 

— 

— 

llannaea 

6,960 

16,680 

27,105 

27,800 

2,.362 

348 

695 

— 

1,390 

3,058 

1,390 

4,170 

3,475 

arms 

6.1'S 

2.1% 

5.3% 

3.6% 

1.1% 

.2%, 

.1% 

— 

.3% 

1.1% 

1.1% 

1.0% 

1.9% 

Diatoma 

2,432 

_ 

4,170 

3,335 

_ 

— 

— 

— 

— 

— 

696 

— 

1,390 

hiifjialf 

2.1% 

— 

.8% 

.4%, 

— 

— 

— 

— 

— 

— 

.5% 

— 

.8% 

Diattrma 





1,390 

— 

_ 

_ 

_ 

— 

— 

— 

348 

4,170 

5,560 

teiiue 

— 

_ 

.3%, 

— 

— 

— 

— 

— 

— 

— 

.3% 

1.0% 

3.1%. 

Dialoma 

5,912 

12,510 

2,085 

8,895 

2,780 

1,668 

15,845 

3,335 

20,016 

4,865 

4,450 

9,730 

4,865 

vulnare 

3.1% 

1.6% 

.4% 

1.2% 

1.3% 

.7% 

1.7%, 

1.2% 

4.3% 

1.8% 

3.  .5% 

2.3% 

2.7% 

Frti^lUiria 

— 

— 

2,780 

695 

_ 

696 

695 

104,805 

10,285 

8,340 

1,042 

1,390 

695 

— 

— 

.5% 

.1% 

— 

.31% 

.1% 

37.7% 

2.2% 

3.1%. 

.8% 

.3% 

.4% 

\feridion 

_ 

12,510 

6,9.50 

2,780 

— 

— 

— 

— 

— 

347 

— 

1,390 

— 

— 

1.6% 

1.4%. 

.4% 

— 

— 

— 

— 

— 

.1% 

— 

.3% 

— 

Synedra 

6,602 

46.702 

11,675 

22,795 

7,200 

5,560 

20,8.50 

9,730 

20,8.50 

10,703 

17,653 

33,360 

8,340 

5.8% 

6.0% 

2.3% 

3.0% 

3.3% 

2.. 5% 

2..5% 

3.5% 

4.5% 

4.0% 

13.7%. 

7.8% 

4.6%, 

Achnanthes 

1,740 

.37,5.30 

22,240 

61,150 

18,725 

26,000 

49,6.50 

9,730 

43,090 

22,935 

6,960 

18,070 

15,290 

1..5% 

4.8% 

4.3% 

8.0% 

8.6% 

11.5% 

5.4%. 

3.. 5% 

9.2% 

8.5% 

5.4% 

4.2% 

8.5% 

Cocconeis 

1,390 

— 

695 

1,390 

696 

6,255 

6,096 

_ 

2,780 

3,0.58 

1,668 

2,780 

695 

1.2% 

— 

.1% 

.2% 

.3% 

2.8% 

.7% 

— 

.6% 

1.1% 

1..3%. 

.7% 

.4% 

Rhoicos- 

— 

1,042 

1,390 

695 

— 

— 

— 

— 

— 

— 

— 

— 

— 

phfTiio 

— 

.1% 

.2% 

.1% 

— 

— 

— 

— 

— 

— 

— 

— 

— 

Amphipli-ura 

— 

— 

— 

— 

_ 

— 

— 

_ 

695 

695 

— 

1,390 

— 

— 

— 

— 

— 

— 

— 

— 

— 

.1% 

.2% 

— 

.3% 

— 

Cyrosi^ma 

- 

- 

- 

- 

- 

- 

- 

695 

.3% 

- 

- 

— 

1,390 

.3% 

- 

Navicula  cf. 

695 

1,042 

I 

695 

I 

I 



695 





2,085 

8,340 

2,085 

capitata 

.6% 

.1% 

— 

.1% 

— 

— 

— 

.3% 

— 

— 

1.6% 

2.0% 

1.2% 

Navicula  cf. 

— 

— 

2,780 

2,085 

— 

3,052 

45,035 

1,390 

5,560 

1,042 

— 

— 

4,865 

rhyncocephala 

— 

— 

.5% 

..3% 

— 

1.4%. 

4.9%. 

.5% 

1.2% 

.4% 

— 

— 

2.7% 

Navicula  cf. 

— 

— 

— 

18,070 

10,007 

7,225 

56,155 

7„505 

19,460 

9,313 

,5,838 

18,070 

13,205 

tripunctata 

— 

— 

— 

2,4% 

4.6% 

3.2%. 

6.1%. 

2.7% 

4.2% 

3.4% 

4.5% 

4.2%. 

7.3% 

Other 

11,468  141,760 

67,550 

94,290 

36,585 

33,323 

107.010 

11,120 

72,280 

59,353 

10,842 

52,820 

15,985 

Navicula 

lo.n 

18.2'-, 

13.0% 

12.4% 

16.8% 

14.4% 

11.5% 

4.0%. 

15., 5%. 

22.0% 

8.5% 

12.4% 

8.9% 

Pinnularia 

- 

1,042 

.1%, 

- 

- 

- 

- 

- 

- 

- 

347 

.1% 

- 

- 

- 

Staurnncis 

- 

- 

- 

- 

- 

- 

- 

695 

.1% 
53,375 

- 

- 

695 

.4% 
20,155 

CiomphnjttTiia 

13,553 

194,7.37 

79,785 

69,500 

16,675 

23,2,59 

54,210 

10,285 

21,545 

17,653 

76,4.50 

11.9% 

25.0% 

15.5% 

9.1% 

7.6% 

10.. 3%. 

5.8%. 

3.7% 

11.3% 

8.0% 

13.7% 

17.9% 

11.2% 

Cymbclla 

.38,920  159,.584 

11.5,925 

230,740 

73,250 

73,250 

215,4.50 

33,915 

90,350 

64,218 

31,970 

102,860 

46,565 

34.2% 

20.5% 

22.5%. 

30.2% 

.33.6% 

32.4% 

32.2% 

12.2% 

19.4% 

23.7% 

24.8% 

24.1%, 

25.9% 

Epithcniia 

- 

1,042 

.1% 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

— 

Nitzschia 



6,115 

1,390 

2,780 

3,052 

6,096 

2,362 

2,780 





1,390 



acicularis 

— 

— 

1.2%. 

.2% 

.7% 

1.4% 

.7% 

3.5% 

.6% 

— 

— 

.3% 

— 

Other 

20.880 

133,440 

85,345 

102,960 

26,2.50 

30,250 

337,770 

43,590 

113,980 

56,990 

23,908 

86,180 

34,055 

Nilzschia 

18.4% 

17.1% 

16.6% 

13.  .5% 

12.6% 

13.. 3%. 

36.47n 

13.0% 

24.5% 

21.1% 

18.5%. 

20.2% 

18.9% 

Surirella 

348 

9,172 

2,780 

4,170 

1,390 

348 

9,730 

1,390 

4,170 

1,390 

2,363 

2,780 

2,085 

.3% 

1.2% 

..5% 

.6% 

.2%. 

.2%, 

1.1% 

.5% 

.9% 

.5% 

1.8%. 

.7%, 

1.2% 

Other 

5,210 

4,170 

5,560 

16,000 

_ 

1,042 

— 

— 

_ 

_ 

_ 

— 

— 

Pennaies 

4.6% 

.6% 

1.1%. 

2.1% 

— 

.5% 

— 

— 

— 

— 

— 

— 

— 

Dinobryon 

— 

— 

15,290 

1,390 

6,255 

6,5.50 

— 

35,305 

2,085 

— 

— 

— 

— 

— 

— 

3.0%, 

.2% 

2.9% 

2.9% 

— 

12.7% 

.4% 

— 

— 

— 

— 

Total  Algae 

116,110  772.963 

514,150 

763,795 

218,145 

225,903 

926,677 

277,937 

465,925 

270,283 

128,866 

426,730 

180,005 

Biol<)(;k:ai.  Series,  Vol.  18.  No.  2       Ai.c.^E  of  Huntincton  C.\nyon,  Utah 


65 


Table  16.    Number  of  organisms  per  cm-  and  relative  abundance  ol  periphyton  on  glas.s  slides  in  a  pool  at  campground 

(Site  4) 


Algae 

5/13 
1971 

6/8 
1971 

6/29 
1971 

7/.30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

11/15 
1971 

Cyclotella 

— 

— 

— 

— 

— 

52 

.2% 

62 

.5% 

— 

Astcrioncllu 

— 

— 

85 
.1% 

1,020 

.4% 

102 

.4% 

103 

.5% 

— 

— 

Ihmnaeu 
anus 

1,020 
2.0* 

5,459 

2.6% 

648 

.4% 

304 

.1% 

— 

— 



206 
.6% 

Diittomu  liUiHulf 

z 

607 

.3% 

242 
.2% 







— 

— 

Di(tti)m(t  tcnuc 

— 

— 

— 

— 

— 

— 

— 

— 

Diut(,inia  vuli^are 

810 
1.6? 

1,213 
.6% 

909 

.5% 

1,522 
.6% 

— 

206 
1.0% 

762 

6.4% 

1,441 
3.9% 

Frit^ilarid  crotunensis 

— 

— 

I 

— 

— 



62 

.5% 

3,532 
9.5% 

Mcrkliuii 

— 

— 

— 

— 

102 

.4% 

— 

— 

— 

Si/iicdro 

2,677 

5.2* 

7,919 

3.7% 

85 
.1% 

.304 

.1% 

— 

154 

.7% 

762 
6.4% 

1,544 

4.2% 

Achuanthc\ 

2,677 

5.2% 

27,298 
12.8% 

123,650 
76.0% 

196,100 

75.3% 

3,685 
14.9% 

,3,398 
16.0% 

412 

3.5% 

4,602 

12.4% 

Cocconeis 

243 

.5% 

— 

648 

.4% 

102 

.1% 

1,020 

4.1% 

1,853 

8.7% 

268 

2.3% 

31 

.1% 

Navicula  cf. 
ciii)it(it<i 

102 

.2% 

2,426 
1.2% 

— 



— 



— 

— 

Navicula  cf. 
rhyncoccplwla 

— 

— 

85 

.1% 

890 

..3% 

304 

1.2% 

968 

4.6% 

— 

— 

Navicula  cf. 
tripttnctatd 

— 

— 

3,006 
1.6% 

3,583 
1.4% 

890 

3.6% 

1,133 
5.. 3% 

618 

5.2% 

1,1.33 
3.5% 

Other  Navintla 

21,210 
41.0? 

20,606 
9.7% 

4,674 
2.9% 

10,684 
4.1% 

3,690 
15.0% 

2,255 
10.6% 

2,821 
23.8% 

4,221 
11.4% 

Gomphonema 

4,633 
9.0% 

.30,861 

14.. 5% 

3,583 
2.2% 

.3,152 

1.2% 

2,224 
9.0% 

350 

1.6% 

1,235 

10.4% 

1,205 

3.2% 

Cymhclla 

14,9.32 
29.0% 

70,784 

33.3% 

19,770 

12.0% 

29,948 
11.5% 

2,224 
9.0% 

2,265 
10.6% 

2,327 
19.7% 

9,915 
26.6% 

Nitz-schiti  acicularis 

— 

— 

— 

890 

..3% 

102 

.4% 

— 

— 

— 

Other  Nitz-schia 

3,033 
5.9% 

40,0.32 

18.8% 

2,887 
1.8% 

10,600 
4.1% 

3,920 
15.9% 

8,2.37 
38.7% 

2,327 
19.7% 

7,279 
19.6% 

Surinlla 

152 
.3% 

607 

.3% 

85 
.1% 

I 

304 
1.2% 

52 
.2% 

62 

.5% 

103 

..3% 

Other  Fennales 

102 

.2% 

3,642 
1.7% 

648 
.4% 

I 

— 

— 

— 

31 
.1% 

Dinohryoii 

— 

— 

— 

— 

102 
.4% 

I 



— 

Oscillataria 

— 

— 

536 

..3% 

1,190 

.5% 

406 

1.6% 

154 

.7% 



206 
.6% 

Other  Oscillatoriaceae 

— 

— 

— 

— 

5,644 
22.9% 

— 

62 
.5% 

1,514 
4.1% 

Ulolhrix 

— 

1,213 
.6% 

— 

102 

.1% 

— 

52 

.2% 

62 

.5% 

31 

.1% 

Stificocloniuni 

— 

— 

— 

102 

— 

— 

— 

31 

(Table  16  continued  on  p.  66) 


— 

318 

— 

— 

.4% 

— 

102 

318 

812 

.1% 

.4-? 

2.2% 

324 

1,719 

1,590 

406 

,5« 

1.9^ 

2.0* 

1.1% 



318 

— 

— 

A'i 

— 

g6  Brigiiam  Young  University  Science  Bulletin 

—  —  —  .1%  —  -  -  .1% 
0«/(>gonii/;N                                  —                 —                 —                 —                 —                       52           —                 — 

CAadophora  —  —  536  —  —  —  —  72 

—  —  .,3%  _  _  _  _  .2% 

Closterium  _  _  _  204  —  —  —  31 

—  -  —  .1%  —  —  —  .1% 

Euglena  51  —  —  —  —  —  —  — 

Hi/drunis  —  —  536  —  —  —  —  — 

—  —  .3%  —  —  —  -  - 

Total  Algae  51,642      212,667       162,613      260,697         24,719         21,284         11,842         37,128 

Table  17.   Number  of  organisms  per  cm-  and  relative  abundance  of  periphvton  on  glass  slides  in  a  riffle  at  campground 
(Site  4) 

Algae  5/13  6/8  6/29  7/30  8/20  2/19  3/11 

1971      1971      1971      1971      1971      1972      1972 

Cyclotetia 

Astcriimclla 

Haniuicu 
arcus 

Diatonid  hii'nuilr 

Didtinnti  triiuc  —  —  — 

Diittiiimi  inlfiiirc  486  708  636 

.7%  .8%  .8* 

Fnigiliiria  croloncnsis  —  —  — 

Meridion 

Si/ncdrii 

Achnantltes 

Cocconeis 

Wivictda  cf. 
rhyncocc'phala 

Navicula  cf. 
tripunctata 

Other  Navicula 

Gomplwnrmd 

C.ymbella 

iVi  ( r.SY'/i  ia  acicu la ris 

Other  \itzschia 

Surirt'lla 


6,075 

— 

12.7% 

— 

103 

154 

.2% 

.9% 

3,295 

1,287 

6.9% 

7.9% 

204 

206 

1.54 

,2% 

.5% 

.9% 

— 

51 

— 

.3% 

— 

102 

— 

— 

— 

103 

— 

— 

.1% 

— 

— 

— 

.2% 

- 

7,113 

4,040 

1,272 

— 

204 

7,928 

1,493 

11.0% 

4.. 5% 

1.6% 

- 

.2% 

16..5% 

9.2% 

1,.375 

2,928 

23,532 

20,400 

43,200 

2,780 

1,184 

2.1? 

3.2% 

28.1% 

54.6% 

43.2% 

5.8% 

7.3% 

81 

— 

— 

3,248 

1,624 

103 

— 

.1% 

— 

— 

8.7% 

1.6% 

.2% 

- 

— 

— 

318 

204 

1,020 

— 

— 

— 

— 

.4% 

.5% 

1.0% 

- 

— 

— 

1,617 

6,678 

406 

3,040 

1,.544 

— 

— 

1.8% 

8.0% 

1.1% 

3.0% 

3.5% 

- 

7,923 

5,982 

10,.540 

2,028 

10,276 

4,015 

1,184 

12.1% 

6.6% 

12.5% 

6..5% 

10.3% 

8.4% 

7..3% 

15,131 

24,015 

2,226 

2,670 

2,670 

2,574 

1,287 

23..3% 

26.6% 

2.7% 

7.1% 

2.7% 

5.4% 

7.9% 

24,099 

33,963 

18,762 

3,490 

16.510 

5,554 

5,714 

.37.2% 

.37.6% 

22.4% 

9..3% 

16.  .5% 

11.1% 

35.0% 

— 

— 

— 

406 

812 

— 

— 

— 

— 

— 

1.1% 

.9% 

— 

- 

8,080 

13,820 

12,720 

1,886 

17,503 

8,546 

3,088 

12.5% 

15.3% 

1,5.2% 

5.0% 

17.4% 

17.8% 

18.9% 

— 

102 

— 

— 

204 
(Table 

17  continued 

103 
on  p.  67 ) 

Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah  67 


— 

.1% 

— 

— 

.2% 

— 

.8% 

Other  Pennales 

81 
.5% 

943 
1.0% 

1,908 

2.3% 

204 

.5% 

— 

2,162 

4.5% 

I 

Dinobryon 

— 

102 
.1% 

I 

— 

— 

— 

Chroococcales 

— 

— 

I 

612 
1.6% 

— 

— 

— 

Oscillatoria 

81 

.5% 



1,272 
1.6% 

I 

406 

.4% 

103 

.2% 

— 

Other  Oscillatoriaceae 

z 

— 

— 

— 

2,228 
2.2% 

103 

.2% 

— 

Ulothrix 

81 
.5« 

— 



— 

— 

I 

51 
.3,% 

Clostcrium 

— 

— 

— 

204 

.5% 

— 

— 

— 

Hy  drums 

— 

20.3 

.2% 

1,272 
1.6% 

— 

2,986 
6.2% 

566 

3.5% 

Total  Algae 

64,855 

90,346 

83,680 

36,976 

99,901 

47,980 

16,316 

68  Bbigham  Young  University  Science  Bulletin 

Table  18.  Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  Tie  Fork  Pond  (Site  5) 


Algae 

4/15 
1971 

5/13 
1971 

6/8 
1971 

6/29 
1971 

7/30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

Chroococcales 

— 

— 

12.4 
1.3? 

I 

540.0 
4.1% 

876.0 

8..3? 

250.0 

.8? 

288.0 
5.0% 

Lynghya 

— 

— 

19.0 
2.0% 

10.5 

.4% 

36.0 

.3% 

195.0 
1.8% 

300.0 
.9% 

45.0 

.8% 

Oscillatoria 

86.0 
15.6* 

39.0 
9.0? 

291.0 
30.3? 

25.5 
.9% 

90.0 

.7% 

2,100.0 
20.0% 

2,000.0 
6..3? 

275.0 
4.8% 

Anabaena 

— 

.39.0 
9.0? 

15.5 
1.6% 

4.5 
.2% 



45.0 

.4% 

200.0 
.6% 



Cidothrix 

— 

— 

— 

— 

— 

— 

150.0 

.5? 

— 

Chlamydomona.1 

— 

— 

— 

— 

330.0 

2.5% 

186.0 

1.7% 

2,750.0 

8.7% 

87.5 
1.5% 

Pandorina 

— 

7.7 
1.8% 

— 

— 

246.0 
1.9% 

276.0 

2.5% 

400.0 
1.3? 

70.0 
1.5% 

Other  Volvocaceae 

— 

— 

— 

— 

— 

— 

— 

37.5 

.7% 

Gloeocystis 

— 

— 

— 

— 

— 

— 

— 

38.0 

.7% 

Oedogonium 

— 

85.0 
19.6% 

127.0 
13.2? 

— 

156.0 
1.2% 

780.0 

7.4? 

250.0 
.8? 

137.5 
2.4% 

Cladofihora 

— 

— 

7.7 
.8% 

10.5 

.4? 

81.0 
.6? 

22.5 
.2% 

700.0 

2.2% 

200.0 

3.5% 

Ankistrodesmus 

I 

46.7 
10.8% 

I 

— 

— 

— 





Mougeotia 

93.0 
16.9? 

— 

193.0 
20.1% 

1,335.0 

45.3* 

11,250.0 
86.4? 

4,710.0 

44.8? 

15,555.0 
49.0? 

4,275.0 

73.8% 

Spirogyra 

46.5 

8.5? 

7.7 
1.8? 

147.0 
15.3% 

1,345.5 

45.7% 

66.0 

.5? 

255.0 

2.4% 

6,750.0 

21. .3% 

100.0 
1.7% 

Zygnema 

I 

.39.0 
9.0% 

43.5 

4.5% 

120.0 
4.1% 

30.0 

.2% 

705.0 
6.7% 

450.0 
1.4% 

— 

Other  Filamentous 
Chlorophyta 

Closterium 

185.0 
33.6% 

69.5 
16.0? 

7.7 
1.8? 

61.5 
6.4% 

23.0 
2.4? 

100.5 
3.4% 

120.0 
.9% 

7.5 
.1% 

37.5 
.3% 

50.0 

.2% 

12.5 
.2% 

Euglena 

1.39.5 
25.4? 

85.0 
19.6% 

7.7 
.8% 

4.5 

.2? 

45.0 

.3% 

315.0 
2.9% 

1,850.0 

5.8% 

187.5 

3.2% 

Pyrrophyta 

— 

I 

I 

I 

30.0 

.2% 

7.5 
.1% 

I 

12.5 
.2% 

Ophiocytium 

— 

7.7 
1.8% 

— 

I 

— 

— 

I 

25.0 
.4? 

Vaucheria 

— 

— 

12.4 

1.3? 

— 

— 

— 

— 

— 

Total  Algae 

550.0 

434.0 

960.7 

2,946.0 

13,020.0 

10,518.0 

31,655.0 

5,791.0 

Bi()L()C:k:ai,  Sehies,  \'oi..  18.  No.  2       .^i.fi.vE  of  IIuntincton  Canyon,  Utah  69 

Table  19.   Number  of  organisms  per  liter  and  relative  abundance  of  nannoplankton  at  Tie  Fork  Pond  (Site  5) 


Algae 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

Cyclotella 

— 

— 

7,645 

3.8% 

— 

— 

— 

— 

— 

— 

Astcrioiiclla 

_ 

_ 

2,780 

2,088 

5,004 

— 

— 

1.3% 

1.3% 

.6% 

— 

— 

— 

— 

Didtomd 

— 

3,476 

9,035 

1,042 

12,525 

348 

2,780 

348 

1,043 

— 

1.3% 

4.3% 

.7% 

1.5% 

.2% 

.7% 

.2% 

16.7% 

Fraiiiluriu 

— 

— 

7,228 

40,310 

23,775 

4,875 

2,780 

2,363 

— 

crotoiiciisi.s 

— 

— 

3.5% 

25.5% 

2.8% 

2.4% 

.7% 

1.5% 

— 

Fni'^ihiriti 

5,143 

— 

1,390 

4,448 

85,950 

4,444 

9,730 

6,533 

— 

viresccus 

6.2% 

— 

.7% 

2.8% 

10.5% 

2.3% 

2.5% 

4.1% 

— 

Meridicit 

— 

4,170 
1.6% 

— 

— 

— 

— 

— 

— 

— 

Si/ui'itra 

4,448 

16,680 

26,828 

6.255 

13,.350 

348 

5,560 

5,8.38 

1,043 

5.4% 

6.4% 

12.9% 

4.0% 

1.6% 

.2% 

1.4% 

3.7% 

16.7% 

Achiiantlics 

5,143 

7,.505 

17,.375 

2,088 

4,170 

1,042 

4,170 

1,390 

— 

6.2« 

2.9% 

8.3% 

1.3% 

.5% 

.5% 

1.1% 

.9% 

— 

Cocconcis 

13,733 

1,589 

— 

— 

1,042 

4,875 

1,.390 

348 

— 

16.6% 

.6% 

- 

— 

.1% 

2.5% 

.4% 

.2% 

— 

Aniphipli-urti 

— 

— 

3,475 

1,390 

— 

— 

2,085 

348 

— 

— 

— 

1.7% 

.8% 

— 

— 

.5% 

.2% 

— 

CyrosijJitui 

— 

696 

— 

348 

— 

— 

1,390 

1,043 

1,043 

— 

.3% 

— 

.2% 

— 

— 

.4% 

.7% 

16.7% 

Navicula 

19,734 

34,611 

9.175 

6,185 

19,852 

4,170 

9,035 

12,510 

2,085 

23.8% 

13.0% 

4.4% 

3.9% 

2.4% 

2.1% 

2.3% 

7.9% 

33.4% 

PinnuUirid 

2,084 

— 

695 

1,042 

2,084 

348 

695 

3,475 

— 

2.5% 

— 

.3% 

.7% 

.2% 

.2% 

.2% 

2.2% 

— 

Sttmroiieis 

2,084 

1,589 

— 

1,390 

3,127 

348 

695 

1,043 

— 

2.5% 

.6% 

— 

.8% 

.4% 

.2% 

.2% 

.2% 

.7% 

GoinpliDnema 

348 

69,500 

1,042 

2.432 

7,086 

— 

1,390 

3,085 

— 

.4% 

26.1% 

.5% 

1.5% 

.8% 

— 

.4% 

2.0% 

— 

Ci/inhelt<i 

2,084 

67,275 

3,058 

4,686 

5,004 

1,042 

2,362 

4,865 

— 

2.5% 

25.2% 

1.5% 

3.0% 

.6% 

.5% 

.6% 

3.1% 

— 

Epitliemid 

1,390 

696 

696 

5,837 

159,750 

37,585 

82,010 

7,228 

— 

1.7% 

..3% 

.3% 

3.7% 

19.. 5% 

19.2% 

20.7% 

4.6% 

— 

Sitzachid  dciculdris 

4,868 

— 

13,900 

696 

2,084 

— 

8,895 

2,780 

— 

5.9% 

— 

6.7% 

.4% 

.3% 

— 

2.2% 

1.8% 

— 

Other  Mtz-schia 

12,507 

45,035 

39,968 

25,397 

85,950 

6,550 

36,695 

24,603 

1,043 

15.2% 

16.9% 

19.1% 

16.0% 

10.5% 

3.4% 

9.3% 

15.6% 

16.7% 

Surircllu 

— 

3,335 

— 

348 

1,042 

— 

— 

348 

— 

— 

1.3% 

— 

.2% 

.1% 

— 

— 

.2% 

— 

Other  Pennales 

— 

10,.575 

696 

696 

— 

— 

— 

— 

— 

— 

4.1% 

.3% 

,4% 

— 

— 

- 

— 

— 

Chrooeoeeales 

— 

— 

2,710 

41,282 

91,160 

— 

22,795 

— 

— 

— 

— 

1..3% 

26.1% 

11.1% 

- 

5.7% 

— 

— 

Aiidbucna 

— 

— 

695 

— 

8,340 

1,042 

— 

— 

— 

— 

— 

.3% 

— 

1.0% 

.5% 

— 

— 

— 

Aiikislrodcsmus 

— 

— 

2,362 

— 

— 

5,140 

6,950 

— 

— 

— 

— 

1.1% 

— 

— 

2.6% 

1.8% 

— 

— 

ClofilcriDpsis 











20,475 

— 

— 

— 

— 

— 

— 

— 

— 

10.5% 

— 

- 

— 

S'cplirocijtium 







— 

84,000 

11,120 

34,750 

695 

— 









10.2% 

5.7% 

8.8% 

.4% 

— 

(Table  19  continued  on  p.  70) 


70 

Scenedesmus 

1,390 

1.7% 

Cosmarium 

1,042 

1.3« 

Closterium  rostrata 

— 

Euustnim 

— 

Spluierozosma 

— 

Stuurii.stnun 

— 

Other  desmids 

— 

Fhacus 

— 

Truchc'lomonas 

6,533 

i.m 

Vcruiininm 

— 

DiiKthryon 

— 

Total  Algat- 

82,513 

Bricham  Young  Univehsiti'  Science  Bulletin 


266,732 


— 

2,362 

113,125 

23,620 

29,745 

11,398 

— 

— 

1.5« 

13.8« 

12.1* 

7.5* 

7.2% 

— 

— 

2,780 

9,225 

5,987 

2,085 

1,043 

— 

— 

\.m 

lA'i 

3.1!f 

..5* 

.7? 

— 

— 

— 

— 

1,390 
.6% 

— 

— 

— 

348 



16,725 





I 

.2% 

— 

2.0? 

— 

— 

— 

— 

— 

— 

57,075 

49,.5O0 

101,470 

5,838 

— 

— 

— 

6.8% 

25.4'l 

25.6* 

3.7* 

— 

— 

5,560 

4,170 

1,390 

— 

348 

— 

— 

3.5% 

.5* 

.7? 

— 

.2% 

— 

— 

— 

— 

4,444 

— 

3,475 

— 

— 

— 

— 

2.3* 

— 

2.2* 

— 

— 

— 

— 

- 

2,780 

.7* 

- 

— 

6,533 



5,004 

5,175 

23,6.30 

41,978 



3.1% 

— 

m 

2.7* 

6.0* 

26.7* 

— 

— 

— 

— 

— 

— 

14,873 

— 

— 

— 

— 

— 

— 

9.4* 

— 

50,735 

— 

— 

— 

695 

— 

— 

24.3? 

- 

- 

— 

.2* 

— 

— 

108,369 

158,562 

820,619 

195,258 

396,562 

157,793 

6,257 

Biological  Series,  Vol.  18,  No.  2       Al(;.\e  of  Huntington  Canyon,  Ut.vii 


71 


Table  20.     Number  ot   organisms  per  cm^  and   relative  abundance  of  periphyton  on  glass  slides  at  Tie  Fork   Poud 
(Site  5) 


Algae 

5/13 
1971 

6/8 
1971 

6/29 
1971 

7/30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

11/15 
1971 

Cyclotella 

— 

51 

.2% 

I 

I 

612 

1.0% 

52 
.1% 

— 

I 

A\tcriitncUii 

— 

1,964 
6.1% 

— 

— 

I 

I 

— 

— 

Didtdinii  Icriue 

— 

363 
1.1% 

— 

— 

— 

15,8.56 
36.0% 

412 
l.,5% 

793 
20.8% 

Other  Diatoina 

— 

— 

102 
.6% 

I 

102 

.2% 

— 

— 

— 

Franilaria  crotnncnses 

— 

707 

2.3% 

699 

3.8% 

151 

.8% 

— 

103 

.2% 

— 

206 

5.4% 

Fragilaria  virescens 

2,420 

3.7% 

607 
1.8% 

204 
1.1% 

6.56 

3.4% 

1,280 

2.2% 

9,267 

21.1% 

1,380 
5.0% 

165 

4.3% 

Meridian 

— 

— 

— 

— 

— 

— 

— 

26 

.7% 

Syticdra 

4,213 
6.4% 

4,751 
14.9% 

1,319 

7.1% 

254 
1.3% 

406 

.7% 

865 
2.0% 

3,098 

11.2% 

124 

3.. 3% 

Hannaea  amis 

— 

— 

I 

I 

z 

52 
.1% 

— 



Achnimthes 

2,992 

4.5% 

6,308 
19.7% 

1,624 

8.7% 

51 
..3% 

304 

.5% 

247 
.6% 

62 

.2% 

206 

5.4% 

Cocconeis 

242 
.4% 

— 

102 

.6% 

850 

4.4% 

612 
1.0% 

206 

.5% 

62 

.2% 

— 

Rhoicosphcnia 

— 

— 

— 

— 

I 

103 

.2% 





Aniphiplfurct 

— 

.505 

1.6% 

102 
.6% 

— 

I 

— 

144 

.5% 

— 

Gyrosigma 

1,133 

1.7% 

51 

.2% 

— 

— 

— 

247 
.6% 

474 

1.7% 

— 

Navicula  cf.  tripunctata 

— 

1,108 

3.5% 

608 

3.3% 

243 
1.3% 

102 

.2% 

1,2.36 

2.8% 

144 

.5% 

51 

1..3% 

Other  Navicula 

27,652 
41.9% 

3,375 
10.6% 

1.330 
7.0% 

451 

2.3% 

597 
1.1% 

103 

.2% 

2,059 

7.5% 

258 
6.8% 

Pinnularia 

3,420 
5.2% 

243 

.7% 

— 

102 

.5% 

204 

.4% 

247 
.6% 

350 

1..3% 

— 

Stauroneis 

— 

— 

102 
.6% 

— 

102 

.2% 

3.50 

.8% 

144 

.5% 

— 

Comphoncma 

324 

.5% 

445 
1.4% 

204 

1.1% 

406 

2.1% 

486 

.8% 

1,544 

3.5% 

268 
1.0% 

51 
1..3% 

Cymhella 

972 

1.5% 

1,108 

3..5% 

1,105 
6.0% 

306 
1.6% 

— 

556 
l.,3% 

762 

2.8% 

165 

4.3% 

Epitlwmia 

890 

1..3% 

607 
1.9% 

486 

2.6% 

1,224 
6.. 3% 

3,220 
5.6% 

206 

.5% 

1,442 
5.2% 

26 

.7% 

Sitzschia 

6,308 
9.6% 

4,893 
15.. 3% 

1,976 
10.6% 

1,.581 

8.1? 

3,248 
5.6% 

6,837 
15..3% 

12,293 

44.5% 

1,416 

.37.1% 

Surirella 

161 

.2? 

— 

— 

I 

— 

52 

.1% 

.556 
2.0% 

— 

Ophiocytium 

242 

.4% 

— 

.304 

1.7% 



— 

— 

— 

— 

Diniihrijon 

— 

2,730 
8..5% 

204 

1.1% 

z 



— 

62 

.2% 

— 

Chroococcales 

242 
A'i 

102 

.3% 

1,.376 

7.4% 

2,011 
10.. 3% 

7,745 
1.3.4% 

247 
.6% 

762 
2.8% 

— 

Lyngbya 

— 

— 



243 
1.3% 

5,4.50 
0.4% 

(Table 

62          - 
.2%            - 
20  continued  on  p.  72) 

72  BmcHAM  Young  University  Science  Bulletin 

Oscillatoria 

Other  Oscillatoriaceae 

Anabaena 

Calothrix 

Chlamydomonas 

Pandorina 

Other  Volvocaceae 

Oedogonium 

Cladophora 

Rhizoclonium 

Characium 

Pediastrum 

Ankistrodesmus 

Nephrocytium 

Scenedesmus 

Mougeotia 

Spirogyra 

Zygnema 

Other  Fihimentous 
Chlorophyta 

Closterium 

Cosmarium 

Micrasterias 

Pleurotaenium 

Sphaerozosma 

Staurustrtim 

Euglena 

Phacus 

Trachelomonas 

Total  Algae  66,011         31,953         18,573         19,458         57,778         43,961         27,601  3,816 


9,300 

— 

204 

102 

— 

515 

272 

— 

14.1% 

— 

1.1% 

.5% 

— 

1.2% 

1.0% 

— 

— 

— 

— 

— 

102 

52 

— 

— 

— 

— 

— 

— 

.2% 

.1% 

— 

— 

— 

505 

204 

1,020 

304 

52 

474 

— 

— 

1.6% 

1.1% 

5.2% 

.5% 
406 

.1% 

1.7% 

— 

— 

102 



510 

.8% 
1,624 

313 

— 

— 

— 

.3% 

— 

2.6% 

2.8% 

.7% 

— 

— 

— 

— 

— 

1,.326 

486 

— 

— 

26 

— 

— 

— 

6.8% 

.8% 

— 

— 

.7% 

81 

— 

— 

204 

— 

— 



— 

.1% 

— 

— 

1.0% 

— 

— 

— 

— 

648 

363 

2,960 

— 

1,280 

154 

247 

226 

1.0% 

1.1% 

15.9% 

— 

2.2% 

.4% 

.9% 

6.1% 

— 

— 

102 

— 

— 

412 

— 

51 

— 

— 

.6% 
204 

— 

— 

.9% 

— 

1.3% 

242 

— 

1.1% 
408 

812 

— 

— 

— 

— 

.4% 

— 

2.2% 

4.2% 

— 

— 

— 

— 

— 

— 

102 

.306 

— 

— 

— 

— 

— 

— 

1.1% 

1.6% 

— 

— 

— 

— 

— 

152 

304 

— 

— 

— 

206 

— 

— 

.5% 

1.7% 

— 

— 

— 

.7% 

— 

— 

— 

— 

969 

1,624 

— 

— 

26 

— 

— 

— 

5.0% 

2.8% 

— 

— 

.7% 

648 

— 

102 

2,428 

15,600 

154 

206 

— 

1.0? 

— 

.6% 

12.4% 

27.0% 

.4% 

.8% 

— 

— 

505 

— 

1,323 

972 

247 

618 

— 

— 

1.6% 

— 

6.8% 

1.7% 

.6% 

2.2% 

— 

— 

— 

304 

102 

204 

103 

268 

— 

— 

— 

1.7% 
304 

.5% 

.4% 

.2% 

1.0% 

— 

1,698 

— 

1.7% 
1,020 

153 

— 

247 

— 

— 

2.6% 

— 

5.5% 

.8% 

— 

.6% 

— 

— 

161 

— 

102 

51 

— 

— 

62 

— 

.2% 

— 

1.1% 

..3% 

— 

— 

.2% 

— 

161 

102 

— 

1,267 

306 

52 

— 

— 

.2% 

.3% 

51 

.2% 

— 

6.5% 

..5% 

.1% 

— 

— 

— 

— 

— 

— 

3,040 

52 

62 

.2% 

144 

— 

— 

— 

— 

— 

5.3% 

.1% 

.5% 

— 

81 

203 

102 

— 

— 

— 

— 

.1% 

.6% 

.6% 

— 

— 

— 

— 

890 

51 

— 

204 

3,730 

2,470 

247 

1..3% 

.2% 

— 

1.0% 

6.5% 

5.5% 

.9% 

— 

— 

304 

152 

1,210 

515 

62 

— 

— 

1.7% 

.8% 

2.1% 

1.2% 

.2% 

890 

— 

— 

— 

2,420 

247 

206 

1.3% 

— 

— 

— 

4.2% 

.6% 

.8% 

66,011 

31,953 

18,573 

19,458 

57,778 

43,961 

27,601 

Biological  Series,  Vol.  18.  No.  2       Algae  of  Huntington  Canyon,  Utah  73 

Table  21.   Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  Stuart  Station  (Site  6) 


.^lga<. 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Chroococcales 

- 

- 

- 

- 

- 

- 

- 

1.8 

4.3% 

- 

- 

- 

- 

- 

Os<^ll<itoria 

69,5 

93.0 

46.5 

11.2 

3.8 

7.5 

1.2 

3.7 

16.2 

13.0 

3.1 

23.0 

45.0 

34.7% 

32.9% 

9.77o 

9.1%. 

1.8% 

7.1% 

3.9% 

8.9% 

21.0%, 

25.07-, 

9.8% 

14.. 3% 

15.9% 

Other  Oscilla- 

23.0 

— 

— 

— 

11.2 

.3.8 

8.7 

14.2 

55.3 

19.8 

4.1 

2.3 

6.3 

tonaccae 

11.5% 

- 

— 

— 

.5.. 5% 

3.6% 

28.1% 

34.0% 

71.8%, 

38.2% 

13.0% 

1.4% 

2.2% 

AnabaiTia 

— 

— 

— 

3.8 

— 

— 

1.2 

— 

— 

— 

.5 

— 

— 

— 

— 

— 

3.0% 

— 

— 

3.9% 

— 

— 

— 

1.6% 

— 

— 

Chlamydomonas 

— 

— 

3.9 

— 

3.8 

— 

— 

.6 

— 

— 

— 

— 



— 

— 

.8% 

— 

1.8% 

— 

— 

1.4% 

— 

— 

— 

— 

— 

Pandorina 

— 

— 

— 

— 

7.5 

_ 

— 

.6 

_ 

_ 

— 

— 

— 

moruin 

— 

— 

— 

— 

3.7% 

— 

— 

1.4% 

— 

— 

— 

— 

— 

Sephrocytium 

_ 

_ 

_ 

— 

— 

— 

— 

.6 

— 

— 

_ 

_ 

_ 

— 

— 

— 

— 

— 

— 

— 

1.4% 

— 

— 

— 

— 

— 

Ulothrix 

— 

15.5 

31.0 

.3.8 

— 

— 

— 

— 

— 

_ 

1.3 

— 

— 

5.4% 

6.5% 

3.0% 

— 

— 

— 

— 

— 

— 

— 

.8% 

— 

Stigeoclonium 

— 

— 

— 

— 

— 

7.7 

— 

.6 

1.2 

1.3 

.5 

— 

— 

— 

— 

— 

— 

— 

7.3% 

— 

1.4% 

1.6% 

2.5%, 

1.6^, 

— 

— 

Oedogonium 

— 

_ 

23.0 

7.5 

.3.8 

— 

3.7 

3.0 

.6 

— 

— 

1.7 

1.3 

— 

— 

4.8% 

6.1% 

1.8% 

— 

11.9% 

7.2% 

.8% 

— 

— 

1.1% 

.4% 

Cladophora 

— 

7.7 

— 

— 

— 

11.2 

— 

3.5 

2.5 

5.1 

.5 

.6 

— 

— 

2.7% 

— 

— 

— 

10.7", 

— 

8.4% 

3.2% 

9.8%, 

1.6% 

.4% 

— 

Mougeotia 

— 

— 

— 

3.8 

127.0 

3.8 

8.7 

3.7 

— 

— 

— 

— 

_ 

— 

— 

— 

3.0%, 

61.7% 

3.6% 

28.1% 

8.9% 

— 

— 

— 

— 

— 

Sinrogyra 

_ 

_ 

3.9 

— 

7.5 

15.0 

.3.7 

1.1 

.6 

.6 

_ 

.6 

_ 

— 

— 

.8% 

— 

3.7%, 

14.3% 

11,9% 

2.6% 

.8% 

1.2% 

— 

.4% 

— 

Zygnema 

— 

— 

_ 

— 

3.8 

.30.0 

— 

1.1 

— 

— 

1.0 

— 

1.3 

— 

— 

— 

— 

1.8% 

28.6% 

— 

2.6% 

— 

— 

3.2% 

— 

.4% 

Clostcrium 

— 

— 

3.9 

3.8 

37.8 

22.5 

— 

2.5 

.6 

— 

— 

— 

— 

— 

— 

.8% 

3.0% 

18.4% 

21.4% 

— 

6.0% 

.8% 

— 

— 

— 

— 

Cosniarium 

— 

— 

— 

— 

— 

— 

1.2 
3.9% 

— 

— 

— 

— 

— 

— 

Euglena 











.3.8 

1.2 



_ 







— 

— 

— 

— 

— 

3.6% 

— 

2.9% 

— 

— 

— 

— 

— 

Ccratium 

— 

— 

— 

— 

— 

— 

2.5 

.6 



— 

— 

— 

— 

hirundincUa 

— 

— 

— 

— 

— 

— 

8.1% 

1.4%, 

— 

— 

— 

— 

— 

HydrUTUs 

108.0 

170.0 

368.0 

90.0 

— 

— 

— 

— 

— 

12.1 

21.9 

131.0 

229.0 

foctidus 

53.9% 

59.4% 

76.6% 

72.8% 

— 

— 

— 

— 

— 

23.3%, 

69.3% 

81.5% 

81.0% 

Vaucheria 

- 

- 

- 

- 

- 

- 

- 

3.0 

7.2% 
41.8 

- 

- 

- 

- 

- 

Total  Algae 

200.5 

286.2 

480.6 

123.9 

206.2 

10.5.3 

.30.9 

77.0 

51.9 

31.6 

160.5 

282.9 

74 


Bricham  Young  University  Science  Bulletin 


Table  22.   Number  of  organisms  per  liter  and  relative  abundance  of  nannoplankton  at  Stuart  Station  (Site  6) 


Algae 

4/15 
1971 

5/13 
1971 

6/8 
1971 

6/29 
1971 

7/30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

11/15 
1971 

12/17 
1971 

1/20 
1972 

2/19 
1972 

3/11 
1972 

Cyclotella 

- 

- 

- 

- 

- 

- 

- 

- 

- 

347 
.1% 

348 

.1% 

— 

z 

Hannat-a  arcus 

- 

696 

.7% 

- 

348 

.1% 

348 

.1% 

— 

I 

z 

I 

695 

.2% 

348 

.1% 

— 



Piatffma 

1,390 

.4% 

— 

2,085 

.7% 

1,042 

.4% 

— 

I 

— 

— 

— 

— 

— 

1,390 

.4% 

— 

Diatonta 
vul^arc 

2,780 

.8% 

348 

.3% 

3,048 
1.0% 

4,338 

1.5% 

3,480 

1.3% 

1,000 

.9% 

3,752 
1.2% 

7,645 
11.5% 

22,935 
8.1% 

.30,858 
9.27o 

9,7.30 

3.4% 

4,170 

1.3% 

2,085 
1.6% 

Fragilaria 

— 

1,390 

1.4% 

695 

.2% 

I 

348 

.1% 

— 



277 

.4% 

— 

— 

— 





Meridion 

— 

— 

.5,7.55 
1.9% 

— 

— 

500 

.4%, 

I 

— 

— 

— 

— 

— 



Syncdra 

20,8.50 

6.2% 

41.700 

41.7% 

3,048 
1.0% 

7,922 

2.7% 

1,044 

.4% 

500 

.4% 

12.092 

3.9% 

11,538 

17.4% 

30,587 
10.8%. 

35,445 
10.6% 

2.5,715 
9.1% 

23,6.30 

7.2% 

13,205 
9.9% 

Achnanthes 

10,286 

:3.17r 

4,170 

4.2% 

11,125 

3.6% 

9,312 

3.2'5 

14,875 

.5.  .5% 

9,000 

7.7%. 

13,482 

4.3%. 

972 
1.5% 

12,510 

4.4% 

21,128 
6., 3% 

16,680 
5.9% 

24,325 

7.4% 

5,560 

4.2% 

VocconeiH 

696 

.2% 

— 

— 

696 

.2% 

12,800 

4.7%. 

1.200 

1.0% 

7,922 

2.6% 

389 

.6% 

4.865 

1.7'r, 

2,085 

.6% 

3,057 

1.1% 

4,170 

1..3% 

1,390 
1.0% 

Hhoicosphenia 

— 

— 

— 

— 

348 

.1% 

— 

— 

I 

696 

.2% 

I 

I 

— 

— 

Amphipleura 

- 

348 

.3% 

- 

- 

- 

- 

- 

- 

- 

- 

348 
.1% 

— 

— 

Gyrosigma 

6,115 
1.8% 

348 
.3% 

- 

- 

1,044 

.4% 

- 

- 

- 

- 

695 

.2% 

695 

.2% 

695 

.5% 

Savicula  cf. 
capitate 

— 

— 

— 

1.042 

.4% 

3,480 

1.3% 

4,500 

3.8%, 

14,456 

4.7% 

2,362 
3.6% 

9,035 

3.2% 

7,923 
2.4% 

15.290 

5.4% 

14,595 
4.5% 

3,475 
2.6% 

Navicula  cf. 
rhyncocephala 

— 

— 

— 

348 

I 

2,610 

2.2% 

14,177 

4.6% 

972 

1..5% 

4,445 

1.6'-, 

— 

— 

— 

— 

Navicula  cf. 
tripunctata 

12,510 

3.7% 

— 

10,008 

3.2% 

9,312 

3.2% 

12,800 

4.7% 

10.332 
8.8%. 

19,460 

6..3% 

4,865 

7..3% 

14,177 
.5.0% 

15,290 

4.6% 

12.075 

4.3% 

1.3,900 

4.3% 

8,340 
6.3% 

Other 

Navicula 

155,682 

46.2% 

25,020 

25.0% 

40,656 

13.1% 

24.115 

8.4% 

37,555 
13.8% 

21,888 
18.8% 

42,395 
13.6% 

3,752 
6.6% 

24,602 

8.77r 

49,345 

14.8% 

47.538 
16.9% 

37,530 

11.3% 

12,510 

9.3% 

Pinnularia 

- 

1,042 

1.1*^. 

- 

- 

- 

- 

- 

- 

- 

- 

— 

— 

— 

StauToncis 

- 

- 

- 

- 

250 

.2% 

348 

.1% 

- 

- 

- 

- 

- 

- 

Gomphonema 

31,135 

9.2% 

696 

.T7. 

131,633 

42..5% 

19,460 

6.8% 

15.425 

5.7'7r 

8.694 

7.4% 

28,495 

9.2% 

3,752 

5.6%. 

34.375 
12.2% 

46.148 

13.8% 

39.615 
14.1% 

33,350 
10.2% 

21,545 
16.1% 

Cytnhella 

7,505 

2.2% 

3,057 

3.1% 

60,743 
19.6% 

189,040 
65.6% 

100,075 

36.8% 

23,760 
20.3% 

28,772 
9.3%, 

10,702 
16.1% 

61.437 

21.7% 

66,720 
20.0% 

59.770 

21.2% 

115,370 

35.2% 

43,090 

32.3% 

Epithemia 

- 

- 

- 

— 

— 

— 

348 

.1% 

— 

— 

— 

— 

— 

— 

Nitzxchia 
acicularis 

- 

- 

- 

1,042 

.4% 

4.5,.500 
16.7% 

1,697 
1.5% 

8,310 

2.7% 

3,197 

4.8% 

2,362 

.8% 

- 

- 

- 

- 

Other 

Nitzschia 

47,815 

14.2% 

20,850 
20.8%. 

35.723 
11.. 5% 

15,985 

5.5%, 

21,525 
8.0% 

28,620 

24.4% 

111,120 

35.8% 

14,456 

21.8% 

52,820 

18.7% 

52,820 
15.8% 

47,955 
17.0% 

47,955 

14.7% 

19,460 
14.6% 

Surirella 

37,530 
11.1% 

— 

3.753 
1.2% 

— 

— 

1,200 
1.0% 

5.142 
1.7% 

696 

1.0% 

7,922 

2.8% 

4,448 
1.3%, 

3.057 
1.1% 

2,085 

.6% 

2,085 

1.6% 

Other 

Fennales 

— 

— 

1,668 

.5% 

4,450 
1.5%, 

348 

.1% 

I 

I 

I 

— 

— 

— 

4,170 
1.3% 



Oinohrypn 

— 

348 

.3% 

I 

348 

.1% 

348 

.1% 

250 

.2% 

— 

— 







— 

— 

Anabaena 

2,780 

.8% 

- 

- 

— 

- 

- 

- 

— 

— 

— 

— 

— 

— 

Trachelomonas 

- 

- 

- 

- 

- 

- 

277 
.4% 
65,852 

- 

- 

- 

- 

- 

Total  Algae 

337,074  100,013 

309,940 

288,800 

271,343 

116,001 

310,271 

282,768 

333,947 

281.526 

327,335 

133,440 

Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah  75 

Table  2.3.    Number  of  organisms  per  cm^  and  relative  abundance  of  periphyton  on  glass  slides  at  Stuart  Station 
(Site  6) 


Algae 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

Cyclotclla 

— 

— 

— 

— 

— 

52 

— 

— 

- 

- 

— 

— 

— 

— 

— 

.\% 

— 

— 

— 

— 

Hannaea  arcus 

— 

51 

— 

— 

— 

— 

— 

— 

— 

— 

— 

.1% 

— 

— 

— 

— 

— 

— 

— 

— 

Diatmna 

5,459 

705 

19,000 

204 

203 

103 

3,357 

20,593 

16,062 

1,338 

1.7% 

1.7% 

9.4% 

.4% 

.3% 

.2% 

5.2% 

6.8%: 

7.27. 

4.07o 

Fragilaria 

_ 

_ 

— 

— 

— 

52 

— 

— 

1,082 

— 

crotoncnscs 

— 

— 

— 

— 

— 

.1% 

— 

— 

.57o 

— 

\tendion 

— 

404 

204 

_ 

— 

— 

— 

— 

— 

— 

— 

1.0% 

.170 

— 

— 

— 

— 

— 

— 

— 

Synedra 

27,901 

825 

11,980 

— 

51 

412 

5.704 

18,945 

23,630 

1,647 

8.7<!!- 

2.0% 

6.1% 

— 

.1% 

.8% 

8.9%, 

6.2%. 

10.6% 

4.9% 

Achnanthes 

6,066 

1,928 

16,500 

29,500 

.37,290 

32,989 

5,148 

125,615 

25,947 

4.221 

1.9% 

4.7%, 

8.1% 

60.9% 

5.3.1% 

61.2% 

8.07o 

41.37, 

11.6% 

12.. 57, 

Cocconeis 

241 

— 

102 

2.7.50 

7,900 

3,851 

762 

1,853 

1,082 

— 

.1% 

— 

.1% 

.5.7% 

11.2%. 

7.1% 

1.27, 

.6% 

.5% 

— 

Savictila  cf. 



— 

— 

— 

204 

— 

824 

4,119 

1,082 

206 

capitata 

— 

— 

— 

— 

..3% 

— 

l.,3% 

1.47, 

.57. 

.67c 

Savicuta  cf. 

— 

— 

_ 

204 

— 

1,133 

— 

— 

— 

— 

rhyiicocfphala 

— 

— 

— 

.2% 

— 

2.1% 

— 

— 

— 

— 

\at'icula  cf. 





— 

1,320 

1,115 

1,380 

3,.501 

4,5.30 

2,471 

309 

tripunctata 

— 

— 

— 

2.7% 

1.67,. 

2.6% 

5.5%. 

1.5%, 

1.17, 

.97c 

Other  Naticula 

42,410 

7,122 

18,604 

7,950 

4,304 

.3,274 

11,594 

28,006 

22,085 

3,295 

13.2'-, 

17.. 5% 

9.2% 

16.4% 

5.9% 

6.0%, 

18.07, 

7.8% 

9.97, 

9.7% 

Gomphortcma 

129,764 

13,647 

12.680 

486 

742 

1,894 

8,442 

.3.5,213 

46,488 

1,493 

40.2%. 

33.5% 

6.3% 

1.0%, 

1.1% 

3.5%, 

13.27o 

11.6% 

20.97, 

4.47c 

Cymbetla 

77,153 

8,694 

111,200 

3,590 

1,601 

1,071 

5,004 

28,624 

60,697 

13,436 

23.9% 

21.3% 

54.8% 

7.47o 

2.37,, 

2.0% 

7.8% 

9.47o 

27.3%, 

40.0%, 

Nitzschia 

— 

— 

— 

304 

1,218 

206 

1,235 

— 

— 

— 

acicularis 

— 

— 

— 

.6% 

1.7-;; 

.4% 

1.9% 

— 

— 

— 

Other  \itzschia 

21,593 

6,924 

7,600 

1,320 

.5,274 

7,195 

17,154 

32,372 

12,047 

3,552 

6.7% 

17.0% 

3.7% 

2.7% 

7.5% 

13.37r 

26.87c 

10.67f 

5.4% 

10.57o 

Surirella 

1,213 

202 

1,518 

102 

153 

154 

679 

2,0.59 

1,699 

257 

.4% 

.5% 

.7% 

.2%. 

.27» 

.37o 

1.1% 

.77, 

.87o 

.87, 

Other  Pennales 



51 

2,550 

102 

102 

52 

144 

— 

— 

— 

— 

.1% 

1.2% 

.2% 

.27o 

.1% 

.27,, 

— 

— 

— 

Chroococcales 

2,729 

— 

— 

— 

406 

— 

— 

— 

— 

— 

.8% 

— 

— 

— 

.6% 

— 

— 

— 

— 

— 

Oscitlatoria 

1,213 

— 

_ 

406 

509 

103 

350 

2,059 

1,082 

154 

.4% 

— 

— 

.8% 

.7% 

.2% 

.6% 

.7% 

.5% 

..5% 

Other 

— 

_ 

— 

— 

9,188 

— 

144 

— 

— 

— 

Oscillatoriaceae 

— 

— 

— 

— 

13.1% 

— 

.27, 

— 

— 

— 

Utolhrix 

972 

— 

406 

102 

_ 

— 

— 

— 

1.54 

— 

.3% 

— 

.2% 

.2% 

— 

— 

— 

— 

.1% 

— 

Closterium 

— 

_ 

204 

102 

102 

— 

62 

— 

— 

— 

— 

— 

.1% 

.2% 

.2% 

— 

.17o 

— 

— 

— 

Euglena 

241 

.1% 

5,459 

- 

- 

- 

— 

— 

— 

— 

— 

— 

Hy  drums 

202 

406 

I 









7,722 

3,964 

1.7% 

.5% 

.2%. 

— 

— 

— 

— 

— 

3.. 5% 

11.77o 

Total  Algae 

322,414 

40,755 

202,954 

48,442 

70,362 

53,921 

64,105 

303,988 

223,3.30 

33,872 

76  Bricham  Young  University  Science  Bulletin 

Table  24.   Number  of  organisms  per  liter  and  relative  abundance  of  net  plankton  at  Bear  Canyon  (Site  7) 


Algae 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

1971 

1971 

1971 

1071 

1971 

1971 

Chroococcales 



— 

— 

3.7 

— 

— 

— 

— 

— 

6.6% 

— 

— 

Oscillatoria 

15.0 

.30.0 

3.0 

10.0 

6.2 

28.7 

3.3% 

14.4% 

3.9% 

17.9% 

20.9% 

25.6% 

Other  Oscillatoriaceae 

4.5 

22.5 

— 

8.7 

1.2 

35.0 

1.0% 

10.8% 

— 

15.5% 

4.1% 

31.2% 

Rivularia 

15.0 

— 

— 

— 

— 

— 

3.3% 

— 

— 

- 

— 

— 

Chlamydomoruis 

— 

25.5 
12.2% 

— 

2.5 
4.5% 

— 

— 

Pandorina  morum 

— 

— 

- 

1.2 

— 

— 

— 

— 

— 

2.1% 

— 

— 

Scenedesmus 





— 

1.2 

— 

— 

— 

— 

— 

2.1% 

— 

— 

Ulothrix 

90.0 

11.2 

3.0 

— 

— 

5.0 

19.9% 

5.4% 

3.9% 

— 

— 

4.5% 

Cylindrocapsa 

— 

I 

10.5 

13.7% 

— 





Stigeoclonium 

— 

— 

z 

I 

— 

1.7 
1.5% 

Oedogoixium 

4.5 

18.0 

4.5 

10.0 

15.5 

37.5 

1.0% 

8.6% 

5.9% 

17.9% 

52.4% 

33.4% 

Cladophora 

I 

15.0 

7.2% 

7.5 
9.8% 

10.0 

17.9% 



.6 

.5% 

Mougeotia 

4.5 
1.0% 

7.5 
3.6% 

— 

2.5 

4.5% 

— 



Spirogyra 

— 

— 

I 

5.0 

8.9% 

— 

— 

Zygnema 

— 

3.8 

3.0 

— 

3.7 

1.2 

— 

1.8% 

3.9% 

— 

12.5% 

1.1% 

Closterium 

4.5 

67.5 

42.0 

1.2 

.6 

2.5 

1.0% 

.32.4% 

54.9% 

2.1% 

2.1% 

2.2% 

Pleurotaeriium 

— 

— 

— 

— 

.6 

— 

— 

— 

— 

— 

2.1% 

— 

Euglena 

— 

— 

3.0 

3.9% 

— 

.6 

2.1% 

— 

Other  Euglenophyta 

— 

— 

I 

— 

1.2 
4.1% 

— 

Hydmrus  foetidus 

31.5.0 
69.5% 

7.5 
3.6% 

— 

— 

I 



Total  Algae 

453.0 

208.5 

76.5 

56.0 

29.6 

112.2 

Biological  Series,  Vol.  18,  No.  2       Alcae  of  Huntington  Canyon,  Utah 


77 


Table  25.    Number  of  organisms  per  liter  and  relative    abundance  of  nannoplankton  at  Bear  Canyon  (Site  7) 


Algae 


8/20 
1971 


9/15 
1971 


10/8 
1971 


11/15 
1971 


Diatoma  vulgare 

Meridian 

Synedra 

Achnanthes 

Coccimeis 

Rhoicosjihenia 

Naviculci  cf 

capituta 
Navicula  cf 

rhyncoceplwla 
Navicula  cf 

tripunctata 
Other  Navicula 

Stauroueis 

Gomphonema 

Cymbt'lla 

Epithemia 

Nitzschia 

acicidaris 
Other  Nitzschia 

Surircllu 

Trachclomonax 

Total  Algae 


1,390 

2,085 

554 

1,390 

.6% 

1.0% 

.5% 

.5% 

348 

— 

— 

2,085 

.2% 

— 

— 

.8% 

1,042 

4,170 

3,890 

12,787 

.5% 

1.9% 

3.5% 

4.8% 

20,125 

21,127 

23,907 

19,460 

9.3* 

9.7% 

21.3% 

7.3% 

13,200 

5,142 

3,335 

6,245 

6.1% 

2.4% 

3.0% 

2.3% 

696 

— 

554 

— 

.3% 

— 

.5% 

— 

— 

1,390 

— 

348 

— 

.6% 

— 

.1% 

5,150 

4,445 

2,500 

6,950 

2.4% 

2.0% 

2.2% 

2.6% 

20,475 

12,510 

5,837 

7,500 

9.5% 

5.7% 

5.5% 

2.8% 

39,125 

29,190 

13,065 

37,807 

18.1% 

13.4% 

11.4% 

14.2% 

696 

— 

— 

— 

.3% 

— 

— 

— 

12,075 

25,020 

4,725 

23,630 

5.6% 

11.5% 

4.2% 

8.8% 

69,250 

45,452 

33,637 

78,535 

32.1% 

20.8% 

30.0% 

29.4% 

348 

— 

— 

— 

.2% 

— 

— 

— 

1,668 

4,170 

— 

3,475 

.8% 

1.9% 

— 

1.3% 

28,250 

57,267 

19,460 

59,770 

1.3.1% 

26.3% 

17.3% 

22.4% 

1,042 

1,390 

831 

2,711 

.5% 

.6% 

.7% 

1.0% 

696 

4,865 

— 

4,448 

.3% 

2.2% 

— 

1.7% 

215,576 

218,223 

112,295 

267,141 

78  Bhigham  Younc  Univfj\sity  Science  Bulletin 

Table  26.    Frf(|iicn(.v,  percent  cover,  and  pcrcenl  composition  of  the  visiljlc  hcnlhu   ilora  at  6  localities  in  llinitington 
Creek,  June  1971 -March  1972 


6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

2/19 

.3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

Lawrence 

Total  Frecjiiency 

91 

100 

100 

100 

100 

100 

98 

95 

— 

Total  C'over 

51 

81 

65.7 

89.1 

60.6 

H6.9 

73.8 

17.7 

— 

Cladoplwra 

Frequency 

91 

77 

37 

33 

20 

15 

24 

5 

— 

Cover 

34 

43 

4.3 

6.6 

1.6 

4,5 

3.6 

.13 

— 

Composition 

67 

53 

6.0 

8.0 

2.6 

5.0 

4.8 

1 

— 

Ot'(/()g(HliIiH^ 

Frequency 

68 

100 

— 

— 

— 

— 

— 

— 

Cover 

17 

38 

— 

— 

— 

— 

— 

— 

— 

Composition 

33 

47 

— 

— 

— 

— 

— 

— 

— 

Chiira 

Frequency 

— 

— 

70 

50 

82 

85 

88 

90 

— 

Cover 

— 

— 

37.4 

38.3 

48.0 

63.6 

61.0 

15.5 

— 

Composition 

— 

— 

57 

43 

79.3 

73 

82.6 

87 

— 

Protodcniui 

Frequency 

— 

— 

— 

28 

12 

— 

— 

— 

— 

Cover 

— 

— 

— 

2.2 

1.8 

— 

— 

— 

— 

Composition 

— 

— 

— 

2.0 

3.0 

— 

— 

- 

- 

r<)f()»i()<;<(()ii 

Fretpiency 

— 

— 

70 

57 

49 

40 

41 

34 

— 

Cover 

— 

— 

24 

42 

9.2 

18.8 

9.2 

2.1 

— 

Composition 

— 

— 

37 

47 

15.1 

22 

12.5 

12 

— 

Highway  10 

Total  Frecjuency 

100 

81 

100 

100 

100 

93 

94 

73 

— 

Total  Cover 

25 

57 

1.5.6 

18.9 

22.7 

26.6 

29.3 

11 

— 

Cladophora 

Frecpiency 

100 

81 

97 

59 

25 

48 

61 

20 

— 

Cover 

25 

57 

13.4 

2.5 

1.4 

2.5 

5,8 

,5 

— 

Composition 

100 

100 

86 

13.0 

6.0 

9.0 

19.9 

5 

— 

Clidra 

Fretjuency 

— 

— 

21 

49 

46 

71 

51 

64 

— 

Cover 

— 

— 

2.2 

16.4 

20.5 

24.1 

22.8 

10,5 

— 

Composition 

— 

— 

14.0 

87 

90.0 

91.0 

77.8 

95 

— 

Polomogeton  sp. 

_ 

Frequency 

— 

— 

— 

— 

11 

— 

14 

— 

— 

Cover 

— 

— 

— 

— 

.8 

— 

.7 

— 

— 

Composition 

— 

— 

— 

— 

4.0 

— 

2.4 

— 

— 

Plant  Site 

Total  Frtxpiency 

— 

— 

— 

— 

— 

— 

— 

89 

10 

Total  ("over 

— 

— 

— 

— 

— 

— 

— 

24 

1 

I  ly  drums 

Frecjuency 

— 

— 

— 

— 

— 

— 

— 

89 

10 

Cover 

— 

— 

— 

— 

— 

— 

— 

24 

1 

Composition 

— 

— 

— 

— 

— 

— 

— 

100 

100 

C^ampground 

Total  Fretpiency 

75 

— 

— 

77 

— 

— 

— 

.30 

— 

Total  Clover 

25 

— 

— 

6.4 

— 

— 

— 

1,5 

— 

Oscillutoria 

Fre<piency 

— 

— 

— 

77 

— 

— 

— 

— 

— 

Cover 

— 

— 

— 

6.) 

— 

— 

— 

— 

— 

Composition 

— 

— 

- 

1(H) 

— 

— 

/  T"    i_i  _    r»/ 

— 

.1    '70\ 

(Table  26  contiinied 


HioLociKVM.  Skiues,  \'ou.  18,  No.  2       Ai.cAE  or  Huntincton  Canyon,  Utah 


79 


llijdnirus 
Frequency 
Cover 

75 
25 

— 

Composition 

100 

— 

Stuart  Station 

Total  Friijut-ncy 

100 

22 

Totiil  Cover 

30 

.55 

Hi/dnirtts 
Fr«iuency 
Cover 

100 
30 

18 
.45 

Composition 

100 

82.0 

Cladophora 

Frequency 
Cover 

— 

4 
.1 

Composition 

— 

18.0 

Oscillutoria 

Freijuency 

— 

— 

Cover 

— 

— 

Composition 

— 

— 

Bear  Canyon 

Total  Frefjuency 

— 

— 

Total  Cover 

— 

— 

Oedogouiiim 

Frequency 
Cover 

I 

I 

Composition 

— 

— 

Hydrurus 
Frixjuency 
Cover 

— 

— 

Composition 

— 

— 

— 

— 

— 

30 

— 

— 

— 

— 

1.5 

— 

— 

— 

100 

68 

83 

74 

83 

88 

6.7 

10.6 

1.8 

14 

25 

83 

88 

— 

— 

— 

14 

25 

— 

— 

— 

100 

100 

61 

83 

74 



6.21 

10.5 

1.8 

— 

94.0 

99 

100 

— 

18 

4.5 





.44 

.11 

— 

— 

6.0 

1.0 

— 

— 

79 

86 

88 

_ 

12.3 

7.2 

4.4 

— 

79 

86 

88 

12.3 

7.2 

3.7 

— 

100 

100 

84 

— 

30 


16 


80 


Brigham  Young  UNivERsrri-  Science  Bulletin 


Table  27.  Physical  and  chemical  data  from  Huntington  Canyon.  Water  temperature  (°C). 


Site 

4/15 

5/13 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Lawrence 

9 

10.5 

13 

15 

16 

23 

13 

9 

3 

-1 

0 

0 

4 

Highway  10 

nd 

nd 

nd 

12 

14 

20 

13 

9 

3 

-1 

0 

0 

3 

Plant  Site 

5 

4 

8 

10 

12 

18 

13 

8 

1.5 

0 

.2 

1 

3 

Campground 

5 

4 

8 

9 

11 

17 

13 

7 

1.5 

0 

1 

1 

3 

Tie  Fork 

15 

14.5 

13 

20 

22 

23 

16 

13 

nd 

nd 

nd 

nd 

2 

Stuart  Station 

8.8 

8 

6 

12 

15 

17 

13 

7 

.5 

0 

1 

1.5 

3 

Bear  Canyon 

nd 

5 

6 

U 

15 

18 

14 

11 

3 

nd 

nd 

nd 

nd 

nd  =  no  data  available 


Table  28.   Physical  and  chemical  data  from  Huntington  Canyon.  Turbidity  (JTU). 


6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1071 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

nd 

58 

10 

7 

40 

5 

15 

30 

80 

140 

170 

nd 

nd 

nd 

5 

10 

5 

10 

10 

65 

65 

140 

12* 

40 

0 

15 

20 

13 

65 

5 

15 

5 

20 

20* 

15 

0 

5 

9 

13 

12 

15 

0 

0 

0 

nd 

nd 

18 

35 

40 

3 

nd 

nd 

nd 

nd 

75 

6* 

0 

0 

20 

22 

1 

5 

15 

5 

0 

5 

nd 

5 

5 

10 

15 

1 

2 

nd 

nd 

nd 

nd 

Lawrence 
Highway  10 
Plant  Site 
Campground 
Tie  Fork 
Stuart  Station 
Bear  Canyon 

nd  =  no  data  available 

♦Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Young  University. 


Table  29.   Physical  and  chemical  data  from  Huntington  Canyon.  pH. 


Site 


6/8 
1971 


6/29 
1971 


7/30 
1971 


8/20 
1971 


9/15 
1971 


10/8 
1971 


11/15 
1971 


12/17 
1971 


1/20 
1972 


2/19 
1972 


3/11 
1972 


Lawrence 
Highway  10 
Plant  Site 
Campground 
Tie  Fork 
Stuart  Station 
Bear  Canyon 


8.85 

8.1 

8.0 

8.1 

8.2 

8.3 

8.1 

7.65 

7.8 

8.. 35 

7.9 

nd 

nd 

nd 

7.7 

8.3 

8.3 

8.0 

8.0 

7.8 

8.4 

7.9 

8.2* 

7.6 

8.2 

8.4 

8.4 

8.3 

8.1 

8.2 

8.2 

8.6 

8.1 

8.45 

7.6 

8.4 

8.35 

8.3 

8.5 

8.2 

8.35 

8.2 

8.4 

8.1 

8.30 

7.8 

8.8 

8.6 

8.8 

8.9 

nd 

nd 

nd 

nd 

7.4 

8.30 

7.0 

8.4 

8.2 

8.25 

8.3 

8.2 

8.1 

8.1 

8.5 

7.9 

8.3* 

8.4* 

8.4* 

8.65 

8.25 

8.2 

8.2 

nd 

nd 

nd 

nd 

nd  =  no  data  available 

•Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Young  University. 


liioi.i.cK  Ai.  Si  nil  s.  \iii,.   IS,  No.  2       Ai.<:ak.  <>i-   IK'ntincion  C^xnvon.  I'taii  81 

Table  30.    Physical  and  chemical  data  fmm  Huntington  Canyon.   Dissolved  oxygen  (mg/1). 

Site  6/8  6/29         7/30  8/20  9/15  10/8  U/1.5        12/17        1/20  2/19  3/11 

1971         1971         1971         1971         1971         1971         1971         1971         1972         1972         1972 

Lawrence  9  5  9  9  10  8  6  .3  8  911 

Highway  10 

Plant  Site 

Campground 

Tie  Fork 

Stuart  Station 

Bear  Canyon  11*  7*  9*  8*  8  10  7  nd  nd  nd  nd 

nd  =  no  data  available 

*Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies.  Brigham  Yoinig  University. 


Table  31.   Physical  and  chemical  data  from  Huntington  Canyon.   Dissolved  carbon  dioxide  (mg/1). 


nd 

nd 

nd 

9 

10 

8 

10 

4 

6 

9 

11 

10* 

9 

9* 

9* 

9 

8 

9 

7 

.5 

9 

11 

11 

10 

9* 

10* 

9 

7 

7 

9 

8 

10 

11 

8 

5 

nd 

10 

14 

8 

nd 

nd 

nd 

nd 

5 

11 

9 

9* 

9* 

8 

8 

8 

7 

5 

9 

9 

Site  6/8  6/29         7/30  8/20  9/15  10/8  11/15        12/17        1/20  2/19  3/11 

1971  1971  1971  1971  1971  1971  1971  1971  1972  1972  1972 


Lawrence 
Highway  10 
Plant  Site 
Campgroimd 
Tie  Fork 
Stuart  Station 
Bear  Canyon 


2 

4 

12.8 

12 

4 

2 

6 

24 

16 

18 

8 

nd 

nd 

nd 

12 

4 

0 

4 

14 

20 

6 

4 

0* 

1 

4.8 

8 

0 

0 

2 

6 

6 

2 

2 

1.4 

2 

6 

12 

1 

2 

2 

5 

6 

2 

2 

0 

0 

0 

0 

0 

2 

nd 

nd 

nd 

nd 

24 

2 

3 

3.6 

4 

2 

2 

2 

6 

4 

2 

2 

nd 

0* 

nd 

0 

1 

2 

2 

nd 

nd 

nd 

nd 

nd  =  no  data  available 

*Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Vonng  University. 


Table  -32.   Physical  and  chemical  data  from  Huntington  Canyon.   Phosphate  (mg/1) 


Site 

6/8 

6/29 

8/20 

12/17 

1/20 

2/19 

.3/11 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Lawrence 

1.43 

.10 

.24 

.16 

.72 

..30 

.15 

Highwav  10 

nd 

nd 

.31 

.06 

.20 

..32 

.15 

Plant  Site 

nd 

.15 

.07 

.08 

.18 

.22 

.11 

Campgrotuid 

4.0 

..35 

..57 

.07 

.04 

.13 

.05 

Tie  Fork 

7..5 

nd 

nd 

nd 

nd 

nd 

.15 

Stuart  Station 

1.31 

.25 

.04 

.02 

.04 

.18 

.03 

Bear  Canyon 

nd 

nd 

.08 

nd 

nd 

nd 

nd 

nd  =  n<i  data  .i\  ailable 


1.0 

..30 

1..5 

..57 

.68 

.60 

.49 

.60 

.45 

.49 

.18 

nd 

nd 

lul 

.05 

.07 

.06 

.24 

..33 

..32 

.42 

.20 

.10* 

.40 

.0:5 

.03 

.08 

.04 

.22 

.;30 

.24 

..34 

.14 

.10 

.:)0 

.0.3 

.03 

.02 

.0.5 

.20 

..30 

.26 

..35 

.17 

.40 

ml 

.02 

ncl 

.06 

.04 

n<l 

nd 

nd 

nd 

.11 

.40 

.20 

.10* 

.07 

.03 

.04 

.26 

.31 

.27 

..35 

.27 

nil 

.10* 

.40* 

.03 

.06 

.10 

.37 

nd 

nd 

nd 

nd 

82  BiiK.iiA.M  Vou.NG  Univehsity  Scienck  Bulletin 

Table  33.  Physical  and  chemical  data  I'rom  Huntington  Canyon.   Nitrate  nitrogen  (mg/1). 

Site  6/8  6/29         7/,30  8/20  9/1.5  10/8  11/15        12/17        1/20  2/19  .3/11 

1971         1971         1971         1971         1971         1971         1971         1971         1972         1972         1972 

Lawrence 
Highway  10 
Plant  Site 
Canipgronnd 
Tie  Fork 
Stnart  Station 
Bear  Canyon 

nd  =  no  data  available 

*Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmenta 
Studies,  Brigham  Young  University. 

Table  34.   Physical  and  chemical  data  from  Huntington  Canyon.  Sulfate  (mg/1). 
Site 

Lawrence  nd  13,50*     .3000       2.500      2600       22,50       26(K)       2700       17.50       1200      625 

Highway  10  nd  nd  nd  nd         1.300       1.500       16,50       1,300       1300         .3,50       190 

Plant  Site 

Campground 

Tie  Fork 

Stuart  Station 

Bear  Canyon  nd  2*       nd  4*  5  5  6         nd  nd  nd  nd 

nd  =  no  data  available 

*Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Young  University. 


6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

12 

8* 

17 

7 

10 

8 

36 

28 

20 

15 

.30 

11 

3* 

5 

7 

10 

10 

25 

22 

18 

10 

20 

nd 

nd 

7 

nd 

22 

57 

nd 

nd 

nd 

nd 

75 

10 

6* 

8* 

6 

12 

11 

20 

20 

20 

11 

15 

Table  35.    Physical 

and  chemical  dat. 

a  from 

Hnntiii 

gton  Canyon.    C 

alclum 

and  magnesium 

hariluf' 

ss  (mg/1  CaCOs). 

Site 

6/8 
1971 

6/29 
1971 

7/.30 
1971 

8/20 
1971 

9/15 
1971 

10/8 
1971 

11/15 
1971 

12/17 
1971 

1/20 
1972 

2/19 
1972 

3/11 
1972 

Lawrence 

Ca  Hardness 

nd 

760 

770 

660 

580 

11.50 

9.50 

10,50 

6,50 

7(K) 

.300 

Ml^  ]  lardness 

nd 

2.50 

6480 

460 

870 

850 

WO 

9,50 

6,50 

1000 

200 

Total 

nd 

1010 

7250 

1120 

14.50 

1900 

18.50 

20t)0 

1.300 

17(H) 

.500 

Highway  10 
Ca  Hardness 

nd 

■id 

ml 

540 

640 

1100 

7.50 

800 

7(K) 

300 

250 

Mg  Hardness 

nil 

nd 

ml 

160 

180 

400 

550 

,500 

4.50 

.3(K) 

200 

Total 

nd 

ml 

ml 

7(K) 

820 

1.500 

1  500 

13(X) 

11,50 

6(M) 

450 

Plant  Site 

Ca  Hardness 

11.5* 

120 

120 

120 

100 

120 

1,50 

140 

170 

140 

140 

Mg  Hardness 

45* 

55 

60 

40 

60 

60 

80 

110 

40 

UK) 

no 

Total 

160* 

175 

180 

160 

160 

180 

2.30 

2,50 

210 

240 

250 

Campground 
Ca  Hardness 

120* 

120 

115 

110 

UO 

120 

160 

140 

1.50 

1.50 

140 

Mg  Hardness 

35* 

.50 

45 

40 

70 

60 

80 

110 

60 

90 

90 

Total 

155* 

170 

160 

1,50 

180 

180 

240 

250 

210 

240 

230 

Tie  Fork 

Ca  Hardness 

ml 

55 

60 

60 

60 

70 

ml 

nd 

nd 

ml 

2.30 

Mg  Hardness 

ml 

185 

2,50 

260 

220 

310 

ml 

ml 

nd 

ml 

170 

Total 

mi 

240 

310 

.320 

280 

.380 

ml 

ml 
(  Lihlc 

nd 
3.5  cm 

ml 
itinui'il 

400 

on  p.  83) 

Bi<)[.()(a<:Ai,  Si;iui-.s,  \i)i..   hS,  \(i. 


Alcae  ok  Humingion  Canyon,  Utah 


83 


Stuart  Station 
Ca  Hardness 
Mg  Hardness 
Total 

Bear  Caiivon 
()a  Hardness 
Mg  Hardness 
Total 


100* 

135 

130 

140 

130 

140 

140 

140 

150 

130 

110 

50* 

40 

45 

100 

60 

70 

60 

70 

50 

100 

100 

150* 

175 

175 

240 

190 

210 

200 

210 

200 

230 

210 

nd 

80* 

110* 

120 

120 

105 

130 

nd 

nd 

nd 

nd 

nd 

50* 

35* 

120 

60 

55 

60 

nd 

nd 

nd 

nd 

nd 

130* 

145* 

240 

180 

160 

190 

nd 

nd 

nd 

nd 

nd  =  no  data  available 

*Data  recorded  dnring  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Young  University. 


Table  36.  Physical  and  chemical  data  from  Huntington  Canyon.   Bicarbonate  alkalinity  (mg/1  CaCOs). 


Site 

6/29 

7/30 

8/20 

9/15 

10/8 

11/1.5 

12/17 

1/20 

2/19 

3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Lawrence 

315 

330 

290 

300 

330 

380 

410 

300 

330 

250 

High  way  10 

nd 

nd 

280 

320 

340 

360 

370 

340 

270 

2.50 

Plant  Site 

175 

170 

160 

170 

200 

210 

240 

200 

220 

220 

Campground 

175 

160 

160 

170 

200 

210 

2.30 

220 

230 

220 

Tie  Fork 

2.50-' 

270'' 

280'' 

250^ 

3.50 

nd 

nd 

nd 

nd 

.380 

Stuart  Station 

165 

170 

180 

190 

210 

210 

220 

210 

210 

200 

Bear  Canyon 

nd 

nd 

170 

1.30 

170 

160 

nd 

nd 

nd 

nd 

nd  =  no  data  available 

■'Number  includes  75  mg/1  of  carbonate  alkalinity 
''Number  includes  .30  mg/1  of  carbonate  alkalinity 
^'Number  includes  20  mg/1  of  (!arbonate  alkalinity 


Table  37.   Physical  and  chemical  data  from  Huntington  Canyon.   Silica  (mg/1  SiOa) 


Site 

6/8 

6/29 

7/30 

8/20 

9/15 

10/8 

11/15 

12/17 

1/20 

2/19 

.3/11 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1971 

1972 

1972 

1972 

Lawrence 

7.3 

8.75 

8.75 

9.0 

9.3 

10.5 

13.0 

16.0 

14.5 

17.0 

10.0 

Highway  10 

nd 

nd 

nd 

10.5 

14.5 

12.5 

18.0 

18.0 

16.0 

12.0 

9.0 

Pl.int  Site 

3.9* 

3.5 

3.4 

.3.2 

4.2 

4..35 

6.75 

7.5 

8.3 

8.0 

7.5 

Campground 

1.9 

4.0* 

.31 

.3.6 

3.8 

4.. 35 

6.5 

4.0 

8.3 

8.0 

7.3 

Tie  Fork 

6.2 

nd 

1.7 

7.5 

2.4 

5.0 

nd 

nd 

nd 

nd 

16.5 

Stuart  Station 

4.1 

3.5 

6.13 

6.4 

5.6 

6.25 

6.5 

8.5 

7.5 

8.5 

8.0 

Bear  Canyon 

nd 

3.5* 

7.2* 

5.75 

5.2 

6.65 

6.6 

nd 

nd 

nd 

nd 

nd  =  no  data  available 

♦Data  recorded  during  corresponding  time  periods  by  Dr.  Robert  Wingett,  Center  for  Health  and  Environmental 
Studies,  Brigham  Young  University. 


84 


Biiif:HAM  Young  U.NivERsiTi'  Science  Bulletin 


APPENDIX  II 


ALGAE  COLLECTED  FROM  HUNTINGTON 
CANYON  OCTOBER  1970  -  MARCH  1972 

Division  Ghlorophyta 
A.  Class  Chlorophyceae 
1.    Order  Volvocales 

a)  Family  Chlamydomonadaceae 
Carteria  klebsii  (Dang.)  Dill 
Chlamydomonas  sp. 

b)  Family  Volvocaceae 
Pandorina  morum  (Muell.)  Bory 
Volvox  terlius  A.  Meyer 


Order  Tetrasporales 
a)   Family  Gloeocystaceae 
Gloeocystis  sp. 

Order  Chlorcoccales 

a)  Family  Chlorococcaceae 
Characium  ambiguum  Hermann 
C.  obtusum  A.  Braun 

b)  Family  Oocystaceae 
Ankistrodesmus  falcatus    (Corda)    Ralfs 
Closteriopsis  longissima  var.  tropica  West 

and  West 
Nephrocytium  lunatum  W.  West 
Oocystis  gigas  Archer 

c)  Family  Dictyosphaeriaceae 
Botryococcus  sudeticus  Lemmermann 

d)  Family  Scenedesmaceae 
Scenedesmus  bijuga  (Turp.)  Lagerheim 
S.  denliculatus  Lager. 
S.  quadricauda  (Turp.)  de  Brebisson 

e)  Family  Hydrodictyaceae 
Pediastrum  telras  (Ehr.)  Ralfs 

Order  Ulotrichales 

a)  Family  Ulotrichaceae 
Stichococcus  sublilis   (Kutz.)   Klercker 
Ulothriz  aequalis  Kutz. 
U.  lenerrima  Kutz. 
U.  tenuissima  Kutz. 
U.  zonata  (Weber  &  Mohr)  Kutz. 

b)  Family  Microsporaceae 
Microspora  willeana  Lagerheim 

c)  Family  Cylindrocapsaceae 
Cylindrocapsa  conjerta  W.  West 

Order  Chaetophorales 

a)  Family  Chaetophoraceae 
Draparnaldia  plumosa  (Vauch.)  C.  A. 

Agardh 
Protoderma  viride  Kutz. 
Sligeoclonium  attenuatum  (Hazen) 

Collins 
5.  stagnatile  (Hazen)  Collins 

b)  Family  Aphanochaetaceae 
Aphanochaete  repens  A.  Braun 

c)  Family  Coleochaetaceae 
Coleochaete  irregularis  Pringsheim 

Order  Oedogoniales 
a)   Family  Oedogoniaceae 
Oedogonium  spp. 

Order  Cladophorales 

a)   Family  Cladophoraceae 

Cladophora  fracla  (Dillw.)   Kutz. 

C.  glomerala  (L.)   Kutz. 

Rhizoclonium  hicroglyphicum  (C.  A. 
Kutz. 

Order  Zygnematales 

a)   Family  Zygnemataceae 

Mougeotia  capucinn  (Bory)  C.  A. 
Agardh 


M.  genufleia  (Dillw.)  C.  A.  Agardh 
M.  parvula  Hassall 
Spirogyra  decimina  (Muell.)  Kutz. 
S.  dubia  Kutz. 
S.  porticalis  (Muell.)  Cleve 
S.  spp. 

Zygnema  insigne  (Hass.)  Kutz. 
Z.  spp. 
b)   Family  Desmidiaceae 

Closteriuni  acerosum   (Schr.)  Ehr. 

C.  dianae  Ehr. 

C.  ehrenbergii  Menegh. 

C.  lanceolatum  Kg. 

C.  motiilifrruni  Ehr. 

C.  rostratum  Ehr. 

C.  spp. 

Cosmarium  margaritiferum  Menegh. 

C.  ochthodes  Nord. 

C.  ovale  Ralfs 

C.  quinarium  Lund 

C.  tinctum  Ralfs 

C.  spp. 

Euastrum  sp. 

Micrasterias  sp. 

Pleurotaenium  ehrenbergii  Ralfs 

P.  sp. 

Sphaerozosma  filiforme  Rabh. 

Stauraslrum  eustephanum    (Ehr.)    Ralfs 

lS.  gracile  Ralfs 

5.  mutica  Breb. 

B.  Class  Charophyceae 
1 .    Order  Charales 

a)   Family  Characeae 

Chara  vulgaris  Linnaeus 

IL     Division  Euglenophyta 
A.  Class  Euglenophyceae 
1 .    Order  Euglenales 

a)   Family  Euglenaceae 
Euglena  acus  Ehrenberg 
E.  gracilis  Klebs 
£.  minuta  Prescott 
E.  sp. 

Eutreptia  sp. 

Phacus  acuminatus  Stokes 
P.  pyrum   (Ehrb.)  Stein 
P.  sp. 
Trachelomonas  robusta  Swirenko 

IIL  Division  Pyrrhophyla 
A.  Class  Dinophyceae 
I.    Order  Peridiniales 

a)  Family  Peridiniaceae 
Peridinium  cinctum   (Muell.)   Ehrenberg 

b)  Family  Ceratiaceae 
Ceratium  hirundinella  (Muell.)  Dujardin 

IV.  Division  Chrysophyta 
A.  Class  Xanthophyceae 

1 .  Order  Heterococcales 

a)  Family  Characiopsidaceae 
Characiopsis  acuta  (A.  Braun)  Borzi 
C.  longipes   (Rabh.)   Borzi 

b)  Family  Chlorotlieciaceae 
Ophiocytium  sp. 

2.  Order  Tribonematales 
Ag.)  a)   Family  Tribonemataceae 

Tribonema  bombycinum  (C.  A.  Ag.) 
Derbes  &  Solier 

3.  Order  Vaucheriales 
a)    Family   Vaucheriaceae 

Vaucheria  geminata  (Vauch.)  De  Candolle 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


85 


B.  Class  Chrysophyceae 

1.  Order  Chromulinales 

a)   Family  Hydniraceae 

Hydrurus  foetidus  (Vill.)  Trev. 

2.  Order  Ochromonadales 
a)   Family  Dinobryaceae 

Dinobryon  cylindricum  Imhof 

C.  Class  Bacillariophyceae 

1.  Order  Centrales 

a)   Family  Coscinodiscaceae 

Cyclotella  meneghiniana  Kutz. 

2.  Order  Peimales 

a)  Family  Fragilariaceae 
Asterionella  formosa  Hassall 
Diatoma  anceps  var.  linearis  M.  Perag. 
D.  hiemale  var.  mesodon  (Ehr.)  Grunow 
D.  tenue  var.  etongatum  Lyngb. 

D.  vulgare  Bory 

D.  vulgare  var.  breve  Grunow 

Fragilaria  construens  var.  binodus  (Ehr.) 

Grunow 
F.  construens  var.  venter  (Ehr.)  Grunow 
F.  crotonensis  Kitton 
F.  leptostauron  (Ehr.)   Hust. 
F.  pinnata  var.  lancettula  (Schum.)  Hust. 
F.  virescens  Ralfs 
Hannaea  arcus  (Ehr.)  Patrick 
Hannaea  arcus  var.  amphioxys  (Rabh.) 

Patrick 
Meridian  circulare  var.  constrictum 
(Ralfs)   v.  Heur. 
Synedra  acus  Kutz. 
5.  affinis  Kutz. 
S.  delicatissima  W.  Sm. 
S.  pulchella  Ralfs 

S.  pulchella  var.  lanceolata  O'Meara 
S.  radians  Kutz. 
S.  ulna  (Nitz.)  Ehr. 

S.  ulna  var.  ozyrhynchus  (Kutz.)  v.  Heur. 
S.  ulna  var.  subequalis  (Grun.)  v.  Heur. 
Tabellaria  feneslrata   (Lyngb.)   Kutz. 

b)  Family  Eunotiaceae 

Eunotia  curvata  (Kutz.)   Lagerst 

c)  Family  Achnanthaceae 
Achnanthes  defleia  Reim. 
A.  hauckiana  Grunow 

A.  lanceolata  (Breb.)  Grunow 
A.  lanceolata  var.  dubia  Grunow 
A.  lanceolata  var.  haynaldii  (Istv.- 

Scaarsch.)   CI. 
A.  linearis  fo.  curta  H.  L.  Sm. 
A.  minutissima  Kutz. 
Cocconeis  disculus   (Schum.)   Cleve 
C.  pediculus  Ehr. 
C.  placentula  var.  euglypta  (Ehr.) 

Cleve 
C.  placentula  var.  lineata  (Ehr.)  v. 

Heur. 
C.  rugosa  Sov. 
Rhoicosphenia  curvata  (Kutz.)  Grunow 

d)  Family  Naviculaceae 
Amphipleura  pellucida  Kutz. 
Amphiprora  alata  (Ehr.)  Kutz. 
Anomoeoneis  vitrea  (Grun.)  Reim. 
Caloneis  ventricosa  (Ehr.)  Meist. 
Diploneis  pseudovalis  Hust. 
Gyrosigma  acuminatum   (Kutz.)   Rabh. 
G.  spenceri  (Quek.)  Griff.  &  Henfr. 
Mastogloia  smithii  Thwaites 
Navicula  bicephala  Hust. 

N.  capitata  Ehr. 
N.  cryptocephala  Kutz. 
N .  cuspidata  var.  major  Meist. 
N.  elginensis  (Greg.)  Ralfs 
N.  elginensis  var.  rostrata  (A.  mayer) 
Patrick 


A',  exigua  Greg. 

A',  lanceolata   (Ag.)  Kutz. 

N.  minima  Grun. 

N .  odiosa  Wallace 

N.  pelliculosa  (Breb.)  Hilse 

A',  peregrina  (Ehr.)  Kutz. 

A',  pseudoreinhardtii  Patrick 

A',  papula  Kutz. 

A',  radiosa  Kutz. 

A',  radiosa  var.  tenella  (Breb.)  Grunow 

A',  rhyncocephala  Kutz. 

A',  secreta  var.  apiculata  Patrick 

A',  tripunctata  var.  schizonemoides  (v. 

Heur.)   Patrick 
Neidium  affine  var.  longiceps  (Greg.) 

Cleve 
N.  binode  (Ehr.)  Hust. 
Pinnularia  brebissonii  (Kutz.)  Rabh. 
P.  viridis  var.  minor  Cleve 
Pleurosigma  delicatulum  W.  Sm. 
Stauroneis  anceps  Ehr. 
S.  phoenicenteron   (Nitz.)   Ehr. 
S.  phoenicenteron  fo.  gracilis  (Ehr.)  Hust. 
S.  smithii  Grunow 

e)  Family  Gomphonemataceae 
Gomphonema  acuminatum  Ehr. 
G.  constrictum  Ehr. 

C.  gracile  Ehr. 

G.  intricatum  Kutz. 

G.  olivaceum   (Lyngb.)   Kutz. 

f)  Family  Cjonbellaceae 
Amphora  ovalis  Kutz. 
Cymbella  amphicephala  Naeg. 
C    cuspidata  Kutz. 

C.  cymbiformis  Agardli 
C.  gracilis  (Ehr.)  Kutz. 
C.  parva  (W.  Sm.)  Wolle 
C.  ventricosa  Kutz. 

g)  Family  Epitliemiaceae 
Denticula  elegans  Kutz. 
Epithemia  argus  Kutz. 

E.  turgida  var.  westermanni  Ehr. 

Rhopalodia  gibba  (Ehr.)  O.  Muell. 
h)   Family  Nitzschiaceae 

Nitzschia  acicularis  (Kutz.)  W.  Sm. 

A',  angularis  var.  affinis  Grun. 

A',  communis  Rabh. 

N.  dissipata  (Kutz.)  Grun. 

A',  frustulum  var.  perpusilla  (Rabh.) 
Grunow 

A',  hungarica  Grun. 

A',  linearis  W.  Sm. 

A',  palea  (Kutz.)  W.  Sm. 

A',  sigmoidea  (Ehr.)  W.  Sm. 

A',  vermicularis  (Kutz.)  Hantz. 
i)   Family  Surirellaceae 

Cymatopleura  elliptica  (Breb.)  W.  Sm. 

C.  solea  (Breb.)  W.  Sm. 

Surirella  angustata  Kutz. 

S.  baileyi  Lewis 

S.  ovalis  Breb. 

5.  ovaia  Kutz. 

V.     Division  Cyanophyta 
A.  Class  Myxophyceae 

1 .  Order  Chroococcales 

a)   Family  Chroococcaceae 

Chroococcus  limneticus  Lemm. 
C.  minutus   (Kutz.)   Nag. 
Gloeocapsa  sp. 

Gomphosphaeria  aponina  Kutz. 
Merismopedia  elegans  A.  Br. 
M.  glauca  (Ehr.)  Nag. 
M.  tenuissima  Lemm. 

2.  Order  Chamaesiphonales 

a)   Family  Chamaesiphonaceae 
Chamaesiphon  sp. 


86 


Bhk;ham  Young  University  Science  Bulletin 


3.    Order  Oscillatoriales 

a)   Family  Oscillatoriaceae 

Lyngbya  aerugineo-coerulea   (Kutz.) 

Gomont 
L.  aestuarii   (Mert.)   Leib. 
L.  major  Meneg. 
L.  martensiana  Meneg. 
L.  spp. 

Oscillatoria  agardhii  Gomont 
O.  amphibia  Ag 
O.  limosa  Ag. 
O.  tenuis  Ag. 
O.  spp. 
Phormidium  sp. 


Schizothrii  fragilis   (Kutz.)   Gomont 

Spirulina  major  Kutz. 

S.  princeps  (West  &  West)  G.  S.  West 

4.    Order  Nostocales 

a)  Family  Nostocaceae 
Anabaena  circinalis  Rabh. 
A.  spp. 

Nostoc  paludosum  Kutz, 
A',  piscinale  Kutz. 

b)  Family  Scv-tonemataceae 
Tolypothrix  lanata  Wartm. 

c)  Family  Rivulariaceae 
Calothrix  sp. 


LITERATURE  CITED 


Allen,  Winpred  E.  1920.  A  quantitative  and  statis- 
tical study  of  the  plankton  of  the  San  Joaquin 
River  and  its  tributaries  in  and  near  Stockton, 
California  in  1913.  Univ.  of  Calif.  Pub.  in  Zool., 
22(l):l-292. 
American  Public  Health  Association  (APHA), 
American  Water  Pollution  Control  Federation 
(WPCF),  American  Water  Works  Association 
(AWWA).  1971.  Standard  methods  for  the  ex- 
amination of  water  and  wastewater.  13th  ed.  Amer- 
ican Public  Health  Association,  Washington,  D.C. 
874  pp. 
Blum,  John  L.  1956.  The  ecolog>-  of  river  algae. 
Bot.  Rev.,  22(5):291-341. 

.     1957.     An  ecological  study  of  the  Saline  River. 

Michigan.    Hydrobiologia,    9:361-408. 
Bbinley,   F.  J.     1950.     Plankton  populations  of  certain 
lakes  and  streams  in  the  Rocky  Mountain  National 
Park,    Colorado.    Ohio   Jour.    Sci.,    50:243-250. 
Butcher,    R.    W.     1932.     Studies    in    the    ecology    of 
rivers:    W.    The   microflora    of   rivers,    with    special 
reference   to   the  algae   of   the  riverbed.   Ann.   Bot., 
46:813-861. 
Chatvvin,    S.    L.     1956.     The    vertical    distribution    of 
phytoplankton    of    Deer    Creek    Reservoir,    Wasatch 
Col,   Utah.   M.A.   Thesis,  Univ.  of  Utah,   Salt  Lake 
City,  Utah. 
Clark,  W.  J.     1958.     The  phytoplankton  of  the  Logan 
River,  Utah,  a  mountain  stream.  Ph.D.  Thesis,  Utah 
State  Univ.,  Logan.  Utah. 
Coombs,  Robert.     1964.     A  floristic  and  ecological  sur- 
vey of  the  algal  flora  of  the  western  Uinta  Moun- 
tains   and    adjacent    areas.    M.S.    Thesis.    Univ.    of 
Utah.  Salt  Lake  City. 
Daily,  William  A.     1938      A  quantitative  studv  of  the 
phytoplankton    of    Lake    Michigan   collected   in   the 
vicinity    of    Evanston,    Illinois.    Butler    Univ.    Bot. 
Studies.  4:65-83. 
Daubenmire.     R.     1968.     Plant     communities.     Harper 

and  Row,  New  York.  300  pp. 
Dillard.    Gary    E.     1966.     A    floristic    and    ecological 
study    of    benthic    algae    in    two    North    Carolina 
streams.   Ph.D.  Tliesis.  North  Carolina  State  Univ., 
Raleigh,  North  Carolina. 
Dob,   Inka.     1970.     Production   rate   of   the   periphyton 
in    I^ake    Tiberias    as    measured    bv    the    glass-slide 
method.  Israel  J.  of  Bot..  19:1-15. 
Dustans.  William  A.     1951.     A  comparative  study  of 
dredged  and  undredged  portions  of  the  Provo  River. 
Utah.  M.S.  Thesis.  Univ.  of  Utah.  Salt  Lake  City. 
Dutton,    C.    E.     1880.     Report   on   the   geology    of   the 
high  plateaus  of  Utah.  U.  S.  Geog.  and  Geol.  Surv.. 
Gov't    Printing   Office,   Washington    D.    C.    307   pp. 
Flowers.  Seville.     1959.     Vegetation  of  Glen  Canyon. 
In    Ecological    studies    of    the    flora    and    fauna    in 
Glen  Canyon.   Univ.   Utah  Anthropological   Papers, 
40:21-61. 


.     1960.     Vegetation  of  Flaming  Gorge  Reservoir 

Basin.  In  Ecological  studies  of  the  flora  and  fauna 
of  Flaming  Gorge  Reservoir  Basin,  Utah  and  Wyo- 
ming. Univ.  LTtah  Anthropological  Papers,  48:1-48. 

.     n.d.    (a).      Common    algae   of   Utah.    Univ.   of 

Utah.  70  pp.  Mimeo. 

n.d.      (b).     The  blue  green  algae  of  Utah.  69 


pp.   Mimoo, 

Foehster,  J.  A.  and  B.  S.  Corrin.  1970.  Preliminary 
study  of  the  Dulaney  Valley  Stream.  Publ.  No.  1, 
Enviromnental  Studies  Program,  Goucher  College, 
Baltimore,   Maryland. 

Fritsch,  F.  F.  1906.  Problems  in  aquatic  biolog>', 
with  special  reference  to  the  studv  of  algal  periodic- 
ity.   New    Phytol.,   5:149-169. 

Galtsoff.  p.  S.  1924.  Limnological  observations  in 
the  Upper  Mississippi.  U.S.  Bur.  Fish.  Bui.,  39:347- 
438. 

Hanna,  G.  D.  1949.  A  synthetic  resin  which  has 
unusual  properties.  J.  Roy.  Microscop.  Soc.  London, 
Ser.  3,  69(l):25-28. 

HoHN.  M.  H.  AND  J.  Hellerman.  1963.  The  taxon- 
omy and  structure  of  diatom  populations  from 
three  eastern  North  American  rivers,  using  three 
sampling  methods.  Trans.  Amer.  Microscop.  Soc, 
82:250-329. 

Hynes,  H.  B.  N.  1970.  Tlie  ecolog>-  of  running 
waters.  Univ.  of  Toronto  Press,  Toronto.  Canada. 
555  pp. 

KoFoiD,  C.  A.  1903.  The  plankton  of  the  Illinois 
River,  1894-1899.  widi  introductory  notes  upon 
the  hydrography  of  the  Illinois  River  and  its  basin. 
Part  I.  Quantitative  investigations  and  general  re- 
sults.  Bui.   111.   St.   Nat.   Hist.   Surv..  6:95-629. 

.     1908.     The  plankton  of  the  Illinois  River.  1894- 

1899.  Part  II.  Constituent  organisms  and  their  sea- 
sonal distribution.  Bui.  111.  St.  Nat.  Hist.  Surv.. 
8:1-360. 

Longley,  Glenn  J.  1969.  Plankton  associations  in 
Antelope  Flat  area.  Flaming  Gorge  Resen'oir.  Ph.D. 
Thesis.   Univ.   of   Utah.   Salt  Lake  City. 

McConnell,  William  J.  and  W.  F.  Sigler.  1959. 
Chlorophyll  and  productivity  in  a  mountain  river. 
Limnol,  and  Ocean..  4:335-351. 

Miller.  Ga\NT  L.  1959.  An  investigation  of  pollu- 
tion in  the  Price  River,  Carbon  Countv.  Utah. 
M.S.    Thesis.    Univ.    of   Utah,   Salt    Lake   City. 

Newcombe.  Curtis  L.  1949.  Attachment  materials  in 
relation  to  water  productivity.  Trans.  Amer. 
Microscop.  Soc.  64(4) : 355-361. 

Norrington,  Annie.  1925.  Phycological  study  of  the 
Wasatch  and  Uinta  ranges  in  Utah.  Ph.D.  Thesis. 
Univ.  of  Chicago,  Chicago. 

Odum,  H.  T.  1957.  Trophic  structure  and  productiv- 
ity of  Silver  Springs,  Florida.  Ecol.  Monogr.,  27: 
55-112. 


Biological  Series,  Vol.  18,  No.  2       Algae  of  Huntington  Canyon,  Utah 


87 


Palmer.  Mervin  C.  1961.  AJgae  in  rivers  of  the 
United  States.  In  Algae  and  metropolitan  wastes. 
Trans.  1960  Seminar.  R.A.  Taft  San.  Eng.  Ctr., 
Cincinnati,    Ohio,    Tech.    Rpt.    W61-3:34-38. 

Palmer,  Mervin  C.  and  T.  E.  Maloney.  1954.  A 
new  counting  slide  for  nannoplankton.  Amer.  Soc. 
Limnol.    Ocean.,    Spec.    Publ.    No.    21.    6   pp. 

Patrick,  Ruth,  M.  H.  Hohn,  and  J.  H.  Wallace. 
1954.  A  new  metliod  for  determining  the  pattern 
of  the  diatom  flora.  Notul.  Nat.  Acad.  Philad., 
No.  259:1-12. 

PiRANiAN.  George.  1937.  The  plankton  of  the  Bear 
River  Migratory  Water  Fowl  Refuge,  Utah.  M.S. 
Thesis,   Utah   State  Univ..  Logan,  Utah. 

Pratt,  Gene  A.  1957.  Studies  on  the  periodicity  of 
certain  plankton  species  of  Salem  Lake,  M.S.  The- 
sis.  Brigham  Young  University,  Provo,  Utah. 

Prescott,  Gerald  W.  1962.  Algae  of  the  western 
Great  Lakes  area.  Wm.  C.  Brown  Co.,  Dubuque, 
Iowa.  977  pp. 

QuiNN.  Barry  G  1958.  The  effects  of  sugar  beet 
wastes  upon  the  periphyton  of  the  Jordan  River. 
M.A.  Thesis.  Univ.   of  Utah,   Salt  Lake  City. 

Rice,  C.  H.  1938.  Studies  in  the  phytoplankton  of  the 
River  Thames.  Ann.  Rot,  2:539-581. 

Samuelson,  John  A.  1950.  A  quantitative  compari- 
son of  the  algal  populations  in  two  Wasatch  Moun- 
tain streams.  Proc.  Utah  Acad.  Sci.,  Arts  and  Let- 
ters. 27:76. 

Sladeckova,  Alena.  1962.  Limnological  investigation 
methods  for  the  periphyton  community.  Bot.  Rev., 
28:287-350. 

Smith,  Ger,4LD  R.  1959.  Effects  of  pollution  on  the 
Weber  River.  Utah.  M.S.  Thesis,  Univ.  of  Utah, 
Salt  Lake  City. 


Spieker,  E.  M.  and  J.  B.  Reeside  Jr.  1925.  Cretaceous 
and  tertiary  formations  of  the  Wasatch  Plateau, 
Utah.  Geol.   Soc.  Amer.   Bui.,  36:435-454. 

Spieker,  E.  M.  and  M.  P.  Billings.  1940.  Glaciation 
and  the  Wasatch  Plateau,  Utah.  Geol.  Soc.  Amer. 
Bui.,  51:1,173-1,198. 

U.  S.  Dept.  Interior,  U.  S.  Dept.  Agriculture,  and 
LI.  S.  Dept.  Transportation.  1971.  Draft  of  en- 
vironmental statement — Huntington  Canyon  genera- 
tion station  and  transmission  line.  90  pp. 

Ward,  Henry  B.  and  George  C.  Whipple.  1918. 
Fresh  water  biology.  John  Wiley  and  Sons,  Inc., 
New  York,  N.  Y.  1.111  pp. 

Weber,  Cornelius  I.  1970.  Methods  of  collection 
and  analysis  of  plankton  and  periphyton  samples  in 
the  water  pollution  surveillance  system.  Fed.  Water 
Qual.  Adinin.,  Div.  of  Water  Qual.  Res.,  Anal. 
Qual.   Control   Lab.,   Cincinnati,   Ohio.   22  pp. 

Weber,  Cornelius  I.  and  R.  L.  Raschke.  1970.  Use 
of  a  floating  periphyton  sampler  for  water  pollu- 
tion surveillance.  Fed.  Water  Qual.  Admin..  Div. 
of  Water  Qual.  Res.,  Anal.  Qual.  Control  Lab.,  Cin- 
cinnati, Ohio.  26  pp. 

Welch,  P.  S.  1952.  Limnology.  2nd  Ed.  McGraw-Hill 
Book  Co.,  New  York.  N.Y.  538  pp. 

Whitford,  L.  a.  and  G.  J.  Schumacher.  1963.  Com- 
munities of  algae  in  North  Carolina  streams  and 
their  seasonal   relations.   Hydrobiologia,   22:133-196. 

Young,  Orson  W.  1945.  A  limnological  investigation 
of  periphyton  in  Douglas  Lake,  Michigan.  Trans. 
Amer.  Microsc.  Soc,  64:1-20. 

Zhadin,  V.  I.  AND  S.  V.  Gebd.  1961.  Fauna  and  flora 
of  the  rivers,  lakes,  and  reservoirs  of  the  U.S.S.R. 
tran.  1963,  Israel  Program  for  Scientific  Transla- 
tions, Jerusalem,  Israel. 


^•^NA  -  ^(ro^o) 


Brigham  Young  University 
MuacoNH-zoou  Science  Bulletin 

LIBRARY 

NOV    510/3  **Hte«-^ 

u'nBRKding  ecology  of  raptors 
in  the  eastern  great  basin 

OF  UTAH 


by 

Dwight  G.   Smith 

and 
Joseph   R.   Murphy 


BIOLOGICAL  SERIES  — VOLUME  XVIII,  NUMBER  3 
JUNE   1973/ISSN   0068-1024 


BRIGHAM  YOUNG   UNIVERSITY   SCIENCE  BULLETIN 
BIOLOGICAL  SERIES 

Editor:   Stanley  L.  Welsh,  Department  of  Botany, 

Brigham  Young  University,  Provo,  Utah 

Acting  Editor:  Vernon  J.  Tipton,  Zoology 

Members  of  the  Editorial  Board: 

Ferron  L.  Andersen,  Zoology 
Joseph  R.  Murdock,  Botany 
WiLMER  W.  Tanner,  Zoology 

Ex  officio  Members: 

A.   Lester  Allen,  Dean,  College  of  Biological  and  Agricultural 
Sciences 

Ernest  L.  Olson,  Director,  Brigham  Young  University  Press 

The  Brigham  Young  University  Science  Bulletin,  Biological  Series,  publishes 
acceptable  papers,  particularly  large  manuscripts,  on  all  phases  of  biology. 

Separate  numbers  and  back  volumes  can  be  purchased  from  University  Press 
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of  Gifts  and  Exchange,  Brigham  Young  University  Library,  Provo,  Utah  84602. 


I 


Brigham  Young  University 
Science  Bulletin 


BREEDING  ECOLOGY  OF  RAPTORS 

IN  THE  EASTERN  GREAT  BASIN 

OF  UTAH 


by 

Dwight   G.    Smith 

and 
Joseph    R.    Murphy 


BIOLOGICAL  SERIES  — VOLUME  XVIII,  NUMBER  3 
JUNE    1973/ISSN   0068-1024 


TABLE    (W   CONTENTS 

ABSTRACT    1 

INTRODUCTION     1 

REVIEW    OF    LITERATURE  2 

STUDY     AREA    3 

Location    and    Topography    3 

Climate    3 

Vegetation     3 

Faunal   Elements   5 

Human    Utilization    5 

METHODS    6 

RESULTS    7 

Basic  Population  Data  7 

Population   Composition   and   Density 7 

Seasonal    Activity    Timetables    9 

Nest    Site    Requirements    13 

Productivity    23 

Territoriality     29 

Hunting  Activity  Patterns  and  Habitat  43 

Predation     45 

DISCUSSION    AND    CONCLUSIONS 54 

Populations   54 

Nest  Site  55 

Productivity    58 

Territoriality     62 

Predation     64 

The   Ferruginous   Hawk  67 

The  Long-eared  Owl   68 

Effect  of  the   Investigator  69 

SUMMARY    70 

ACKNOWLEDGMENTS   71 

APPENDIX  —  WEIGHTS  OF  PREY  SPECIES  USED  LN   THE   BIOMASS   CALCULATIONS    71 

LITERATURE    CITED  72 


BREEDING   ECOLOGY   OF   RAPTORS   IN   THE 
EASTERN   GREAT  BASIN   OF   UTAH 


by 
Dwight  G.  Smith'  and  Joseph  R.  Murphy- 


ABSTRACT 


A  comparative  study  of  the  breeding  ecology 
of  12  raptor  species  was  conducted  in  the  east- 
em  Great  Basin  from  1967-1970.  The  project 
was  designed  to  deteiTnine  the  composition  and 
densities,  habitat  selection,  territoriahty  and 
predatory  habits  of  raptorial  birds  in  a  semi- 
arid  en\iromnent.  All  topics  were  analyzed  com- 
parativeh',  relating  the  requirements  and  activi- 
ties  of  the   12  raptor  species. 

Average  vearly  population  densities  of  all 
species  approximated  0.5  pairs  per  square  mile, 
but  much  of  the  available  habitat  was  not  util- 
ized. Predominant  raptors  were  the  Ferruginous 
Hawk  and  Great  Horned  Owl.  Other  important 
raptors  included  the  Golden  Eagle,  Red-tailed 
Ha\\'k  and  Raven. 

The  breeding  activities  of  the  collective  rap- 
tor populations  occurred  over  a  period  of  eight 
months.  Great  Homed  Owls  and  Golden  Eagles 
\\ere  the  first  raptors  to  initiate  nesting  activi- 


ties, usually  in  late  January  and  early  February. 
The  raptor  breeding  season  tenninated  with  the 
fledging  of  the  young  Cooper's  Hawks  and  Bur- 
rowing Owls  in  late  August. 

The  fecundity  of  the  raptor  populations 
varied  between  years.  Specific  causes  of  mortal- 
ity of  eggs  and  voung  included  nest  desertion 
and  destruction,  predation,  apparent  egg  infer- 
tility, and  accidents,  most  of  which  could  be 
directly  attributed  to  some  fonn  of  human  inter- 
ference. 

The  observed  home  ranges  of  the  raptor 
species  were  a  function  of  their  body  size  and 
breeding  status. 

The  food  of  the  raptors  included  at  least  55 
different  prev  species,  but  most  relied  heavily 
on  only  one  or  two  species.  A  correlation  be- 
tween raptor  size  and  mean  prey  weight  was 
evident.  No  examples  of  raptor  predation  on 
game  or  domestic  livestock  were  found. 


INTRODUCTION 


Raptorial  birds  generally  occupy  the  top 
levels  of  their  food  webs  and  as  such  exert 
considerable  influence  on  local  mammal  and 
avian  prev  populations.  Shelford  ( 1963)  classifies 
them  as  major  permeant  influents  and  sug- 
gests that  the  raptor  populations  of  the  Great 
Basin  desert  fulfill  roles  equivalent  to  such 
inannnalian  predators  as  the  bobcat  (  Li/nx 
Tufiis),  coyote  (Canis  latram).  kit  fox  (Vtilpes 
uiacrotis),  and  badger  {Taxklca  taxtis).  Their 
declining  numbers  and  economic  relationships 
warrant  additional  interest,  and  studies  of  total 
raptor  populations  are  needed  as  a  means  by 
wliich  we  ma\'  elucidate  their  responses  to 
changing  pressures  and  environmental  condi- 
tions. Although  their  large  size  and  predatory 
habits  render  them  conspicuous,  their  extensive 


territorial  recjuirements  present  difficulties  to 
raptor  ecologists  desiring  to  obtain  data  on  rep- 
resentative populations.  Hence,  there  have  been 
few  previous  attempts  to  study  collective  rap- 
tor  populations    in   detail. 

The  objective  of  this  study  is  tc;  provide 
quantitative  data  on  the  breeding  ecology  of 
central  Utah  raptors.  Aspects  of  the  study  which 
are  emphasized  include  raptor  populations  and 
their  distribution,  yearly  productivit)',  territo- 
riality, and  predation.  All  topics  are  treated 
comparatively,  relating  the  requirements  and  ac- 
tivities of  the  12  raptor  species.  The  species 
studied  include  four  buteonids,  the  Golden 
Eagle  (Aqtiila  chrysaetos),  Red-tailed  Hawk 
(Buteo  jnmaicensis) ,  Fernaginous  Hawk  (Buteo 
recalls),   and   Swainson's   Hawk    (Buteo  swain- 


'I)ep.trtnipnt    nt    Biology.     Sonlliciii     Coniiciticiil    Slalo    ('oIIckc     New    Iliivon.    <  oiinot  lu  ill    Oft'jl') 
-DepiTrtlilcnl    of    Zoology.    lirit'.Ii.im    Voiiii^    t,^iivci\ily.    I'rovii.     lll.ili    84()0i 


HiuciiAM  VouNc  University  Sf:iENCE  Bulletin 


sonii);  two  falcons,  tlic  Prairit>  Falcon  (Falco 
incxicantis) ,  and  Sparrow  Hawk  (Falco  spar- 
vcrius);  three  owls,  the  Great  Horned  Owl 
(Bubo     virginkiniis).    Short-eared    Owl     (Asia 


fltiiniiicus),  and  Burrowing  Owl  [Speotyto  cuni- 
ciihiria);  the  Marsh  Hawk  (Cirnis  cijaneus), 
Cooper's  Hawk  {Accipiter  coopcrii),  and  Raven 
(Corviis  corax). 


REVIEW  OF  LITERATURE 


netaili'd  studies  on  eiilleeti\e  raptor  popula- 
tions in  North  America  have  been  conducted 
ill  Michigan  and  W\i»ming  (Craighead  and 
Craighead,  1956),  the' Alaskan  tundra  ( Pitelka, 
Toni'ich  and  Treichel,  1955a,  19551)),  and  the 
Tule  Lake  region  of  northern  California  (Dixon 
and  Bond,  1937;  Bond,  1939).  In  other  popula- 
tion studies  Mathisen  and  Mathisen  (1968)  ex- 
plored tin-  species  and  seasonal  abundance  of 
raptors  in  Nebraska,  and  Baunigartner  and 
Bauingartner  (1944)  examined  the  food  habits 
and  population  fluctuations  of  hawks  and  owls 
in  Oklahoma.  Recenth'  Hicke\'  ( 1969)  has  sum- 
marized much  information  on  the  general  status 
and  broad  trends  of  cuiTcnt  raptor  populations, 
but  his  work  centers  around  the  Peregrine  Fal- 
c(.n  (Fiiico  peregrinufi) .  Other  comparative 
studies  have  dealt  with  the  ecology  of  Great 
I'orned  Owls  and  Rcd-tailcd  Hawks.  The  more 
informative  of  these  have  been  conducted  in 
Wisconsin  (Orians  and  Kuhlman,  1956),  New 
York  (Hagar,  1957),  and  Minni'sota  (LeDuc, 
1970).  Brown  (1966,  1970)  has  provided  much 
inlormation  on  African  raptor  populations,  par- 
tieularlv  with  respect  to  their  niclu'  allocation. 

Other  associative  studies  have  focused  on 
a  ]-)articular  aspect  of  raptor  ecology,  most  coni- 
niDiih  predation.  Specific  comparative  food 
habits  studies  on  hawks  and  owls  have  been  con- 
ducted bv  Fisher  (1895),  Errington  (1932c, 
1933),  Mendall  (1944),  and  Craighead  and 
Craighead  (1956);  on  hawks  by  McAtce  (1935), 
Errington  and  Breckinridge  (1938),  Hamerstrom 
;iii(l  Ilamcistroin  (  1951),  and  Storer  (1966);  and 
on  owls  bv  Cahn  and  Kemp  (1930),  Wilson 
(1938),  Fitch  (1947).  Kirkpatrick  and  Conway 
(1947),  Pear.son  and  Pearson  (1947),  Marti 
(1969a),   and   Earhait  and  Johnson    (1970). 

Life  history  studies  of  most  of  the  raptors 
have  been  conducted  in  a  varietN'  of  habitats, 
and  many  of  them  have  been  summarized  in 
the  works  of  Rent  (1937,  19.38)  and  Brown  and 
Amadon  (1968).  The  following  arc  among  the 
more  noteworthv  of  a  large  amount  of  published 
literature  on  various  phases  of  the  nesting  ecol- 
ogy of  the  raptors  studied  in  this  report,  to- 
gether with  the  rcjgions  in  which  they  were 
studied: 


Golden  Eagle.  C-'ameron  (1905),  McGahan 
(1967,  1968),  Montana;  Finley  (1906),  Dixon 
(19.37),  Carnie  (1954),  California;  Arnold 
(1954),  North  America;  Wellein  and  Ray 
(1964),  Boeker  and  Ray  (1971),  Rocky  Moun- 
tains; Sandeman  (1957),  Watson  (1957),  Brown 
and  Watson  (1964),  Lockic  (1964),  Brown 
(1969),  Scotland. 

Great  Homed  Old.  Dixon  (1914),  Fitch 
(1940),  California;  Errington  (19.32b,  1938), 
Iowa;  Swenk  (1937),  Missouri  Vallev;  Baum- 
gartner  (1938,  1939),  Iowa  and  New  York;  Er- 
rington, Hamerstrom  and  Hamerstrom  ( 1940), 
north  central  United  States;  Houston  (1971), 
Saskatchewan. 

Ferruginous  Hank.  Cameron  (1914),  Mon- 
tana; Bowles  and  Decker  (1931),  Angell  (1968), 
Washington;    Salt    (19.39),   Canada. 

Red-tailed  Hawk.  English  (1934),  Michigan; 
Fitch,  Swenson  and  Tillotson  (1946).  California; 
Austing  (1964),  North  America;  Luttich,  et  al., 
(1970),  Luttich,  Keith  and  Stephenson  (1971), 
Canada;    Scidensticker    (1970),    Montana. 

Swainson's  Hawk.  Cameron  (1908,  1913), 
Montana;  Bowles  and  Decker  (1934),  Wash- 
ington. 

Prairie  Falcon.  Decker  and  Bowles  (19.30), 
Washington;  Fowler  (1931),  California;  Bailey 
and  Niedraeh  (1933).  Webster  (1944),  Ender- 
son  (1964),  Colorado;  Edwards  (1968),  Alberta. 

Marsh  Hawk.  Breckinridge  (1935),  Minne- 
sota; Errington  and  Breckinridge  (1936),  north- 
central  United  States;  Hammond  and  Henry 
(1949),  North  D;ikota;  Hamerstrom  (1969), 
Wisconsin.  i 

Cooper'.s  Hawk.  McDowell  (1941),  Schrivcr 
(1969),  Pennsylvania;  Meng  (1959),  New  York 
and  Pennsylvania. 

S})arrow     Hawk.     Sherman     (1913),     Iowa;      i 
Rocst    (1957),    Oregon;    Endcrs(m    (1960),    II-      ' 
linois;    Heintzelman    (1964),    Heintzelman    and 
Nagv    (1968),    Pennsylvania;    Wilkmghbv    and 
Cade   (1964),   New  York. 

Short-eared  Owl.  Kitchin  (1919),  Washing- 
ton; Sinder  and  Hope  (19.38),  Toronto;  Lockic 


BiOLor.iCAi,  Sf.hies,  \'ol.   18,  No.  3        BuEEniNC.  Ecology  of  Utah  Raptohs 


(1955),  Scotland;  Johnson  (1956),  California; 
BorrtTO  (1962),  Colombia;  Short  and  Drcw- 
(1962),    Michigan;    Munyer    (1966),   Illinois. 

BurroiL'ing  Old.  Rhoades  (1892),  Florida; 
Errington  and  Bennett  (1935),  Scott  (1940), 
Iowa;  Grant  (1965),  Minnesota;  Coulombc 
(1971).  Thomsen   (1971),  California. 

Raven.  Oberholser  (1918),  North  America; 
Harlow  (1922),  Pennsylvania;  Bowles  and 
Decker  (1930),  Washington;  Nelson  (1934), 
Oregon;    Cushing    (1941),    California;    Parslow 


(1967),   Holyoak  and  Ratcliffe    (1968),    Great 
Britain  and  Ireland;  Ratcliffe  (1962),  England. 

Literature  pertaining  to  raptors  of  the  Great 
Basin  includes  egg-collecting  notes  (Wolf, 
1928);  population  studies  of  wintering  eagles 
(Edwards,  1969);  nesting  studies  of  the  Golden 
Eagle,  Great  Horned  Owl,  and  Ferruginous 
Hawk  (Murphy,  et  al.,  1969);  raptor  population 
trends  ( White,  1969a ) ;  and  notes  on  interactions 
between  Red-tailed  Hawks  and  Great  Homed 
Owls  (Smith,  1970). 


STUDY  AREA 


Location  and  Topography 

This  study  was  conducted  in  an  80-square- 
niile  section  of  the  eastern  edge  of  the  Great 
Basin  Desert  in  north  central  Utah.  It  included 
parts  of  Utah  and  Tooele  Counties,  in  Town- 
ships 7  and  8  South,  Range  3  West,  Salt  Lake 
base  and  Meridian  (Fig.  1).  The  area  chosen 
is  a  representative  portion  of  the  habitat  of 
this  part  of  the  Great  Basin.  Its  coverage  is 
thought  to  be  sufficient  to  enable  the  compila- 
tion of  an  accurate  record  of  the  raptor  species 
populations. 

The  topography  is  characterized  bv  broad, 
flat,  alkaline  valle\s  separated  b\-  high  ridges 
and  hills.  Its  major  ph\siographic  featines,  from 
east  to  west,  include  Cedar  Valley,  the  Thorpe 
and  Topliff  Hills  of  the  Tintic  Range,  and  Rush 
Valley.  Valley  elevations  range  from  4800  ft  in 
Cedar  Valley  to  5300  ft  in  Rush  Valle\ .  Maxi- 
mum elevations  were  6190  ft  in  the  Thorpe  Hills 
and  6453  ft  in  the  Topliff  Hills. 

A  major  feature  of  the  hills  was  tht-  numer- 
ous sandstone  and  limestone  cliffs  and  rock 
outcroppings  resulting  from  the  erosion  of  a 
series  of  Paleozoic  strata  ranging  in  age  from 
the  Lower  Cambrian  to  Upper  Pennsylvanian 
(Bullock,  1959;  Bissell,  et  al.,  1959)  (Fig.  2). 
A  second  striking  feature  of  the  hills  is  the  pres- 
ence of  several  large  quarries,  originally  mined 
for  clay,  calcite,  or  limestone,  but  long  since 
abandoned.  These  cjuarries  are  characterized  by 
steep,  sheer  walls  occasionalK'  reaching  over 
200  feet  in  height. 

Climate 

The  general  climatic  conditions  of  this  por- 
tion of  the  Great  Basin  have  been  characterizi'd 
by  Fautin  (1946)  and  Shelford  (1963).  The 
mean  annual  precipitation  is  16  inches  at  the 
extreme   northern   edge  of   the  study   area  and 


12  inches  over  the  majority  of  the  rest  of  the 
area.  Slight  local  variations  occur,  with  the  high- 
er elevations  receiving  larger  amounts  ( Feltis, 
1967).  Although  the  area  receives  some  snow- 
fall, most  of  the  moisture  falls  from  March 
through  May  and  July  through  August.  Ex- 
posure particularly  alters  the  pattern  with  re- 
spect to  snowfall  accumulation  and  persistence, 
and  north  facing  slopes  may  have  from  3  to  12 
inches  of  snow  for  over  a  month  after  southern 
exposures  are  bare. 

Approximate  annual  temperatures  range  from 
-30°C  to  65°C.  Wide  seasonal  and  daily  varia- 
tions occur,  amounting  to  as  much  as  30°C  or 
more  during  the  summer  months.  July  is  the 
hottest  month  of  the  year,  averaging  23°C.  Sub- 
zero temperatures  can  be  expected  for  short 
periods   from   December  through  mid-March. 

High  winds  are  a  common  feature  of  the 
early  spring  months  and  rnay  result  in  locally 
heavy  dust  stonns.  These  become  less  severe  but 
may  persist  throughout  all  months  of  the  year. 

Water  flow  is  ephemeral  and  no  permanent 
streams,  seeps,  ponds,  or  impoundments  are 
present  within  the  study  area. 

Vegetation 

Two  distinct  vegetational  associations  occur, 
the  northern  desert  shrub  and  the  dwarf  conifer 
communit\-.  The  desert  shrub  community  is 
present  over  lower  elevations  of  most  of  the 
valley  floors  and  consists  of  various  shrubs  and 
grasses  (Fig.  3).  Several  of  these,  becoming  lo- 
cally dominant  and  fonning  large,  continuous 
stands,  include,  in  order  of  their  importance, 
l)ig  sagebrush  (Artemisia  tridentata  ),  rabbit- 
i)rush  (Cliri/sothamnu.s  nau.scosu.s) ,  shadscale 
(Alriplex  confeitifolia).  i^reast'wood  {Sarcoha- 
ttis   vermiculatus) ,   winterfat    (Eurotia   hiiuita), 


HiuciiAM  Voi'SG  Univeivsity  Science  Bulletin 


Fig.   1.     Location,   topograpliv  .iiul   wgetation  of  flic  shulv  area. 


Hi(n.(H;K:\i.  Skhiks.  Vol.   18,  No.  3        Bueedinc  Kcologv  ok  Utah  IIaptoivs 


;l#^- 


Fig.  2.     \i(\\    of   a   portion   of   the   Thorpe    Hills,    showing    tho>    nnmeroiis 
anil    the   seattered    nature   of   the   Pinyon-Juniper   community. 


limestone    and    sandstone    cliff    lines 


Russian  thistle  (Salsola  kali)  ami  hoisobriisli 
{Tctnuhjmia  ghibnita).  Both  Indian  liccgiass 
(On/zopsis  hijmenoides)  and  cheat  gias.s  {Bro- 
mus  tectorum)  arc  present  throughout  most  of 
the  shrub  stages,  with  the  latter  apparently  in- 
creasing its  coverage  ( Christensen  and  Hutchin- 
son. 1965). 

The  better  drained  slopes  and  hills  support 
the  pigm^'  conifer  forest  or  woodland  biome 
(Kendeigh,  1961  j.  Tiiis  is  characterized  by  the 
uniform  physiognomy  of  its  principal  species,  the 
two  most  important  being  Utah  juniper  {Juni- 
pertis  osteospcrma)  and  pinyon  pine  (Pimi.i 
mdnoplu/Ua).  The  trees  average  approximately 
10-1.3  ft  in  height  and  occur  in  stands  varying 
in  densit\-  from  10  to  100  trees  per  acre  ( Smith, 
1968).  Important  shrubs  of  the  underston'  in- 
clude matchweed  (Gutierrczia  sarothrac)  and 
Ephedra  {Ephedra  sp. ).  Other  components  pres- 
ent in  lesser  amounts  include  cliffrose  (Cowania 
mcxicana)  and  mountain  mahogany  (Cercocar- 
ptts  ledif alius). 

Faunal  Elements 

Fautin  (1946)  listed  a  total  of  i286  animals 
known  to  occur  in  the  northern  desert  shrub 
communit\',  including  28  mammals,  45  birds 
(exchisi\'e  of  the  raptors  and  aquatic  species), 
10  reptiles  and  203  insects.  Most  of  these  also 
occur  within  the  pinvon-juniper  community 
which   to  dat(^  has   recei\ed  no  in-depth  study 


in  this  area.  Hardy  ( 1945 )  did  record  79  bird 
species  of  the  pigmy  conifers  and  noted  that  14 
species  were  summer  residents. 

The  major  mammalian  herbivores  include  the 
mule  deer  (Odocoilciis  hemiomts),  black-tailed 
jackrabbit  (Lepus  califoruicus),  Townsend's 
ground  squiiTcl  {Spermo])hilus  townsendi),  an- 
telope ground  squirrel  [Ammospermophilus 
leucunis),  desert  cottontail  {Sylvilagus  audu- 
houi),  and  desert  wood  rat  {Dipodomys  sp. ), 
pocket  mouse  (Perognathus  sp.),  and  several 
miuids  and  cricetids.  Carnivores  other  than  rap- 
tors include  the  mountain  lion  (Felts  concolor), 
coyote  (Canis  latrans),  kit  fox  (Vulpes  macro- 
tis),  bobcat  {Lynx  mfiis),  and  badger  {Taxidea 
taxus).  Two  of  the  more  common  summer  bird 
species  include  the  Honied  Lark  {Eremophila  al- 
f)cstris)  and  Mourning  Dove  {Zenaidura  ma- 
croura).  Common  reptile  species  include  the 
gopher  snake  {Pituophis  melanoleucus),  striped 
racer  {Coluber  taeniatus),  collared  lizard 
(Crotaphytus  collaris),  and  Uinta  lizard  {Uta 
stamburiana) . 

Human  Utilization 

Two  small  settlements  are  present  immedi- 
ately northeast  of  the  study  area  and  portions  of 
the  adjacent  land  are  dry-fanned,  but  the  most 
important  human  activities  include  livestock 
raising  and  hunting.  Most  of  the  valleys  and 
lower  elevations  are  seasonally  utilized  for  sheep 


HiuciiAM  VouNG  Univeksity  Science  Bulletin 


range  and  are  heavily  overgrazed.  In  addition, 
the  direct  infkicncc  of  Hvestock  interests  has 
resulted  in  the  initiation  of  predator  control 
programs  and  govennnent  trappers  periodically 
remove  coyotes,  bobcats,  and  kit  foxes. 


Recreational  hunting  activities  assume  major 
proportions.  Almost  all  parts  of  the  area  are 
accessible  by  graded  dirt  roads,  and  large  num- 
bers of  deer  hunters  in  season  and  rabbit  hunters 
throughout  the  year  utiUze  the  area  for  sport. 


ii'-?«'»gT;s.'«.: 


Fig.    .3.      Sagebrush    ami    IniiR-hgrass    comiiiuiiit\    iif   Cedar  X'allev. 


METHODS 


The  stud\'  was  conducted  from  December 
1966  until  August  1970.  Most  of  the  field  work 
took  placi'  duiing  the  four  breeding  seasons  but 
observations  were  recorded  during  every  month 
of  the  year.  Intensive  field  work  began  in  De- 
cember of  each  \  ear  and  continued  through 
August.  During  this  time  at  least  weekK'  or  bi- 
weekly \isits  were  made,  but  often  the  observa- 
tion periods  were  more  frequent.  Throughout 
the  four  breeding  seasons  the  longest  interval  of 
time  between  successive  visits  was  13  days  in 
April  1970, 

Field  data  cards  were  designed  and  printed, 
and  copies  of  that  portion  of  the  study  area 
mapped  by  the  U,S.  Geological  .Survey  were 
Xeroxed.  All  observations  on  raptor  nests,  ac- 
tivities, and  locations  were  recorded  on  them 
and  supplemt^nted  by  tape  recorded  notes. 

The  major  task  of  the  observer  during  each 
breeding    season    involved    the    location    of    all 


raptor  nests.  These  were  found  by  systematically 
searching  all  potential  nest  sites;  that  is,  all  cliff 
lines,  rock  outcioppings,  and  wooded  areas  were 
methodicalh'  examined.  Discovered  nests  were 
plotted  on  an  area  survey  map,  then  gaps  in 
the  distribution  wen-  intensively  reexamined 
lor  missed  nests  or  signs  of  raptor  activit\'  sev- 
eral times  dmintr  the  breedini:  season.  Addi- 
tional  techniques  were  employed  to  discover 
nests;  these  included  observations  of  behavioral 
patterns  (particularK  displays  and  tiTritorial 
postures),  the  mapping  of  old  nests,  and  the 
utilization  of  a  fixed  wing  monoplane  for  aerial 
surve\s.  The  latter  proved  to  be  of  limited  use, 
due  prinuuilv  to  its  miniminn  speed  and  altitude 
re(|nirenu'nts,  but  was  useful  in  checking  the  oc- 
cupane\'  of  nests  of  the  previous  years. 

Instances  in  which  apparently  nonnesting 
pairs  or  individuals  were  occupying  an  area 
necessitated  numerous  additional  and  time-con- 


Biological  Stints,  \ol.   18,  \i 


BiittDJNc;  Ecology  of  Utah  Haitous 


suming  checks  to  ensure  the  accuracy  of  their 
status.  Apparent  transients  required  similar  ef- 
forts. 

Certain  raptor  species  required  proportion- 
all\'  greater  efforts  than  others  in  locating  their 
nests.  This  proved  to  be  particularly  true  of  the 
Great  Homed  Owl  and  Short-cared  Owl.  Their 
secluded  nest  sites  and  nocturnal  habits  re- 
quired several  earlv  morning  and  late  evening 
visits  in  an  effort  to  locate  hooting  males.  Baum- 
gartner  (1939)  and  Errington  (1932b)  employed 
this  method  successfully  in  other  habitats,  but 
the  extreme  ruggedness  of  most  of  the  study 
area  terrain  allowed  only  partial  success.  How- 
ever, both  owl  species  were  observed  occasion- 
ally during  these  two  time  periods,  particularly 
on  overcast  davs  or  on  rainy  or  snowv  days.  In 
contrast,  Burrouing  Owls  were  easily  located 
because  of  their  great  diurnal  activit\',  more  ac- 
cessible nesting  sites,  and  the  habit  of  one  or 
both  of  the  adults  of  roosting  atop  or  alongside 
the  burrow.  Onl\  t\\'o  of  the  diurnal  raptors,  the 
Marsh  Hawk  and  Sparrow  Hawk,  presented 
problems  with  respect  to  the  location  of  their 
nests.  Both  species  are  conspicuous  during  their 
daily  acti\'ities  but  verv  secretive  relative  to  the 
actual  location  of  their  nests.  These  were  most 
easily  found  by  continuous  observation  of  the 
adult  pairs,  one  of  which  would  eventually  re- 
turn to  the  nest  site.  Three  of  the  Marsh  Hawk 
nests  were  found  only  after  the  increased  de- 
velopment of  the  \oung  had  rendered  their  loca- 
tion conspicuous. 

The  tendencN'  of  raptors  to  reoccupy  their 
nest  sites  and  territories  (to  be  discussed  in 
detail  later)  greatly  facilitated  the  task  of  lo- 
cating nests  during  the  last  three  years  of  study. 

Data  used  to  compute  the  raptor  activity 
timetables  is  based  primariK'  on  the  more  readily 
accessible  nests.  In  addition,  the  necessary  time 
period  between  field  observation  days  promotes 
a  possible  time  error  of  two  days.  Tlie  presence 
of  the  investigators  may  have  accelerated  some 


events  in  the  nesting  cycle,  with  the  fledging 
period  being  particularly  vulnerable  to  change. 

Raptor  territories  and  food  habits  were  de- 
termined during  the  nesting  seasons  of  1969  and 
1970.  Territories  were  plotted  by  observations 
of  pair  activities  from  blinds  and  by  plotting 
sight  locations.  The  points  of  maximum  distance 
from  the  nest  site  were  then  connected  and  the 
encompassed  area  determined  with  a  compen- 
sating polar  planimeter.  The  determined  terri- 
tory has  been  described  as  maximum  territory 
(Odum  and  Kunezler,  1955)  or  home  range 
(Craighead  and  Craighead,  1956).  Food  habits 
of  all  raptors  were  determined  by  weekly  tabu- 
lations of  prey  items  and  analyses  of  pellets 
gathered  from  the  nest  site.  Again  the  more  ac- 
cessible nests  were  checked  most  frequently. 
After  the  prey  had  been  identified  and  counted 
it  was  removed  from  the  nest.  An  exception  was 
to  leave  fresh  prey  for  the  young,  after  marking 
it  for  identification.  Pellet  contents  were  identi- 
fied by  comparison  with  specimens  of  the  Brig- 
ham  Young  University  Life  Sciences  Museum 
collection,  following  techniques  described  by 
Errington  (1930,  1932a),  Glading,  Tillotson  and 
Sellech  (1943),  and  Moon  (1949).  Dr.  V.  A. 
Nelson,  entomologist.  Southern  Connecticut 
State  College,  New  Haven,  Connecticut,  assisted 
in  the  identification  of  some  insect  remains. 

All  statistical  analyses  followed  programs  for 
the  Epic  Model  .3000  computer  except  regres- 
sion, which  was  determined  using  Fortran  pro- 
grams. Numerical  data  within  the  text  is  normal- 
ly presented  as  mean  data,  followed  by  the  stan- 
dard error,  sample  number,  and  range.  The  "t" 
test,  anah'sis  of  variance  and  chi-square  tests 
were  used  to  compare  data,  and  linear  regression 
analysis  was  used  to  test  the  significance  of 
correlated  variables.  The  level  of  significance  is 
0.05  unless  otherwise  noted.  All  analytical  meth- 
ods are  discussed  by  Goldstein  ( 1964 )  and 
Simpson,    Roe,   and   Lewontin    ( 1960 ) . 


RESULTS 


Basic  Population  Data 

The  study  area  supported  a  total  of  .354  in- 
dividuals of  12  raptor  species  during  the  four 
years  of  study.  This  included  141  nesting  pairs, 
20  nonnesting  pairs  and  32  individuals.  The 
species  breakdown  was  as  follows:  Golden 
Eagle,  17  pairs;  Great  Homed  Owl,  31;  Fer- 
ruginous Hawk,  40;  Red-tailed  Hawk,  26;  Swain- 
son's  Hawk,  5;  Prairie  Falcon,  3;  Marsh  Hawk, 


5;  Cooper's  Hawk,  I;  Sparrow  Hawk,  10;  Short- 
eared  Owl,  1;  Burrowing  Owl,  6;  Raven,  16. 

Population  Composition  and  Density 

Annual  species  populations  are  presented  in 
Tables  \-4.  Both  the  total  nesting  population 
and  the  number  of  nesting  species  varied  from 
year  to  year.  The  collective  raptor  population 
consisted  of  8  species   in   1967  and   1968,  9  in 


8 

Biuf:ii,\M   VouNC   I'nivehs 

nv  S(:ii-.N(  K 

Bulletin 

Table   1 .     Summarv 

of  raptor 

nesting  populations.   1967. 

No. 

No.    of 

No. 

No. 

No.   re- 

No.  successful 

No.   of  nests 

No.    sq. 

Species 

of 

nesting 

single 

nesting 

nesting 

nesting 

incomplete 

miles  per 

pairs 

pairs 

birds 

failures 

attempts 

attempts 

histories 

pair 

Golden  Eagle 

4 

3 

1 

1 

0 

_ 

0 

20 

Great  Horned  Owl 

5 

4 

1 

0 

- 

- 

0 

16 

Ferniijinous  Hawk 

8 

8 

2 

3 

0 

- 

0 

10 

Red-tailed  Hawk 

5 

4 

0 

0 

0 

- 

0 

16 

Swainson's   Hawk 

1 

1 

0 

0 

- 

- 

0 

80 

Prairie  Kalcon 

0 

- 

1 

- 

- 

- 

- 

- 

Marsh  Hawk 

0 

_ 

1 

_ 

_ 

_ 

_ 

_ 

Cooper's  Hawk 

1 

1 

0 

? 

? 

- 

1 

80 

Sparrow  Hawk 

4 

3 

1 

1 

0 

_ 

1 

20 

S  lort-eared  Owl 

0 

_ 

2 

_ 

_ 

_ 

_ 

_ 

Burrowing  Owl 

0 

- 

1 

- 

- 

- 

- 

_ 

Raven 

4 

4 

0 

0 

- 

- 

0 

20 

Totals 

32 

28 

10 

5 

0 

- 

2 

- 

Table  2.     Summary 

of  raptor 

nesting  populati 

ons,   1968. 

No. 

No.    of 

No. 

No. 

No.   re- 

No.  successful 

No.   of  nests 

No.    sq. 

Species 

of 

nesting 

single 

nesting 

nesting 

lencsting 

incomplete 

miles  per 

pairs 

pairs 

birds 

failures 

attempts 

.lUeiupts 

histories 

pair 

Golden  Eagle 

4 

4 

2 

0 

0 

0 

20 

Great  Horned  Owl 

10 

9 

5 

0 

0 

2 

8 

Ferruginous  Hawk 

10 

9 

2 

0 

0 

0 

8 

Red-tailed  Hawk 

i 

7 

3 

2 

1 

1 

11 

Swainson's  Hawk 

1 

1 

0 

- 

0 

0 

80 

Prairie  Falcon 

1 

1 

1 

0 

0 

0 

80 

Marsh  Hawk 

0 

- 

- 

- 

_ 

- 

- 

Cooper's  Hawk 

0 

- 

- 

- 

- 

- 

- 

Sparrow  Hawk 

3 

3 

1 

0 

0 

0 

27 

S  lort-earcd  Owl 

0 

- 

- 

- 

0 

- 

- 

Burrowing  Owl 

0 

- 

- 

- 

- 

- 

- 

Raven 

4 

4 

0 

0 

- 

- 

0 

20 

Totals 

40 

38 

6 

14 

2 

1 

3 

- 

Table  3.     Summary  of  raptor  nesting  populations,   1969. 


Species 


No. 

of 

pairs 


No.    of 

nesting 

pairs 


No. 
single 
birds 


No. 
nesting 
failures 


No.   re-        No.  successful   No.   of  nests        No.   sq. 
nesting  nesting  incomplete         miles   per 

attempts  attempts  histories  pair 


Golden   Eagle  .54121 

Great  Horned  Owl  S  8  1                    2                     0 

Ferruginous  Hawk  13  12  1                    2                     0 

Bed-tailed  Hawk  7  6  12                     1 

Swainson's  Hawk  2  2  12                     0 

Piairic  I'aleon  0  -  1                      —                      - 

Marsh  Hawk  2  2  0                    10 

(.'ooper's   Hawk  0  -  0                     -                      - 

Sparrow  Hawk  2  2  2                    10 

Short-eared  Owl  0  -  1                    -                     - 

Burrowing  Owl  3  3  0                    10 

Raven  4  4  110 

Totals  46  43  10                 14                   2 


0 


16 
10 
6 
11 
40 

40 

40 

27 
20 


1969,  and  11  in  1970.  Only  7  of  the  12  species 
nested  in  all  four  study  \ears.  Of  the  more 
sporadic  nesters,  3,  the  Prairie  Falcon,  Marsh 
Hawk  and  Burrowing  Owl,  nested  during  two 
of  the  four  years  (not  necessarily  consecutively ) 
and  2,  the  Short-eared  Owl  and  Cooper's  Hawk, 
nested  in  only  one  of  the  four  \(\irs.  .Ml,  how- 
ever,   were    represented    bv    either    nonnesting 


pairs  or  individuals  during  one  or  more  of  their 
nonbreeding  \ears,  and  are  therefore  considered 
to  be  a  minor  but  nonnal  element  of  the  raptor 
breeding    population    of    this    area. 

The  minimum  and  maximum  sizes  of  the 
total  raptor  population  varied  from  74  to  102 
iiidi\icluals  and  from  32  to  46  pairs.  Individuals 
coiniiioiiK    comprised   from   9  to    13  percent  of 


Bioi.or.icAi,  SiiiiiEs,  Vol.   IS,  No.  .3        Hui  i  dino  Ecology  ok  I'nii  H.^i'tou.s 
Table  4.     Summary  of  raptor  nesting  populations,   1970. 


No. 

No.    of 

No, 

No. 

No.    re- 

No.  successful 

No.    of  nests 

No.    sq. 

Specie.s 

of 

nesting 

single 

nesting 

nesting 

nesting 

incomplete 

miles    per 

pairs 

pairs 

birds 

failures 

attempts 

attempts 

histories 

pair 

Golden  Eagle 

4 

3 

0 

0 

_ 

_ 

0 

20 

Crt-at  Horned  Owl 

8 

6 

19 

3 

1 

1 

0 

10 

Kemiginous  Hawk 

9 

y 

2 

2 

0 

- 

0 

9 

Ked-lailed  Hawk 

( 

4 

0 

1 

0 

(1 

0 

11 

SwainsDiis   Hawk 

1 

1 

1 

0 

- 

- 

0 

80 

Prairiu  Falcon 

2 

2 

0 

1 

0 

- 

0 

40 

Marsh  Hawk 

3 

2 

1 

1 

1 

0 

1 

27 

Cooper's  Hawk 

0 

- 

1 

- 

- 

- 

- 

- 

Sparrow  Hawk 

1 

1 

1 

0 

- 

- 

- 

80 

Short-eared  Owl 

1 

1 

0 

1 

0 

- 

0 

80 

Burrowing  Owl 

.3 

3 

0 

1 

0 

_ 

0 

27 

Raven 

4 

■-) 

0 

0 

- 

- 

0 

20 

Totals 

43 

32 

24 

10 

2 

1 

1 

- 

the  total  population.  Raptor  populations  in- 
creased from  1967  (32  pairs,  10  individuals)  to 
1969  (46  pairs,  10  individuals)  and  then  de- 
clined slightly  in  1970  (43  pairs,  6  individuals). 
The  peak  number  of  nesting  raptor  species  did 
not  coincide  with  the  peak  raptor  populations 
but  rather  occurred  one  year  later.  The  yearly 
variation  in  populations  was  due  in  part  to  some 
shifting  of  raptor  nesting  sites  onto  the  study 
area  from  previous  nesting  sites  and  territories 
immediatelv  adjacent  to  the  study  area.  Other 
possible  reasons  will  be  discussed  later. 

Five  species,  the  Golden  Eagle,  Great  Horned 
Owl,  Ferruginous  Hawk,  Red-tailed  Hawk  and 
Raven  comprised  over  81  percent  of  the  average 
vearlv  raptor  populations.  Of  these,  the  Fernigi- 
nous  Hawk  was  consistently  the  numerically 
dominant  raptor,  averaging  approximatel\'  25 
percent  of  the  annual  breeding  population.  The 
next  most  numerous  species  were,  in  order  of 
their  abundance,  the  Great  Homed  Owl  (which 
approximated  over  19  percent).  Red-tailed 
Hawk,  Golden  Eagle,  and  Raven.  Of  the  re- 
maining raptors.  Sparrow  Hawks  were  almost 
twice  as  abundant  as  Swainson's  Hawks,  Marsh 
Hawks,  and  Burrowing  Owls,  while  the  Cooper's 
Hawk  and  Short-eared  Owl  were  relatively  rare 
breeding  elements.  Although  a  conspicuous 
pemianent  resident,  the  Prairie  Falcon  rarely 
achieved  breeding  status  and  comprised  less 
than  t\\'0  percent  of  the  average  yearly  breed- 
ing population.  The  relative  percent  composition 
of  the  large  raptors  varied  only  slightly  and 
each  species  maintained  its  proportional  abun- 
dance during  the  four  study  years.  Thus  the 
population  increase  from  1967  to  1969  reflected 
a  similar  increase  in  the  number  of  pairs  of 
each,  with  the  notable  exception  of  the  Raven 
population,  whicli  remained  stal)le.  The  limited 
populations  of  the  smaller  raptors  prevent  clear- 
cut  evaluations.  Both  the  Marsh  Hawk  and  Bur- 


rowing Owl  populations  became  established  dur- 
ing the  last  two  study  years,  but  the  Sparrow 
Hawk    population    declined. 

Yearly  population  densities  averaged  0.5  pairs 
per  square  mile  (range  0.4-0.58),  based  on  the 
80-square-mile  study  area.  However,  approxi- 
mately one-half  of  the  area  was  apparently  not 
utilized  for  any  purposes  by  the  nesting  rap- 
tors. This  was  particularly  true  of  the  lower 
\'alley  elevations  which  were  situated  far  from 
potential  nesting  sites.  If  this  area  were  elimi- 
nated from  the  determinations,  then  the  raptor 
nesting  densities  would  be  increased  to  1.0  pairs 
per  square  mile  (range  0.8-1.16). 

Seasonal  Activity  Timetables 

Winter  Populations.  Central  Utah  supports  a 
large  and  varied  winter  raptor  population.  Im- 
portant permanent  year-round  residents  winter- 
ing in  the  area  include  Golden  Eagles,  Ravens, 
Great  Homed  Owls,  and  Prairie  Falcons.  Gold- 
en Eagles  and  Ravens  occur  singly  or  in  small 
groups  of  two  to  five  individuals.  Some  Golden 
Eagles  may  form  hunting  contacts  and  share 
communal  roosts  with  Bald  Eagles  {Haliaetus 
leucocephahis).  Estimated  average  yearly  win- 
ter populations  of  each  were  13  Golden  Eagles 
and  9  Ravens.  In  contrast.  Great  Horned  Owls 
and  Prairie  Falcons  were  less  common.  A  few 
Great  Homed  Owls  were  flushed  in  the  vicinity 
of  their  nesting  site  of  the  previous  year  and  a 
single  Prairie  Falcon  was  obsei-ved  every  year, 
occupying  a  large  winter  territory  in  Cedar  Val- 
ley. It  was  occasionally  obser\'ed  hunting  among 
flocks  of  Homed  Larks  and  Dickcissels  (Spiza 
americana). 

Large  influxes  of  Bald  Eagles  and  Rough- 
legged  Hawks  {Buteo  lagopus)  began  arriving 
in  the  valleys  in  late  November  and  December. 
These  conspicuous  winter  residents  rosted  com- 


10 


Biur.iiAM  YouNC  Uni\  i-.nsirv  Scmknc:!-.  Bi'i.i.etin 


munallv  in  canyons  and  lightlv  wooded  areas 
near  settlements.  Dnriiig  the  daylight  hours  the\' 
ranged  widely  to  hunt  in  the  \allevs,  returning 
to  a  communal  roost  shortly  before  dark  ( Ed- 
wards, 1969).  Estimated  populations  of  each  in 
the  study  area  were  30  Bald  Eagles  and  18 
Rough-legged  Hawks. 

Winter  live  trapping  studies  revealed  5  Long- 
eared  Owls  ( Asio  ottis ) ,  and  a  number  of  Short- 
eared  Owls.  The  latter  were  frequently  observed 
(up  to  8  individuals  per  group)  ranging  out- 
ward from  their  diurnal  communal  roosting 
sites  during  the  late  evening  hours. 

An  average  of  25  Marsh  Hawks,  2  Shai^p- 
shinned  Hawks  (Acripitcr  striatus),  3  Red-tailed 
Hawks,  1  Ferruginous  Hawk,  and  1  Screech  Owl 
(Ottis  asio)  were  present  in  the  \'alleys  during 
the  winter  months.  The  Marsh  Hawk  popula- 
tions indicated  a  major  influx  of  this  species  into 
the  area  during  the  winter,  but  the  status  of  the 
wintering  Red-tailed  Hawks  and  Ferruginous 
Hawks  was  uncertain.  Two  of  tlie  Red-tailed 
Hawks  wintered  in  the  yieinit\'  of  a  previously 
used  Red-tailed  I  lawk  nesting  site  and  ma\  have 
been  permanent  residents. 

The  populations  of  these  winter  residents 
fluctuated  and  appeared  to  be  related  to  climatic 
changes,  particularly  temperature.  Their  num- 
bers declined  sharply  in  late  JanuaiT  and  earl\' 
February,  and  they  left  the  area  by  mid-March, 
a  transition  coinciding  with  the  arrival  and 
rapid  buildup  of  the  breeding  populations. 

Transients.  Known  transients,  including  Red- 
tailed,  Swainson's,  and  Cooper's  Hawks  were  ob- 
served from  late  Februan"  to  carK'  Maw  Large 
numbers  of  transient  Sparrow  Hawks  were  ob- 
served between  early  April  and  mid-Ma\-,  simul- 
taneously with  the  arri\al  of  tlie  breetliiiu 
population  of  Sparrow  Hawks.  A  single  Osprev 
{Pdiuliiin  liali(ictus)  was  observed  roosting  in  a 
dead  cottonwood  in  Cedar  Valley  on  29  April 
in  the  late  e\-ening  and  presumabh'  roosted 
overnight.  The  niajorit\'  of  the  transients  re- 
mained onK  one  or  two  da\s  in  the  area,  par- 
ticularh'  those  observed  later  in  the  breeding 
season. 

Activitij  timetables.  The  \cdv\v  aeti\'it\-  tiTne- 
tables  of  the  raptor  populations  are  presented 
in  Tables  .5-8.  The  breeding  activities  of  the 
populations  occurred  over  a  period  of  eight 
months  and  avi'raged  202.7  da\s  a  year  (range 
163-22S  da\s).  Ho\\e\er.  the  in(li\idual  species 
activities  occupied  only  a  portion  of  this  period. 
.\lthough  slight  yearly  variations  in  the  timing 
and  duration  of  the  events  of  the  nesting  c\cle 
were  evident,  the  chronological  sequene(>  of 
each    raptor    species    reniaincxl    essentialh     un- 


changed with  respect  to  the  total  raptor  popu- 
lations. 

Golden  Eagles  and  Great  Horned  Owls  were 
the  first  raptors  to  initiate  their  nesting  activity. 
Golden  Eagles  were  observed  occupying  their 
territories  as  early  as  20  Januars',  and  courtship 
displa\s  were  observed  from  this  time  onward. 
Their  nests  were  constnicted  or  rebuilt  in  Febru- 
ary and  early  March  and  decorated  with  green- 
ery. A  Great  Horned  Owl  was  recorded  on  its 
nest  site  of  the  previous  year  on  2  December 
and  pair  fonnation  had  occurred  as  early  as  10 
January  in  some  years.  Average  egg  deposition 
dates  for  both  species  ranged  from  mid-February 
to  earl\'  March,  with  Golden  Eagles  generally 
preceding  Great  Honied  Owls  b\-  one  or  two 
weeks. 

Red-tailed  and  Fenaiginous  Hawks  were  the 
first  of  the  migrator\-  raptors  to  arri\'e  in  the 
study  area  each  year.  The  first  Red-tailed  Hawks 
were  observed  in  the  vicinit\'  of  previous  nesting 
sites  during  the  first  week  in  Febniar)'  and  were 
paired  within  one  or  two  weeks,  .^t  this  time 
pairs  would  react  aggressively  when  the  nest 
site  was  approached,  screaming  and  soaring  in 
increasingly  higher  circles  overhead.  Onl\'  three 
pairs  were  observed  constructing  nests,  but  the 
process  was  a  mutual  activit\',  with  both  mem- 
bers of  a  pair  transporting  juniper  branches  to 
the  nest  site.  Eggs  were  usually  deposited  in 
late  March  and  earlv  April.  Tlu'  first  Ferrugi- 
nous Hawks  were  obsened  from  two  to  five 
weeks  later,  usually  during  the  first  week  in 
March  but  as  earl\  as  25  February.  Eggs  were 
usualK  deposited  in  mid-.\pril.  As  with  Red- 
tailed  Hawks,  nests  were  constructed  rapidly 
In-  both  members  of  a  pair  until  finished,  usual- 
K  within  one  to  three  da\s.  Both  species  were 
higliK  secretive  during  nest  eonstniction  and 
if  intirrupted  would  fre(iuentl\'  stop  building 
activities  and  begin  another  nest  at  a  new  site. 
FiMruginous  Hawks  exhibited  a  greater  tenden- 
e\  to  abandon  newly  constructed  nests  ( 12  oc- 
eurrenc(\s)  than  Red-tailed  Hawks  (5  occur- 
rences ) . 

Swainson's  Hawks  were  the  last  of  the  Buteos 
to  nest,  appearing  in  the-  \alle\s  in  earlx  and 
inid-.\pril  and  beginning  their  nesting  between 
two  and  three  weeks  later. 

Of  the  medium  and  small  sized  raptors,  the 
Ra\-ens  were  the  first  to  begin  nesting,  usually 
from  late  Februarv-  to  mid-Mareh.  Fairs  of  Prai- 
rie Falcons  and  Marsh  Hawks  were  observed 
in  late  March  and  early  April.  The  Prairie  Fal- 
cons were  \er\  aggressive  at  this  time  both 
toward  humans  and  other  raptors,  particularly 
(ireat    Horned   (a\]s.   which   if   flusliefi   were  at- 


Biological  Stiuii.s,  \'ol.   KS,  \i 


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Biological  Sf.hiks.  Vol.   IS,  No.  3       Bkeedino  Ecology  oi'  Ut.mi  Uai'toiis 


13 


tacked,  although  no  actual  contacts  were  ob- 
served. The  1969  egg  deposition  dates  of  the 
Marsh  Hawk  were  computed,  using  the  results 
from  the  1970  data  for  this  species.  Individual 
Short-eared  Owls  were  observed  in  the  vicinity 
of  their  nesting  territon'  in  the  first  week  in 
March,  and  activit)'  dates  computed  from  the 
data  of  Bent  (1938)  and  Craighead  and  Craig- 
head ( 1956 )  indicate  that  egg  deposition  oc- 
curred within  three  weeks.  Sparrow  Hawks 
were  observed  as  early  as  10  April,  perched  on 
conspicuous  locations  in  the  vicinity  of  their 
future  nesting  sites.  Pair  bonding  had  occurred 
by  27  April  and  egg  deposition  from  two  to 
three  weeks  later.  By  late  April  Burrowing  Owls 
were  seen  roosting  beside  the  entrance  to  their 
nest  holes  and  protested  vigorously  when  in- 
vestigated. Their  activity'  timetables  were  com- 
puted from  the  date  of  fledging  on  the  basis 
of  data  given  by  Bent  (1938). 

Only  egg  dates  are  available  for  the  Cooper's 
Hawk,  but  backdating  31  days  (average  from 
Craighead  and  Craighead,  1956)  suggests  that 
in  this  area  their  territories  are  selected  by  mid- 
April. 

The  breeding  raptor  populations  were  well 
established  by  April  and  Mav,  which  were  the 
months  of  ma.\inium  activity.  By  late  May  and 
early  June  nests  of  the  Great  Horned  Owl  were 
terminated  with  the  fledging  of  the  voung.  By 
the  end  of  June  and  the  first  week  of  July, 
Red-tailed  Hawks,  Ferruginous  Hawks,  Golden 
Eagles,  Ravens,  Prairie  Falcons,  and  Marsh 
Hawks  had  all  completed  their  nesring  activities, 
and  Swainson's  Hawks,  Burrowdng  Owls,  and 
Sparrow  Hawks  had  finished  their  nesting  ef- 
forts bv  late  July  and  earlv  August. 

The  newly  fledged  young  of  most  species 
remained  within  the  nesting  tcnitor\-  for  a  period 
after  fledging  and  were  frequently  seen  in  fam- 
ily hunting  groups.  Defense  of  the  young  by 
adults  was  particularly  strong  during  this  time 
period  but  gradually  lessened.  Within  three  to 
five  weeks  the  young  had  drifted  out  of  the 
nesting  area  and  into  other  parts  of  the  valley. 

The  migratory  species  began  moving  out  of 
the  area  in  late  August  and  early  September. 
Their  replacement  by  the  first  elements  of  the 
wintering  population  was  not  as  sudden  as  the 
spring  transition,  and  the  interim  raptor  popu- 
lations consisted  only  of  pemianent  residents 
which  were  consequently  comparatively  low  in 
number. 

Nest  Site  Requirements 

Spatial  Disirihution.  Figures  4-7  show  the 
\early  distribution  of  raptor  nests   (all  species) 


on  the  study  area  and  clearly  indicate  that  the 
nests  were  unevenly  distributed.  The  majority 
of  sites  were  present  at  middle  and  higher  ele- 
vations and  consistently  distributed  along  the 
periphery  of  the  central  mountains  or  within  the 
woodland.  Only  Burrowing  Owl,  Marsh  Hawk, 
and  Fenuginous  Hawk  (one  nest)  nest  sites 
were  present  in  the  valleys,  below  the  fringes 
of  the  Pinyon-Juniper  woodland. 

Nest  Site.  The  nest  site  selections  of  the  12 
raptor  species  are  summarized  in  Table  9.  The 
raptors  nesting  on  the  study  area  utilized  a  wide 
variety  of  sites,  but  some  species  exhibited  a 
narrower  range  of  selection  than  others.  Actual 
sites  chosen  by  one  or  more  species  included 
cliffs,  quarries,  abandoned  mining  structures, 
trees,  burrows,  or  the  ground. 

Almost  35  percent  of  the  nesting  sites  se- 
lected were  located  in  cliffs.  The  choice  of  cliff 
sites  by  five  of  the  raptor  species  appears  to  be 
related  to  several  factors,  including  the  physiog- 
raphy of  the  cliff,  its  vertical  height,  aspect, 
position,  altitude,  and  height  above  the  valley 
floor.  Excluding  the  rock  walls  of  quarries,  which 
are  actually  artificial  structures,  the  maximum 
height  of  cliffs  within  the  study  area  did  not 
exceed  150  feet,  and  the  great  majority  averaged 
less  than  50  feet.  Two  distinct  types,  sandstone 
and  limestone,  are  present.  Limestone  cliffs, 
because  of  their  distinctive  weathering  patterns 
which  result  in  numerous  crevices  and  ledges, 
provided  greater  numbers  of  suitable  nesting 
sites  and  were  heavilv  utilized  bv  the  raptors. 
The  position  of  the  cliff  refers  to  its  remoteness. 
Cliff  sites  which  overlooked  the  valleys  were 
preferred  over  similar  cliffs  located  in  the  in- 
terior of  the  hills.  Sites  were  frequently  chosen 
in  the  first  large  cliff  (over  20  feet  high)  above 
the  valley  floor.  This  was  particularly  evident  in 
locations  where  several  cliff  lines  were  available 
at  increasingly  higher  elevations  in  stairstep 
fashion. 

Several  abandoned  quarries  within  the  study 
area  were  utilized  for  nesting  sites  by  at  least 
six  of  the  raptor  species.  The  amount  of  use 
was  related  to  the  size  and  ruggedness  of  the 
quarr\-  walls  and  was  apparently  independent 
of  the  amount  of  human  disturbance.  The  larg- 
est quarries  were  utilized  simultaneously  by 
two  or  three  raptor  species  ever\'  year. 

Trees  were  also  a  common  nesting  site  (34.6 
percent)  on  the  study  area.  The;  majorit)'  were 
located  in  junipers,  the  predominant  tiees  in  the 
area,  but  a  few  were  constmcted  in  pinyon, 
cliffrose,  and  cottonwood.  Nests  in  jimipers  and 
cliffrose  were  most  frequently  constructed  in 
the    tops    of   the    trees,    approximately    11    feet 


14 


BiuGiiAM  Young  University  ScitNCE  Bulletin 


1 

2 

3 

4 

5 

6 

7 

8 

9 
10 
11 
12 

\_J      nesting  pairs 

I      I      non-nesting  pairs 

/\     individuals 


Golden  Eagle 
Great  Horned  Owl 
Ferruginous  Hawk 
Red-tailed  Hawk 
Swainson's  Hawk 
Prairie  Falcon 
Marsh  Hawk 
Cooper's  Hawk 
Sparrow  Hawk 
Short-eared  Owl 
Burrowing  Owl 
Raven 


Fig.  4.     Distribution    of     the    raptor    breeding    population  in  1967. 


Biological  Series,  \'ni,    18.  No.  3       Bueeding  Ecology  of  Ut..\h  H.m'iohs 


15 


1  Golden  Eagle 

2  Great  Horned  Owl 

3  Ferruginous  Hawk 

4  Red-tailed  Hawk 

5  Swainson's  Hawk 

6  Prairie  Falcon 

7  Marsh  Hawk 

8  Cooper's  Hawk 

9  Sparrow  Hawk 

10  Short-eared  Owl 

11  Burrowing  Owl 

12  Raven 

\_)  nesting  pairs 

I      I  non-nesting  pairs 

/\  individuals 


Fig.   5.     Distrihution    of    the    raptor     breeding    populatinn  in  1968. 


16 


Bnir.HAM  Young  Univfksity  Science  Bulletin 


® 


1  Golden  Eagle 

2  Great  Horned  Owl 

3  Ferruginous  Hawk 

4  Red-tailed  Hawk 

5  Swainson's  Hawk 

6  Prairie  Falcon 

7  Marsh  Hawk 

8  Cooper's  Hawk 

9  Sparrow  Hawk 

10  Short-eared  Owl 

11  Burrowing  Owl 

12  Raven 

\^  nesting  pairs 

I     I  non-nesting  pairs 

/\  individuals 


Fig.   6.      Dislritiiitimi     of     the     raptor     breeding     population   in    1969. 


Biological  Sehils,  \'ol.   18,  No. 


Bueedinc  Ecology  of  Utah  Uaptoiis 


17 


r. 


1  Golden  Eagle 

2  Great  Horned  Owl 

3  Ferruginous  Hawk 

4  Red-tailed  Hawk 

5  Swainson's  Hawk 

6  Prairie  Falcon 

7  Marsh  Hawk 

8  Cooper's  Hawk 

9  Sparrow  Hawk 

10  Short-eared  Owl 

11  Burrowing  Owl 

12  Raven 

\_J  nesting  pairs 

I      I  non-nesting  pairs 

/\  Individuals 


Fig.   7.      Distrihufion     of     the     niptor     breeding    population  in   1970. 


18 


BiuciiAM  YnvNc  Un'ivkhsity  .St:iEVf:E  Bulletin 


Table  9.     Summary  of  nesting  site  selections  of  raptors  on  the  study  area,  1967-1970. 


Quarrv 
Site' 

Structure 
Site 

Tree 

Site 

Pinyon 

Juniper 

Cliffrose 

Cottonwood 

Species 

No. 

% 

No. 

% 

No. 

•I 

\n. 

% 

No. 

% 

No. 

% 

Colden    Eagle 

4 

2.8 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Great    Horned   Owl 

7 

5.0 

0 

0.0 

0 

0,0 

4 

2.8 

0 

0.0 

0 

0.0 

Ferruginous    Hawk 

0 

0.0 

0 

0.0 

0 

0.0 

24 

17.0 

1 

0.7 

0 

0.0 

Ked-tailed    I  lawk 

•2, 

1.4 

0 

0.(1 

.! 

2.1 

7 

.5.0 

1 

0.0 

1 

0.7 

Swainson's    Hawk 

(1 

0.0 

0 

0  0 

0 

0.0 

5 

3.5 

0 

0.0 

0 

0.0 

Prairie    Falcon 

1 

0.7 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Marsh    Hawk 

0 

0.0 

0 

0.0 

0 

0,0 

0 

0.0 

0 

0.0 

0 

0.0 

Cooper's  Hawk 

0 

0.0 

0 

0.0 

0 

0,0 

1 

0.7 

0 

0.0 

0 

0.0 

Sparrow    Hawk 

5 

3.5 

2 

1.4 

0 

0.0 

O 

1.4 

0 

0.0 

0 

0.0 

Short-eared    Owl 

0 

0.0 

0 

0.0 

0 

(1,0 

0 

0.0 

0 

0.0 

0 

0.0 

Burrowing    Owl 

0 

0.0 

(1 

0.0 

(1 

(1,0 

(1 

0.0 

0 

0.0 

0 

00 

Haven 

1 

0.7 

0 

DO 

0 

0,(1 

0 

0.0 

0 

0.0 

0 

0.0 

Totals 

20 

14.1 

2 

1.4 

3 

2.1 

43 

30.4 

0 

0.7 

1 

0.7 

Ciround    Site 

chlf 

Site 

Sagebi 

■ush 

Shadscale 

Greasewood 

5-25 

25-75 

75-150 

Species 

No 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

3 

No. 

% 

Colden  Eagle 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

9 

6.4 

1 

0.7 

Great   Horned  Owl 

0 

0.0 

0 

0.0 

0 

0.0 

3 

2.1 

13 

9.2 

0 

0.0 

Ferruginous   Hawk 

s 

5.7 

3 

2.1 

0 

0.(1 

0 

0.0 

0 

0.0 

0 

0.0 

Red-tailed    Hawk 

0 

0.0 

0 

0.(1 

0 

0.0 

-T 

1.4 

5 

3.5 

i 

0.7 

Swaiiisoo's   Hawk 

0 

0.0 

0 

0,(1 

0 

0.(1 

0 

0.0 

0 

0.0 

0 

0.0 

Prairie   Falcon 

0 

0.0 

0 

0.(i 

0 

0,(1 

(1 

0.0 

0 

1.4 

0 

0.0 

Marsh    Hawk 

2 

1.4 

2 

1.4 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Cooper's    H;iwk 

0 

0.0 

0 

0,0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Sparrow    Hawk 

0 

0.0 

(1 

0,0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Short-cared    Owl 

1 

0.7 

0 

0.0 

0 

(1,(1 

0 

0.0 

0 

0.0 

0 

0.0 

Burrowing  Owl 

0 

0.0 

1 

0.7 

5 

3.5 

0 

0.0 

0 

0.0 

0 

0.0 

Haven 

0 

0.0 

0 

0.0 

0 

0.0 

3 

2.1 

7 

5.0 

3 

2.1 

Totals 

11 

7.8 

6 

4.2 

5 

3.5 

8 

5.6 

36 

25.5 

5 

3.5 

above  ground,   which  is   the  average  height  of 
the  pigmy  woodland  trees  of  this  area. 

The  majority  of  the  nests  had  western  ex- 
posures ( 33  percent ) ,  but  27  percent  faced 
south  and  25  percent  east,  while  only  15  percent 
faced  north.  Tree  nest  exposure,  determined  b}' 
the  inclination  of  the  slope,  is  included  in  the 
above  (sec  Table  10).  With  reference  to  alti- 
tude, 25  percent  of  the  nests  were  situated  be- 
tween 48(X)-5200  feet,  63  percent  between  5200- 
.5800   feel    and    II    percent   l)et\\een   5800-6400 


feet.  The  data  of  Table  11  indicate  that  several 
of  the  raptor  species  exhibited  a  vertical  strati- 
fication of  nesting  sites. 

Nests  of  the  Golden  Eagle  were  built  on 
cliffs,  rock  outcroppings,  and  in  (|uarries.  None 
were  constructed  in  trees,  but  ground  nests  and 
artificial  structures  were  utilized  in  areas  im- 
mediatelv  adjacent  to  the  stud\'  area.  Occupied 
e\ries  averaged  5690  ±:  62.0  feet  (range  5380- 
6170  feet).  No  apparent  exposure  preference 
was  exhibited.  All  pairs  maintained  from  one  to 


I'.ililr    1(1.      .Suiniii.irv    of   exposures  of   occupiod   nests,    I9'iT- 1^)7(1. 

North                         West 

South 

East 

Species                                   No.              %              No.                % 

No.              % 

No. 

% 

Golden  Eagle 
C»reat  Horned  Owl 
Ferruginous  Hawk 
Red-tailed  Hawk 
Swainson's  Hawk 
Prairie  Falcon 
Marsh  Hawk 
Gooper's  Hawk 
Sparrow  Ihiwk 
Short-eared  Owl 
Burrowing  Owl 
Raven 

Totals 


4 
1 
3 
4 
0 
1 
0 
0 
4 
0 
0 
4 
21 


2.8 
0.7 
2.1 
2.8 
0.0 
0.7 
0.0 
0.0 
2.8 
0.0 
0.0 
2.8 
14.7 


4 

15 

10 

6 

0 

2 

0 

1 

1 

0 

0 

8 

47 


2.8 
106 
7.1 
4.3 
0.0 
1.1 
0.0 
0.7 
0.7 
0.0 
0.0 
5.7 
33.3 


3 
8 

15 
6 
1 
0 
0 
0 
3 
0 
0 
2 

38 


2.1 
.5.7 

10.6 
4.3 
0.7 
0.0 
0.0 
0.0 
2.1 
0.0 
0.0 
1.4 

26.9 


3 

2.1 

3 

2.1 

8 

5.7 

5 

3.5 

4 

2.8 

0 

0.0 

4 

2.8 

0 

0.0 

1 

0.7 

1 

0.7 

6 

4.3 

0 

0.0 

35 

24.7 

Bioi.or.K  At.  Sfkiks,  \ 

'OL. 

18.  No, 

.  :^ 

BMiiiiniNc  1' 

^COl.OG^ 

;■    (IF 

Ut..\h 

Raftohs 

19 

Table  11.     Summary 

of  ; 

iiltitudinal  distribution  of 

raptor 

nests,  1967-1970. 

4800 

5000 

5200 

5400 

5600 

5800 

6000 

6200 

5000 

5200 

5400 

5600 

5800 

6000 

6200 

6400 

Species 

No. 

.     % 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

Golden    Eagle 

0 

0.0 

0 

0.0 

1 

0.7 

4 

2.8 

6 

4.3 

0 

0.0 

3 

2.1 

0 

0.0 

Great  Homed  Owl 

0 

0.0 

0 

0.0 

5 

4.0 

9 

6.4 

10 

7.0 

1 

0.7 

0 

0.0 

2 

0.1 

Ferruginous   Hawk 

1 

0.7 

8 

5.7 

17 

12.1 

16 

11.3 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Red-tailed  Hawk 

1 

0.7 

2 

0.1 

10 

7.0 

5 

4.0 

0 

0.0 

3 

2.1 

0 

0.0 

0 

o.n 

Swainson's  Hawk 

0 

0.0 

4 

2.8 

1 

0.7 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Prairie    Falcon 

0 

0.0 

0 

0.0 

1 

0.7 

0 

0.0 

2 

0.1 

0 

0.0 

0 

0.0 

0 

0.0 

Marsh   Hawk 

4 

2.8 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Cooper's    Hawk 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

1 

0.7 

0 

0.0 

0 

0.0 

Sparrow    Hawk 

0 

0.0 

0 

0.0 

6 

4.3 

0 

0.0 

3 

2.1 

0 

0.0 

0 

0.0 

0 

0.0 

Short-eared  Owl 

1 

0.7 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.(1 

0 

0,0 

0 

0.0 

Burrowing  Oul 

6 

4.3 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

0 

0.0 

Raven 

0 

0.0 

0 

0.0 

0 

0.0 

3 

2.1 

1 

0.7 

1 

0.7 

7 

5.0 

2 

0.1 

Totals 

13 

9.2 

14 

8.6 

41 

29.5 

37 

26.6 

22 

14.2 

6 

4.2 

10 

7.1 

4 

0.2 

five  alternate  nests,  and  one  or  more  of  tliese 
would  also  be  decorated  at  the  onset  of  the 
breeding  season. 

Great  Horned  Owls  selected  chffs,  trees,  and 
quarries  for  breeding  sites.  Quarries  were  a  fre- 
quently utilized  site  (almost  26  percent  of  all 
Great  Homed  Owl  nests  were  in  quarries),  and 
each  year  at  least  one  pair  nested  in  the  niches, 
ledges,  or  cracks  of  an  abandoned  quarry.  None 
of  the  pairs  showed  any  attempt  at  nest  con- 
struction but  instead  occupied  old  nests  of 
Ravens,  Red-tailed  Hawks,  Ferruginous  Hawks, 
or  deposited  the  eggs  directly  on  the  dirt  or  rock 
floor  of  a  crevice  or  ledge.  Tree  nests  were  found 
only  in  junipers  within  the  study  area,  but  the 
owls  did  use  old  Rod-tailed  Hawk  nests  situated 
in  tall  cottonwoods  in  canyons  located  outside 
and  to  the  north  of  the  study  area.  Nests  aver- 
aged 5640  ±  5.3.7  feet  (range  5340-6320  feet) 
in  altitude.  Over  55  percent  of  the  nests  faced 
west  and  almost  30  percent  had  southern  ex- 
posures, while  less  than  1  percent  faced  north. 
Nests  were  selected  in  cliffs  wliich  ranged  from 
21  to  65  feet  in  height,  but  sheer  size  of  cliff 
appeared  to  be  less  important  than  seclusion, 
and  crevices  were  more  frequently  occupied 
than  ledges. 

Ferruginous  Hawks  were  selective  in  their 
choice  of  nesting  sites.  Nests  were  constructed  in 
junipers,  cliffrose,  on  low  ledges  ( less  than  five 
feet  high)  or  directlv  on  the  groimd  (Fig.  8). 
The  most  common  nesting  site  was  in  a  low  tree 
or  shrub,  either  on  the  peripher\-  of  the  wood- 
land or  in  ver\'  lightK'  wooded  areas  of  the  foot- 
hills. The  average  altitude  of  all  Ferruginous 
Hawk  nests  was  5290  ±  2.5  feet  (range  4990- 
5500  feet).  Low  foothills  and  knolls  appeared  to 
offer  the  best  sit(>s  and  were  heavily  utilized.  In 
contrast,  no  nests  were  located  in  steep-sided 
canyons,    cliffs,    or    heavily    wooded    areas,    al- 


though such  sites  were  equally  available  in  these 
same  localities. 

Red-tailed  Hawks  exhibited  a  wide  choice  of 
nesting  sites  somewhat  paralleling  that  of  the 
Great  Horned  Owl.  Their  most  common  nest 
sites  were  in  junipers,  but  other  localities  in- 
cluded cliffs,  quarries,  pinyons,  and  cottonwoods 
(Fig.  9).  Nests  averaged  5380  ±  52.4  feet,  but 
had  a  wide  altitudinal  amplitude  (range  4880- 
5880  feet).  Unlike  Ferruginous  Hawks,  Red- 
tailed  Hawks  constructed  their  nests  in  a  variety 
of  habitats.  Tree  nests  were  most  commonh' 
built  on  the  periphery  of  the  woodland  or  in 
lightly  wooded  areas  but  a  few  were  also  con- 
structed in  the  center  of  dense  woodlands  and 
in  steep-wallcd  canyons.  Cliff  sites  were  usually 
in  large  rugged  cliff  lines  but  again  some  varia- 
tion occurred  and  some  nests  were  consti-ucted 
on  cliffs  only  10-15  feet  high.  Red-tailed  Hawks 
were  frequently  usurped  from  their  nesting  sites 
by  the  earlier  nesting  Great  Horned  Owls;  they 
then  chose  secondary,  more  exposed  nesting 
sites  a  short  distance  away. 

The  choice  of  nesting  sites  by  the  Swainson's 
Hawks  showed  considerable  overlap  with  Fer- 
ruginous Hawks.  Their  nests  were  without  ex- 
ception constructed  in  low  junipers  and  averaged 
5130  ±  30.4  feet  in  elevation  (range  5080- 
5240  feet).  As  with  Ferruginous  Hawks,  their 
most  common  nesting  site  was  on  a  low  foothill 
or  knoll  or  at  the  edge  of  a  juniper  woodland. 

Nesting  sites  of  the  Prairie  Falcon  averaged 
5.590  ±:  88.3  feet  (range  .5.380-5760  feet).  Of  the 
three  nests  on  the  study  area,  two  were  located 
in  (luarries  and  one  in  a  limestone  cliff  crevice. 
One  quarry  site  was  also  located  in  a  crevice 
but  the  second  was  located  in  an  unused  Gold- 
en Eagle  nest.  Heights  of  the  nests  above  the 
cliff  base  ranged  from  13-78  feet.  In  1970  a  pair 


20 


Bricham  Young  University  Science  Bulletin 


Fig.  8.     Ferruginous   Hawk   ground   nest   in   central  Cedar   Valley- 
hatched  egg.    May,  1968. 


Till'    nest   contains    two   chicks   and   one   un- 


Fig.  9.  Hed-tailed  H:nvk  nest  in  juniper  tree,  Skull 
Vallev.  Tooele  Co..  I'tah.  Two  vouiig  visible  al 
top  of  tiest.  May  1972. 


of  Prairie  Falcons  prevented  a  pair  of  Great 
Homed  Owls  from  successfully  completing  their 
nesting  attempt  and  then  took  over  the  aban- 
doned nest  site   (  Fig.   10 ) . 

The  four  Marsh  Hawk  nests  were  situated 
in  Cedar  Valley  and  averaged  4930  ±  27.6  feet 
in  elevation  (range  4870-4990  feet).  All  nests 
were  located  in  thick  sag(>bmsh  and  rabbitbrush. 
Although  all  were  ground  nests,  their  location 
within  the  extensive  sagebrush  growth  rendered 
them   relatively   inaccessible. 

Tlic  only  nesting  of  the  Cooper's  Hawk  on 
the  study  area  was  in  a  juniper  at  an  elevation 
of  6020  feet.  The  site  was  located  deep  within 
a  dense  juniper  stand  atop  a  ridge  between  two 
adjacent  peaks,  and  overlooked  Rush  Valley. 
The  nest  was  small  and  hidden  within  the  mid- 
dle branches  of  the  tree. 

Sparrow  Hawks  nested  in  junipers,  quarries 
and  abandoned  mining  structures.  Nests  aver- 
aged 5460  •  49.7  feet  in  elevation  (range  5.350- 
5670  fe(!t).  Quarr)'  sites  were  actually  small 
crevices  in  the  \-ertical  walls  which  ranged  from 
<S-32  feet  abo\'c  the  (juany  floor.  The  scrape  of 
these  nests  was  most  often  simply  a  hollowed 
out  portion  of  the  dirt  floor.  Both  tree  nests 
w(>re  sitiiatetl  in  small  crevices  within  the  tree 
tmnks.  Both  types  of  nesting  sites  were  also  used 


BioLcx;icAL  Seiues,  \'()l.  18,  No.  3       Bheeuing  Ecology  of  Utah  IUptoks 


21 


Fig.   10.     Cliff    nesting    site    of    Prairir    Falcons    and    Great   Homed   Oivls   in   the   western   Thorpe   Hills. 


l)V  Starlings  (Stunii.s  vulgaris)  nesting  in  the 
same  localities. 

The  onh'  Short-eared  Owl  nest  on  the  study 
area  was  located  at  an  elevation  of  4S90  feet. 
The  nest  site  was  placed  at  the  base  of  a  large 
clump  of  sagebmsh  and  was  partially  sheltered 
and  hidden  b\'  its  branches.  A  few  twigs  had 
been  arranged  on  the  nest  floor  and  down  was 
placed  among  them;  otherwise,  no  nest  con- 
struction  was   attempted. 

Nests  of  the  Burrowing  Owl  averaged  4920 
±  1.6  feet  in  elevation  (range  4920-49.30  feet). 
The  three  nests  of  the  1969  season  and  two  of 
the  1970  season  were  grouped  together,  fomiing 
small  colonies  which  were  located  in  a  stand  of 
grea.sewood,  in  dry  sand  and  soil  ( Fisj.  11). 
The  remaining  nest  was  located  in  the  bank  of 
a  dr)'  reservoir.  All  were  within  unused  burrows 
of  kit  foxes,  badgers,  or  Townsend's  ground 
squirrels. 

With  feu'  exceptions  Raven  nests  were  lo- 
cated in  the  most  remote,  inaccessible  regions 
of  the  study  area.  Their  average  elevation  was 
5950  *-  65.5  feet  (range  5590-6;32()  feet).  All 
were  well  constructed,  compact,  and  set  far 
back  into  a  protective  crevice.  All  had  an  over- 


hanging   ledge    or    rockshelf    which    prevented 
direct  exposure  of  the  nest   (Fig.   12). 

Reoccupation  of  Nests  and  Nesting  Localities. 
Most  of  the  regularly  nesting  raptor  species 
showed  a  strong  tendency  to  reoccupv  their  ter- 
ritories and  often  their  exact  nesting  sites  of  the 
previous  year.  This  was  particularly  true  of 
crevice-nesting  raptors,  and  it  is  probable  that 
these  partially  protected  sites  are  used  for  an 
indefinite  number  of  breeding  seasons.  Table  12 
summarizes  the  reoccupation  data.  Unfortunately 
it  was  not  possible  to  mark  individuals,  hence 
it  is  impossible  to  detemiine  if  the  same  pairs 
were  present  each  vear.  However,  many  pairs 
and  individuals  of  pairs  exhibited  distinctive 
color  or  plumage  patterns  and  behavioral  char- 
acteristics and  could  be  identified  on  this  basis. 

Most  of  the  large  raptors  selected  different 
nest  sites  within  the  same  territory  each  vear. 
This  was  particularly  true  of  the  Fermginous 
Hawk  which  selected  a  different  nest  site  75 
percent  of  the  time,  but  also  remained  within 
the  same  locality  for  suc-eessive  years  77  percent 
of  the  time.  Similarly,  pairs  of  Golden  Eagles, 
Great  Homed  Owls,  Red-tailed  Hawks,  and 
Svvainson's  Hawks  showed  strong  attachments  to 


22 


Hkigiiam  Young  Univeksity  Sciknce  Bulletin 


,  ,  «««C*»/. 


'» 


^%^. 


■4i 


»        ■-*' 


'»•„♦ 


Fig.   11.      Burrowing    Ov 
moiincl. 


nesting     site     in     northeastern    Cedar    Valley,    July    1970.     Both    adults    are    on    the 


a  particular  area  and  were  often  found  there 
even  during  years  in  which  tliey  did  not  nest. 
Long  term  consecutive  occupation  of  a  nest  site 
was  more  rare.  One  pair  each  of  Great  Homed 
Owls  (nesting  in  a  cliff  site)  and  Ferruginous 
Hawks  (nesting  in  a  tree  site)  occupied  their 
same  respective  nest  sites  for  all  four  vears  of  this 
study.  Another  Great  Horned  Old  pair  liad  oc- 
cupied their  nest  site  for  the  fourth  consecutive 
year  but  were  displaced  by  a  Prairie  Falcon  pair. 
Several  pairs  of  Golden  Eagles,  Great  Homed 
Owls,  Fcrrusinous  Hawks,  and  Red-tailed  Hawks 
reoccupied  the  same  nesting  site  for  three  con- 
secutive years,  and  every  large  raptor  occupied 
at  least  one  nesting  site  for  two  consecutive 
years.  Most  commonh-,  those  species  which 
nested  in  a  different  site  selected  a  new  site 
veiy  near  that  of  the  previous  Near.  For  example, 
a  pair  of  Golden  Eagles  selected  three  sites  in 
the  same  (juarr\-  for  three  a>nsecutive  vears, 
each  but  3()  feet  from  the  previous  years  site. 
The  same  phiMiomenon  was  observed  in  Fer- 
ruginous, Ri'd-tailed,  and  Swainson's  Hawks. 
The  amount  of  shifting  appeared  to  be  related 
to  the  dei^ri'c  of  disturbance  as  well  as  the 
success  of  the  pre\'ious  year's  nest,  but  pairs 
would  often  tolerate  considerable  disturbance 
and  ri'main  within  the  same  nesting  localitv. 

Of  the  medimn  and  small  raptors,  thi'  Raven 
showed    the    greatest    population    stabilitv'.    The 


Fig.    12.      Raven    nest   located   in   \v<'ll-[>rotected   crevice. 


Biological  Sehies,  \'ol.  18,  No.  3       BiiEiiiiiNC  Ecology  of  Utah  IIaptohs 


23 


Tablf  12.     Siimman,'  of  reoccupation  of  nesting  sites  and  territories. 


No.  years  occupation  of  a 

L  nest  site 

No. 

years 

territorial  occupatior 

[• 

I 

2 

3 

4 

1 

2 

3 

4          Total  no. 

Species 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

% 

No. 

%      of 

sites 

Golden  Eagle 

5 

55.6 

.7 

22.3 

2 

22.2 

0 

0.0 

0 

0.0 

0 

0.0 

2 

40.0 

3 

60.0 

9 

Great    Horned    Owl 

6 

40.0 

7 

46.7 

1 

6.7 

1 

6.7 

0 

0.0 

4 

400 

3 

30.0 

3 

30.0 

15 

Ferruginons    Hawk 

18 

75.0 

2 

8.3 

3 

12.5 

1 

4.2 

1 

1 . 1 

0 

1,5.4 

4 

30.S 

6 

46.2 

24 

Red-tailed    H.iuk 

8 

57.1 

5 

35.7 

1 

7.1 

0 

0.0 

0 

0.0 

1 

14.3 

1 

14.3 

5 

71.4 

14 

Swainson'-.    Hawk 

1 

.33..3 

■T 

68.7 

0 

0.0 

0 

0.0 

1 

50.0 

0 

0.0 

0 

0.0 

1 

.50.0 

3 

Prairie   Falcon 

3 

1(10.0 

0 

0.0 

(1 

0.0 

0 

0.(1 

1 

.33.0 

2 

67.0 

0 

0.0 

0 

0.0 

3 

Marsh   Hawk 

5 

1 00.0 

(1 

0.0 

0 

0.0 

0 

oo 

1 

1 00.0 

2 

67.0 

0 

0.0 

0 

0.0 

5 

Cooper's   Hawk 

1 

100.0 

0 

0.0 

0 

0.0 

n 

0,0 

1 

lOOO 

0 

0(1 

0 

0.0 

0 

0.0 

1 

Sparrow   Hawk 

4 

66.7 

1 

16.7 

1 

16.7 

0 

0,0 

0 

0.0 

1 

25  0 

3 

75.0 

0 

0.0 

6 

Short-cared  Owl 

I 

100.0 

0 

0.0 

0 

0.0 

0 

0  (1 

1 

100.0 

0 

0.0 

0 

0-0 

0 

0.0 

1 

Burrowing  Owl 

6 

UHi.O 

(1 

0,0 

0 

0.0 

0 

0,(1 

2 

50.0 

2 

.50.0 

0 

0.0 

(1 

0,0 

6 

Raven 

0 

33.3 

1 

16.7 

2 

33.3 

1 

16,7 

0 

0.0 

0 

0.0 

0 

0.0 

4 

100.0 

6 

Totals 

60 

71.75 

20 

17.9 

10 

8.2 

3 

2.3 

8 

36.7 

14 

23.2 

13 

15.8 

22 

29.7 

93 

'Tulais  iniluilo  nc:>tiTig  and  nonnesting  pans 


four  pairs  of  Ravens  on  the  stuch'  area  occupied 
their  respecti\e  territories  for  four  consecutive 
years  and  selected  but  six  different  nesting  sites. 
Sparrow  Hawks  also  tended  to  reoccupv  the 
same  territories,  but  their  fluctuating  popula- 
tions altered  their  reoccupation  frequencies. 
None  of  the  Burrowing  Owl  or  Marsh  Hawk 
pairs  reoccupied  their  exact  nesting  sites  of  the 
pre\ious  \  ear,  but  all  returned  and  nested  with- 
in the  same  locality.  The  Prairie  Falcons  chose 
three  different  sites  in  three  different  nesting  at- 
tempts, two  of  which  were  located  within  the 
same  torriton'. 

Productivitv 

Clutch  Size.  The  summan'  of  clutch  size  fre- 
quencies from  1967-1970  is  presented  in  Table 
13.  Golden  Eagle  clutches  on  the  study  area 
averaged  2.07  ±  0.07  eggs  ( 14  clutches,  range 
2-3).  Differences  between  the  mean  clutch  size 
of  each  of  tlie  four  study  years  was  not  signifi- 
cant. Total  fecundit)-  averaged  6.75  ±  0.96 
eggs  a  year. 

Great   Homed   Owl   clutches   averaged   2.82 


±  0.15  eggs  (22  clutches,  range  1-4).  Clutches 
of  1968  and  1969  were  significantly  larger  than 
clutches  of  1967  and  1970  (t--=  2.53;  2.63,  re- 
spectively) but  not  significantly  different  from 
one  another  (t=  1.26).  In  addition,  clutches  of 
1967-1970  were  also  not  significantly  different 
(t=  1.15).  Total  vearh'  fecundit)-  averaged 
15.5   ±   3.3  eggs. 

Clutches  of  the  Fenuginous  Hawks  aver- 
aged 3.23  ±:  0.12  eggs  (34  clutches,  range  2-4). 
Clutches  of  1968  and  1969  were  significantly 
larger  than  clutches  of  1967  and  1970  (t=  2.56; 
2.75,  respectively)  but  not  significantly  different 
from  one  another  (t=  0.05).  Again,  clutches  of 
1967  and  1970  were  not  significantly  different 
(t=  1.35).  Total  yearly  fecundity-  averaged  28.3 
±   5.6  eggs. 

Red-tailed  Hawk  clutches  averaged  2.89  ± 
0.13  eggs  ( 19  clutches,  range  2-4).  Although 
clutch  size  showed  an  increasing  trend  through- 
out the  tour  study  \ears,  none  of  the  possible 
differences  betwen  yearh'  clutch  sizes  was  sig- 
nificant. Total  yearly  productivity  averaged  13.8 
±   1.43  eggs  a  year. 


Table    1.3.     Summar)'   of   frequency   distribution   of   raptor  tlutch  sizes  from  1967-1970. 


No. 

eggs  in 

clutch 

Species 

1 

3 

3 

4 

5 

6 

7 

Golden  Eagle 

0 

13 

1 

0 

0 

0 

0 

Great  Horned  Owl 

1 

5 

13 

3 

0 

0 

0 

Ferruginous    Hawk 

0 

5 

13 

16 

0 

0 

0 

Red-tailed  Hauk 

0 

4 

13 

2 

0 

0 

0 

Swainson's   Hawk 

0 

-1 

1 

0 

0 

0 

0 

Prairie  Falcon 

0 

0 

0 

0 

1 

0 

0 

Marsh  Hauk 

() 

0 

1 

0 

0 

0 

1 

Cooper's    Hawk 

0 

0 

1 

0 

0 

0 

0 

Sparrow  Hawk 

0 

0 

0 

3 

3 

1 

2 

Short-eared  Owl 

0 

0 

0 

0 

0 

0 

1 

Burrowing  Owl 

? 

? 

? 

? 

? 

p 

p 

Raven 

0 

0 

1 

3 

4 

2 

4 

Totals 

1 

31 

44 

27 

8 

3 

9 

24 


BiiK.iivM  YouNC  Univihshv  Sciknck  Buli.ktin 


Clutches  of  the  Svvainson's  Hawk  averaged 
2.2  ±  0.17  eggs  (.5  clutches,  range  2-3).  There 
were  no  significant  variations  in  clutch  size  be- 
tween any  of  the  foin-  study  years.  Total  yearly 
fecundity  averaged  2.7.5  ±  0.6  eggs,  rating  low- 
est of  the  large  raptors  on  the  study  area. 

(Comparisons  of  the  average  clutch  sizes  of 
the  large  raptors  indicate  that  the  mean  clutch 
size  of  Ferruginous  Hawks  was  significantly 
larger  than  the  Golden  Eagle  (t=  8.23),  Great 
Horned  Owl  (t=  2.11),  and  Swainson's  Hawk 
(t=  4.76)  average  clutches  but  did  not  differ 
significantly  from  average  Red-tailed  Hawk 
clutch  size  (t=  1.01).  Red-tailed  Hawk  clutches 
averaged  significantly  larger  tlum  those  of  Gold- 
en Eagle  (t—  .5.72)  and  Swainson's  Hawk 
(t=  3.2)  but  did  not  differ  significantly  from 
Ferniginous  Hawk  or  Great  Homed  Owl  (t  = 
4.47  for  both)  and  Swainson's  Hawk  clutches 
(t=2.63).  Golden  Eagle  and  Swainson's  Hawk 
clutches  did  not  differ  significantly  from  one 
another  (t=  0.678). 

Of  the  smaller  raptors,  onlv  Sparrow  Hawks, 
Marsh  Hawks,  and  Ravens  had  sufficient  clutch 
size  data  for  analysis. 

Sparrow  Hawk  clutches  averaged  5.22  ± 
0.38  eggs  ( 9  clutches,  range  4-7 ) .  No  significant 
differ<>nces  between  \earl\'  clutch  sizes  were 
found.  Total  yearly  productivity  averaged  10.0 
±   2.18  eggs. 

Clutches  of  the  Marsh  Hawk  averaged  5.0 
±1.4  eggs  (2  clutches,  range  3-7).  No  compari- 
sons were  possible. 

Raven  clutches  on  the  study  area  averaged 
5.35  ±  0.,34  eggs  ( 14  clutches,  range  3-7).  There 
were  no  significant  differences  between  yearly 
clutch  size.  Total  productivity  averaged  18.8 
±    1.9  eggs. 

No  significant  differences  were  found  be- 
tween th(>  average  clutch  sizes  of  the  Marsh 
Hawk,  Sparrow  Hawk,  and  Raven  but  all  were 
significantly  larger  than  the  clutches  of  the 
large  raptors  on  th(>  study  area. 

Ilatchahilitij.  In  1967  the  ov(>rall  hatching 
success  of  the  efforts  of  all  nesting  raptors  on 
the  study  area  was  82.5  ±  7.6  percent,  the  high- 
(>st  of  the  foiu-  study  years.  In  1968  the  overall 
hatching  success  was  77.4  ±  5.7  percent,  but  in 
contrast  the  lowest  hatching  success  occurred 
during  the  1969  season  (75.6  ±  9.2  percent). 
In  1970  the  overall  hatching  success  was  slightly 
higher  at  82.0  '  4.7  percent.  There  were  no 
significant  variations  in  yearly  overall  hatching 
success  between  any  of  the  four  study  years. 
The  overall  hatching  success  of  the  five  large 
raptor  species  when  calculated  separately 
showed  no  significant  differences  between  years. 


with  the  hatching  percentages  being  as  follows: 
1967,  84.7  ±  8.7  percent;  1968,  75.9  ±  7.6 
percent;  1969,  76.7  ±  10.24  percent;  1970,  84.2 
±    7.1  percent. 

From  1967-1970  Golden  Eagle  nesting  ef- 
forts hatched  70.8  it  14.9  percent  of  all  eggs  for 
an  average  of  1.2  young  per  nest  per  year.  How- 
ever, the  breeding  seasons  of  1967  and  1970 
were  highly  successful,  hatching  100  percent  of 
all  eggs  produced  for  an  average  of  2.0  young 
per  nest;  whereas  the  combined  results  of  1968 
and  1969  revealed  a  two-year  hatching  success 
of  less  than  42  percent  and  an  average  of  but 
0.88  young  per  nest. 

The  average  hatching  success  of  Great 
Horned  Owls  from  1967-1970  was  89.4  ±  3.6 
percent  for  an  average  of  2.5  young  per  nest 
per  year.  Great  Horned  Owl  hatching  efforts 
were  most  successful  in  1967  ( 100  percent 
hatched,  average  of  2.0  young  per  nest)  and 
least  successful  in  1969  (80  percent  hatched)  al- 
though the  efforts  of  1969  actualh-  resulted  in  a 
greater  number  of  young  (2.5)  produced  per 
nesting  effort. 

The  average  hatching  success  of  Fermginous 
Hawks  on  the  study  area  from  1967-1970  was 
65.2  ±  5.2  percent  for  an  average  of  2.3  young 
produced  per  nest  per  \'car.  Ferruginous  Hawk 
nesting  success  was  lowest  in  1967  (5.3.3  percent 
hatched,  1.3  young  per  nest)  but  highest  in  1969 
(81.8  percent  hatched,  3.0  \()ung  per  nest).  The 
hatching  success  was  comparati\el\-  low  during 
all  four  breeding  seasons,  and  a  total  of  .35 
eggs  produced  no  young. 

Red-tailed  Hawk  nesting  efforts  successfully 
hatched  76.7  :^-:  .3.9  percent  of  all  eggs  produced 
from  1967-1970  for  an  average  of  2.3  \'oung 
per  nest  per  year.  As  with  Ferruginous  Hawks, 
Red-tailed  Hawk  hatching  success  was  highest 
in  1969  (88.9  percent  hatched,  2.5  young  per 
nest)  but  lowest  in  1970  (69.2  percent  hatched, 
2.2  )'oung  per  nest). 

Swainson's  Hawks  had  the  highest  hatching 
success  of  an\-  raptor  on  the  study  area,  success- 
fully hatching  all  eggs  produced  each  year. 
Swainson's  Hawks  averaged  2.2  yoimg  per  nest 
per  year  but  hatched  2.5  young  per  nest  in  1969, 
their   most   jiroductive   \-ear. 

The  Prairie  Falcon  nest  for  which  the  initial 
clutch  size  was  known  hatched  all  five  eggs. 
Hatching  success  is  unknown  for  the  Cooper's 
Hawks  and  liunowing  Owls  (the  latter  because 
of  the  inaecessibilitN'  ot  the  nests).  The  only 
Short-eared  Owl  nest  on  the  study  area  hatched 
six  young  from  a  clutch  of  seven  eggs  (85.7 
percent).  The  two  Marsh  Hawk  nests  for  which 
clutch  size  data  are  available  hatchcxl  70  percent 


Biological  .Seiuiss,  \'ol.   18,  No.  3        Bheedinc  Ect)Loc;v  oi-   Utah  HArrons 


25 


of  the  eggs  for  an  average  of  3.5  young  per  nest, 
but  the  figures  are  misleading  inasmuch  as  one 
nest  successfulh'  liatchcd  all  seven  eggs  of  the 
clutch  whereas  the  other  nest  failed  to  produce 
any  young. 

Sparrow  Hawk  hatchabilits'  is  known  for 
1968-1970.  During  this  time  their  hatching  suc- 
cess averaged  94.1  ±  4.9  percent  for  an  average 
of  4.7  young  per  nest.  Their  hatching  success 
was  greatest  in  1969  and  1970  ( 100  percent 
hatched  in  both  \ears). 

From  1967-1970,  Ravens  successfully  hatched 
70.5  ±  7.6  percent  of  all  eggs  produced  for  an 
average  of  3.64  young  per  nest.  Raven  hatching 
success  was  highest  in  1970  (85  percent  hatched, 
5.0  \oung  per  nest)  but  lowest  in  1969,  when 
less  than  46  percent  of  the  total  eggs  produced 
hatched  young  for  an  average  of  2.2  young  per 
nest. 

Comparisons  of  hatching  success  between  the 
different  raptor  species  reveals  that  Swainson's 
Hawks  had  a  significantly  greater  degree  of 
overall  success  than  Ferruginous  Hawks  (t^ 
6.70)  and  Red-tailed  Hawks"  (t:=  5.85)  but  did 
not  differ  significanth'  from  the  other  large  rap- 
tors. Great  Horned  Owls  had  the  second  highest 
overall  hatching  success,  significantly  higher 
than  Feniiginous  Hawks  (t=r:  3.S3)  but  did  not 
var\'  significanth-  from  that  of  the  other  larger 
raptors. 

Fled<iino  Success.  The  overall  fledging  suc- 
cess of  all  raptors  on  the  study  area  was  highest 
in  1970  (61.6  ±  8.5  percent)  and  lowest  in  1969 
(53.4  ±  6.1  percent),  with  the  1967  and  1968 
breeding  seasons  showing  intemiediate  success 
(60.2  ±  7.4;  59.7  ±  6.8"percent,  respectively). 
There  were  no  significant  differences  in  fledging 
success  between  any  of  the  study  years.  Data 
involving  only  the  large  raptor  species  of  the 
study  area  revealed  a  similar  overall  fledging 
success,  with  1970  again  being  the  most  success- 
ful breeding  season  (77.8  ±  10.6  percent), 
1969  the  least  successful  (57.7  ±  7.8  percent), 
and  1967  and  1968  again  having  intermediate 
degrees  of  success  (61.3  ±  8.9;  62.9  ±  9.1  per- 
cc^nt,  respectively).  Again  there  were  no  signifi- 
cant differences  in  fledging  success  among  am- 
of  four  study  years. 

From  1967-1970,  Golden  Eagle  nests  on  the 
stud\-  area  successfully  fledged  .S5.2  ±  13.4 
percent  of  their  original  clutches  for  an  average 
of  1.0  young  fledged  per  nest.  Fledging  rates 
were  highest  in  1967  and  1970,  when  combined 
data  indicate  a  survival  rate  of  75.0  percent  and 
1..33  young  fledged  per  nest,  and  lowest  in  1968 
and  i969,\vhich  had  a  combined  fledging  aver- 
age of  35.4  percent  and  0.75  young  per  nest. 


The  overall  fledging  success  of  Great  Homed 
Owls  from  1967-1970  was  75.6  ±  7.2  percent 
for  an  average  of  2.0  young  fledged  per  nest. 
The  yearly  fledging  range  varied  from  100  per- 
cent (2.0  young  per  nest)  in  1967  to  a  low  of 
70  percent  in  both  the  1968  and  1969  breeding 
seasons  ( 1.75  young  per  nest;  2.33  young  per 
nest,  respectively).  Great  Homed  Owls  success- 
fully fledged  the  highest  percentage  of  young 
each  year  among  the  large  raptors  on  the  study 
area,  but  Fermginous  Hawks  fledged  a  similar 
overall  average  of  2.0  young  per  nest. 

Ferruginous  Hawks  on  the  study  area  suc- 
cessfully fledged  an  overall  average  of  56.2  ± 
5.3  percent  for  an  average  of  2.0  young  per  nest 
per  year.  Fen-uginous  Hawks  were  most  success- 
ful in  1969  and  fledged  an  average  of  2.67  young 
per  nest  during  this  season,  the  highest  number 
fledged  per  nest  by  any  of  the  large  raptors  dur- 
ing any  study  year.  In  contrast,  their  relative 
fledging  success  during  the  other  three  study 
years  was  but  50.6  percent  for  an  average  of 
1.63  young  fledged  per  nest  for  each  of  the 
three  years. 

From  1967-1970  the  average  fledging  suc- 
cess of  Red-tailed  Hawks  was  58.9  ±  4.6  per- 
cent for  an  average  of  1.74  NOimg  fledged  per 
nest.  As  with  the  Ferruginous  Hawks,  Red-tailed 
Hawks  had  their  greatest  fledging  success  in 
1969  (72.2  percent)  and  also  produced  the  great- 
est number  of  young  per  nest  (2.17  fledged  per 
nest)   during  this  breeding  season. 

Swainson's  Hawks  had  the  second  highest 
fledging  success  on  the  study  area,  averaging 
72.5  ±  13.4  percent  during  the  four  study  years. 
Although  their  average  clutch  size  was  highest 
in  1969,  they  fledged  but  1.0  young  per  nest  this 
vear,  the  lowest  of  the  four  study  years. 

Of  the  medium  and  small  raptors,  Prairie 
Falcons  in  1970  fledged  but  20  percent  of  their 
clutch  of  fi\'e  eggs  while  Short-eared  Owls 
fledged  none  of  six  young. 

Burrowing  Owls  fledged  an  average  of  10 
\-oung  per  xcar  in  1969  and  1970,  for  an  average 
of  3.33  \-oung  per  nest  per  year. 

From  196S-1970  the  average  fledging  success 
of  Sparrow  Hawks  on  the  study  area  was  59.1 
±  8.8  percent  for  an  average  of  2.83  young 
fledged  per  nest.  Sparrow  Hawk  fledging  suc- 
cess was  highest  in  1970  (80  percent,  4.0  young 
per  nest)  but  low  in  1968  and  1969;  the  com- 
bined data  for  these  two  \ears  indicates  a  fledg- 
ing success  of  48.7  percent  for  an  average  of  2.6 
voung  fledged  per  nest  per  year. 

The  overall  fledging  success  of  Ravens  on 
the  study  area  was  47.4  ±  3.3  percent  for  an 
average  of  2.57  young  per  nest.  Raven  fledging 


26 


BmcnAM  Young  Uni\  khsity  Science  Bulletin 


success  was  consistently  low,  but  was  higher  in 
1967  (57.1  peiccmt,  3.0  \oung  per  nest)  than 
during  the  remaining  study  years. 

Mortaliti/.  The  hatching  and  fledging  per- 
centages presented  in  Tables  14-17  are  based  on 
the  total  number  of  eggs  produced.  The  mor- 
tality percentages  of  each  of  these  stages  can 
therefore  be  detemiined  by  subtracting  the  rep- 
resented figures  from  100  percent.  Specific 
causes  of  the  loss  of  eggs  or  young  were  often 
difficult  or  impossible  to  determine,  but  im- 
portant causes  included  nest  desertion  or  de- 
struction, human  interference,  predation  and 
apparent  egg  infertility   (sec  Table  18). 

Nest  desertion  was  observed  in  evciy  raptor 
species  except  the  Raven  and  Cooper's  Hawk, 
with  24.1  percent  of  the  established  nests  even- 
tualK'  being  deserted  before  the  fledging  of  the 
young.  The  majority  were  deserted  before  eggs 


had  been  deposited,  and  all  species  showed  an 
increasing  tendencv  to  tolerate  disturbance  after 
the  young  had  hatched.  Human  interference, 
including  the  presence  of  the  investigators,  was 
the  probable  cause  of  the  greatest  number  of 
desertions,  but  many  raptor  pairs  tolerated  a 
considerable  amount  of  disturbance  and  yet 
retained  their  nests  (see  Smith  and  Wilson 
[1971]for  a  discussion  of  individual  and  species 
differences  in  toleration  of  disturbance). 

Red-tailed  Hawks  and  Great  Homed  Owls 
exhibited  a  tendencv  to  desert  their  nests  (33.3 
and  25.9  percent  respectively).  Both  select  very 
similar  nesting  sites  and  often  utilize  the  same 
site  in  alternate  years.  In  1968  and  again  in 
1969  a  Great  Horned  Owl  flushed  from  its  nest 
was  attacked  by  a  pair  of  Red-tailed  Hawks 
nesting  in  close  pro.ximitv.  In  both  cases  the 
Red-tailed    Hawk    nests    (both    containing    full 


Table   14.     Summaiy  of  productivity  of  raptor  nesting  populations,   1967. 


Species 

No. 
tomplete 
clutclies 

.•\v. 

clutch 

size 

Range    of 

clutch 

size 

Total 

no.    of 

eggs 

producea 

No. 
young 
hatched 

Perecnt 
young 
hatched 

No. 
young 
fledged 

Percent 
young 
fledged 

Golden  Eagle 

3 

2.0 

_ 

6 

4 

66.7 

2 

33.3 

Great  Horned  Owl 

4 

2.0 

1-3 

8 

8 

100.0 

s 

100,0 

Ferruginous  Hawk 

6 

2.5 

2-4 

15 

8 

53.3 

7 

46.7 

Red-tailed   Hawk 

4 

2.5 

2-3 

10 

7 

70.0 

6 

60.0 

Swainson's  Hawk 

1 

2.0 

- 

2 

2 

100.0 

1 

50.0 

Prairie  Falcon 

0 

- 

- 

- 

- 

- 

- 

- 

Marsh  Hawk 

9 

- 

- 

- 

- 

- 

- 

- 

Cooper's  Hawk 

1 

3.0 

- 

? 

? 

? 

? 

? 

Sparrow  Hawk 

2 

4.5 

4-5 

9 

? 

? 

? 

? 

Short-eared  Owl 

0 

- 

- 

- 

- 

- 

- 

- 

Burrowing  Owl 

0 

— 

- 

- 

- 

- 

- 

- 

Raven 

4 

5.2 

4-7 

21 

15 

71.4 

12 

57.1 

Totals 

34 

- 

- 

71 

44 

- 

36 

- 

Tabk-    15.     Summary   i 

if  produci 

livity  of 

raptor  nesting 

p  ipulations 

,   1968. 

Species 

No- 
romplete 
clutches 

.\v. 

clutch 

size 

Range   of 

clutch 

size 

Total 
no.    of 

produced 

No. 
young 
hatched 

Perecnt 
young 
hatched 

No. 
young 
fledged 

Percent 
young 
fledged 

Golden  Eagle 

4 

2.0 

- 

8 

4 

50.8 

3 

37.5 

Great  Horned  Owl 

8 

3.0 

2-4 

24 

21 

87.5 

15 

62.5 

F'erruginous   Hawk 

9 

3.7 

3-4 

33 

21 

63.6 

19 

57.6 

Red-tailed   Hawk 

5 

2.8 

2-3 

14 

11 

78.6 

8 

57.1 

Swainson's  Hawk 

1 

2.0 

- 

2 

2 

100.0 

2 

100.0 

Prairie  Falcon 

1 

? 

p 

? 

0 

- 

- 

- 

Marsh   Hawk 

0 

- 

- 

- 

- 

- 

- 

- 

Cooper's  Hawk 

0 

- 

- 

- 

- 

- 

- 

- 

Sparrow  Hawk 

3 

5.7 

4-7 

17 

14 

82.4 

9 

52.9 

S  lort-eared    Ow  1 

0 

_ 

- 

- 

- 

— 

- 

- 

Burrowing  Owl 

0 

_ 

— 

- 

- 

- 

- 

- 

Raven 

4 

5.0 

3-6 

20 

16 

80.0 

10 

50.0 

Totals 

35 

- 

- 

118 

89 

- 

66 

- 

Biological  Series,  \'ol.   18,  No.  3       ISheeuinc;  Ecology  ■•h-   Uiaii  Kai'i'oh.s 


27 


Table   16.     Summary  of  productivity  of  raptor  nesting  populations,  1969. 


Species 


No. 
toniplete 
clutclies 


Av. 

clutch 

size 


Range   of 

clutch 

size 


Total 

no.    of 

eggs 

produced 


No. 
yoiuig 

hatched 


Perecnt 
young 
hatched 


No. 
young 
fledged 


Percent 
young 
fledged 


Golden   Eagle 
Great  Horned  Owl 
Ferriiginou.s   Hawk 
Red-tailed   Hauk 
Swainson'.s  Hawk 
Prairie    Falcon 
Marsh    Hawk 
Gooper's  Hawk 
Sparrow   Hawk 
Short-eared    Owl 
Burrowing  Owl 
Raven 

Totals 


4 
6 
12 
6 
2 
0 
2 
0 
2 

0 

3 

4 

41 


2.2 
3.3 
3.7 
3.0 

2.5 


4.5 


5.5 


2-3 

9 

3 

3-4 

20 

16 

3-4 

44 

36 

2-4 

18 

16 

2-3 

5 

5 

4-5 


? 

■3 

9 

4-7 

22 

10 

_ 

127 

95 

33.3 

3 

80.0 

14 

81.8 

32 

88.9 

13 

100.0 

2 

? 

5 

100.0 

4 

? 

8 

45.5 

9 

— 

90 

33.3 
70.0 
81.8 
72.2 
40.0 


44.4 

p 
40.9 


Table   17.     Summary  of  productivity  of  raptor  nesting  population.s,  1970. 


Species 


No 
complete 
clutches 


Av. 

clutch 

size 


Golden  Eagle  3 

Great  Horned  Owl  4 

Ferruginous  Hawk  7 

Red-tailed  Hawk  4 

Swainson's   Hawk  1 

Prairie  Falcon  1 

-Marsh    Hawk  2 

Gooper's  Hawk  0 

Sparrow  Hawk  1 

Short-eared  Owl  1 

Burrowing  Owl  3 

Raven  2 

Totals  29 


2.0 
2.5 
3.0 
3.3 
2.0 
5.0 
5.0 

5.0 
7.0 

6.0 


Total 
Range    of  no.    of 

clutch  eggs 

size  produced 


2-3 
2-4 
3-4 


5-7 


6 

10 

21 

13 

2 

5 
10 

5 

7 
p 

12 

91 


No 
young 
hatched 


6 

9 

13 

9 

2 
3 


young 
hatched 


100.0 
90.0 
61.9 
69.2 

100.0 
60.0 
70.0 

100.0 

85.7 
p 

85.0 


No 
>oung 
fledged 


6 

7 
10 
6 
2 
1 
5 

4 

0 

12 

5 

58 


Percent 
young 
fledged 


100.0 
70.0 
47.6 
46.2 

100.0 
20.0 
50.0 

80.0 
0.0 

? 

41.7 


clutches)  uere  subsequenth'  abandoned  as  was 
the  Great  Horned  Owl  nest  of  1968  (Smith. 
1970).  Their  most  commonly  chosen  siti's,  i.e., 
quarries,  are  in  highh  vulnerable  situations 
which  inxite  human  presence  and  interference. 
Twice  in  1968  Red-tailed  Hawks  built  nests  in 
quarr\'  sites  which  were  almost  daily  subject  to 
human  disturbances.  In  both  cases  the  nests 
were  subsequentl)'  abandoned  before  eggs  were 
deposited.  In  1970  a  Great  Horned  Owl  occu- 
pied its  quarr\'  nest  of  the  former  three  seasons. 
Later  interaction  with  a  Prairie  Falcon  appar- 
enth'  caused  it  to  abandon  this  crevice  site  be- 
fore egg  deposition  took  place.  This  Great 
Horned  Owl  pair  successfully  renested  only  42 
feet  from  their  original  site  which  was  then 
occupied  (  unsuccessfulh' )  1)V  the  Prairie  Falcon 
pair.  Nest  desertion  frequently  led  to  renesting 
attempts   by    Red-tailed    Hawks,   particularK    if 


nests  had  been  deserted  before  egg  deposition 
occurred.  None,  however,  were  successful  dur- 
ing the  four-year  study. 

Golden  Eagles  also  frequently  deserted  their 
nests,  with  25.9  percent  of  all  nesting  attempts 
temiinated  b\  desertion.  As  with  Great  Homed 
Owls  and  Red-tailed  Hawks,  the  most  frequent 
cause  of  nest  desertion  was  some  form  of  human 
interference.  Two  pairs  each  deserted  their 
nests  in  two  of  the  three  years  in  which  they  at- 
tempted to  nest.  Egg  collecting  and  photogra- 
pliv  activities  were  observed  around  these  nests 
before  their  desertion.  A  renesting  attempt  oc- 
curred in  1969  but  was  unsuccessful. 

Ferruginous  Hawks  deserted  nests  22.2  per- 
cent of  the  time.  Several  of  the  pairs  would 
tolerate  no  activity  around  the  nest,  particularly 
during  the  time  period  immediately  after  egg 
deposition  had  been  completed;  these  birds  de- 


DiiiciiANt  Young  Universitv  Science  Bulletin 


Tabic  18.     Summar)' of  causes  of  mortality,  1967-1970. 


Total  no. 

Successful   nests" 

Unsuccessful  nests 

\cst  (iestniction 

Nest  destruction 

'•KR'' 

t-gg 

losses 

[uvenile  losses 

Egg  not        Eggs 

E^s™. 

faff 

Species 

prodviced 

Infertile 

Other 

All  causes 

laid 

laid 

Young 

Young 

Golden   Eagle.s 

27 

2(  2) 

K  1) 

i(  1) 

1 

3(  7) 

0 

0 

0 

1(  2) 

Great   Horned   Owl 

62 

2( 

2) 

2(   3) 

4(  4) 

5 

K   3) 

K  3) 

1 

0 

1(   3) 

Fermftinou.s  Ilauk 

11.3 

8( 

9) 

5(  6) 

5(  6) 

2 

6(18) 

0 

0 

1(   2) 

K   4) 

Red-tailed   Hawk 

.55 

0 

5(  7) 

4(   4) 

4 

2(   5) 

1(  3) 

0 

0 

K  3) 

Swainson's    Hawk 

11 

0 

K   1) 

0 

0 

0 

1(  3) 

0 

0 

0 

Prairie  Falcon 

5 

K 

1) 

K   1) 

K  1) 

2 

0 

0 

0 

0 

0 

Mar.sh   Hawk 

■p 

■? 

p 

1(  2) 

0 

1(   3) 

0 

0 

0 

0 

Cooper's  Hawk 

.3 

■? 

? 

v 

? 

? 

■p 

p 

■p 

p 

Sparrow  Hawk 

40 

0 

0 

3(  5) 

1 

1(  3) 

0 

0 

0 

1(   5) 

Short-eared   Owl 

7 

1( 

1) 

0 

0 

0 

0 

1(   6) 

0 

0 

0 

Burrowing    Owl 

? 

? 

? 

'J 

2 

p 

p 

a 

p 

■> 

Haven 

75 

4( 

5) 

7(18) 

11(16) 

0 

0 

0 

0 

0 

0 

Totals 

398 

18(: 

20) 

22(37) 

.30(39) 

17 

14(39) 

4(15) 

1 

1(   2) 

5(   17) 

•Numbers    in    uiliimns   i 

efpr    l^   nuiiil>ri 

of   iicsts.    nmntwrs    in    parpiilli 

icMs   following  refer 

til  mini 

tier  of  eggs  or  young. 

serted  their  sites  immediately  after  the  nesting 
tree  had  been  chmbed  or  ground  site  ehc-eked. 
However,  none  of  tht;  nests  were  abandoned 
after  the  adults  had  hatched  young. 

In  1969  one  Swainson's  Hawk  nest  with 
three  young  aged  1.5  weeks  was  deserted.  Only 
one  of  the  pair  was  seen  in  the  nest  vicinity. 
Three  days  later  several  pieces  of  the  remains 
of  a  Swainson's  Hawk  were  found  beneath  the 
roost  of  a  pair  of  Golden  Eagles  which  main- 
tained a  territorv  in  the  same  area.  Evidently 
this  predation  caused  the  termination  of  the 
Swainson's  Hawk's  nesting  aetixitics. 

Prairie  Falcons  abandoned  two  ot  three 
nesting  sites  because  of  human  activities.  In  ad- 
dition, Marsh  Hawks,  Sparrow  Hawks,  Short- 
eared  Owls,  and  Burrowing  Owls  also  deserted 
one  or  more  of  their  nests  because  of  human 
presence  or  interference.  Marsh  Hawks  deserted 
a  nest  containing  three  eggs  which,  when 
checked,  were  infertile.  Prairie  I'aleons  aban- 
doned one  nest  due  to  aggress  on  eonhicts  willi 
Great  Horned  Owls  (pre\ionsl\  disci:ssed)  and 
deserted  anotlier  nest  located  in  a  <|uarry  whicli 
was  frequently  visited  b\  hunters  and  campers. 
Sparrow  Hawks  abandoned  two  nests  because 
of  similar  activities.  Apparentlv  our  investiga- 
tions were  the  cause  of  th<>  nest  desertion  b\' 
Burrowing  Owls  and  the  Short-(uued  Owl. 

Nest  destruction  occurred  in  4.9  percent  ot 
the  141  initiated  nests.  Causes  of  nest  destruc- 
tion included  human  interference  and  accidents. 
Human  interference  in  this  case  refers  to  the 
destruction  of  the  young  and/or  adults.  An  ex- 
posed quarr\'  site  was  occupied  in  196S  by  a 
pair  of  Great  Horned  Owls.  lDespil<'  distur- 
bances they  persisted  in  their  attention  to  the 
nest  and  succeeded  in  hatching  three  young, 
but  both  the  ni'st  and  \()ung  were  su])se(iiientlv 
destroyed.    In  1969  the  same  site  was  occupied 


by  a  Red-tailed  Hawk  pair  which  also  succeeded 
in  hatching  thre(>  voung.  Again  the  nest  was 
destroyed  before  the  young  fledged.  Another 
Great  Horned  Owl  nest  occupied  in  1969  was 
destroyed  before  egg  deposition.  The  body  of 
one  of  the  adults  was  found  beneath  the  nesting 
tree,  minus  its  feet  and  several  tail  feathers. 
Two  Ferruginous  Hawk  nests  were  similarly 
destroyed.  One  containing  two  eggs  was  located 
alongside  a  well-traveled  road.  The  female  was 
later  found  shot,  the  eggs  broken  and  the  nest 
destroyed  (Weston  and  Ellis,  1968).  The  second 
nest  was  located  in  a  favorite  rabbit  hunting 
locale  and  produced  four  \()ung.  Shortly  before 
the  young  would  have  fledged,  the  nest  was 
found  destroyed,  with  three  shotgun  shells  King 
beneath  the  nesting  tree.  One  Sparrow  Hawk 
nest  was  also  destroNcd.  This  nest  was  located 
among  the  ruins  of  an  abandoned  mining 
structure  and  had  been  deliberatcK-  exposed. 

An  accident  destroyed  a  Golden  Eagle  nest 
in  1967,  the  onl\'  observed  instance  of  the  nat- 
ural destruction  of  a  raptor  nest.  The  nest  had 
been  positioned  in  a  loose  shale  quarry  wall 
which  collapsed,  killing  both  voung  ( Murph\- 
et  al.,  1969). 

Based  on  tlie  successful  nests  (i.e.,  those 
wliich  fledged  at  least  one  young)  6.5  percent 
ot  ail  eggs  produc(Hl  by  all  raptors  species 
were  apparenth'  infertile  and  another  11.4  per- 
cent were  lost  before  hatching.  Eggs  which 
did  not  hatch  after  a  suitable  time  period  were 
judged  infertile;  how^ever,  additional  eggs  may 
have  been  infertile  but  were  destroyed  prior  to 
our  cheeking  them.  Ferruginous  Hawks  had  the 
highest  apparent  percentage  of  infertile  eggs 
(10.1  percent)  of  an\'  raptor  species.  Seven 
Ferruginous  Hawk  nests  contained  one  infertile 
egg  each  and  one  contained  bvo.  Most  com- 
monly,  one  of  a   clutch   of  three  or  four  eggs 


Biological  Seuies,  X'ol.  IS,  Ni 


Bheedinc  Ecolocv  ■  >!■•  Utah  Kaitohs 


29 


was  infertile.  Both  Golden  Eagles  and  Great 
Horned  Owls  also  produced  infertile  eggs.  In 
1968  a  Golden  Eagle  pair  produced  a  clutch  of 
two  eggs.  One  egg  disappeared  early  during 
the  incubation  period,  but  the  adult  continued 
to  incubate  the  remaining  egg.  After  49  days 
the  egg  had  not  hatched  and  was  subsequenth' 
abandoned.  Raven  nests  also  appeared  to  pro- 
duce a  high  number  of  infertile  eggs  on  the 
studv  area,  with  6.7  percent  of  their  total  eggs 
judged  to  be  infertile. 

Reasons  for  other  egg  losses  are  mostly  un- 
known, but  the  eggs  usually  disappeared  during 
incn])ation.  Howe\er,  one  case  is  interesting.  In 
196S  a  Red-tailed  Hawk  pair  produced  a  clutch 
of  two  eggs.  During  the  incubation  period  one 
member  of  the  pair  was  found  destroyed  (pre- 
sumabh'  shot).  One  egg  disappeared  but  the 
remaining  adult  rcmated  with  a  new  individual 
and  successfully  incubated  and  then  fledged 
a  )'Oung  from  the  remaining  egg. 

Losses  of  young  are  also  combined  because 
of  lack  of  knowledge  of  specific  causes.  Juvenile 
mortalit\'  occurred  most  commonly  in  Raven 
nests,  but  Golden  Eagle,  Great  Horned  Owl, 
Ferruginous  Hawk,  and  Red-tailed  Hawk  juve- 
niles also  occasionalb'  disappeared. 

Little  infomiation  was  obtained  on  post- 
fledging  mortality,  although  this  is  the  period 
during  which  the  majority  of  deaths  among 
first-year  birds  occurs  (Hickey,  1949;  Lack, 
1954;  Sprunt,  1963).  In  previous  studies  on 
raptor  mortalit\'  in  this  area,  Ellis,  Smith,  and 
Murphy  (1969)  recorded  a  high  percentage  of 
juveniles  among  birds  which  had  been  illegally 
shot  b\-  hunters  and  suggested  that  juveniles  are 
particularly  \'ulernable  to  tliis  fonn  of  destnic- 
tion. 

Territoriality 

The  definition  and  concept  of  a  territory  has 
been  much  discussed  in  the  literature  (Noble, 
1939;  Nice,  1941,  194.3;  Odum  and  Kuenzlcr, 
1955).  Within  the  study  area,  however,  the 
minimal  amount  of  intraspecific  home  range 
overlap  coupled  with  the  ver\-  few  instances  of 
observed  territorial  defense  suggests  that  the 
most  applicable  concept  is  the  "maximum  home 
range"  category-  as  described  by  Odum  and 
Kuenzler  (1955).  Using  this  method,  the  ex- 
treme positions  and  movements  (jf  raptors  arc 
plotted  and  connected  and  the  area  contained 
within  is  the  derived  liome  rantje.  The  home 
ranges  plotted  in  1969  and  1970  were  deter- 
mined from  a  minimum  of  25  obser\ations  per 
pair. 

Home  Range  Estahlislitnetit  ami  Defense. 
Home   range   establishment   dates   of   all    raptor 


species  from  1967-1970  have  been  previously  pre- 
sented in  Tables  5-8.  At  the  beginning  of  the 
raptor  breeding  season,  the  permanent  residents 
selected  their  future  nesting  sites  and  confined 
their  activities  within  a  restricted  area.  During 
this  period  Golden  Eagles  were  often  observed 
in  such  conspicuous  activities  as  soaring,  court- 
ship display,  and  occupying  a  prominent  perch. 
Great  Horned  Owls  were  frequently  active  in 
the  early  evening  hours  making  short  flights 
from  one  perch  to  another.  Both  individuals 
and  pairs  were  observed  hooting  from  the 
cover  of  one  perch,  then  making  a  short  flight 
to  a  new  perch  and  hooting  again.  No  intra- 
specific or  interspecific  actions  were  observed 
during  this  period,  although  on  a  few  occasions 
a  Golden  Eagle  of  one  nesting  pair  flew  within 
sight  of  the  nesting  locale  of  a  neighboring  pair, 
maintaining  a  good  distance  from  the  actual 
nest  site.  Indeed,  the  pairs  at  times  seemed  to 
be  keeping  watch  on  their  neighbor's  nest  while 
establishing  their  own  territorial  rights,  much 
in  the  manner  described  by  Di.xon  (1937).  No 
Golden  Eagle  and  Great  Homed  Owl  interac- 
tions occurred,  although  pairs  nested  in  close 
proximity  in  1968,  1969",  and  1970.  There  is  little 
or  no  overlap  in  their  respective  activity  pat- 
terns and  they  do  not  usually  come  in  contact 
with  one  another.  Unlike  other  large  raptors. 
Golden  Eagles  did  not  attack  flushed  Great 
Homed  Owls  e\'en  when  owls  were  flushed 
within  50  feet  of  active  Golden   Eagle  nests. 

Returning  migratory  pairs  rapidly  occupied 
their  territories  and  assumed  territorial  estab- 
lishment acti\'ities.  Ferruginous,  Red-tailed,  and 
Swainson's  Hawks  were  highly  aggressive  at 
this  time.  In  several  locales  Ferruginous  Hawk 
pairs  nested  in  close  proximity.  Their  morning 
and  evening  soaring  flights  frequently  provoked 
interaction,  and  at  times  members  of  three  pairs 
would  be  observed  soaring  but  short  distances 
from  one  another.  Usually  the  act  of  soaring 
kept  the  pairs  distant,  but  occasionally  one 
would  apparently  venture  too  close  and  provoke 
a  response.  One  or  both  members  of  a  pair 
would  posture  and  chase  one  or  both  members 
of  another  pair  simultaneously,  although  no 
actual  contact  was  ever  observed.  In  one  ex- 
ample of  interspecific  contact,  a  Ferruginous 
Hawk  pair  attacked  a  Great  Horned  Owl  \\'hich 
had  landed  some  30  feet  from  its  cliff  nest.  The 
Hawks  dov(>  at  it  in  turn  several  times,  each 
time  coining  to  within  3-9  feet  of  its  head  but 
a\oiding  contact.  The  owl  in  turn  met  each  at- 
tack by  raising  its  wings  in  defense  posture 
and  vigorously  clapping  its  beak.  The  hawks 
persisted  until  the  owl  flew  into  a  nearby  cliff 
crevice,    whereupon    the    hawks    resumed    their 


30 


Bbioiiam  Young  Univehsity  Science  Bulletin 


soaring.  In  this  case  the  Ferruginous  Hawks 
had  arrived  in  the  area  and  occupied  their  terri- 
tory of  the  previous  year  in  the  moniing  and 
were  activel)-  defending  it  in  the  late  afternoon 
of  the  same  day. 

Hed-tailed  Hawk  pairs  defended  their  terri- 
tories against  Great  Horned  Owls,  Ferruginous 
Hawks,  and  Golden  Eagles  but  no  intraspecific 
conflicts  were  observed.  Red-tailed  Hawks  al- 
ways attacked  flushed  Great  Horned  Owls  and 
on  at  least  three  occasions  struck  from  above 
with  open  talons,  although  never  visibly  injuring 
them.  The  owls  made  no  attempt  to  defend 
themselves  during  such  attacks  but  instead  flew 
to  the  nearest  cover.  On  one  occasion  a  Red- 
tailed  Hawk  pair  attacked  and  drove  a  Golden 
Eagle  out  of  their  territory.  Tlie  eagle  was  per- 
sistently attacked  from  above  when  approxi- 
mately 1  1/5  miles  from  the  Red-tailed  Hawk 
nesting  site  and  rapidh'  flew  out  of  the  area, 
followed  for  a  distance  by  the  red-tails.  Red- 
tailed  Hawks  also  threatened  Ravens,  but  onlv  if 
close  to  the  nest  site.  The  Ravens  maintained 
a  cautious  distance  from  soaring  Red-tailed 
Hawks  and  usuallv  onlv  a  swoop  in  their  direc- 
tion sufficed  to   chase  them  away. 

Encounters  between  Swainson's  Hawks  and 
FerRiginous  Hawks  often  occurred  and  are  dis- 
cussed by  Murphy,  et.  al.,  (1969). 

Prairie  Falcons  quickly  and  aggressively  re- 
acted to  the  presence  of  anv  raptors  within 
their  nesting  vicinitv  during  this  period.  How- 
ever, Ravens  were  tolerated  surprisingly  close 
to  the  nesting  vicinity,  and  in  1970  a  pair  of 
Ravens  nested  within  75  feet  of  an  active  Prairie 
Falcon  e\rie.  Both  sites,  however,  were  out  of 
sight  of  one  another  and  hidden  within  recesses 
in  cliffs. 

Ver\'  little  information  was  obtained  on  ag- 
gression and  territorial  reactions  of  the  medium- 
and  small-sized  raptors  during  this  period.  Gen- 
erally their  nests  were  widely  spaced  and  showed 
no  overlap,  with  the  exception  of  the  Burrowing 
Owls.  A  Sparrow  Hawk  pair  was  observed  at- 
tacking a  Red-tailed  Hawk  flying  about  50 
feet  above  its  nest  site,  but  reacted  passively 
to  the  presence  of  Ravens  and  Golden  Eagles. 
Burrowing  Owls  vigorously  protested  distur- 
bances from  investigators  but  allowed  Marsh 
Hawks  to  fly  within  their  home  ranges.  Marsh 
Hawks  were  similarly  tolerant  of  the  Burrowing 
Owls  and  on  two  occasions  nested  within  the 
home  range  of  Short-eared  Owls. 

As  the  breeding  season  progressed,  the 
raptors  generally  became  less  aggressixe  toward 
one  another  and  fewer  aggression  contacts  were 
observed.    At  times  much  tolerance  was  shown 


toward  other  raptor  species  flying  over  the  nest 
site,  while  on  other  occasions  they  would  be 
attacked  and  driven  away.  Definite  vertical  ter- 
ritoiy  limits  appear  to  be  present  and  were 
easily  observed  during  the  reactions  of  a  pair 
to  the  presence  of  investigators.  On  several  oc- 
casions a  second  and  sometimes  a  third  pair 
were  observed  soaring  above  a  nesting  pair 
which  were  themselves  attacking  the  investi- 
gators. At  these  times  the  intruding  pairs  re- 
mained unchallenged  as  long  as  they  maintained 
their  higher  altitudes.  However,  in  one  such 
instance  a  Ferruginous  Hawk  pair  from  a  near- 
by nest  flew  over  a  Red-tailed  Hawk  nest  at  low 
altitude;  the  intruders  were  immediately  attacked 
b\'  the  nesting  pair,  which  suceessfulh'  drove 
them  awav  after  one  grappled  with  one  of  the 
Ferruginous  Hawks. 

Home  Range  Coverage.  The  home  ranges  de- 
termined during  the  breeding  seasons  of  1969 
and  1970  are  plotted  in  Fig.  13-21.  Generally 
the  specific  size  and  shape  of  the  raptor  home 
ranges  appeared  to  be  a  function  of  their  size 
and  breeding  status  ( i.e.,  nesting  pair,  nonnest- 
ing pair,  or  individual),  the  topography  of  the 
surrounding  locale,  and  apparently  the  breeding 
population  densities.  Home  ranges  of  nesting 
raptor  pairs  were  usually  larger  than  home 
ranges  of  nonnesting  pairs  and  both  maintained 
larger  home  ranges  than  individuals  of  the 
same  species.  Almost  all  of  the  raptors  nesting 
in  the  foothills  had  home  ranges  extending  far 
into  the  desert  but  only  short  distances  into  the 
interior  of  the  hills.  Their  nests,  therefore,  were 
usuall)'  located  at  the  edge  of  the  home  range. 

Average  home  ranges  of  all  raptors  except 
Swainson's  Hawks,  Sparrow  Hawks,  and  Bur- 
rowing Owls  were  larger  in  1970,  correlating 
with  the  overall  decreased  raptor  population 
densities.  None,  however,  were  significantly 
larger  than  the  average  home  ranges  of  1969. 
Additional  home  range  information  of  the  raptor 
species  is  presented  as  follows  (only  home 
ranges  which  were  entirely  within  the  study 
area  limits  are  included  in  the  following  data). 

The  iiome  ranges  of  nesting  Golden  Eagle 
pairs  averaged  9.05  ±  1.1  sq  miles  in  1969  (3 
pairs,  range  6.6  —  11.8  sq  miles)  and  8.98  ± 
0.6  s(i  miles  in  1970  (3  pairs,  range  7.91  -  10.3 
sq  miles).  Maximum  diameters  of  the  home 
rani^es  a\ c-ra,y;ed  4.09  -±  0.4  miles  in  1969  (range 
3.08  -  4.99  miles)  and  3.85  ±  0.4  miles  in 
1970  (range  3.25  —  4.8  miles).  Golden  Eagles 
possessed  the  largest  home  ranges  of  any  raptor 
nesting  within  the  stud\'  area  and  appeared  to 
be  little  aifeeted  1)\  topograpliic  barriers.  They 
also    appear    to    eoiisistenti\     utili/.e    a    sizeable 


Biological  Stuiiis,  \'ol.   18,  No.  3        Bueeding  Ecology  ok  I'taii  Haptous 


31 


Kig.    13.     Home    ranges    ot    Cioldfn    Eagles     (1)    and    .Swainson's  Hawks  (5)  in  1969. 


32 


Bi<i(.ii\M  Young  Uninkhsitv  Sciknce  Bulletin 


Fig.    14.     Home    raiims    of    Great    Horned    Owls    (2)    in   1969. 


Biological  Sehils,  \  ol.  hS,  No.  3       Bueeding  Ecology  of  Utah  IUptobs 


33 


FiiT.    15.     Home    ranges    of    FerniKiiioiis     Hawks     (3)     iti  1069. 


34 


Bhicham  Young  Univkiisity  Science  Bulletin 


Kig.    10.      Home    ranges    cil     licd-lailcd    Hawks    (4)    in    I9()9. 


Biological  Seiuks,  \'i>l.   ly,  Xo.  3        Biu;t;i)iNG  Ecology  of  Utah  Hai'tohs 


35 


Fig.    17.      Home    ranges    of    Prairie    Falcons    (6),    Marsh    Hawks    (7),    Sparrow    Hawks    (9),    Short-eared    Owls 
(10),    Burrowing    Owls     (11)    and    Ravens    (12)    in  1969. 


36 


BnioHAM  Young  Univkhsity  Science  Bulletin 


Fig.    18.     Home    ranges    of    Golden    Kagle.s      (1),    Red-t.nled   Hawks    (4)    and   Swainson's    Hawks    (5)    in    1970. 


Bk)looic;al  Suuts,  \'oi..  18,  \ii.  3        Bukkding  Ec:olo(::y  of  Uiaii  IUptohs 


37 


Fig.    19.      Home    raiip's    of    Great    Iliirncd    Owls    (2)    in   1970. 


38 


Bnir.nA%r  Young  University  Scienck  Bulletin 


Kij;.   20      lloiiu'    rallies    1)1    Kcrniniiioiis    Hauks    (3)    in    l!)7(l. 


BiOLOciCAi,  Skmies,  \'oi..   1,S,  No.  ,5        Bhkkding  I'a:olo(;y  ok  Utah  liAPioi 


39 


Fig.  21.     Home    ranges    of    Prairie    Falcons     (6),    Marsli    Ilauks    (7).    .Sparrow    Hawks    (<)),    .Short-eared    Owls 
(10).    Burrowing    Owls    (11)    ami    Ravens    (12)     in  I970. 


40 


Bricham  Young  University  Science  Bulletin 


portion  of  their  home  range,  in  contrast  to 
many  of  the  smaller  raptor  species  on  the 
study  area.  In  1969  an  individual  Golden  Eagle 
occupying  a  home  range  in  the  southeast  por- 
tion of  tlie  stiul\'  area  maintained  a  home  range 
of  2.48  s(i  miles  with  a  maximum  diameter  of 
2.33  miles,  although  it  was  far  removed  from 
the  home  ranges  of  the  nesting  Golden  Eagle 
pairs. 

Home  ranges  of  Great  Horned  Owl  pairs 
averaged  1.88  ±  0.1  sq  miles  in  1969  and  2.16 
=t  0.2  sq  miles  in  1970  (7  pairs  in  1969  and 
1970  each,  range  1.62  —  2.22  sq  miles  and  1.36 
—  2.7  sq  miles,  respectively).  Maximum  diame- 
ters of  home  ranges  in  1969  averaged  1.87  ± 
0.1  miles  (range  1.3  —  2.53  miles)  and  2.1  ± 
0.3  miles  in  1970  (range  1.89  —  2.8  miles). 
Great  Horned  Owls  ranged  widely  into  the  des- 
erts from  their  nesting  sites  in  the  foothills  and 
maintained  large  home  ranges.  Their  home 
ranges  appeared  to  he  restricted  by  the  topogra- 
phy of  the  nesting  locale,  and  pairs  from  two 
nests  only  0.46  miles  apart  but  on  opposite  sides 
of  the  Thorpe  Hills  showed  no  home  range 
ox'crlap  although  both  nesting  sites  were  active 
during  all  four  breeding  seasons.  Instead,  the 
pairs  hunted  in  opposite  valleys  and  were  never 
observed  near  the  tops  of  the  intervening  ridges. 
In  other  areas,  however,  slight  overlaps  in  ad- 
jacent home  ranges  were  observed  between 
three  pairs  in  1969  and  two  pairs  in  1970.  In 
1970  two  nonnesting  Great  Horned  Owl  pairs 
maintained  home  ranges  of  1.64  d=  0.2  sq 
miles,  significantly  smaller  than  the  average 
home  ranges  of  the  five  nesting  pairs  (t  = 
3.2).  The  observed  home  range  of  an  individual 
on  the  study  area  in  1969  was  about  1.04  sq 
miles  with  the  maximum  diameter  of  1.72  miles, 
relatively  smaller  than  the  home  ranges  main- 
tained by  either  nesting  pairs  or  nonnesting 
pairs. 

The  home  ranges  of  Ferruginous  Hawk  pairs 
averaged  2.04  ±  0.2  s(j  miles  in  1969  (9  pairs, 
range  1.36  —  3.02  sq  miles)  and  2.52  ±  0.2 
sq  miles  in  1970  (5  pairs,  range  1.76  —  3.10 
sq  miles).  Maximum  diameters  a\eraged  2.0S6 
±  0.1  miles  (range  1.51  —  2.61  miles)  in  1969 
and  2.02  ±  0.1  miles  in  1970  (range  1.75  - 
2.6  miles).  As  with  Great  Horn(>d  Owls  their 
shapes  and  boundaries  were  in  large  part  de- 
termined by  topography,  and  all  observed  home 
ranges  extended  widely  into  th(<  valleys  but 
only  short  distances  into  the  hills  in  which  the 
nesting  site  was  located.  Five  adjacent  home 
ranges  overlapped  in  1969  and  three  in  1970, 
although  in  no  case  was  the  degree  of  overlap 
extensive.    In   1970  a  nonnesting  pair  possessed 


a  home  range  of  1.76  sq  miles,  the  smallest  home 
range  of  any  Ferruginous  Hawk  pair  of  that 
year  and  significantly  smaller  than  the  average 
home  ranges  of  the  1970  nesting  pairs  (t  = 
3.0.3,  at  the  0.001  level  of  probability).  Home 
ranges  of  individuals  tm  the  study  area  in  1969 
and"  1970  averaged  1.51  ±  0.07  sq  miles  (3  indi- 
viduals, range  1.36  —  1.66  sq  miles)  and  were 
significantly  smaller  (t  =  3.7)  than  the  home 
ranges  of  1969  and  1970  pairs. 

In  1969  the  home  ranges  of  four  Red-tailed 
Hawk  pairs  averaged  2.19  ±  0.2  sq  miles 
(range  1.48  —  2.78)  and  had  average  maximum 
diameters    of   2.21    ±    0.13   miles    (range    1.79 

—  2.48  miles).  In  1970  the  home  ranges  of 
four  Red-tailed  Hawk  pairs  averaged  2.805  ± 
0.3  sq  miles  (range  2.16  —  3.74  sq  miles)  and 
had  average  maximum  diameters  of  2.25  ±  0.09 
miles  (range  2.07  —  2.52  miles).  Home  ranges 
of  Red-tailed  Hawks  were  larger  than  the  home 
ranges  of  other  Butco  and  Great  Horned  Owl 
pairs  but  smaller  than  Golden  Eagle  home 
ranges.  In  1969  home  range  overlaps  occurred 
between  four  adjacent  Red-tailed  Hawk  pairs 
and  in  1970  between  two  adjacent  pairs.  As 
with  other  large  raptors,  the  home  ranges  of 
Red-tailed  Hawks  ranged  widely  into  the  des- 
erts but  very  little  into  the  hills.  The  average 
home  ranges  of  two  nonnesting  pairs  in  1970 
were  2.59  :h  0.3  sc]  miles,  significantly  less  than 
the  average  home  ranges  of  nesting  pairs  (t 
=  3.95).  The  home  range  of  an  individual 
present  on  the  stud\  area  in  1969  was  0.92  sq 
miles,  also  significantly  smaller  (t  —  5.4)  than 
the  average  home  ranges  of  the  1969  Red-tailed 
Hawk  pairs. 

Swainson's  Hawk  pairs  possessed  the  small- 
est home  ranges  of  any  of  the  large  raptors  on 
the  study  area  and  averaged  1.83  ±  0.23  sq 
miles  in  1969  (2  pairs,  range  1.6  —  2.06  sq 
miles)  and  1.18  s(j  miles  in  1970  (1  pair).  The 
average  maxinmm  diameter  of  the  1969  home 
ranges  was  2.09  miles   ±0.1  miles  (range  1.94 

-  2.23  miles)  and  that  of  the  1970  home  ranges 
1.51  miles.  As  Swainson's  Hawks  were  few  and 
widely  spaced,  no  overlap  of  home  ranges  oc- 
curred. Indi\iduals  (one  each  year)  were  pres- 
ent in  both  1969  and  1970  and  maintained  aver- 
age home  ranges  of  but  0.87  ±  0.03  sq  miles, 
significantly  smaller  (t  =  3.51)  than  the  aver- 
age home  ranges  of  the  pairs. 

The  home  ranges  of  two  Prairie  Falcon 
pairs  in  1970  aviTaged  2.35  ±  0.12  sq  miles 
(range  2.18  —  2..52  sc}  miles)  with  average 
maximum  diameters  of  2.09  ±  0.05  miles  (range 
2.01  —  2.17  miles).  Prairie  Falcons  maintained 
the  largest  home  range  of  any  of  the  medium- 


Biological  Sehies,  \()L.   18,  No.  3       Bueedinc  Ecology  ok  Utah  IUftohs 


41 


and  small-sized  raptors  but  they  were  also  larger 
than  the  average  lionie  ranges  of  the  Swain- 
son's  Hawks  nesting  in  1970.  Craighead  and 
Craighead  (1956)  found  similar  large  Prairie 
Falcon  home  ranges  ni-ar  Moose,  Wyoming. 
Possible  reasons  for  the  maintenance  of  such 
large  territories  b\  a  medium-sized  raptor  are 
presented  by  Schoener  (1968).  In  1969  an  in- 
dividual Prairie  Falcon  maintained  a  narrow 
home  range  of  1.64  sq  miles  with  a  maximum 
diameter  of  2.59  miles. 

The  home  ranges  of  two  Marsh  Hawk  pairs 
in  1969  averaged  1.62  ±  0.3  sq  miles  (range 
1..58  ~  1.66  s(|  miles)  and  had  average  maxi- 
mum diameters  of  1.83  ±  0.09  miles  (range 
1.7  —  1.95  miles).  In  1970  the  home  ranges 
of  three  pairs  a\eraged  1.74  ±  0.15  sq  miles 
(range  1.38  —  2.02  sq  miles)  and  had  maxi- 
mum home  range  diameters  averaging  1.97  ± 
0.13  miles  (range  1.58  —  2.62  miles).  Marsh 
Hawk  home  ranges  were  entirely  within  the 
Cedar  \'allev  area  east  of  the  Thorpe  and  Top- 
liff  Hills. 

Sparrow  Hawk  home  ranges  averaged  0.31 
±  0.08  sq  miles  in  1969  (4  pairs,  range  0.18 
—  0.56  sq  miles)  and  0.26  sq  miles  in  1970. 
Maximum  diameters  of  the  ranges  averaged 
0.743  ±  0.003  miles  ( range  0.63  ~  0.81  miles ) 
in  1969  and  0.62  miles  in  1970.  None  of  the 
wideh'  spaced  Sparrow  Hawk  nests  overlapped. 
In  1970  an  individual  maintained  a  home  range 
of  0.16  sq  miles  with  a  maximum  diameter  of 
0.58  miles. 

In  1969  the  a\erage  home  ranges  of  three 
Burrowing  Owl  pairs  was  0.36  ±  0.11  sq  miles 
(range  0.16  —  0.62  sq  miles).  In  1970  the  aver- 
age home  range  of  three  Burrowing  Owl  pairs 
was  0.28  ±  0.04  sq  miles  ( range  0.20  —  0.36  sq 
miles).  The  avera,u;e  maximum  diameters  of 
the  1969  home  ranges  was  0.71  ±  0.09  miles 
(range  0.53  —  0.91  miles)  and  of  the  1970  home 
ranges  was  0.593  zt  0.05  miles  ( range  0.51-0.72 
miles).  All  Burrowing  Owl  home  ranges  were 
located  east  of  the  Thorpe  and  Topliff  Hills  and 
confined  to  the  valley  floor,  primaril)-  within 
the  greasewood  communities.  The  home  ranges 
of  the  three  adjacent  pairs  of  1969  and  two  ad- 
jacent pairs   of    1970  overlapped  considerably. 

The  only  Short-eared  Owl  pair  on  the  study 
area  occupied  in  1970  a  home  range  of  1.48  sq 
miles,  with  a  maximum  diameter  of  1.76  miles. 
In  1969  an  individual  Short-eared  Owl  had  oc- 
cupied the  same  territory  but  had  maintained  a 
home  range  of  only  0.66  s(j  miles  with  a  maxi- 
mum diameter  of  1.21  miles.  In  both  cases  the 
home  range  extended  o\cr  the  vallev  floor  and 
did  not  enter  the  foothills  or  hills. 


In    1969    two    Raven    pairs    possessed   home 
ranges  averaging 2.31  ±:  0.32  sq  miles  (range  1.86 

—  2.76  sq  miles )  with  average  maximum  diame- 
ters of  2.22  ±  0.15  miles  (range  2.07  —  2.53 
miles).  In  1970  two  Raven  pairs  maintained 
home  ranges  of  2.74  =t  0.17  sq  miles  (range  2.5 

—  2.98  sq  miles)  with  average  maximum  di- 
ameters of  2.12  ±  0.26  miles  (range  1.76  — 
2.48  miles).  Raven  pairs  maintained  larger  home 
ranges  than  all  of  the  other  raptor  species  ex- 
cept Red-tailed  Hawks  and  Golden  Eagles. 
They  also  appeared  to  be  little  influenced  by 
topography  and  possessed  widely  ranging  terri- 
tories. 

Intraspecific  and  Interspecific  Associatioi^. 
Nesting  and  home  range  associations  between 
raptor  species  are  examined  as  follows  through 
( 1 )  an  analysis  of  observed  hostile  interactions 
between  species,  (2)  the  degree  of  overlap  of 
intra-  and  interspecific  home  ranges,  and  (.3) 
measurements  of  distances  to  nearest  neighbors 
of  all  raptor  species. 

A  catalog  of  obsei'ved  hostile  interactions  is 
presented  in  Table  19.  All  forms  of  interactions, 
including  stooping,  pursuits,  fights,  and  displays 
are  combined.  Most  of  the  observed  interac- 
tions concerned  territorial  disputes  or  nest  de- 
fense or  displacement  activities  caused  by  the 
presence  of  the  investigator;  this  has  been  pre- 
vioush'  discussed  in  other  sections  of  this  paper. 
The  two  most  aggressive  species  appear  to  be 
the  Ferruginous  and  Red-tailed  Hawk,  and  one 
is  tempted  to  suggest  that  their  aggressiveness 
directly  results  in  their  high  nesting  populations 
and  positions  of  dominance.  Undoubtedlv  their 
high  populations  and  competition  for  similar  nest- 
ing sites  produce  some  conflicts  both  within  the 
species  populations  and  between  these  and  other 
raptor  species  with  similar  habitat  requirements, 
such  as  Swainson's  Hawks.  The  similar  habitat 
requirements  of  Red-tailed  Hawks  and  Great 
Horned  Owls  almost  certainl\-  produces  the 
same'  degrees  of  hostile  interactions.  Unfor- 
tunately, many  of  the  observed  interactions  were 
prompted  by  disturbance  caused  by  the  investi- 
gators. This  is  particularly  true  of  the  previ- 
ously discussed  attacks  on  Great  Horned  Owls 
by  Red-tailed  Hawks,  Ferruginous  Hawks,  and 
Prairie  Falcons,  and  it  is  probable  that  this  noc- 
turnal species  has  little  or  no  contact  with  these 
hawks  in  its  normal  activity  patterns,  although 
both  Cameron  (1914)  and  Weigand  (1967) 
observed  Ferruginous  Hawks  attacking  Great 
Horned  Owls. 

Few  interactions  of  any  kind  were  observed 
ix'tween  an\  of  the  medium-  and  small-sized 
raptors.    Their  small  populations  and  wide  dis- 


42 


BiucnAM  VouNo  University  Science  Bulletin 


Table   19.     Catalog  of  interspecific  and  intraspecific  interactions  observed  on  the  study  area  from   1967-1970. 


1 

3 
o 

n3 

Ul 

"s 

be 

Species  Attacking 

13 

es  p 

£S 

OX 

■l1 

O 

.2  c 

U   O 

l| 

UK 

ll 

o 

ll 

1 

> 

Golden   Eagle 

0 

0 

1 

3 

0 

1 

0 

0 

0 

0 

0 

0 

Great  Horned  Owl 

0 

0 

4 

12 

0 

4 

0 

0 

0 

0 

0 

2 

FernigiiioMS  Hawk 

0 

0 

5 

6 

4 

0 

0 

0 

0 

0 

0 

0 

Red-tailed    Hawk 

0 

0 

6 

2 

0 

0 

0 

0 

2 

0 

0 

0 

Swainson'.s    Hawk 

2 

0 

12 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Prairie    Falcon 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Marsh  Hawk 

0 

0 

0 

0 

0 

1 

0 

0 

0 

0 

0 

0 

Cooper's    Hawk 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Sparrow  Hawk 

2 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Short-cared    Owl 

1 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Burrowing   Owl 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Raven 

3 

0 

0 

3 

0 

1 

0 

0 

1 

0 

0 

2 

Totals 

8 

0 

28 

26 

4 

7 

0 

0 

3 

0 

0 

4 

persal  account  for  at  least  part  of  this  lack  (par- 
ticularly intraspecific  contacts),  but  their  dif- 
fering habitat  requirements  also  prevent  much 
interspecific  contact  with  the  large  raptor 
species.  However,  this  is  not  true  of  the  Prairie 
Falcon,  which  ranks  third  in  aggressiveness  on 
the  basis  of  observed  aggression  contacts.  In 
this  case,  however,  Prairie  Falcons  are  a  raptor 
with  habitat  requirements  similar  to  those  of 
the  larger  species. 

Information  on  intraspecific  and  interspecific 
overlap  of  home  ranges  is  useful  in  estimating 
the  degree  of  association  of  the  various  raptor 
species  and  is  detemiined  from  the  pooled  data 
of  the  home  range  determinations  of  1969  and 
1970.  The  large  Golden  Eagle  home  ranges 
overlapped  to  some  extent  with  ever)-  nesting 
raptor  species.  Golden  Eagle  home  ranges  over- 
lapped with  almost  one-half  of  the  nesting  Great 
Horned  Owl  pairs  in  amounts  ranging  from 
6-100  percent  overlap;  with  45  percent  of  the 
Ferruginous  Hawk  home  ranges  in  amounts 
varving  from  6-100  percent;  with  one-third  of 
the  Red-tailed  Hawk  home  ranges  in  amounts 
varying  from  5-90  percent;  with  2.5  percent  of 
the  Swainson's  Hawks  in  amounts  varying  from 
lS-65  percent  and  with  most  of  the  small-  and 
medium-si'/ed  raptors  in  amounts  varying  from 
slight  (as  with  the  Burrowing  Owls)  to  consid- 
erable, (ireat  Horned  Owl  home  ranges  showed 
very  similar  overlaps  with  the  majority  of  the 
raptors  but  did  not  overlap  with  home  ranges 
of  tlie  Short-eared  Owl  and  Bunowing  Owl, 
supporting  Errington's  supposition  (1938)  that 
they  will  tolerate  no  other  owls  within  their 
home  range. 

Overlap  between  adjacent  Great  Homed  Owl 


pairs  was  present  in  32  percent  of  the  popula- 
tion but  in  \er\  slight  (2-5  percent)  amounts. 
Ferruginous  Hawk  home  ranges  also  over- 
lapped with  the  majority  of  the  raptor  species 
in  amounts  varying  from  appro.ximatcly  2-100 
percent.  In  1969  and  again  in  1970,  three  close 
nesting  Ferruginous  Hawk  pairs  in  the  extreme 
southeast  portion  of  the  study  area  overlapped 
approximately  5-10  percent  of  their  adjacent 
boundaries,  but  in  vers'  slight  amounts.  The 
majoritx'  of  the  medium-  and  small-sized  raptors 
had  home  ranges  overlapped  by  the  large  rap- 
tors as  discussed  previously.  No  intraspecific 
overlap  between  adjacent  ranges  of  Sparrow 
Hawks,  Marsli  Hawks  or  Ravens  occurred,  but 
most  were  widely  spaced.  Marsh  Hawk  home 
ranges  did  o\'erlap  with  Short-eared  Owl  home 
ranges  (approximately  24  percent),  Burrowing 
Owl  home  ranges  (6-85  percent),  and  Raven 
home  ranges  (35  percent),  but  did  not  overlap 
with  Sparrow  Hawk  or  Prairie  Falcon  home 
ranges.  With  one  exception  all  Burrowing  Owl 
home  ranges  overlapped,  both  with  adjacent 
pairs  and  extensively  within  all  members  of  the 
small  colony. 

The  distances  to  nearest  neighbors  should  in- 
dicate to  some  extent  the  degree  of  tolerance 
disphui'd  bi'tween  adjacent  pairs  of  the  same 
species  and  that  existing  between  different  rap- 
tor species.  In  the  following,  results  from  all 
four  stud\'  years  are  pooled.  Golden  Eagle 
nests  were  spaced  an  avi-rage  of  2.18  :+:  0.23 
miles  apart  (  14  nests,  range  1.28  —  3.6  miles). 
The  nearest  nests  were  separated  by  the  high 
ridges  of  the  intervening  Thorpe  Hills  and  the 
pairs  tended  to  hunt  in  opposite  valleys.  Dis- 
tances between  (Golden  I'agle  and  Great  Homed 


Biolocic:al  StiuES,  \'i)l.  18,  No.  3        Bkei-dinc  1''.(:()i.()gv  ■ii"  Utah  Raptohs 


43 


Owl  nests  avfiagod  only  0.695  ±  O.IS  miles 
(range  0.05  —  1.52  miles),  but  distances  be- 
tween Golden  Eagles  and  the  large  Butco 
hawks  on  the  study  area  averaged  1.54  ±  0.22 
miles   to   Ferruginous   Hawk   nests    (range  0.55 

-  2.51  miles);  1.52  ±  0.13  miles  to  Red-tailed 
Hawk  nest  sites  ( range  0.83  —  2.65  miles ) ;  and 
2.32  ±  0.994  miles  ( range  0.73  —  3.91  miles )  to 
Swainson's  Hawk  nesting  sites.  Despite  their 
ver\  similar  nesting  requirements,  distances  be- 
tween Golden  Eagle  and  Ra\en  nests  averaged 
1.37  ±  0.21  miles  (range  0.06  —  3.0  miles). 
Distances  between  adjacent  Great  Horned  Owl 
pairs  averaged   1.19    ±   0.21  miles    (range  0.64 

—  3.5  miles).  The  maximum  distances  were  ob- 
served between  nests  across  areas  which  lacked 
suitable  nesting  cliffs  and  had  verv  little  cover. 
Great  Horned  Owl  nests  were  often  in  relatively 
close  proximit\'  to  nests  of  most  of  the  diurnal 
Buteos,  averaging  0.766  ±  0.16  miles  to  Ferru- 
ginous Hawk  nest  sites  (range  0.21  —  1.7 
miles);  0.8S6  ±  0.17  miles  to  Red-tailed  Hawk 
nests  (range  0.004  —  1.4S  miles);  and  0.677 
±  0.09  miles  to  Raven  nests.  As  with  the  Gold- 
en Eagle  nests.  Great  Horned  Owls  nested  far 
from  Swainson's  Hawk  nesting  sites,  averaging 
2.2  -  0.16  miles  distant  (range  1.85  —  2.69 
miles ) . 

Distances  between  adjacent  Ferruginous 
Hawk  nests  averaged  1.55  ±0.1  miles  (range 
0.81  —  3.39  miles).  Ferruginous  Hawks  aver- 
aged 0.826  ±  0.13  miles  (range  0.39-2.06  miles) 
from  Red-tailed  Hawk  nest  sites  and  0.788  ± 
0.13  miles  (range  0.29—1.06  miles)  from  Swain- 
son's Hawk  nests.  In  contrast,  distances  to  nests 
of  the  Riuen  averaged  1.3  ±  0.22  miles  ( range 
0.46  —  2.44  miles).  Distances  between  adjacent 
Red-tailed  Hawk  nests  averaged  2.05  ±  0.18 
miles  (range  1.27  —  4.2  miles)  and  were  the 
most  widely  spaced  of  the  large  raptors  except 
for  those  of  the  Swainson's  Hawk  and  Raven 
nesting  sites,  averaging  1.17  ±  0.07  miles  to 
the  former  (range  0.95  —  1.35  miles)  and  1.08 
*:  0.12  miles  to  the  latter  (range  0.55  —  1.84 
miles). 

Me;isurements  of  distances  between  the 
medium-  and  small-sized  raptors  proved  to  be 
unre;ilistie  because  of  their  small  populations 
and  wide  range  of  habitat  reejuirements.  The 
majority  were  ver\  distant  from  any  of  the 
larg(>  raptor  nesting  sites,  but  exceptions  were 
noted.  Frairie  Falcon  pairs  nested  within  0.013 
miles  (within  the  same  eliffiine)  of  an  active 
Great  Horned  Owl  nest,  and  Ravens  in  1968 
nested  but  0.28  miles  from  a  (iolden  Eagle  nest, 
witli  ,ill  nests  successluli\  ficdging  at  le;ist  one 
\i)ung. 


Adjacent  Marsh  Hawk  nests  averaged  2.39 
±  0.57  miles  apart  (range  1.12  —  3.65  miles). 
Most  of  the  Marsh  Hawk,  Burrowing  Owl,  and 
Short-eared  Owl  nesting  sites  were  in  close 
proximiti}  (i.e.,  less  than  one-half  mile  apart); 
this  is  undoubtedly  a  result  of  their  similar  habi- 
tat requirements.  Nests  of  the  Burrowing  Owl 
colony  averaged  but  0.042  ±:  0.01  miles  apart 
(range  0.015  —  0.08  miles)  and  were  the  most 
closely  spaced  of  anv  intr;ispecific  nests  on  the 
study  area. 

In  summary,  intraspecific  nests  maintained 
minimum  average  distances  apart,  with  the 
noted  exception  of  the  Burrowing  Owl;  but  in- 
terspecific nesting  site  distances  varied  greatly, 
primarily  because  of  apparent  tolerance  differ- 
ences among  species  and  the  influence  of  ac- 
tivity patterns  which  will  be  discussed  later, 
all  of  which  combined  to  reveal  the  habitat  as 
a  mosaic  of  distinct  home  ranges  centering 
around  the  nesting  sites. 

Hunting  Activity  Patterns  and  Habitat 

The  hunting  activity  periods  of  the  raptors 
are  presented  in  Fig.  22  and  23.  These  were 
derixed  from  observations  of  birds  from  blinds 
and  from  notes  on  the  specific  activity  of  rap- 
tors when  sighted.  The  area  contained  within 
the  lines  represents  the  relative  degree  of  ac- 
tivity, and  the  thin  lines  which  may  or  may  not  be 
presi'ut  represent  additional  but  limited  activ- 
ity. Although  it  is  a  well-known  fact  that 
raptors  will  hunt  at  any  time  if  hungry  or  when 
in  need  of  prey  for  their  young,  they  do  exhibit 
definite  hunting  periods.  The  activity  patterns 
of  all  of  the  diurnal  raptors  fall  into  a  pattern 
of  separate  morning  and  afternoon  or  early  eve- 
ning hunting  periods,  and  all  showed  a  lull  or 
midafternoon  period  of  inactivity.  Among  the 
large  raptors,  Ferruginous  Hawks  were  the 
first  to  initiiite  hunting  activities  in  the  day, 
and  their  most  intensive  hunting  periods  oc- 
curred from  first  litijlit,  0545  lirs  to  sunrise  (ap- 
proximately 0600  hrs)  and  between  1745  hrs 
and  2045  !ns  in  the  late  afternoon  and  evening 
until  shortly  after  sunset.  Ferruginous  Hawks 
typic;illy  hunted  over  mixed  sagebrush-grass- 
land areas  but  were  also  observed  hunting  in 
th(>  sagebrush-Tt'fra(/(y;/i/«  areas  near  the  nests. 
Both  Red-tailed  Hawks  and  CJolden  Eagles 
initiated  their  hunting  activities  in  the  mid- 
mornimr  at  approximately  0830  hrs  and  both 
sp(>cies  terminated  their  morning  hunt  near 
1200  hrs.  Golden  Eagles  ranged  over  a  wide 
area  and  have  bc^'u  observed  hunting  in  a 
variety  of  habitats,  liut  Red-tailed  Hawks  most 
frecjuently  hunted  in  sagebrush  stands.  Although 


44 


BmaiiAM  Young  University  Science  Bulletin 


golden   eagle 
great  horned  owl 
swainson's  hawk     - 

RED-TAILED    HAWK      - 
FERRUGINOUS    HAWK  " 


6 

LIGHT 


9  12  3 

NOON 

Fig.  22.     Hunting    activity    patterns    of    the    large    raptors  on  the  study  area. 


9 

DARK 


PRAIRIE    FALCON 
MARSH    HAWK 

COOPER'S    HAWK 
SPARROW    HAWK- 


burrowing  owl- 


Fig.    23.      Iluiiliiig   activity    ])al(crns   of   medium-   and   s[uall-si/cd    raptors. 


lU'cl-tailc'c!  Hawks  also  ranged  widely,  one  pair 
lumted  over  a  small  sagebrnsh  stand  less 
than  0.0.3  miles  from  their  nestiijg  site.  Both 
species  had  similar  intensive  hunting  periods, 
from  approximately  1445  to  1830  hrs,  but  Red- 
tailed  Hawks  tended  to  hunt  throughout  a 
greater  portion  of  the  dav  than  any  other  large 
raptor  species.  The  morning  hunting  periods 
of  the  Swainson's  Hawk  began  well  after  that 
of  the  Ferruginous  Hawk  had  terminated,  and 
their  afternoon  hunting  periods  were  completed 
before     Ferniginous     Hawks     began     to    hunt. 


.Swainson's  Hawks  also  tended  to  hunt  in  the  im- 
mediate n(\sting  \ieinitv  in  habitats  similar  to 
tliose  in  whieli  Ferruginous  Hawks  predomi- 
nantly  hunted. 

.\il  of  the  small  raptors  nesting  (ju  the  study 
arc.  initiated  tlieir  hunting  periods  very  early 
in  tlie  morning  and  generally  before  sunrise. 
Marsli  Hawks  were  partieularh  active  at  this 
time  hut  continued  until  well  into  the  morning 
hours.  .Sparrow  Hawks  were  the  last  of  the 
small  raptors  to  b(\gin  lumting,  initiating  their 
morning  limit  at  approximately  0745  hrs.  Spar- 


Biological  Seiues,  \'ol.   18,  No. 


BlUCKIMNG    KCOLOGV    OF    UlAIl    l{ArTOH,>, 


45 


row  Hawks  probably  hunted  during  more  hours 
of  the  dav  than  anv  other  raptors  on  the  stud\- 
area,  although  still  exhibiting  peak  late  morning 
(1045-1200  hrs)  and  late  afternoon  periods. 
Thev  hunted  o\'er  a  wide  variety  of  habitats  in- 
cluding pinvon-juniper,  winterfat,  and  mixed 
grassland  areas.  Prairie  Falcons  exhibited  simi- 
lar hunting  habitat  preferences.  On  the  other 
hand,  both  Marsh  Ha\yks  and  Ravens  appar- 
ently preferred  to  hunt  o\er  sagebnish  or  mixed 
grassland-rabbitbrush  stands. 

All  of  the  nocturnal  raptors  on  the  study 
area  showed  some  tendency  to  hunt  during 
da\liglit  hours.  Great  Horned  Owls  and  Short- 
eared  Owls  began  hunting  periods  in  the  late 
e\'ening  liours  after  sunset  but  before  darkness. 
Both  showed  essentially  two  periods  of  in- 
tensive hunting,  one  beginning  at  approximateh- 
2030-2045  hrs  and  continuing  until  2400  hrs, 
and  the  other  beginning  in  the  earh'  morning 
hours  from  0430  to  shortly  after  first  light.  On 
two  occasions  Great  Horned  Owls  were  ob- 
served in  the  late  afternoon  from  appro.ximately 
1645  hrs  until  darkness.  In  both  instances  the 
day  was  overcast  and  snowy.  Similar  observa- 
tions of  diurnal  hunting  by  Great  Horned  Owls 
have  been  noted  jjy  Fitch  (1940)  and  \'aughn 
( 1954 ) .  Burrowing  Owls  arc  \er>-  alert  and  ac- 


tive during  the  daylight  hours,  and  their  peak 
aeti\it\'  p(>riods  are  from  approximately  0430  to 
0645  hrs  and  from  1740  to  2330  hrs.  They  were 
also  observed  hunting,  although  infrequently, 
as  late  as  0850  hrs  in  the  morning,  and  may 
occasionally  hunt  at  any  time  of  the  day. 

Predation 

The  prey  of  9  species  of  raptors  was  ex- 
amined in  1969,  and  of  11  in  1970.  A  total 
of  2111  prey  individuals  of  55  prey  species  were 
identified  and  tabulated  (Tables  20-39).  The 
prey  of  the  collective  raptor  population  in- 
cluded 75.2  percent  mammals  ( 1588  prey  indi- 
viduals of  17  mammal  species),  8.5  percent  rep- 
tiles (27  individuals  of  7  species)  and  15  per- 
cent invertebrates  (316  individuals  of  8  families). 
Minor  but  not  significant  variations  in  prey 
species  and  frecjuencv  occurred  l^etween  the 
two  \ears. 

Golden  Eagles  utilized  a  total  of  only  ten 
prey  species,  including  five  mammal  and  five 
avian  species.  Mammals  were  much  more  fre- 
quently preyed  upon  (96.5  percent  of  the  total 
prey)  and  comprised  the  bulk  of  the  prey  bio- 
mass  (99.4  percent),  whereas  birds  comprised 
0.6  percent  of  the  prey  biomass  and  averaged 
only  3.3  percent  of  the  individuals  taken.  Lago- 


Tahle  20.     Food  habits  of  Golden  Eagles  in  1969. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

Lepus  californicus 

155 

74.5 

356,500 

88.6 

St/hilafius  sp. 

43 

20.8 

43,000 

10.7 

Ainin()S))crmophihis  leucurus 

3 

1.4 

435 

0.1 

Pero<i,nathns  formosus 

1 

0.5 

19 

Tr." 

Zenaidtini  macroura 

1 

0.5 

153 

Tr. 

Chanciest es  i^ra m macus 

1 

0.5 

30 

Tr. 

Bufco  snainsoni 

2 

1.0 

988 

0.5 

Asia  flaninieiis 

1 

0.5 

340 

Tr. 

Totals 

207 

99.7 

401,465 

99.9 

"Present  in  trace  nmoiints  only. 


Table  21.      Food  habits  of  Golden  Eadcs  in   1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

Lepus  californicus 

68 

57.1 

156,400 

80.5 

Sijlvilafius  sp. 

35 

29.4 

35,000 

18.0 

Anu>i()S))erniophiltis  leucurus 

9 

7.6 

1,305 

0.7 

Mustclii  frenala 

2 

1.7 

356 

0.2 

Zeiiaidura  macroura 

1 

0.8 

153 

0.1 

Otocoris  alpestris 

3 

2.5 

56 

Tr." 

Buteo  sicainsoni 

1 

0.8 

988 

0.5 

Totals 

119 

99.9 

194,258 

100.0 

'Present   in   trace  amounts  only. 


46 


BiiiciiAM  VouNf.  University  Science  Bulletin 


'HiWe  22.     Food  habits  of  Croat   Ilonu.l  Owls   in    1969. 


No. 

% 

Species 

Indv. 

Indv. 

Leptis  californicus 

165 

58.9 

Siilvil(iii,us  auduboni 

32 

11.4 

Neotoma  Icpidii 

6 

2.1 

Per()L:,milIius  parvus 

2 

0,7 

Dipadditii/s  ruirrops 

8 

2.9 

Dipodoniiia  urdii 

11 

3.9 

Microtiis  sp. 

5 

1.8 

Pertinuisciis  numictduftis 

7 

2.5 

CijanocvpJudus  ciiinwrcpludus 

3 

1.1 

Zcnaidum  macroura 

5 

1.8 

Phalaenopfdtis  mttUdUi 

1 

0.4 

Scorpionida 

35 

12.5 

Totals 

280 

100.0 

.Xppro.v. 

% 

Biomass 

Biomass 

379,500 

91.4 

32,000 

7.7 

1,.302 

0.3 

.30 

Tr." 

520 

0.1 

748 

0.2 

190 

Tr. 

119 

Tr. 

50 

Tr. 

765 

0.2 

62 

Tr. 

30 

Tr. 

415,316 

100.0 

'Present   iti  time  niiKninls  only. 


Table  23.     Food  habits  of  Great  Homed  Owls  in  1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

Lepus  californicus 

83 

49.1 

190,900 

89.6 

Si/hnhiiius  sp  . 

19 

11.2 

19,900 

8.9 

Neotoma  lipida 

1 

0,6 

217 

0.1 

Dipodoniifs  ordii 

24 

14.2 

1,632 

0.8 

Dipitdoitnjs  microps 

3 

1,8 

195 

0,1 

Pcntmiiscus  iiianirtddlus 

12 

7.1 

204 

0.1 

Microdipodops  mc<s.accphalus 

2 

1.2 

48 

Tr. 

Onijchointis  leuco^cistcr 

3 

1.8 

114 

Tr. 

Zcnaidura  macroura 

4 

2.4 

612 

0.3 

Otocoris  alpestris 

1 

0.6 

28 

Tr. 

Pica  pica 

1 

0.6 

173 

Tr. 

Scorpionida 

16 

9.5 

14 

Tr. 

TotaLs 

169 

100.1 

214,037 

99.9 

niorph.s  were  tlic  predominate  food  item  of 
'ioldi'ii  I'las^les  on  the  stiuh'  area  and  con,sti- 
Inted  o\fr  95  percent  of  tlu'  pre\'  in  1969  and 
SO  percent  of  I  he  pre\  in  1970,  contrihutinij; 
98.9  percent  ol  llie  pre\  hioniass  eaeli  yt'ar.  The 
next  mo.st  important  food  item  wa.s  tlie  Antelope 
(ironnd  Scinirrel,  which  averaged  4.5  percent  of 
the  food  items  and  0.4  percent  of  the  volumetric 
diet  lor  tlie  two  N'car.s.  Foiu'  of  tlie  total  of  tt'ii 
pre\  species  taken  h\  (Golden  Eagles  during  tlie 
two  vears  were  hiixfs,  hut  none  contributed  sig- 
nificinti\  to  the  ditt.  'iWo  of  the  bird  species 
weic  raptors  (Short-eared  ( )\\  1  and  .Swainson's 
Hawk)  and  are  examples  of  the  (Golden  I'^agU's 
ability  to  prey  on  other  avian  predators.  Dixon 
(1937),  Arnold  (1954),  Carnic  (1954),  Mc- 
Cahan  (1968),  and  others  iiave  reported  simi- 
lar examples  ot  (Jolden  Eagle  pretlation  on 
other  raptors. 


Great  Horned  Owls  on  the  study  area  uti- 
lized a  total  of  16  prev  species,  including  10 
mammal,  5  bird,  and  1  iin'crtebratc  species. 
M.immals  eonstitutt'd  S.5,6  percent  of  the  prey 
individuals  and  99.7  percent  of  the  total  prey 
biomass,  while  birds  comprised  3.5  percent  of 
the  pre\  items  but  onl\'  0.3  percent  of  the  prey 
biomass,  Imcrtebrates  accounted  lor  11  per- 
ernt  ol  the  pre\'  individuals  but  contributed 
minor  amiiuiits  of  prev  biomass,  Eauomoiphs 
were  the  most  lre([iientl\  taken  pre\  item,  a\er- 
aging  65,3  perci'ut  ol  the  total  prev  individuals 
iccDrded;  the\  contributed  98.9  percent  of  the 
total  pi('\  biomass  during  U}69  and  1970.  Two 
species  ol  Kangaroo  liats  were  the  lU'xt  most 
lre(|uentl\  recorded  prey,  a\'eraging  o\er  11 
percent  (il  the  total  prey  items  but  contributing 
laiK  0.6  penent  ot  the  total  prey  biomass.  Al- 
thouiih  CDiitribntinu  ciiiK'  minor  amounts  to  the 


Biological  Series,  \'ol.  18,  No.  3       BnEEniNO  Ecology  ;)f  Utah  11.\ptohs 


47 


Table  24.      Food  habits  of  Ferruginous  Hawks  in  1969. 


Species 

No. 
Indv. 

% 

Indv. 

Approx. 
Biomass 

% 
Biomass 

Lepus  califonucus 
St/Ivihiius  sp. 
AmmospcniiopJiilus  Icucurus 

105 

6 

IS 

57.7 
3.3 
9.9 

241,500 
6,000 
2,610 

95.0 
2.4 
1.0 

Spcrmoj)Iiihis  touusendi 

2 

1.1 

382 

0.2 

Pc'roiJ.n(ithiis  jxirvus 

1 

0.5 

15 

Tr. 

Dipodomys  ordii 
Dipodomijs  microps 
Onycliointjs  Icucofiaster 
Peroiiti/sctis  numicidatus 

25 
2 
1 
4 

13.7 
1.1 
0.5 
2.2 

1,700 

130 

38 

68 

0.6 
Tr. 
Tr. 
Tr. 

Otucoris  alpcstiis 

9 

4.9 

252 

0.1 

Calamospiza  mehnocorys 
Zcnaidiira  macrouro 

3 
1 

1,6 
0.5 

150 
153 

Tr. 
Tr. 

Pooccctcs  iiramineus 

2 

1.1 

100 

Tr. 

Pituoplii.s  mchinolcticus 

2 

1.1 

744 

0.3 

Cncinidophorus  tif^ris 

1 

0.5 

24 

Tr. 

Totals 

182 

99.7 

253,866 

99.6 

'Present  in   Iiace  amounts  only. 


Table  25.     Food  habits  of  Ferruginous  Hawks 


1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

Lepus  californictis 

97 

56.4 

223,100 

93.0 

Si/hihiiius  sp. 

13 

7.6 

13,000 

5.4 

Amospcrmophihis  Icucurus 

8 

4.7 

1,160 

0.5 

Peroij.nalhus  parvus 

3 

1.7 

45 

Tr. 

Dipodomys  ordii 

17 

9.9 

1,156 

0.5 

Dipodomys  microps 

6 

3.5 

390 

0.2 

Pcromyscus  maniculatus 

9 

5.2 

153 

Tr. 

Otocoris  alpestris 

14 

8.1 

392 

0.2 

Pooccctcs  gramincus 

1 

0.6 

30 

Tr. 

Oreoscoptes  montamis 

1 

0.6 

33 

Tr. 

Pituophis  mehmolcucus 

3 

1.7 

372 

0.2 

TotaLs 

172 

100.0 

239,831 

100.0 

'Present  in  trace  amounts  only. 


T.ible  26.     Food  habits  of   Red-tailed  Hawks  in    1969. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass" 

Lepus  calijornicus 

Ill 

58.4 

255,300 

92.5 

Si/lvihii^us  sp. 

17 

8.9 

17,000 

6.2 

S))cnu()p}iilus  tonnscndi 

4 

2.1 

764 

0.3 

Eutamicis  minimus 

2 

1.0 

146 

Tr. 

Peromyscus  uuniictddttis 

13 

6.8 

221 

Tr. 

Microtus  sp. 

22 

11.6 

836 

0.3 

Olocoris  alpestris 

6 

3.2 

168 

Tr. 

Sialia  currucoidcs 

1 

0.5 

45 

Tr. 

CyamKcphalus  cyamxcphalus 

7 

3.7 

350 

Tr. 

Sturnis  vtdf^aris 

3 

1.6 

252 

Tr. 

Pituophis  mclanolcucus 

1 

0.5 

372 

0.1 

^tastic(}j>his  tacniatus 

3 

1.6 

507 

0.2 

Totals 

190 

99.9 

275,961 

99.6 

'l*ir>«pnt  in  irare  amounts  only. 


48 


HniniiAM  Young  IInivkhsity  Science  Bulletin 


total  l)i()mas.s  of  Great  Horned  Owl  prey,  at 
least  one  species  of  scorpion  was  taken  quite 
frecjuently  during  all  four  study  years  (see 
Murphw  et  al.,  1969).  Although  scoqiions  were 
not  taken  by  all  Great  Horned  Owl  pairs,  they 
showed  up  consistently  and  almost  exclusively 
in  tlie  n(-st  site  pellets  of  a  pair  nesting  in  the 
west  Thorpe  Hills  area,  serving  to  indicate  the 
possibilities  of  error  when  analyzing  food  habits 
of  raptor  pairs.  Interestingly,  the  female  of 
this  pair  had  an  irregular  left  eye  and  it  is 
tempting  to  speculate  that  there  was  a  possible 
connection.  Errington,  Hamerstrom,  and  Hamer- 
strom  ( 1940 )  suggested  that  predation  on  ar- 
thropods is  most  characteristic  of  recently 
fledged  owls,  but  as  previouslv  noted,  the 
scorpions  were  found  every  year  that  this  fe- 
male   was    present.     One    Black-billed    Magpie 


was  taken  by  a  pair  of  Great  Homed  Owls 
nesting  in  pinyon-juniper.  Magpies  were  com- 
mon around  the  towns  and  cultivated  areas  of 
the  northeast  portion  of  Cedar  Valley  and  fre- 
quenth'  nested  in  cottonwoods  and  elms  in 
those  areas.  They  did  not  nest  within  the  study 
area,  probabK'  I)ecause  of  a  combination  of  un- 
suitable habitat  and  possible  predation. 

Ferruginous  Hawks  within  the  study  area 
utilized  a  total  of  17  prey  species,  including  9 
mammal,  6  avian,  and  2  reptile  species.  Mam- 
mals comprised  S9.5  percent  of  the  prey  indi- 
viduals and  99.4  percent  of  the  total  prey 
biomass.  In  contrast,  birds  comprised  only  8.7 
percent  of  the  total  prey  items  and  0.2  percent 
of  the  total  prey  biomass,  while  reptiles  in- 
eluded  1.7  percent  of  the  total  prey  individuals 
and  0..3  percent  of  the  total  prey  biomass.  Lago- 


Table  27.     Food  habit.s  of  Red-tailed  Hawk.s  in   1970. 


No. 

% 

Appro.x. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass" 

Leptis  californicus. 

71 

50.7 

163,300 

90.0 

Sijlviliii:,us-  sp. 

15 

10.7 

15,000 

8.2 

Spennopltihis  townsencU 

1 

0.7 

191 

0.1 

Amiiiospcrmophihis  leucums 

9 

6.4 

1,304 

0.7 

Peromi/scus  mdnicultifiis 

26 

1S.6 

442 

0.2 

Mir  rot  Its  sp. 

1 

0.7 

38 

Tr. 

Thomomi/s  holtac 

2 

1.6 

340 

0.2 

Otecoris  alpcstris 

3 

2.1 

84 

Tr. 

Tt/ranniis  verticalis 

1 

0.7 

36 

Tr. 

Stiirnis  vuli^aiis 

9 

6.4 

756 

0.4 

PHitophis  nichinoleiicits 

1 

0.7 

372 

0.2 

Crot(ip]ii/lus  coUaris 

1 

0.7 

30 

Tr. 

Totals 

140 

100.0 

181,893 

100.0 

'I'rt-'i.i'nl  in   Iraie  iinnninls  onlv- 


Table    28.     Food   habits    of   Swainson's    Hawks   in    1969, 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass" 

Lepiis  californicus 

42 

51.2 

96,600 

95.0 

St/lvihif^us  sp. 

4 

4.9 

4,000 

3.9 

Perotni/sctis  nianiculatus 

7 

8.5 

119 

0.1 

Mirrotits  .v/). 

3 

3.7 

114 

0.1 

Spcrniophiltis  lounsendi 

1 

1.2 

191 

0.2 

Calamospiza  melanoconjs 

3 

3.7 

99 

0.1 

Lanius  ludoviciamis 

1 

1.2 

52 

0.1 

Orcoscoptes  iiwntanus 

1 

1.2 

45 

Tr. 

Sai/ortiis  sat/o 

2 

2.4 

56 

0.1 

Zonotrichia  leucophnjs 

1 

1.2 

30 

Tr. 

Pituophis  mehinoleucHS 

1 

1.2 

372 

0.4 

Locustidae 

15 

18.3 

95 

Tr. 

Carabidae 

1 

1.2 

0.23 

Tr. 

Totals 

82 

99.9 

101,688 

100.0 

•Prc-icril   irt  irate  nnioiints  unlv. 


Bioloc;ic:al  Skiues,  Vol.   18,  No.  3        Ukkicdinc;  E(X)i,<)f:v  oi-  Vt.\u  Hai-tohs 


49 


Table    29.     Food   habits    of   Swainson's    Hawks    in    1970. 


No. 

% 

Species 

Indv. 

Indv. 

Leptis  californicus 

15 

19.0 

St/IvihiiS.tis  audohoni 

9 

11.4 

Pcronujscits  maniculatus 

2 

2.5 

Micwtus  sp. 

1 

1.3 

Otocoris  (dpestiis 

11 

13.9 

Unident.  Pa.s.serincs 

8 

10.1 

Lociistidac 

17 

21.5 

Carabidac 

5 

6.3 

Tcncbrionidac 

2 

2.5 

Grvllidat- 

9 

11.4 

Totals 

79 

99.9 

Appro.x. 

% 

Biomass 

Biomass* 

34,500 

78.2 

9,000 

20.4 

34 

0.1 

38 

0.1 

308 

0.7 

240 

0.5 

11 

Tr. 

1 

Tr. 

1 

Tr. 

4 

Tr. 

44,137 

100.0 

'Piesent  III   tiace  aniounts  only. 


Table  .30.     Food  habits  of  Prairie  Falcons  in   1970. 


Species 

No. 
Indv. 

Amiuospermiipliilus  leuciirtis 

5 

Peromijscus  maniculatus 
Lepus  californicus  (juv. ) 
Otocoris  alpcstris 
Oberholscria  chlorura 
Pooecetcs  L:,rami)icus 

1 
2 
7 
1 
1 

Sturnis  vuli^aris 
Sturnella  neglecta 
Locustidao 

3 
1 
5 

Totals 

26 

Indv. 


19.2 
3.8 
7.7 

26.9 
3.8 
3.8 

11.5 
3.8 

19.2 

99.7 


Appro.\. 
Biomass 


725.0 

17.0 

2,300.0 

196.0 

30.0 

27.0 

84.0 

145.0 

3.2 

3,527.2 


Biomass* 


20.6 
0.5 

65.2 
5.6 
0.9 
0.7 
2.4 
4.1 
Tr. 

100.0 


aiiioiiiits  tmly. 


Table  .31.     Food   habits  of   Marsh   Hawks   in   1969. 


No. 

% 

Appro.x. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass* 

Lepus  californicus  (juv.) 

12 

31.6 

1,200.0 

50.1 

Spennophilus  tounsendi 

5 

13.2 

755.0 

31.5 

Pcroini/scus  maniculatus 

7 

18.4 

119.0 

5.0 

Reifhrodontomi/s  Megalotis 

2 

5.3 

24.0 

1.0 

Otocoris  alpcstris 

4 

10.5 

112.0 

4.7 

Zenaidura  macroura 

1 

2.6 

153.0 

6.4 

Pooecetes  gramineus 

1 

2.6 

30.0 

1.0 

Carabidae 

6 

15.8 

1.4 

1.3 

Totals 

38 

100.0 

2,394.4 

101.0 

*  Present   in  Ii.lie  ^iindiints  imlv. 

iiioiphs  attain  were  the  mo.st  frequent  prev 
item,  averas^ing  62.5  percent  of  the  total  prey 
and  contributing  97.4  percent  of  tlie  prey  bio- 
mass in  each  of  the  two  years.  Tlie  next  most 
frequently  taken  pre\-  items  were,  in  order  of 
their  aNcrage  vearh'  freqiiencv;  Ords  kangaroo 
rat,  C(;nstituting  11.8  percent  of  the  total  prey 
but  only  0.5  percent  of  the  prey  biomass;  the 
antelope    ground    sfjuirrel.    which    averaged    7.3 


percent  of  the  total  prev  individuals  and  0.25 
percent  of  the  prey  biomass;  and  the  Homed 
Lark,  which  averaged  6.5  percent  of  the  total 
prey  and  0.15  percent  of  the  prey  biomass.  The 
two  kangaroo  rat  species  and  pocket  mouse 
reflect  cssentiallv  crepuscular  hunting  activity 
patterns  of  the  Ferruginous  Hawk  as  discussed 
earlier.  Ferruginous  Hawks  also  infrequently 
pre\'ed  on  gopher  snakes. 


50 


BniGiiAM  '^'ouNG  University  Science  Bulletin 


Mammals  wen-  also  the  major  prey  of  Red- 
tailed  Hawks,  coinprisinu;  S9.1  pcreent  of  the 
prey  individuals  and  99.4  percent  of  the  total 
prey  biomass,  while  birds  constituted  9.1  per- 
cent and  0.2  percent,  and  reptiles  accounted  for 
1.8  percent  and  0.3  percent  of  the  total  prey 
items  and  total  pr('\-  biomass,  respectively.  The 
major  items  of  importance  were  again  the  lago- 
morphs,  which  accounted  for  64.4  percent  of  the 
prev  items  and  98.5  percent  of  the  total  prey 
ijiomass.    In  addition.  Red-tailed  Hawks  preyed 


on  6  other  mammal  species,  5  avian,  and  3 
reptile  species.  Other  mammal  species  of  im- 
portance included  tlu'  deer  mouse,  which  com- 
prised 12.7  percent  of  its  total  diet;  meadow 
mice,  comprising  6.2  percent;  and  the  antelope 
ground  sciuirrel,  which  constituted  3.2  percent. 
Starlings  and  Finvon  Javs  were  the  most  fre- 
((ueiitlv  taken  avian  pre\  species.  Starlings  were 
first  recorded  in  Utah  in  1949  in  and  around 
url)an  areas  (Behle,  1954).  Since  that  time  they 
ha\e   spread   widely   throughout   the   state   and 


Table   32.     Food  habits  of   Marsh   Hawks  in   1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Bioma.ss° 

Lepus  californicus 

5 

13.5 

5,000.0 

86.9 

Peroiui/scus  maniculatus 

15 

40.5 

255.0 

4.4 

SpeimopJiiliis  tounscncU 

1 

2.7 

191.0 

3.3 

Otocoiis  (iIjK'stris 

7 

18.9 

196.0 

3.4 

Pooecetcs  ^raminetis 

3 

8.1 

81.0 

1.4 

Demiestidae 

5 

13.5 

1.2 

Tr. 

CrofopJuilus  collaris 

1 

2.7 

30.0 

0.5 

Totals 

37 

99.9 

5,754.2 

99.9 

tit  in  hiifo  anioiiiii'i 


Table  .33.      i'ood  liabits  of  Sparrow  Hauks  in  1969. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass* 

Microtus  sp. 

5 

6.5 

190.0 

17.6 

Peromiisciis  nuiniciilatiis 

18 

23.4 

306.0 

28.3 

Otocoris  alpestris 

6 

7.8 

168.0 

15.6 

Sialia  currucoide.s 

2 

2.6 

90.0 

8.3 

Passer  domcsticus 

2 

2.6 

50.0 

4.6 

Sftirnis  viiliiuris 

3 

3.9 

252.0 

23.3 

Uta  st(insl)uriami 

1 

1.3 

4.0 

0.4 

Aranae 

2 

2.6 

0.8 

Tr. 

Locustidae 

29 

37.6 

18.3 

1.7 

Curculionidae 

7 

9.1 

0.7 

Tr. 

Uniden.  Colcoptcra 

2 

2.6 

0.6 

Tr. 

Totals 

77 

100.0 

1,080.4 

99.8 

'Pirst-nt  in  li.irc  nnioimts  imly. 


Tal)le  34.     Food  habits  of  Sparrow  Hawks  in  1970. 


Species 

No. 
Indv. 

% 

Indv. 

Approx. 
Biomass 

% 
Biomass* 

Peronu/sciis  maniculatus 

7 

21.2 

119.0 

30.4 

Passer  clomesticus 

3 

9.1 

75.0 

19.2 

^Itirnis  vulgaris 

2 

6.1 

168.0 

42.9 

Uta  stansl>uriana 

3 

9.1 

12.0 

3.1 

Pltrynosonia  plat i/ rhinos 

1 

3.0 

9.0 

2.3 

Locustidae 

13 

39.4 

8.2 

2.1 

Curculionidae 

4 

12.1 

0.4 

Tr. 

Totals 

33 

100.0 

391.6 

100.0 

'Present  in  trace  amounts  onlv. 


Biological  Sehies.  \'ol.  18,  No.  .3       Bkeedinc  Ecology  ok  Ut.\h  K.-vptobs 


51 


Table  35.     Food  habits  of  Short-eared  Owls  in  1970. 


No. 

% 

Appro.x. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

Dipodomifs  ordii 

7 

20.0 

476 

37.4 

Reithrodoiitomys  tnei:.(ilotis 

2 

5.7 

24 

1.9 

Peromt/sciis  maniadatus 

19 

54.3 

323 

25.9 

Pcroi:.nathu.s  parvus 

.3 

8.6 

45 

3.5 

Unidentifk'cl  pa.s.scrine 

1 

2.9 

30 

2.4 

Sturnis  vulgaris 

1 

2.9 

84 

6.6 

StttrncIIa  ncjjccta 

2 

5.7 

290 

22.6 

Totals 

35 

100.1 

1,272 

100.3 

Table  36.     Food  habits  of  Burrowing 

Owls  in   1969. 

No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass" 

Dipodomtjs  ordii 

11 

12.4 

748.0 

73.1 

Peroi:.nathtis  formosits 

1 

1.1 

19.0 

1.9 

Microtus  sp. 

2 

2.2 

76.0 

7.4 

Phalaenoptilus  mittali 

1 

1.1 

62.0 

6.0 

Otocoris  alpcsfris 

3 

3.3 

84.0 

8.2 

Vta  staushuriana 

1 

1.1 

4.0 

0.3 

Locustidae 

29 

32.6 

18.3 

1.9 

Scarabidae 

19 

21.3 

5.7 

0.6 

Silphidac 

11 

12.4 

3.3 

0.3 

Carabidae 

7 

7.9 

1.6 

0.2 

Teiu'brionidae 

2 

2.2 

1.1 

0.1 

.■\iaiiae 

2 

2.2 

0.8 

Tr. 

Totals 

89 

99.8 

1,023.8 

100.0 

*  Pi  (-sent  in  liiice  .immmts  only. 


Table  37.     Food  habits   of  Burrowing  Owls  in   1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass 

D'.jxidoiiu/s  ordii 

4 

5.5 

272.0 

61.9 

Pcromt/sctis  iiuinicu 

hit  us 

2 

2.7 

34.0 

7.7 

Reithrodontomys  megalotis 

1 

1.4 

12.0 

2.7 

Otocoris  alpestris 

2 

2.7 

56.0 

12.7 

Passer  doniesticus 

1 

1.4 

25.0 

5.7 

I'td  staml)tiriarm 

3 

4.2 

12.0 

2.7 

Locu.stidac 

34 

46.6 

21.4 

4.9 

Silphidac 

13 

17.8 

3,9 

0.9 

Caial)idae 

8 

11.0 

1.8 

0.4 

Scarabidae 

5 

6.8 

1.5 

0.3 

Totals 

73 

100.1 

439.6 

99.9 

are  perhaps  the  iiKJSt  eoinnion  nestini^  species 
on  the  stiuK'  area  in  such  areas  as  quarries  and 
abandoned  niiiiiiiL!;  structures,  where  they  are 
oceasionalK'  prcNctl  on  1)\'  raptors.  Red-tailed 
Hawks  also  infrecjuently  preved  on  snakes,  the 
two  species  recorded  from  this  stndv  being  tlu' 
gopher  snake  and  striped  racer. 

Swainson's  Hawks  on  the  stndy  area  utilized 
a  total  of  1.5  pre\'  species  ineluding  5  ruamiiial. 


5  a\ian,  1  reptile,  and  4  invertebrate  species.  The 
relati\e  composition  of  the  Swainson's  Hawk 
diet  is  as  follows:  mammals,  51.9  percent  of  the 
total  pre\'  individuals  and  99.1  percent  of  the 
total  pre\'  biomass;  birds,  16.9  and  0.8  percent; 
reptiles,  0.6  and  0,2  percent;  invertebrates,  .30.6 
and  less  tlian  0.1  percent.  Swainson's  Hawks 
were  the  only  large  raptors  studied  in  which  the 
average  frecjuencv  of  lagomorjih  prev  was  less 


52 


BmoiiAM  VouNG  University  Science  Bulletin 


than  lialf  of  tlic  total  diet.  Lagomorphs  thus 
constituted  56.1  pcrct'ot  of  the  diet  in  1969  hut 
onlv  30.4  percent  in  1970.  However,  in  both 
years  the  higonioiphs,  hv  \irtne  of  tlieir  large 
body  size,  comprised  almost  99  percent  of  the 
total  prey  biomas.s.  The  second  most  numerous 
prey  items  were  Locustid  insects  which  com- 
prised an  average  19.9  percent  of  the  yearly 
diet,  although  contributing  comparatively  small 
amounts  of  the  total  biomass.  Other  insects 
taken  included  carabids,  tenebrionids,  and 
gryllids.  Deer  mice  were  taken  iiifrequentlv,  as 
were  meadow  mice.  Horned  Larks  were  the 
most  frequently  taken  avian  species  and  consti- 
tuted almost  7  percent  of  the  total  prev  taken. 

Information  on  the  food  habits  of  the  Prairie 
Falcon  was  obtained  only  during  the  1970 
breeding  season.  Prairie  Falcon  prey  consisted 
of  nine  species,  including  three  mammal,  five 
avian  and  one  insect  species.  Birds  were  the 
most  frequently  taken  prey  and  comprised  49.8 
percent  of  the  prey  individuals  Ijut  only  4.1 
percent  of  the  total  prey  biomass.  Mammals 
comprised  30.7  percent  of  the  prey  individuals 


and  contributed  a  prev  biomass  of  86.3  percent, 
while  invertebrates  accounted  for  19.2  percent 
of  the  prev  individuals  but  for  little  or  no  bio- 
mass. The  two  most  freeiuentlv  taken  prey 
species  were  the  Honied  Lark  (26.9  percent  of 
the  total  prey  individuals)  and  antelope  ground 
squirrel  (19.2  percent),  but  juvenile  black- 
tailed  jackrabbits  comprised  over  65  percent  of 
the  prey  biomass,  even  though  taken  only  one- 
sixth  as  often. 

Tile  food  of  Marsh  Hawks  included  10  prey 
species,  of  which  there  were  4  mammals,  3 
birds,  1  reptile,  and  2  invertebrate  species. 
Marsh  Hawks  preyed  most  fretjuently  on  mam- 
mals (62.5  percent  of  the  prey  items)  which 
also  contributed  the  bulk  of  the  prey  biomass 
(91.9  percent).  Of  the  other  major  prey  groups, 
birds  were  taken  21.4  percent  of  the  time  and 
comprised  8.5  percent  of  the  prev  biomass,  rep- 
tiles 14.7  and  0.7  percent  and  invertebrates  1.4 
and  0.3  percent,  respectively.  The  most  im- 
portant prev  of  the  Marsh  Hawks  included 
black-tailed  jaekral)liits  and  the  deer  mouse. 
The  majorit)   of  rabbits  taken  were  immatures, 


Table  38.     Food  habits  of  Ravens  in  1969. 


No. 

% 

."Vpprox. 

% 

Species 

Indv. 

Indv. 

Bioma.ss 

Biomass" 

Leptis  calif orniciis  ( juv ) 

19 

3L1 

19,000.0 

95.6 

Peromijscus  manicidatus 

12 

19.7 

204.0 

1.0 

Microtus  sp. 

3 

4.9 

114.0 

0.6 

Neotonia  Icpida 

1 

1.6 

217.0 

1.1 

Spizella  passcrina 

1 

1.6 

38.0 

0.2 

Passer  domesticus 

3 

4.9 

75.0 

0.4 

Oreoscoptes  monfunus 

1 

1.6 

45.0 

0.2 

Masticoph is  taeniattis 

1 

1.6 

169.0 

0.9 

Dermestidae 

9 

14.8 

0.9 

Tr. 

Silphidae 

6 

9.8 

1.8 

Tr. 

Curculionidae 

2 

3.3 

0.2 

Tr. 

Unident.  Coleoptera 

3 

4.9 

0.9 

Tr. 

Totals 

61 

99.8 

19,864.8 

100.0 

'Pi<"ioiit    in    ttiiro  nninunts  milv. 


Table  39.      Food  iiabits  of  Ravens  in   1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biomass" 

Si/Ivihii:,us  sp. 

6 

16.7 

6,000.0 

90.7 

Pcroniijsctis  iimniculatiis 

13 

.36.1 

221.0 

3.3 

Otocoris  alpestris 

4 

11.1 

112.0 

1.7 

Sttirnis  vul'j,(iris 

1 

2.8 

84.0 

1.3 

Maslirophis  lacnialus 

1 

2.8 

169.0 

2.6 

Sccl()}>or()us  grasciosus 

2 

5.6 

26.0 

0.4 

Unident.  Coleoptera 

9 

25.0 

2.7 

Tr. 

Totals 

36 

100.1 

6,614.7 

100.0 

•I*resent  in   Irace  amounLs  only. 


Biol()gic:al  Sehiks.  N'ol.  18,  No.  3       Bhkkding  Ecology  of  IItah  Haptohs 


53 


juveniles,  or  carrion  but  they  comprised  22.6 
percent  of  the  total  prey  biomass.  Deer  mice 
were  taken  more  frecjuently,  yet,  by  contrast, 
Townsends  ground  scjuirrels  comprised  only 
8  percent  of  the  prey  items  but  17.4  percent 
of  the  total  prey  biomass.  Horned  Larks  and 
Mourning  Doves  were  also  taken  occasionally. 

Sparrow  Hawks  on  the  study  area  utilized  a 
total  of  12  species,  which  included  2  mammal, 
4  birds,  2  reptiles,  and  4  invertebrates.  The 
relatixe  composition  of  the  prey  frequency  and 
biomass  of  the  major  prey  groups  of  the  Spar- 
row Hawk  is  as  follows:  maiumals,  25.6  percent 
and  .3S.2  percent;  birds,  16.1  and  57.0  percent; 
reptiles,  6.7  and  2.9  percent;  and  invertebrates, 
51.7  and  1.9  percent.  Locustids  were  the  most 
important  ia\ertebrate  prey  species,  averaging 
38.5  percent  of  the  yearly  diet.  The  more  im- 
portant vertebrate  prey  species  included  the 
deer  mouse,  which  comprised  22. .3  percent  of 
the  total  pre\'  items  and  29.5  percent  of  the 
total  prey  biomass,  and  Starlings,  which  con- 
tributed the  bulk  of  the  prey  biomass  (.33.3 
percent),  although  taken  infrequently.  Of  the 
a\ian  prey  species,  English  Sparrows,  Starlings, 
and  Western  Bluebirds  reflect  the  habitat  se- 
lection of  Sparrow  Hawks,  being  the  most  com- 
mon nesting  birds  in  and  around  the  abandoned 
mines,  (juarries,  and  mining  structures.  The  oc- 
currence of  Western  Bluebirds  as  prey  is  inter- 
esting, because  the  disappearance  of  a  bluebird 
and  the  subsecjuent  failure  of  its  nesting  efforts 
coincided  with  the  appearance  of  this  species  in 
tlie  prey  of  a  Sparrow  Hawk  pair.  The  blue- 
birds had  selected  a  nesting  site  within  the 
wooden  walls  of  a  luining  cabin  only  80  feet 
from  tlie  Sparrow  Hawk  nest  and  were  incu- 
l)ating  a  clutch  of  five  eggs  when  checked  the 
day  before  the  disappearance.  Two  days  later 
the  remains  of  a  bluebird  were  found  among 
the  pre\-  items  in  the  Sparrow  Hawk  pair's 
lust.  Powers  (1966)  cites  possible  examples 
of  Sparrow  Hawk  predation  on  bluebirds  in 
Montana,  and  Drinkwater  (1953)  recorded  a 
ease  of  Sparrow  Hawks  capturing  young  blue- 
birds by  nest  robbing. 

Information  on  Short-eared  Owl  food  habits 
was  obtained  only  in  1970  and  is  derived  from 
the  analysis  of  19  pellets  gathered  from  the  un- 
successful nest  site.  Pellet  anahsis  \ielded  a 
total  of  7  prey  species  and  35  individuals,  but 
onl\'  mammals  and  birds  were  present.  Mam- 
mals contributed  SS.6  percent  of  the  prey  indi- 
viduals and  68.2  percent  of  the  prev  biomass, 
while  birds  comprised  11.5  percent  and  31.8 
percent,  respecti\'ely.  The  two  most  important 
prey  species  were  Orel's  kangaroo  rat  and  the 
deer  mouse.    D(>er  iTiiee  were  taken  almost  three 


times  as  often  as  any  other  prey  species  and 
contributed  26.4  percent  of  the  total  prey  bio- 
mass. Ord's  kangaroo  rat  was  the  ne.xt  most 
fre(|uently  taken  prey  and  comprised  37.4  per- 
c(>nt  of  the  prey  biomass.  Western  Meadowlarks 
contributed  22.8  percent  of  the  total  prey  bio- 
mass. 

Burrowing  Owl  prev  included  a  total  of  15 
species  of  which  there  were  5  mammal,  3  avian, 
1  reptile,  and  6  invertebrate  species.  Burrowing 
Owls  preyed  most  frequently  on  invertebrates, 
which  comprised  80.4  percent  of  the  prey  indi- 
\iduals  but  only  4.8  percent  of  the  total  prey 
biomass,  the  lowest  of  all  the  major  animal  groups 
except  the  reptiles.  Mammals  contributed  80.4 
percent  of  the  total  prey  biomass  and  almost  13 
percent  of  the  prey  individuals  taken,  while 
birds  comprised  4.3  percent  of  the  prey  items 
and  16.3  percent  of  the  prey  biomass.  Locustids 
were  taken  more  frequently  than  any  other 
species,  averaging  39.6  percent  of  the  prey  indi- 
viduals but  only  3.4  percent  of  the  total  prey 
l)iomass.  In  contrast,  Ord's  kangaroo  rat  com- 
prised only  9  percent  of  the  yearly  prey  items 
but  contributed  67.5  percent  of  the  total  prey 
biomass.  Burrowing  Owls  lined  the  entrance 
of  their  burrows  with  chewed  up  prey  remains 
and  manure,  a  fact  also  recorded  bv  Stoner 
(1932,    1933),   Bent   (1938),   and  Scott    (1940). 

Ha\'ens  on  the  study  area  utilized  a  total  of 
16  prey  species  which  included  5  mammal,  5 
avian,  2  reptile,  and  4  invertebrate  species.  The 
majority  of  their  food  habits  were  determined 
from  castings  and  prev  remains  at  the  nest,  and 
there  is  the  possibility  that  some  of  the  prey 
brought  to  the  nestlings  may  have  been  carrion. 
Mammals  comprised  55.1  percent  of  the  prey 
individuals  and  96.2  percent  of  the  total  prey 
biomass.  Birds  comprised  11  percent  of  the 
prey  individuals  but  only  1.9  percent  of  the 
total  prey  biomass,  as  did  reptiles.  Inverte- 
brates, entirely  insects  in  this  case,  accounted 
for  28.9  percent  of  the  prey  individuals  but  con- 
tributed only  minor  amounts  to  the  total  prey 
biomass.  Lagomorphs  constituted  the  princi- 
pal prey  and  averaged  23.9  percent  of  the 
yearly  prey  individuals  and  93.2  percent  of  the 
total  prey  biomass.  Although  birds  were  taken 
infrefjuentlv.  Homed  Larks  and  English  Spar- 
rows were  the  most  common  avian  prey  species. 
Dermestids  and  unidentified  beetles  were  the 
most  frefiu(>ntly  taken  invertebrates.  In  1970 
the  deer  mouse  was  the  most  commonly  recorded 
prey  species,  but  no  black-tailed  jackrabbits 
were  found— in  contrast  to  1969.  Almost  two- 
tiiirds  of  the  jackrabbits  were  immatures  or 
juveniles,  and  there  is  the  possibility  that  some 
were  taken  as  carrion. 


54 


BniGHAM  Young  University  Science  Bulletin 
DISCUSSION   AND   CONCLUSIONS 


Populations 

The  average  yearly  raptor  population  sup- 
ported by  this  area  of  the  Great  Basin  is  ap- 
parently low.  Craighead  and  Craighead  (1956) 
recorded  yearly  populations  of  140  raptors  (9 
species,  64  pairs,  12  individuals)  during  a  two- 
year  study  of  a  36-square-mile  Michigan  wood- 
lot  habitat,  and  a  population  of  91  raptors  ( 10 
species,  45  pairs,  1  individual)  in  a  12-s([uare- 
mile  study  area  near  Moose,  Wyoming,  r(>pre- 
senting  average  densities  of  1.8  and  3.8  raptor 
pairs  per  square  mile  in  Michigan  and  Wyo- 
ming, respectively.  These  are  almost  four  and 
ten  times  the  avi-rage  densities  of  raptor  pairs 
recorded  from  this  study.  Additional  compari- 
sons are  available  from  studies  of  particular 
species. 

Golden  Eagles  nesting  on  the  study  area 
average  20  square  miles  per  pair.  Compara- 
tively, Dixon  (1937)  recorded  densities  of  ap- 
proxiinateh'  36  square  miles  per  pair  in  Southern 
California,  and  Arnold  ( 1954 )  found  similar 
pair  densities  in  Colorado.  In  other  studies 
Lockie  (1964)  found  Golden  Eagle  densities 
of  one  pair  per  27.1  square  miles  in  the  Scottish 
Iliglilands  and  McGahan  (196S)  reported  one 
pair  per  66.3  sejuare  miles  in  Montana.  Watson 
(1957)  found  relatively  high  breeding  densities 
of  one  pair  per  9  square  miles  in  another  Scot- 
tish study,  but  in  a  later  study  covering  a  wider 
portion  of  the  same  area  Brown  and  Watson 
( 1964 )  found  Golden  Eagle  pair  densities  rang- 
ing from  approximately  20  to  34  square  miles 
per  pair. 

Great  Horned  Owl  densities  averaged  one 
pair  per  10  square  miles  in  central  Utah.  Studies 
in  other  habitats  have  reported  much  higher 
densities.  I5aunigartner  (19.39)  estimated  pop- 
ulations of  one  pair  per  0.5  scjuare  miles  of 
riparian  habitat  near  Lawrence,  Kansas,  and  one 
pair  to  3  or  4  sciuare  miles  near  Ithaca,  New 
York.  Fitch  (1947)  estimated  a  very  high  popu- 
lation density  of  one  pair  per  0.25  square  miles 
in  California  chaparral.  In  other  studies  Erring- 
ton,  Hamerstrom,  and  Hamerstrom  (1940) 
found  one  pair  per  2  scjuare  miles  near  Prairie 
du  Sac,  Wisconsin;  Orians  and  Kuhlman  (1956) 
recorded  average  densities  of  one  pair  per  5 
square  miles,  also  in  Wisconsin;  and  Ilagar 
(1957)  reported  Great  Horned  Owl  densities  of 
one  pair  per  4.4  scjuare  miles  in  central  New 
York.  Cniighead  and  Craighead  (1956)  found 
average  densities  of  one  pair  per  5.8  square 
miles  in  Michigan  and  one  pair  per  3  square 
miles  of  stud\    area  in  northern  \\'voming. 


Densities  of  Ferruginous  Hawks  on  the  study 
area  averaged  one  pair  per  8  stjuare  miles.  Data 
on  population  studies  from  other  areas  are  lack- 
ing. 

Red-tailed  Hawks  averaged  approximately 
one  pair  per  13  scjuare  miles  on  the  study  area. 
Comparisons  with  other  areas  indicates  these 
densities  to  be  exceptionally  low.  Fitch,  Swen- 
son,  and  Tillotson  (1946)  reported  densities 
of  one  pair  per  0.5  square  miles  in  Madera  Coun- 
ty, California,  and  Orians  and  Kuhlman  (1956) 
found  densities  of  one  pair  per  2.2  and  2.8 
square  miles  in  Wisconsin.  In  other  studies 
Hager  (1957)  reported  densities  of  one  pair 
per  2.2  s(juare  miles  in  central  New  York;  Le- 
Duc  (1970)  found  one  pair  per  1.62  square 
miles  in  southeast  Minnesota;  and  Luttich, 
Keith,  and  Stephenson  ( 1971 )  reported  one  pair 
per  2.7  sfjuare  miles  near  Rochester,  Alberta. 
Craighead  and  Craighead  (1956),  however,  re- 
corded a  similar  low  densit>'  of  one  pair  per 
12.9  square  miles  in  Michigan  but  found  high 
densities  of  one  pair  per  1  square  mile  in  Wy- 
oming. 

Comparable  infonuation  on  the  population 
densities  of  the  majority  of  the  rest  of  the 
raptors  nesting  on  the  study  area  is  lacking,  but 
Craighead  and  Craighead  (1956)  found  greater 
densities  of  Swainson's  Hawks,  Prairie  Falcons, 
Marsh  Hawks,  Short-eared  Owls,  and  Ravens 
than  were  present  in  the  central   Utah  area. 

The  relativelv  low  raptor  population  densi- 
ties encountered  in  this  study  may  be  due  to  a 
number  of  factors.  As  previously  noted,  ap- 
proximately (me-half  of  the  area  ( i.e.,  much  of 
the  inter\ening  vallev  floors)  is  not  used  by 
any  of  the  breeding  raptors  for  any  purpose.  If 
these  areas  are  eliminated,  then  the  relative  rap- 
tor population  densities  become  more  efjuitable 
witli  tliose  of  other  geographic  areas.  In  addi- 
tion, tiie  raptor  population  studies  presented  in 
tlie  literature  are  often  representative  only  of  a 
specific  or  confined  area,  which  was  chosen  be- 
cause of  its  high  concentration  of  raptors  (see 
Craighi'ad  and  Craighead  1956,  p.  5;  Orians 
and  Kuhlman  1956,  p.  .382),  thus  artificially 
eliminating  the  bare  or  dead  areas.  Hence,  the 
raptor  dat;i  ma\-  or  may  not  be  representative 
of  the  entire  area  to  which  they  are  referred. 

Tile  Utah  area  regularly  supports  from  9  to 
11  raptor  species,  fully  as  many  as  was  found 
by  Craiglu'ad  and  Craighead  (1956)  in  both 
Micliigan  and  Wyoming.  In  addition,  a  broad 
overlap  of  raptor  species  occurred  between  these 
;ire;is,  with  fiv(^  of  the  ITtah  stud\-  area  species 


BiOLOCicAi,  Seiues,  \'ol.   18,  No.  3        Bkkkding  Ecology  of  Utah  Hai'tohs 


55 


also  present  in  Micliit!;an  and  seven  in  Wyoming. 
The  majority  of  the  raptors  on  the  stndy  area 
show  a  wide  geographic  range  and  exhibit  con- 
siderable adaptability  to  various  habitats.  That 
this  is  not  a  major  cause  of  the  observed  den- 
sity \'ariations  is  also  shown  bv  the  much  higher 
densities  of  the  same  species  in  man\'  areas  of 
their  range  as  already  noted,  with  the  single 
exception  of  the  Golden  Eagle.  However,  lack 
of  suitable  cover  and  habitat  has  apparently 
limited  the  populations  of  the  smaller  raptors, 
particularly  the  Sparrow  Hawk  and  Cooper's 
Hawk.  The  latter  species,  although  known  to 
nest  occasionally  in  the  pinyon-juniper  com- 
munity (Wolf,  1928;  Bee  and  Hutchings,  1942), 
is  probabh  outside  of  its  optimum  habitat.  It 
would  appear  however,  that  the  relatively  low 
populations  of  most  of  the  raptors  in  the  study 
area  cannot  be  attributed  to  habitat  factors 
alone. 

The  lower  producti\'ity  of  this  Great  Basin 
Desert  biome  should  limit  the  raptor  popula- 
tions to  some  extent,  even  though  mammalian 
predator  control  programs  havt'  resulted  in 
higher  populations  of  lagomorphs  and  rodents, 
the  chief  food  source  of  the  raptors.  Additional 
evidence  supporting  this  possibility  is  derived 
from  the  observed  fluctuations  of  raptor  popu- 
lations in  response  to  lagomoqih  population 
fluctuations,  a  subject  which  will  ])e  discussed 
in  detail  later.  Two  important  raptor  species 
on  the  stud\'  area,  the  Golden  Eagle  and  Ferni- 
ginous  Hawk,  were  not  part  of  the  raptor  popu- 
lation composition  of  the  areas  studied  by 
Craighead  and  Craighead  (1956).  Their  size, 
liome  range  requirements,  and  apparent  intoler- 
ance of  other  raptor  species  almost  certainly 
influenced  the  density  of  small  raptors,  par- 
ticularly in  view  of  the  previously  noted  Golden 
Eagle  predation  on  Short-eared  Owls  and 
Swainson's  Hawks.  Ferruginous  Hawks  appar- 
ently have  restricted  habitat  requirements  and 
did  not  nest  in  the  riparian  cottonuood  com- 
munities in  canyons  to  the  north  and  east  of  the 
study  area.  Here  nesting  Red-tailed  Hawks 
maintained  densities  on  the  order  of  one  pair 
per  0.5  -  2.0  sq  miles,  approximately  similar  to 
those  densities  reported  from  other  parts  of  their 
range,  and  furtlier  indicative  of  the  possible  ef- 
fects of  the  large  and  aggressive  Golden  Eagles 
and  Ferruginous  Hawks. 

Population  Fhictuations.  Variations  in  yearly 
raptor  populations  were  evident  during  the 
four-year  stud\'.  Raptor  populations  were  high- 
est in  1969,  averaging  37.8  percent  above  the 
1967  raptor  populaticm  levels,  while  196S  and 
1970   populations    were   intermediate.     In    addi- 


tion, a  high  proportion  of  pairs  of  the  1969  pop- 
ulation attempted  to  nest  (93.4  percent),  com- 
pared to  87.5  percent  of  the  1967  population, 
95.0  percent  of  the  1968  population,  and  74.4 
percent  of  the  1970  raptor  population.  These 
population  variations  were  due  primarily  to 
yearly  fluctuations  of  several  of  the  large  raptor 
species,  specifically  the  Great  Horned  Owl, 
Red-tailed  Hawk,  Ferruginous  Hawk,  and 
Swainson's  Hawk  and  were  apparently  inde- 
pendent of  the  relatively  stable  populations  of 
the  medium-  and  small-sized  raptors. 

The  tendency  of  pairs  to  reoccupy  nesting 
sites  and  territories  has  the  effect  of  stabilizing 
the  raptor  population.  This  tendency  is  ap- 
parently prevalent  in  almost  all  raptor  species. 
Craighead  and  Craighead  (1956)  reported  that 
almost  75  percent  of  the  raptor  pairs  in  the 
Michigan  and  Wyoming  study  areas  reoccupied 
their  same  nesting  vicinity.  Elsewhere,  Luttich, 
Keith,  and  Stephenson  ( 1971 )  reported  that 
only  12.4  percent  of  their  Red-tailed  Hawk 
pairs  built  a  new  nest  during  the  four-year 
study  near  Rochester,  Alberta,  and  both  Hagar 
(1957)  and  Orians  and  Kuhlman  (1956)  ob- 
served numerous  instances  of  Great  Horned 
Owls  and  Red-tailed  Hawks  reoccupying  their 
nesting  sites  or  territories  of  the  previous  year. 
Cade  ( 1960),  and  more  recently.  White  (1969b) 
have  expressed  the  opinion  that  a  traditional  or 
"genetic"  linkage  may  be  responsible  for  the 
almost  continuous  occupanev  of  certain  cliffs 
or  locales  by  Peregrine  Falcons  ( Falco  pere- 
grintis)  in  Alaska,  and  Herbert  and  Herbert 
( 1965 )  have  suggested  the  same  of  falcons  in 
the  New  York  City  region.  Conceivably,  such 
a  tradition  may  apply  to  other  raptor  species 
equally  as  well,  and  nesting  locales  may  be  re- 
used continuously  for  long  periods  of  time.  Nest 
decay  and  disintegration  in  this  area  of  the 
Great  Basin  is  remarkably  slow,  and  nesting 
sites  which  were  photographed  in  1941-1944  by 
Robert  G.  Bee  (Unpubl.  notes,  BYU  Life  Sci- 
vnccs  Museum)  were  still  present  and  in  some 
cases  in  use  by  the  same  species  in  1967-1970, 
suggesting  a  similar  trend  towards  long  tenn  oc- 
cupancy of  a  particular  site. 

Nest  Site 

Coiiijxirisoius  with  Other  Geographic  Areas. 
The  12  raptor  species  nesting  on  the  study  area 
show  a  wide  variation  in  nesting  selection 
throughout  their  geographic  range.  In  this  por- 
tion of  the  Great  Basin  the  majority  of  Golden 
l]agle  iK-sts  are  located  in  cliffs  ( 100  percent 
in  the  study  area)  but  Murphy,  et  al.,  (1969) 
recorded  a  few  built  on  artificial  structures  or 


56 


UnicHAM  VouNG  University  Science  Bulletin 


dirccth'  on  the  groiiiul,  and  Bcc  and  Uutchings 
(1942)  reported  Golden  Eagles  nesting  in  juni- 
pers and  Douglas  fir.  In  southern  California, 
Dixon  (1937)  found  Golden  Eagles  nesting  al- 
most exclusively  in  cliffs,  oaks,  or  eucal)ptus 
trees.  Carnie  (1954)  also  found  Golden  Eagles 
nesting  in  both  cliffs  and  trees  in  the  coastal 
ranges  of  California.  Elsewhere,  Wellein  and 
Ray  (1964)  reported  that  in  Colorado,  New 
Mexico,  and  Wyoming  87  percent  of  their  Gold- 
en Eagle  nests  were  in  cliffs,  11  percent  in  trees, 
and  1.3  percent  wi-re  on  the  ground.  In  Sas- 
katchewan, Whitfield  et  al.  (1969)  noted  that 
all  Golden  Eagle  uests  were  constructed  in 
cliffs.  In  Scotland,  Watson  (1957)  found  70 
percent  of  the  Golden  Eagles  nesting  in  cliffs 
and  30  percent  in  trees,  but  Gordon  ( 1955)  indi- 
cates that  the  majority  of  nests  in  the  central 
Highlands  are  in  trees,  and  in  cliffs  in  the 
Hebrides. 

In  this  area  59.3  percent  of  the  Great  Horned 
Owl  nests  were  in  cliffs,  25.9  percent  in  quarries, 
and  14.8  percent  in  junipers,  but  in  the  eastern 
portion  of  their  range  most  nest  in  trees.  Orians 
and  Kuhlman  (1956),  LeDuc  (1970),  and  others 
have  recorded  all  (heat  Horned  Owls  nesting 
in  trees.  In  studies  from  the  western  portion 
of  the  range,  Dixon  (1914)  found  Great  Horned 
Owls  in  California  utilizing  cliff  sites  and  Fitch 
(1947)  reported  a  ground  site  in  Madera  Coun- 
ty, California.  In  Utah,  Sugden  ( 1929)  reported  a 
Great  Horned  Owl  nesting  in  the  ruins  of  Indian 
cliff  dwellings,  and  Bee  and  Ilutchiugs  (1942) 
found  nests  in  junipers,  ccjttonwoods,  quarries, 
and  directly  on  the  ground. 

On  the  studv  area.  Ferruginous  Hawks  nested 
in  trees,  primarily  jimipers,  (69.4  percent)  and 
on  the  ground.  Cameron  (1914)  in  Montana 
and  Bowles  (1931)  in  Washington  have  de- 
scribed ground  nests  of  the  Ferruginous  Hawk 
and  Jacot  (19.34)  found  a  bulky  nest  in  a  34- 
foot  c-edar.  Bent  (19.37)  reported  Ferruginous 
Hawks  nesting  in  swamp  oaks  in  North  Da- 
kota. In  Canada,  Godfrey  ( 1966 )  describes 
nesting  sites  in  trees,  ledges,  river  cutbanks, 
and  on  hillsides.  Augell  (  U)68)  observed  a  Fer- 
ruginous Hawk  nest  built  on  a  slight  cliff  ledge 
in  Franklin  County,  Washington.  In  central 
Utah,  Bee  and  Hutchiugs  (1942)  found  Ferni- 
ginoiLS  Hawks  nesting  predominatelv  in  junipers 
but  noted  that  they  also  nest  in  tall  trees  and 
cliff   ledges. 

The  nesting  site  selections  of  Hed-tailed 
Hawks  show  wide  variations  throughout  their 
range.  On  the  study  area  54.5  percent  of  their 
nests  were  constructed  in  tr<'es,  36.4  percent  in 
cliffs,  and  9.1  percent  in  (|uarries.    In  other  parts 


of  the  state.  Wolf  (1928)  reported  them  nesting 
in  trees  and  cliffs  and  Hardy  (1939)  describes 
a  Red-tailed  Hawk  nest  constructed  on  a  pinna- 
cle ill  the  Book  Cliffs  of  central  Utah.  Else- 
where tlu-oughout  most  of  their  range,  they  most 
commonly  nest  in  trees.  In  California,  Fitch, 
Swenson,  and  Tillotson  (1946)  recorded  all  18 
pairs  oi  their  Red-tailed  Hawks  nesting  in  trees, 
as  did  Orians  and  Kuhlman  (1956)  in  Wiscon- 
sin; Hagar  (1957)  in  central  New  York;  Free- 
meyer  (1966)  in  Lyon  County,  Kansas;  Tyler 
and  Saetveit  (1969)  in  South  Dakota  and  Iowa; 
and  LeDuc  (1970)  in  southeast  Minnesota. 
However,  they  will  evidently  nest  in  any  avail- 
able site,  and  Dixon  and  Bond  (1937)  found 
eight  pairs  nesting  in  the  Petroglyph  Cliff  area 
in  northeastern  California. 

All  Swainsons  Hawk  nests  on  the  study 
area  were  constructed  in  low  junipers  in  the 
foothills.  Wolf  (1928)  and  Bee  and  Hutchings 
(  1942)  also  found  this  to  be  the  same  site 
preference  for  their  Swainsons  Hawk  nests.  In 
Montana,  Cameron  (1913)  found  Swainson's 
Hawks  nesting  in  a  variety  of  low  trees,  but 
primarilv  in  ash  and  cottonwoods. 

Two  of  the  three  Prairie  Falcon  nests  on 
tlie  study  area  were  located  in  quarries  and  the 
third  was  located  in  a  limestone  cliff  crevice. 
Cliff  nesting  appears  to  be  the  rule  for  this 
species  throughout  its  range,  and  no  exceptions 
seem  to  have  been  recorded.  Burrowing  Owls 
similarly  show  few  deviations  from  the  typical 
burrow  nest  site.  Both  Marsh  Hauks  and  Short- 
cared  Owls  are  more  commonly  found  nesting 
around  water.  Bent  (19.37)  describes  a  number 
of  nests  located  in  marshes  and  swamps  in 
Massachusetts,  North  Dakota,  and  New  Jersey. 
Bent  also  notes  that  J.  W.  Sugden  wrote  him 
of  a  Marsh  Hawk  nest  site  in  a  dry  wheat  field 
at  least  four  miles  from  water  in  Salt  Lake 
County,  Utah. 

All  of  the  Sparrow  Hawks  on  the  study  area 
nested  in  holes  and  crevices  of  structures,  quar- 
ries, or  junipers.  Hole  nesting  is  apparentlv 
mandatory  for  this  .species  and  the  majorit\'  of 
sites  reported  in  the  literature  are  of  this  type, 
although  the  cavity  may  take  the  fonii  of  a 
nesting  box  ( Heintzelman,  1964). 

Ra\-ens  on  the  stud\-  area  nested  in  high  re- 
mote cliffs,  but  Bee  and  Hutchings  (1942) 
also  found  their  nests  in  mining  structures  and 
tri'es.  Elscnvherc.  Ra\'eiis  hav(>  shown  e(|ual  if 
not  greater  adaptai)ilit\-.  In  Washington,  Bowles 
and  l^ceker  (19.30)  found  Ravens  nesting  in 
clilf  potlioles,  aband(;ned  houses,  on  telephone 
poles  and  oil  derricks,  and  among  the  beams 
of  a  railroad  trestle.    Rent    (1946)   recorded   13 


Biological  Skuii:.s,  \'t)L.  18,  No. 


BiitEDiNG  Hi:()Loi;v  of  Utah  Rai'tors 


57 


of  17  nests  in  cliffs  or  ledges,  and  the  remain- 
ing 4  in  conifers  var\ing  from  45-85  feet.  In 
the  north  they  nest  in  cliffs  or  ledges,  often 
in  close  proximity  to  Peregrine  Falcons  and 
Rough-leggetl  Hawks  (Fay  and  Cade,  1959; 
Cade,  1960).  In  England  they  commonly  nest 
in  high  cliffs  or  in  both  deciduous  and  conifer 
trees  "^(Holyoak  and  Ratcliffe,  196S). 

Differentiation  amonp,  Species'  Nest  Sites. 
The  revieu'  of  the  literature  presented  above 
suggests  that  these  raptor  species  show  a  wide 
range  of  nesting  site  selection  throughout  the 
\arious  portions  of  their  geographic  range.  Yet 
in  areas  where  they  nest  together,  such  as  here 
in  central  Utah,  both  similarities  and  subtle 
differences  may  be  present.  The  similarities 
observed  are,  of  course,  to  some  degree  a  func- 
tion of  the  uniformity  of  the  habitat.  For  the 
larger  raptor  species,  and  many  of  the  smaller 
raptors  also,  the  foothills  and  hills  lying  between 
large  expanses  of  surrounding  desert  provide 
the  most  attractive  of  the  potential  nesting  sites, 
offering  at  once  a  combination  of  remoteness, 
inaccessibility,  and  surveillance  of  possible  ap- 
proaches. All  of  the  raptors  except  the  Marsh 
Hawks  and  Burrowing  Owls  nested  most  often 
in  junipers  or  cliffs,  which  simph  represent  the 
predominant  form  of  available  nesting  sites. 
.Some  species,  however,  selected  a  narrower 
range  of  nesting  sites  than  did  others. 

Both  Ferruginous  Hawks  and  Swainson's 
Hawks  apparenth  required  a  restricted  form  of 
nesting  habitat.  Both  nested  exclusively  on  the 
low  foothills  surrounding  the  perimeters  of  the 
\'allevs  and  in  low  junipers  which  were  either 
isolated  or  situated  on  the  fringes  of  the  pinyon- 
juniper  woodland.  Ferruginous  Hawks  particu- 
larly seemed  to  prefer  isolated  knolls  and  tended 
to  nest  at  higher  elevations  than  Swainsons 
Hawks.  Three  such  knolls  present  in  the  south- 
eastern corner  of  the  studv  area  were  each  con- 
tinuously occupied  by  a  bre("ding  pair  of  Fer- 
ruginous Hawks  during  the  four  study  years. 
Observations  of  nesting  sites  in  adjacent  locales 
reinforce  this  conclusion. 

In  contrast,  Creat  Homed  Owls  and  Red- 
tailed  Hawks  showed  a  much  wider  selection 
of  nesting  sites.  Both  commonly  nested  in  cliffs, 
quarries,  or  trees  but  these  sites  tended  to  be 
more  remote  than  those  of  the  Swainson's  Hawk 
and  Ferruginous  Hawk.  Both  appeared  to  pre- 
fer nesting  sites  in  long  cliff  lines  or  within 
canyons  over  the  more  exposed  tree  sites,  in 
contrast  to  the  Ferruginous  Hawks  and  Swain- 
son's Hawks,  neither  of  which  nested  in  can- 
vons  or  on  high  cliffs.  However,  tree  sites 
were  occasionalK   used,  and  Great  Homed  Owls 


sometimes  nested  in  abandoned  Ft^rruginous 
Hawk  juniper  nests,  such  exposed  sites  utilized 
only  if  they  were  removed  from  active  Ferru- 
ginous Hawk  nests  and  territories.  Although 
Great  Horned  Owls  did  on  occasion  nest  in  rela- 
tively close  proximity  to  active  Ferruginous 
Hawk  nests  (average  distance  of  0.766  ±  0.16 
miles,  minimum  of  0.21  miles),  these  close  nests 
were  always  within  cliff  crevices  and  relatively 
unexposed.  Neither  Great  Homed  Owls  nor 
Red-tailed  Hawks  nested  in  thick  pinyon-juniper 
woodlands,  preferring  instead  to  nest  in  semi- 
isolated  junipers  or  within  50-70  feet  of  the  edge 
of  the  woodland.  On  the  other  hand,  some 
differences  between  the  two  species  were  ap- 
parent. Great  Homed  Owls  tended  to  nest  at 
slightly  higher  elevations  than  Red-tailed  Hawks 
and  preferred  to  nest  within  crevices  or  caves, 
whereas  Red-tailed  Hawks  usually  nested  on 
cliff    ledges. 

Golden  Eagle  nesting  sites  overlapped  con- 
sideiablv  with  those  of  Prairie  Falcons  and  Rav- 
ens and,  to  a  lesser  extent,  with  Great  Horned 
Owls.  Both  Golden  Eagles  and  Prairie  Falcons 
always  chose  cliff  or  quarry  nesting  sites,  which 
may  reflect  their  need  for  high  cliffs;  a  pair  of 
Falcons  nesting  in  1970  utilized  a  Golden  Eagle 
quarr\'  nest  \\'hich  had  been  constructed  the 
previous   vear. 

Of  the  remaining  raptors,  the  Cooper's  Hawk 
showed  virtually  no  overlap  in  its  choice  of  nest- 
ing sites.  No  other  raptor  nested  within  thick 
pinvon-juniper  woodlands  and  at  such  high  ele- 
\-ations.  In  contrast.  Short-cared  Owls  and 
Marsh  Hawks  both  exhibited  similar  choices  in 
nesting  sites  with  both  nesting  in  rabbitbrush- 
sagebrush  stands  on  the  desert  floor.  Burrowing 
Owls  similarly  nested  on  the  valley  floor,  but 
achieved  a  measure  of  isolation  owing  to  their 
utilization  of  buiTOws  for  nests. 

Sparrow  Hawk  nesting  sites  overlapped  with 
none  of  the  medium-  and  small-sized  raptor 
species  on  the  study  area.  Sparrow  Hawks  most 
commonly  nested  in  and  around  human  struc- 
tures. They  did  not  nest  directly  on  the  valley 
floors  except  at  higher  elevations  and  in  juniper 
cover. 

Statistical  comparisons  of  the  average  nest- 
ing elevations  of  the  raptor  species  reinforce 
the  above  statements.  Analysis  of  variance  tests 
indicate  that  the  average  nesting  elevations  of 
the  five  large  raptor  species  differed  significantly 
(p<0.01,  "F"  =  19.1).  Paired  "t"  tests  reveal 
that  all  possible  differences  are  significant  ex- 
cept between  the  CJreat  Horned  Owls  and 
Golden  Eagles.  However,  although  these  two 
species  show  much  overlap  in   nest  site  elcva- 


58 


Biiir.iiAM  YdUNG  University  Science  Bulletin 


tion,  it  has  already  been  sliown  that  they  prefer 
different  sites. 

Siniihir  analysis  of  variance  tests  of  the  five 
medium-  and  small-sized  raptor  species  for  which 
sufficient  comparative  data  is  available  also 
show  significant  differences  in  their  average 
nesting  elevations  but  only  at  p<0.05  levels 
("F"  =  12.2).  Most  of  the  lesser  variation  is 
attributable  to  die  essentially  similar  nesting 
site  elevations  of  Marsh  Hawks,  Short-eared 
Owls,  and  Burrowing  Owls  as  discussed  pre- 
viously; and  paired  "t"  tests  between  those  species 
most  likely  to  be  competitive  revealed  signifi- 
cant differences  in  nesting  elevations  between 
all  medium-  and  small-sized  raptors,  with  the 
three  exceptions  noted.  The  other  three  species, 
i.e.,  Prairie  Falcon,  Cooper's  Hawk  and  Raven, 
nested  in  sites  similar  to  those  of  the  large  rap- 
tor species  (cliffs  and/or  at  high  altitudes). 
Comparisons  lietween  these  and  the  cliff-nesting 
Red-tailed  Hawks,  Great  Horned  Owls,  and 
Golden  Eagles  reveal  that  there  was  no  signifi- 
cant difference  in  average  nesting  elevation  be- 
tween Prairie  Falcons  and  Golden  Eagles,  but 
Ravens  and  Cooper's  Hawks  nested  at  signifi- 
canth-  iiigher  eknation  than  Golden  Eagles, 
Great  Horned  Owls,  and  Ri^d-tailed  Hawks. 

Populations  and  Breeding  Habitat  Require- 
ments. Although  Ferruginous  Hawks  were  the 
predominant  raptor  species  on  the  study  area, 
their  abundance  was  confined  to  certain  locali- 
ties which  can  be  readil\-  described  topographi- 
cally and,  to  an  extent,  by  the  physiognomy  of 
the  surrounding  vegetation.  In  areas  where  the 
optimum  conditions  were  absent,  their  numbers 
dwindled  rapitlly  and  tliey  were  replaced  by 
the  Red-tailed  Hawk.  Red-tailed  Hawks  in  turn 
were  apparently  incapable  of  displacing  Ferru- 
ginous Hawks  from  the  foothill  rdgions,  although 
thev  were  present  in  immediately  adjacent  lo- 
cales if  a  suitably  different  nest  site  (i.e.,  a 
cliff  or  steep-sided  canyon)  was  available.  This 
situation  is  strikingh-  evident  in  areas  where 
the  two  species  nest  in  close  proximity  (<1.0 
miles  apart). 

Woodbury  and  Cottam  (1962)  liave  de- 
scribed the  various  ecological  habitats  of  Utah, 
and  it  miglit  Ik'  useful  to  examine  the  presence 
and  relative  populations  of  the  raptor  species 
within  those  habitats  occurring  in  the  study  area 
and  surrounding  localities.  The  applicable  habi- 
tat tvpes  of  Woodbury  and  Cottam  include  tiie 
following:  pigmy  conifers,  present  o\er  all  of 
the  high<-r,  better  drained  portions  of  tlie  study 
area  and  adjacent  locales;  desert  scrul),  present 
over  the  lower  elevations  of  Cedar  and  Rush 
valleys;    canvonlieads,     present     in     tlic    liiglier 


mountain  ranges  immediately  north  and  south 
of  the  study  area;  and  cultivated  valleys,  not 
one  of  Woodbury  and  Cottam's  original  habitat 
tvpes,  but  nevertheless  present  over  a  large  por- 
tion of  Cedar  N'allev  northeast  of  the  study  area. 

Six  of  the  raptor  species  nested  within  the 
pinyon-juniper  habitat,  but  all  spent  some  if 
not  most  of  their  limiting  activity  periods  in  the 
adjacent  desert  areas.  Of  these  tlie  Cooper's 
Hawk  appears  to  belong  most  exclusively  within 
the  woodland,  nesting  in  relatively  dense  stands 
and  hunting  primarily  in  the  lightly  wooded 
areas  or  o\er  small  hill-top  meadows.  In  con- 
trast, lioth  the  Swainson's  Hawk  and  Ferru- 
ginous Hawk  are  the  least  exclusive  members, 
nesting  on  its  fringes,  or  as  in  the  case  of  the 
Ferruginous  Hawk,  in  the  transitional  area  be- 
tween pigmy  conifers  and  desert  scrub.  Ferru- 
ginous Hawks  constructed  almost  one-third  of 
their  nests  within  the  desert  scrub  commimity, 
well  beyond  the  limits  of  the  woodland,  and 
thev  achieve  their  maximum  populations  in  such 
localities. 

Raptors  associated  with  the  desert  scrub 
community  in  tiie  study  area  include  Marsh 
Hawks,  Short-eared  Owls,  and  Burrowing  Owls. 
These  species  all  nested  on  the  valley  floors  at 
essentially  the  same  altitude  and  appeared  to 
be  restricted  to  tiiis  community.  However,  all 
other  raptors  except  the  Cooper's  Hawk  hunted 
within   tiiis   community. 

The  predominant  raptors  nesting  in  canyons 
included  Great  Horned  Owls  and  Red-tailed 
Hawks  (Fig.  24).  Canyons  apparently  pre- 
cluded Ferruginous  Hawks  and  Swainson's 
Hawks  in  some  way,  as  neither  attempted  to 
nest  within  this  habitat  type,  either  on  the 
study  area  or  in  adjacent  locales.  Large  can- 
yons to  the  northeast  supported  dense  popula- 
tions of  nesting  Red-tailed  Hawks,  with  nesting 
pairs  a\eraging  0.5  linear  miles  apart  in  years 
of  maximum  populations. 

The  cultivated  land  northeast  of  the  study 
area  also  differed  in  raptor  spi'cies  composition 
and  relative  populations.  Here  Sparrow  Hawks 
and  Magpies  were  the  most  common  raptorial 
forms,  with  both  utilizing  the  windrows  of  eot- 
tonwoods  for  nesting  sites.  Red-tailed  Hawks 
and  Great  Honu'd  Owls  infre(]uentl\'  nested 
here  also;  such  nests  were  usualh'  disrupted  or 
destro\('d  by  humans  before  completion  of  the 
e\ele. 

Productivity 

C.lulcli  Size  Comparisons.  Comparisons  with 
other  populations  indicate  slight  variations  in 
a\-eiage  eluteh  size  of  most   of  the  study  area 


Biological  iliauEs,  \'ol.  IS,  No.  3        Bul'.edinc;  Ecology  oi'  Utah  ll,-\rTons 


59 


P 

1 


Fig.  24.     Great    Horned   Owl    nest    in    West   Canvon,    March     1969.       The    nest    was    constructed    the    previous 
year  bv  Red-tailed  Hawks. 


raptors,  but  the  majority  are  in.significant.  Con- 
sequentlv,  a  few  comparisons  should  suffice. 

Yearly  Golden  Eagle  clutches  on  the  study 
area  averaged  2.07  ±  0.07  eggs.  In  a  series  of 
studies  in  Cahfornia  Dixon  ( 1937 )  reported  av- 
erage clutches  of  2.0  eggs,  Hanna  (19.30)  found 
an  average  clutch  size  of  1.7  eggs,  and  Slevin 
(1929)  found  an  average  clutch  size  of  1.95 
eggs  for  21  clutches.  In  Scotland  Gordon  (1927) 
reported  an  average  clutch  size  of  1.91  eggs 
per  clutch  for  82  clutches.  Jollie  (1943)  found 
1.8  eggs  per  clutch  for  five  clutches  in  Colorado, 
and  more  recently  McGahan  ( 1968 )  recorded 
an  average  clutch  size  of  2.1  eggs  for  20  nests 
in  Montana. 

Great  Homed  Owl  clutches  on  the  study 
area  averaged  2.82  ±  0.15  eggs.  Surprisingly, 
only  a  few  studies  are  available  for  comparison. 
Craighead  and  Craighead  (1956)  reported  aver- 
age clutch  sizes  of  1.9  eggs  in  Michigan  and 
2.2  eggs  in  Wyoming.  Wolhuter  ( 1969 )  reported 
an  average  clutch  size  of  1.9  eggs  for  nine  nests 
near  Lawrence,  Kansas,  and  Tyler  and  Saetveit 
( 1969 )  reported  average  clutches  of  2.0  eggs 
for  three  nests  in  South  Dakota  and  Iowa.  In- 


terestingly, all  are  significantly  lower  than  the  av- 
erage Great  Horned  Gwl  clutches  of  this  area(t 
=  5.43  for  the  Kansas  comparison,  t  :=  5.54  for 
the  South  Dakota  and  Iowa  comparison,  and  t 
=  4.49  for  the  Wyoming  area  comparison). 

Insufficient  comparative  data  is  available 
on  the  average  clutch  size  for  Ferruginous 
Hawks. 

Red-tailed  Hawk  clutches  on  the  study  area 
averaged  2.89  ±  0.13  eggs.  In  Michigan,  Craig- 
head and  Craighead  (1956)  recorded  average 
clutches  of  2.0  eggs,  but  in  Wyoming  an  average 
of  2.3  eggs  per  clutch  was  found.  Elsewhere, 
Freemeyer  (1966)  found  an  average  clutch  size 
of  1.9  eggs  for  21  nests  in  Kansas;  LeDuc  ( 1970) 
foimd  an  average  of  2.3  eggs  per  clutch  for 
three  nests  in  Minnesota;  and  Luttich,  Keith, 
and  Stephenson  ( 1971 )  reported  an  overall  av- 
erage of  2.0  ±  0.1  eggs  per  clutch  in  Saskatche- 
wan. Paired  "t"  tests  indicate  that  the  average 
clutch  sizes  recorded  from  this  study  are  signifi- 
cantly larger  than  the  overall  average  clutches 
of  each  of  the  other  areas  noted  above. 

Swainson's  Hawk  clutches  on  the  study  area 
averaged  2.2    ±   0.17  eggs.    In  the  only  other 


60 


Bricham  Young  University  Science  Bulletin 


informative  study  available  Cameron  (1913) 
found  an  average  cluteh  size  of  2.6  ±  0.67 
eggs  in  Montana,  significantly  higher  than  those 
from  this  area. 

The  single  Prairie  Falcon  clutch  contained 
5.0  eggs.  Craighead  and  Craighead  (1956)  re- 
ported average  Prairie  Falcon  clutches  of  5.0 
eggs  in  Wyoming,  but  Enderson  (1964)  found 
an  average  clutch  size  of  4.5  eggs  for  55  nests 
from  the  intemiountain  area. 

Marsh  Hawk  clutches  on  the  study  area 
average  5.0  ^t  1.4  eggs.  Elsewhere,  Hammond 
and  Henry  (1949)  in  a  three-year  study  in 
North  Dakota  found  a  range  of  4.87  ±  0.806  to 
5.25  ±  0.774  eggs  per  clutch  for  60  clutches, 
while  Craighead  and  Craighead  (1956)  found 
average  clutches  of  4.35  eggs  per  clutch  in 
Michigan,  and  Sealey  (1967)  reported  an  aver- 
age clutch  size  of  4.18  eggs  for  21  nests  in  Al- 
berta and  Saskatcliewan. 

The  single  Short-cared  Owl  clutch  contained 
7  eggs.  In  other  areas  Goelitz  (1918)  reported 
an  average  clutch  size  of  7.3  eggs  for  four  nests 
in  Saskatchewan,  but  Kitchin  (1919)  found  an 
average  clutch  size  of  only  3.5  eggs  for  seven 
nests  in  western  Washington.  At  the  northern 
edge  of  the  range,  Pitelka,  Tomich,  and  Treichel 
(1955a,  1955b)  reported  an  average  clutch  size 
of  6.8  eggs  for  22  clutches. 

Sparrow  Hawk  clutches  in  tlie  study  area 
averaged  5.22  ±  0.38  eggs.  In  Michigan  and 
Wyoming  their  average  clutch  sizes  were  4.4 
eggs  (Craighead  and  Craighead,  1956).  Rocst 
(1957)  indicates  an  average  clutch  size  of  5.1 
eggs  irt  Oregon,  and  Heintzelman  and  Nagy 
(1968)  found  an  average  clutch  size  of  4.23 
eggs  for  13  nests  in  Pennsylvania.  In  experi- 
mental propagation  studies,  Willoughby  and 
Cade  ( 1964 )  reported  an  average  clutch  size  of 
3.66  eggs  for  12  clutches. 

Raven  clutches  on  the  study  ari-a  averaged 
5.36  ±  0.34  eggs.  Comparatively,  Craighead 
and  Craighead  ( 1956 )  found  mean  clutch  sizes 
of  three  nesting  pairs  in  Wyoming  to  average 
5.7  eggs.  In  England,  Hatcliffe  (1962)  reported 
an  average  clutch  size  of  4.6  eggs  for  139  nests. 

Hatchin<i  Success.  From  1967-1970,  14  nest- 
ing efforts  of  Colden  Eagles  produci'ti  1.2  young 
per  nest  for  an  overall  hatching  success  of  70.8 
±  14.9  percent.  Comparatively,  Wellein  and 
Ray  (1964)  reported  1.59  voung  iiatched  per 
nest  for  23  nests  in  the  southern  l^ockies,  and 
McGahan  (1968)  found  an  average  of  1.59 
young  per  nest  hatched  in  Montana.  In  central 
Saskatchewan,  Whitfield  et  al,  (1969)  found 
an  average  of  1.8  young  per  nest  from  six 
nests. 


(Jreat  Horned  Owls  on  the  study  area 
hatched  an  average  of  2.5  young  per  nest  per 
year.  Elsewhere,  Craighead  and  Craighead 
(1956)  reported  a  two-year  average  of  1.42 
young  per  nest  in  Michigan  and  2.0  young  per 
nest  hatched  in  Wyoming.  Orians  and  Kuhlman 
(1956)  reported  an  average  of  1.4  young  per 
nest  in  Wisconsin  while  Hagar  (1957)  found 
average  broods  of  1.9  young  per  nest  during 
his  two-year  study  in  central  New  York.  More 
recently,  Marti  (in  Adolphson  and  Jonkel,  1969) 
reported  an  average  of  2.4  young  per  nest  for 
13  nests  in  Colorado;  Dunstan  (in  Adolphson 
and  Jonkel,  1969)  found  1.9  young  in  11  nests 
in  South  Dakota;  and  Adolphson  and  Jonkel  re- 
ported 1.96  young  per  nest  for  21  nests,  also  in 
South    Dakota. 

Ferruginous  Hawk  nests  on  the  study  area 
averaged  65.2  ±  5.2  percent  hatching  success  for 
an  average  of  2.3  young  per  nest.  In  the  onlv 
comparative  study  Adolphson  and  Jonkel  (1969) 
reported  2.66  young  fledged  from  three  nests, 
but  the  hatching  success  is  not  given. 

Red-tailed  Hawks  on  the  study  area  hatched 
76.7  ±  3.9  percent  of  all  eggs  produced  for  an 
average  of  2.3  young  per  nest  per  year.  Else- 
where, Craighead  and  Craighead  (1956)  found 
an  average  of  1.3  young  hatched  per  n(>st  in 
Michigan  and  2.1  young  hatclied  per  nest  in 
Wyoming.  Hagar  ( 1957 )  reported  an  average 
brood  size  of  1.9  young  per  nest  in  New  York 
and  Luttich,  Keith  and  Stephenson  ( 1971 ) 
found  an  overall  hatching  rate  of  1.9  young 
per  nest  of  75  nests  in  ,'\lberta. 

Swainson's  Hawks  on  the  study  area  averaged 
2.2  young  hatched  per  nest  per  year.  Compara- 
tively, Craigliead  and  Craighead  (1956)  reported 
an  a\'eragc  of  1.25  young  hatched  from  four 
clutches  in  Wyoming. 

The  Prairie  Falcon  nest  on  the  study  area 
hatched  3  of  5  eggs.  Elsewhere,  Craigliead  and 
Craighead  ( 19.56 )  ft)und  all  five  eggs  of  a  nest 
in  Wyoming  hatched,  but  more  recently  Ender- 
son (1964)  found  onlv  1.9  voung  hatched  per 
nest  studied. 

The  two  Marsh  Hawk  nests  hatched  an  av- 
erage 3.5  young  per  nest.  Coniparati\'e!v,  Ham- 
mond and  Henry  (1949)  reported  an  axeragc 
iiatching  rate  of  4.07  young  piT  nest  for  60 
nests  in  North  Dakota,  Craighead  and  Craig- 
head (1956)  found  a  very  low  hatching  rate  of 
1.4  young  per  nest  for  13  nests  in  Michigan, 
and  Sealey  (1967)  found  an  average  of  1.55 
young  hatched  per  nest  for  II  nests  in  Alberta 
and  Saskatchewan. 

From  1968-1970  Sparrow  Hawks  on  tlie  study 
arc;i  hatclii'd  an  a\'erage  of  4.7  young  per  nest. 


Biological  Sehies,  \'ol.  18,  No.  3       BiiELniNc:  Ecology  of  Utah  ri.\PTORs 


61 


In  other  areas,  Craighead  and  Craighead  (1956) 
found  an  average  of  2.5  young  hatched  per  nest 
in  Mieliigan  and  4.3  young  hatched  in  Wyo- 
ming. In  another  study,  Ileiiitzehnan  and  Nagy 
(196S)  reported  3.29  young  hatched  per  nest 
for  13  nests  in  central  Penns)'lvania. 

Ravens  produced  an  average  of  3.64  young 
per  nest  on  the  study  area.  In  their  study, 
Craighead  and  Craighead  (1956)  reported  an 
average  of  5.0  young  hatched  per  nest  for 
three  nests  in  Wyoming. 

Fledging  Rates.  During  the  four-year  study. 
Golden  Eagle  nests  fledged  an  average  of  1.0 
young  per  nest.  Elsewhere,  ^Vellein  and  Ray 
( 1964 )  recorded  an  a%'erage  of  1.32  birds  fledged 
per  nest  from  23  nests  in  the  southern  Rockies, 
and  McGahan  (1968)  found  an  average  of  1.37 
young  fledged  per  nest  from  45  successful  nest- 
ings in  Montana.  In  a  series  of  studies  in  Scot- 
land, Watson  (1957)  found  an  average  of  0.8 
yoimg  fledged  per  nest  over  a  twelve-^ear 
study  period,  Sandeman  (1957)  recorded  1.4 
young  fledged  from  19  successful  nests,  and 
Brown  and  Watson  (1964)  reported  1.3  young 
per  nest  from  19  successful  nests.  Recently, 
Dunstan  (in  Adolphson  and  Jonkel,  1969)  found 
an  average  of  1.67  Noung  fledged  per  nest  from 
21  nests  in  South  Dakota. 

From  1967-1970  Great  Horned  Owl  nests 
fledged  an  average  of  2.0  young  per  nest  for 
27  nesting  efforts.  Comparatively,  Craighead 
and  Craighead  (1956)  found  an  average  of 
0.55  young  fledged  per  nest  in  Michigan  and 
2.0  fledged  per  nest  in  \\'yoming;  Orians  and 
Kuhlman  (1956)  reported  an  average  of  1.87 
voung  fledged  per  nest  in  Wisconsin;  and  Hagar 
( 1957)  recorded  an  average  of  1.7  young  fledged 
in  New  York.  Recently,  Wolhuter  ( 1969 )  found 
an  average  of  1.5  young  fledged  per  nest  in 
Kansas. 

Ferruginous  Hawks  fledging  rates  averaged 
2.0  voung  per  nest.  In  comparison,  Dunstan 
(in  Adolphson  and  Jonkel,  1969)  reported  an 
average  of  2.66  \<)ung  fledged  per  nest  for  three 
nests   in   South   Dakota. 

Red-tailed  Hawks  fledged  an  average  of  1.74 
voung  per  nest  on  the  study  area.  Compara- 
tively, tliis  is  higher  than  Craighead  and  Craig- 
head (1956);  Fitch,  Swenson,  and  Tillotson 
(1946);  LeDuc  (1970);  and  Luttich,  Keith  and 
Stephenson  ( 1971 ) ;  but  this  is  lower  than  the 
overall  average  of  1.9  xoung  fledged  per  nest 
reported  by  Orians  and  Kuhlman  (1956)  and 
Hagar  (1957).  Ellis  in  Florida  and  Dunstan  in 
South  Dakota  (in  Adolphson  and  Jonkel,  1969) 
found  an  average  of  1.2  young  and  2.5  young 
fledged  per  nest,  respectively,  for  each  of  the 


two  areas,  with  the  latter  data  obtained  from 
20  nests.  Jonkel  (in  Adolphson  and  Jonkel, 
1969 )  reported  an  average  of  0.52  young  fledged 
per  nest  for  31  nests,  also  in  South  Dakota. 

Swainson's  Hawks  on  the  study  area  fledged 
an  average  of  1.4  young  per  nest.  Craighead 
and  Craighead  (1956)  found  only  0.4  young 
fledged  per  nest  for  five  nests  in  Wyoming. 
Recently,  Adolphson  (1969)  found  an  average 
of  2.0  young  fledged  per  nest  in  South  Dakota. 

The  Prairie  Falcon  nest  fledged  only  one  of 
three  young.  In  Colorado,  Enderson  (1964)  re- 
corded an  average  of  1.2  \oung  fledged  per 
pair  and  Sealey  (1967)  reported  an  average 
of  2.5  young  fledged  per  nest  in  southern  Al- 
berta. 

The  four  Marsh  Hawk  nests  of  1969-1970 
fledged  an  a\'erage  of  2.5  young  per  nest.  Else- 
where, Hammond  and  Henr)'  (1949)  reported 
an  average  of  2.1  young  per  nest  fledged  in 
North  Dakota,  and  Craighead  and  Craighead 
(1956)  found  a  very  low  fledging  rate  of  0.17 
young  per  nest  in  Michigan  for  13  nests. 

From  1968-1970  Sparrow  Hawks  on  the 
study  area  fledged  an  average  of  2.83  young  per 
nest.  Comparatively,  Craighead  and  Craighead 
( 1956 )  found  an  average  fledged  rate  of  3.4 
young  per  nest  in  Michigan  and  3.8  young  per 
nest   in   W\'oming. 

The  six  nests  of  the  Burrowing  Owl  on  the 
study  area  fledged  an  average  of  3.33  young 
per  nest.  In  comparison,  Grant  (1965)  esti- 
mated a  rate  of  3.83  voung  fledged  per  nest 
in   Minnesota. 

Ravens  fledged  onl\'  2.57  voung  per  nest 
on  the  study  area.  Craighead  and  Craighead 
( 1956 )  found  an  average  of  3.3  voung  fledged 
per  nest  in  Wyoming. 

Si/nopsis  of  Mortoliti/  and  Populiifion  Trends. 
As  is  evident  from  the  comparison  of  the  rela- 
tive hatching  success  and  mortality  data  with 
other  studies,  no  significant  differences  exist 
and  most  of  the  variations  existing  are  within  the 
ranges  reported  from  this  study.  The  same  holds 
true  also  for  the  majority  of  the  causes  of  mor- 
tality, with  nest  desertion,  egg  infertility,  and 
human  interference  being  the  principal  causes 
of  the  obser\'ed  mortality  of  eggs  and  voung. 
There  was  no  evidence  of  any  mortality  of  voung 
or  eggs  attributable  to  mammalian  predation, 
even  though  ground  nests  of  Ferruginous  Hawks, 
Red-tailed  Hawks,  and  Golden  Eagles  (the  lat- 
ter outside  the  study  area  l)ut  within  the  same 
habitat  type)  were  directly  accessible,  and  sev- 
eral carnivores,  including  coyotes,  bobcats,  kit 
foxes  and  mountain  lions  were  present  in  the 
study    area.     Angell    (196S)    reported   a    Ferru- 


R2 


limtMiAM  VouNG  Univehsity  .S(:ienc;k  Bulletin 


ginous  Hawk  pair  successfully  defending  their 
brood  against  an  intruding  coyote,  which  sug- 
gests that  these  raptors  are  little  troui)led  l)\ 
such  mammals.  A\ian  predation  could  be  an 
important  factor,  but  it  was  actualh'  only  ob- 
ser\-ed  in  the  two  cases  of  Golden  Eagle  preda- 
tion on  otlier  raptors,  as  previously  mentioned. 

Territoriality 

Co))i])iirisoii.s  iiith  Other  Areas.  Compara- 
tive information  on  home  range  size  is  available 
from  a  tew  published  sources. 

Golden  Kagles  on  the  study  area  maintained 
average  home  ranges  of  9.02  sq  miles.  This  is 
almost  equivalent  to  the  9.0  sq  miles  of  territory 
reported  by  Watson  (1957)  for  five  pairs  in 
Scotland;  however.  Brown  and  Watson  (1964) 
found  average  Golden  Eagle  home  ranges  \ary- 
ing  from  20  to  34  sq  miles. 

Great  Horned  Owls  on  the  study  area  main- 
tained a\-erage  home  ranges  of  2.02  sq  miles. 
Comparaliveiy,  Miller  (1930)  observed  that 
Great  Horned  Owls  maintained  an  irregular 
shaped  territory,  with  the  largest  diameter  of  no 
more  than  one-half  mile,  while  Baumgartner 
(1938)  found  Great  Horned  Owl  territories  to 
haw  a  diameter  of  0.5  miles.  Craighead  and 
Craighead  (1956)  found  h)ur  pairs  near  Moose, 
Wyoming,  to  ha\e  an  average  home  range  of 
0.82  ±  0.15  s(|  miles,  or  roughly  half  that  of 
the  owls  in  central  Utah. 

Red-tailed  Hawk  home  ranges  on  the  study 
are, I  a\eraged  2.5  s([  miles.  Fitch,  Swenson,  and 
Tillotson  (1946)  reported  that  6  Red-tai'ed 
Hawk  territories  in  Ga!ih)rnia  chaparral  ranged 
from  onh  0.125  —  0.313  sq  miles,  but  it  is 
possible  tliat  peripheral  areas  were  not  included 
in  their  d-ti'rminations.  Craighead  and  Craig- 
head ( 1956 )  reported  somewhat  larger  home 
ranges  of  six  pairs  in  Michigan,  which  averaged 
1.45  ±  0.21  s(|  miles.  In  Wvoming,  they  found 
eight  pairs  ha\ing  average  home  ranges  of  0.731 
-+:    O.ll  S((   miles. 

There  is  no  apparent  comparative  data  for 
the  home  ranges  of  Ferruginous  Hawks  and 
Short-eared  Owls. 

Swainson's  Hawk  home  ranges  on  the  stud\ 
area  axcrageil  1.51  s(i  miles  per  pair.  (Craighead 
and  Craighead  (19.56)  reported  an  a\(Mage  of 
0.95   ±  0.55  for  five  pairs. 

Prairie  Falcons  on  the  stud\  area  a\eraged 
2.35  s<i  miles  in  iiome  range  size.  This  is  much 
smaller  than  the  9.96  s((  miles  Craighead  and 
Craighead  (1956)  reported  for  a  pair  in  Wy- 
oming. 

Marsh  Hawks  on  the  stud\'  area  n^aii  taii;ed 
average  home  ranges  of     .68  S(|  miles.  In  Mi  iii 


gan,  Craiglieatl  and  Craighead  (1956)  reported 
tlie  home  ranges  of  11  Marsh  Hawk  pairs  as 
0.974     '    0.17  s(i  miles. 

Burrow  iug  Owls  on  the  studv  area  averaged 
0.32  s(i  miles  in  their  home  range  coverages. 
CJrant  (1965)  reported  territorial  sizes  of  0.025 
and  0.019  s(|  miles  for  two  pairs  in  Minnesota 
and  snggi'sted  that  pairs  in  colonies  maintained 
liome  ranges  of  0.016  to  0.028  s([  miles. 

Sparrow  Hawk  home  ranges  of  the  study 
area  a\iiaged  0.29  sfj  miles.  Comparatively, 
Craighead  and  Craighead  (1956)  reported  aver- 
age home  ranges  of  0.504  it  0.15  scj  miles  for 
five  pairs  in  Michigan  and  0.78  ±  0.14  sq 
miles  for  11  pairs  in  Wyoming. 

Ra\'ens  on  the  studv  area  possessed  average 
home  ranges  of  2.53  sq  miles.  Comparative  data 
from  Moose,  ^^'yoming,  indicates  that  average 
home  ranges  of  three  Raven  pairs  were  3.62  ± 
0.4  s(|  miles  (Craighead  and  Craighead,  1956). 

Home  Raiii^e  Characteristics.  Characteris- 
tically, the  home  ranges  of  raptors  on  the  study 
area  extended  well  out  into  the  desert,  which 
serves  as  their  principal  hunting  area.  Some  of 
the  study  area,  however,  was  imused;  that  is,  it 
contained  no  portions  of  an\'  raptor  home  ranges. 
Such  imused  areas  were  t\pically  far  from  any 
potential  nesting  sites  and  apparently  undesir- 
able in  terms  of  food  resources.  Undoubtedly, 
raptors  which  ha\e  to  travel  less  to  provide  suf- 
ficient food  for  their  young  are  more  efficient 
in  their  reproductive  efforts,  and  it  is  probable 
that  these  peripheral  areas  are  seldom,  if  ever, 
utilized. 

The  rugged  topography  of  the  study  area 
plued  an  importai  t  role  in  preventing  more 
frecpient  intraspecific  coiitaets  and  actually  al- 
lowed two  raptor  populations  to  e.xist,  one  on 
each  side  of  the  centralK"  located  hills. 

Intraspecific  and  interspecific  home  range 
o\er!aps  and  distances  between  active  nests  ap- 
peared to  be  a  function  of  several  factors,  in- 
ehuling  tolerance  antl  population  densities,  spe- 
cific nesting  site  selection,  and  actixity  patterns. 
Intraspecific  home  ranges  only  slightly  over- 
lapped, if  at  all  (except  in  the  Burrowing  Owl 
case),  and  never  o\erlapped  in  the  \'icinit\'  of 
the  nest  sit(\  Inti-rspecific  home  range  o\'erlap 
was  more  common.  Thus,  home  ranges  of 
CJolden  I'^agles,  CJreat  HonKxl  (h\ls,  l'\'rruginous 
Hawks,  Swainson's  Hawks,  and  Ra\ens  all  over- 
lapped to  some  extent  in  amounts  pre\iously 
noted.  Within  this  large  raptor  group,  however, 
home  range  o\'erlaps  between  members  of  the 
same  gemis,  e.g.,  Biiteo.  were  less  extensive  than 
l)etw(X'n  relativeU'  u^  related  raptors.  Hence 
hntli     t^dldei      Kag'e    aid     Havei      home    ranges 


BioLor.icAi.  Sehien,  N'ol.  IS.  No.  .'3       Bueedinc  Kcoi.ogv  :w  Ut.mi  R.\ptoks 


6.3 


showed  \irtuallv  100  per  cent  o\'erlap  with  some 
pairs  of  Ferruginous  Hawks  and  Red-tailed 
Hawks,  and  in  one  year  with  Swainson's  Hawks 
also.  However,  the  actual  nest  site  of  each  of 
these  diurnal  raptors  w  as  relatively  far  removed 
from  nest  sites  of  other  species,  and  their  flight 
patterns  indicated  a  form  of  altitudinal  terri- 
toriality which  pemiitted  movement  to  their 
more  commonly  utilized  hunting  areas. 

Home  range  overlaps  between  Great  Horned 
Owls  and  other  raptors  were  common  and  often 
extensive.  In  addition,  their  average  distances 
to  nearest  interspecific  neighbors  were  the  low- 
est of  any  of  the  large  raptors  on  the  study  area. 
That  this  is  a  reflection  of  their  acti\ity  patterns 
is  indicated  by  the  aggressiveness  with  which 
other  raptors  react  to  their  presence  when 
flushed.  Ob\iously  then,  Great  Horned  Owls 
are  able  to  take  advantage  of  a  large  portion 
of  the  total  habitat  available  compared  to  the 
diurnal  Buteos  because  of  the  direct  absence 
of  interspecific  territorial  competition,  although 
their  populations  are  smaller  than  those  of  the 
Ferruginous  Hawk. 

Most  of  the  smaller  raptore  on  the  study  area 
nested  within  the  home  ranges  of  one  or  more 
of  the  larger  raptors  and  occasionally,  as  pre- 
viously noted,  were  pre\  ed  upon  by  them.  Home 
ranges  of  these  smaller  raptors  seldom  over- 
lapped between  two  species  of  comparable  size, 
e.g.,  the  Sparrow  Hawk  and  Burrowing  Owl, 
but  much  variation  occurred  in  other  cases.  Bur- 
rowing Owls  displaced  the  greatest  interspecific 
tolerances,  but  their  differing  activity  patterns 
contributed  to  the  allowance  of  their  observed 
home  range  overlaps  with  Marsh  Hawks.  Simi- 
larly, the  close  nesting  and  high  degree  of  over- 
lap between  Marsh  Hawk  and  Short-eared 
Owl  home  ranges  can  also  be  attril)uted  to  dif- 
fering activity  patterns  which  pre\ented  direct 
confrontation  between  the  two  species.  Marsh 
Hawk  pairs  were  generally  tolerant  of  intra- 
specific  and  interspecific  home  range  overlaps. 
Raven  pairs,  however,  tolerated  little  intraspe- 
cific  home  range  overlap  even  though  their  large 
home  ranges  overlapped  considerably  with  other 
species. 

Relationship  of  Speciei'  Home  Raniie  Sizes. 
With  few  exceptions  there  is  an  e\ident  rela- 
tionship between  raptor  weight  and  territorial 
size,  with  the  Sparrow  Hawks  maintaining  the 
smallest  and  Golden  Eagles  the  largest  observed 
home  ranges.  Schoener  (1968)  has  shown  a 
strong  relationship  between  territorial  size  and 
body  weight  iov  a  number  of  herl)i\'orous  and 
predatory  bird  species.  The  determination  of  a 
similar  regression  of  bodv  weight  to   territorial 


size  in  the  raptors  results  in  a  positive  slope  of 
0.0022  ±  0.0004,  significantly  larger  than  zero 
(t  =  9.36)  at  the  0.001  level  (Fig.  25).  This 
suggests  that  their  larger  bodv  weights  require 
higher  energy  budgets,  which  in  turn  necessi- 
tate larger  home  ranges  to  provide  adequate  food 
supply.  The  slightly  smaller  home  ranges  of  the 
Ferruginous  Hawks  and  Swainson's  Hawks  (com- 
pared to  those  raptors  of  similar  size,  such  as 
the  Great  Horned  Owl  and  Red-tailed  Hawk) 
may  reflect  their  nesting  site  preferences  which 
place  them  nearer  to  their  prey  source  in 
the  \'alleys.  On  the  other  hand,  the  relatively 
large  home  ranges  of  the  Prairie  Falcons  do  not 
appear  to  be  explicable,  except  perhaps  in 
terms  of  the  wide-ranging  food  procurement  of 
tills  raptor. 

Relationship  between  Home  Range  Sizes 
and  Raptor  Population  Densities.  Home  ranges 
of  the  Great  Horned  Owl,  Red-tailed  Hawk,  and 
Swainson's  Hawk  on  the  study  area  are,  on  the 
whole,  much  larger  than  those  recorded  in 
studies  from  other  regions,  suggesting  that  these 
desert-nesting  raptors  range  more  widely  for 
food.  The  increased  home  range  sizes  may  also 
reflect  the  nature  of  the  habitat,  which  provides 
nesting  sites  in  the  hills  and  foothills  and  there- 
by promotes  the  location  of  nests  on  the  perime- 
ter of  the  home  range.  Another  aspect  of  the 
relatively  larger  territories  may  relate  to  the 
low  population  densities  of  these  central  Utah 
raptor  populations.  The  1970  home  ranges  of 
Great  Horned  Owls,  Ferruginous  Hawks,  Red- 
tailed  Hawks,  Marsh  Hawks  and  Ravens  were 
larger  than  the  comparable  home  ranges  of  the 
denser  1939  populations  of  these  species,  but  the 


1500 

Raptor    weight    in  gms. 


Kif^.  2,5.  Hflationship  between  raptor  weight  and  terri- 
torial size.  Niimlier.s  refer  to  raptor  .species  as 
previously  noted. 


64 


HiuciiAM  Young  Univeusiiy  Science  Bulletin 


diffcrcnci's  arc  not  statistically  significant  and 
tiic  correlation  cannot  he  made  until  additional 
data  arc  acciinuilatcd.  Other  studies  ha\i'  shown 
such  a  relationship  hetween  territory  size  and 
population  density,  with  territories  becoming 
larger  as  popidation  densities  decrease  (Craig- 
liead  and  Craighead,  1956;  Krebs,  1970;  South- 
ern, 1970).  However,  the  already  large  home 
ranges  on  the  study  area  suggest  that  any  addi- 
tional increase  in  size  over  those  recorded  might 
be  negated  by  the  reduced  efficiency  of  food 
procurement,  although  we  have  no  way  of  dem- 
onstrating this  at  present. 

Functiom  of  the  Home  Ranges.  The  classic 
concept  of  the  function  of  territorial  behavior 
suggests  that  it  is  a  method  of  population  regu- 
lation in  birds  and  other  vertebrates  (Howard, 
1920;  Wynne-Edwards,  1955,  1962).  All  raptors 
residing  on  the  study  area  maintained  definite 
home  ranges  and  largely  confined  their  activities 
within  them.  Pairs  reoccupying  their  territories 
of  the  previous  breeding  season  maintained  simi- 
lar home  ranges  from  year  to  year  (within  the 
noted  size  changes  previously  discussed)  if  the 
same  nest  site  was  reoccupied,  but  modified 
their  boundaries  somewhat  if  a  new  nest  site  was 
chosen,  with  the  new  territorial  shape  confonii- 
ing  to  the  pattern  of  radiation  away  from  the 
iK'w  nesting  site.  In  a  few  cases,  the  new  home 
ranges  differed  grcatl\-  in  shape  and  specific 
boundaries  compared  with  the  previous  breed- 
ing season,  perhaps  due  to  the  replacement  of 
one  or  both  members  of  a  pair.  Southern  ( 1970 ) 
found  tliat  Tawnv  Owl  territories  changed  \er\' 
little  from  year  to  year,  even  with  changes  in 
nesting  sites.  This  may  reflect  the  differences 
between  the  nonmigratory  Tawny  Owls,  which 
maintain  year-round  territories,  versus  the  mi- 
gratory species  nesting  on  the  Utah  study  area, 
wliicli  each  year  must  return  and  reclaim  their 
territories. 

Thus,  although  all  raptors  on  th<>  study  area 
were  in  a  sense  territorial,  it  is  questionable  as 
to  wliether  territoriality  limited  or  regulated 
their  populations.  Brown  (1969)  has  suggested 
types  of  territorial  behavior  which  acting  as  a 
functiem  of  population  densities  would  not  be 
limiting  at  low  densities  (i.e.,  all  raptors  would 
be  able  to  breed),  but  they  would  tend  to  be 
limiting  at  high  population  levels  because  some 
pairs  would  be  excluded  from  Ijreeding.  Un- 
forttmately,  none  of  his  categories  exactly  fits 
the  territorial  behavior  of  the  raptor  population 
within  the  present  study  area  which,  as  we  have 
already  shown,  depends  primarily  on  tiie  relative 
food  supply  as  a  breeding  stimulus. 


Territoriality  certainly  regulated  the  indi- 
\id\ial  species  popidations  and  probablv  also  the 
combined  Butco  species  populations  in  regions 
of  tlie  studs'  area  with  di-nse  raptor  populations, 
but  of  course  it  would  not  be  operative  in  the  re- 
gions of  low  population  density.  In  addition, 
evidence  of  old  nests  was  present  in  many  re- 
gions of  the  study  area  which  remained  unused 
by  the  raptors  during  this  study.  This  tends  to 
preclude  the  possibilitv  that  territory  was  a 
major  limiting  factor  in  regulating  breeding 
populations,  except  locally,  and  suggests  instead 
that  the  raptor  population  of  this  area  may  be 
undergoing  a  long-tenn  overall  decline  caused 
l)v  an  as  vet  unidentified  factor  or  factors. 

Predation 

Comparison.'i  iiith  Other  Areas.  Raptors  are 
considerably  opportunistic  in  their  predatory 
hal)its  and  take  a  variety  of  prey  throughout 
different  parts  of  their  range.  For  this  reason, 
and  because  literature  on  food  habits  of  the 
various  species  of  raptors  is  plentiful,  compari- 
sons will  be  limited  only  to  the  major  food  items. 

All  of  the  large  raptors  in  this  area  relied 
heavily,  indeed  almost  completely,  on  tlu'  lago- 
moiphs  for  their  chief  food  source.  Although 
the  frequency  of  lagomorphs  to  total  prey 
items  in  the  diet  varied  somewhat  between  the 
five  large  raptor  species,  their  relative  contribu- 
tion to  tlic  total  prey  l)iomass  was  consistently 
above  90  percent  for  each  species,  with  the  re- 
maining prey  species  contributing  only  minor 
amounts  to  the  total  prey  biomass  and  common- 
ly to  the  total  prey  frequency  . 

Elsewhere,  the  studies  of  Gloyd  (1925),  Mc- 
Atee  (1935),  Woodgerd  (1952),  Arnold  (1954), 
Carnie  (1954),  McGahan  (1968),  Whitfield  et 
al.  (1969),  and  Packard  et  a).  (1969)  have 
shown  a  similar  predominance  of  lagomorphs 
(Lepus  and  Sijh:Hiii!,us  sp. )  ranging  from  28  to 
96  perc(Mit  in  Colden  Eagle  diets.  Other  impor- 
tant prey  items  from  these  studies  included 
ground  si|iiirrels  (principally  Sj)crmophihis), 
wliicli  constituted  over  26  percent  of  tlic  prey 
taken  by  California  Golden  Eagles  in  Carnie's 
(1954)  study,  and  a  variety  of  avian  species 
wliieh  gcMicrally  constituted  less  than  15  percent 
of  the  total  prey  items.  Murie  (1944)  reported 
an  Alaskan  population  which  fed  prim;u-ily  on 
ground  squirrels  (CiteUus  unduhitus).  A  number 
of  European  studies  ha\-e  reported  high(M-  avian 
prev  bcqueneiis  ( Hagaii,  1952;  Lockie  and 
Stephen.  19.39;  Uttendorfer,  19.39);  Watson,  1957; 
iJrown  and  Watson,  1964),  and  the  latter  re- 
ported that  Red  Grouse  and  Ptarmigan  ( Lago- 
pus  s\).  )  comprised  60  percent  ol  the  total  mim- 


BiOLOciCAi,  Seiuks,  Vol.  IS,  No.  3       Bheedinc  Et:oi.or.Y  of  Utah  Rm-fobs 


65 


bt-r  of  prey   iti-ins  of  a  Scottish  Golden  Eagle 
population. 

Errington  (1932c),  Ellington,  Hanierstrom 
and  Hamerstrom  (1940),  Alcorn  (1942),  Baum- 
gartner  and  Baumgartner  (1944),  Fitch  (1947), 
brians  and  Kuhlman  (1956),  Crawford  (1968), 
Seidensticker  (1968),  and  Marti  (1969a)  also 
found  lagomorphs  to  be  the  principal  volumetric 
contribution  to  the  Great  Horned  Owl  diets 
within  their  respective  study  areas,  but  found 
most  other  prey  species  more  important  in  temis 
of  frequency.  Thus,  Fitch  (1940)  found  wood- 
rats  (Neotoma  fuscipes)  and  Jerusalem  Crickets 
(Stenapclmatus)  being  taken  most  commonlv; 
Brodic  and  Maser  (1967),  Crawford  (1968), 
Seidensticker  (1970).  and  Marti  (1969a)  found 
murids  taken  most  frequently;  and  Baumgart- 
ner and  Baumgartner  (1944)  reported  cotton 
rats  (Sigmodon  hispidus)  as  the  most  frequently 
taken  prev  item  on  their  study  area.  In  other 
areas  lagt)morphs  were  absent  or  negligible  con- 
stituents of  Great  Horned  Owl  diets.  Burns 
(1952)  reported  a  Florida  Great  Horned  Owl 
family  preying  primarily  on  American  coots 
(Fulica  americana),  and  Bond  (1940)  found 
harvest  mice  (Reithrodontomt/s  mcg.aIotis)  to 
be  the  principal  constituent  of  the  diet  of  a  Ne- 
vada  population. 

Red-tailed  Hawk  diets  similarlv  show  wide 
variations  throughout  their  range,  and  lago- 
morphs are  often  unimportant  constituents. 
Fisher  (1895)  and  McAtee  (1935)  found  murids 
to  be  the  principal  food  item  of  their  food  habits 
studies,  and  Errington  (1932c)  and  Errington 
and  Breckinridge  (193S)  reportctl  almost  e([ual 
numbers  of  mice  and  ground  squirrels.  Later  stud- 
ies ha\e  also  revealed  the  importance  of  ground 
squiiTels,  which  comprised  the  majority  of  prey 
items  of  studies  in  Wyoming  ( Craighead  and 
Craighead,  1956),  California  (Fitch.  Swenson, 
and  Tillotson,  1946),  and  Canada  ( Meslow  and 
Keith,  1966).  Recently,  Luttich  et  al.  (1970) 
have  shown  the  Richardson's  ground  s<{uirrt'l 
(Spermophilits  ricJiardsonii)  to  be-  the  most  im- 
portant constituent  of  the  total  prey  biomass  of 
Alberta  Red-tailed  Hawk  populations.  In  con- 
trast to  the  heavy  utilization  of  inamiiials  noted 
from  the  above  studies,  Orians  and  Kuhlman 
( 1956)  foimd  their  Wisconsin  population  preying 
consistentl)'  upon  birds,  of  which  pheasants 
(Phdiiauits  colchinus)  were  tlie  most  iiiipoitant 
item.  However.  Hardv  (1939)  found  the  most 
important  pre\  of  a  Red-tailed  Hawk  nest  in 
central  Utah  to  consist  of  lagoin(n[)]is  and  blow- 
snakes. 

In  Montana,  Cameron  (1914)  found  Fer- 
ruginous   Hawks    to    !)(■    feeding    primarilv    on 


prairie  dogs  ( Ct/nomt/s  sp. )  and  meadow  mice, 
but  Fisher  (1895)  and  Angell  (1968)  reported 
that  lagomorphs  comprised  the  greater  propor- 
tion of  prey  items  from  their  studies,  followed 
by  ground  squirrels.  Both  Cameron  (1914) 
and  Angell  (1968)  noted  that  birds  were  taken 
most  fretjuently  during  the  first  weeks  after  the 
young  had  hatched,  an  observation  in  agree- 
ment with  the  present  study. 

Food  habits  of  Swainson's  Hawks  apparently 
vary  greatly.  Cameron  (1913),  Munro  (1929), 
Fisher  (1S95),  and  White  (1966)  have  all  re- 
ported large  numbers  of  insects  taken  by  this 
species,  but  their  principal  volumetric  prey  items 
are  apparenth'  ground  squirrels  (Craighead 
and  Craighead,  1956).  In  Utah,  Stanford  (1929) 
reported  a  pair  feeding  on  field  mice  and  crick- 
ets. 

Prairie  Falcons  on  the  Utah  study  area 
preyed  most  fre(]uently  upon  Horned  Larks  and 
ground  squirrels,  but  juvenile  lagomorphs  con- 
tributed much  of  their  total  prey  biomass.  Else- 
where, the  studies  of  Fowler  (1931),  McAtee 
(1935),  Bond  (1939),  Enderson  (1964),  and 
Edwards  ( 1968 )  reported  similar  prey  prefer- 
ence's, with  the  exception  of  the  lagomorphs.  In 
other  studies,  T\ler  (1923)  reported  the  virtu- 
ally complete  utilization  of  birds  by  a  Cali- 
fornia population,  while  Craighead  and  Craig- 
head (1956)  found  both  meadow  mice  and 
ground  scjnirrels  to  be  taken  twice  as  often  as 
avian  prey. 

Marsh  Hawks  on  the  study  area  preyed  pri- 
marily upon  deer  mice,  although  birds  were 
also  taken  and  juvenile  lagomorphs  were  im- 
portant constituents  of  the  total  prey  biomass. 
McAtee  (1935)  found  birds,  particularly  Song 
Sparrows  (Melo.spiza  sp.),  to  be  the  most  fre- 
(|uent  species  in  the  stomachs  he  examined,  fol- 
lowed by  meadow  mice  and  lagomorphs.  Breck- 
inridge (1935)  and  Errington  and  Breckinridge 
(1936)  also  reported  a  predominance  of  avian 
prey  but  found  that  gnnmd  squirrels  and  cotton- 
tails comprised  the  larger  portion  of  the  total 
prey  biomass.  In  contrast,  Craighead  and  Craig- 
head ( 1956 )  reported  meadow  mice  occurring 
most  frequently  in  Michigan,  followed  by  birds, 
\\itii  rabbits  and  ground  s((uirrels  each  com- 
prising relatively  nnnor  amoxnits  of  the  total 
prey  biomass. 

Short-eared  Owls  on  the  study  area  utilized 
prim:uily  white-footed  deer  mice,  followed  by 
kangaroo  rats.  Elsewhere,  Short-eared  Owls 
seem  to  exhibit  a  distinct  preference  for  small 
mannnais,  paiticularK  deer  mice  and  meadow 
nnce,  and  Errington  (1932e),  Snyder  and  Hope 
(1938),    Fischer    (1947),   Kirkpatrick   and   Con- 


66 


IJmciiAM  Young  Univehsitv  Sciknck  Bulletin 


way  (1947),  Johnston  (1956),  Short  and  Drew 
(1962),  and  Munyer  (1966)  all  recorded  high 
incidences  of  these  two  prey  species.  In  addi- 
tion, all  of  the  above  studies  also  recorded  large 
numbers  of  birds  taken  as  prey. 

Sparrow  Hawks  on  the  study  area  took  a 
wide  variety  of  prey,  but  invertebrates  were 
their  main  dietary  item,  particularly  grasshop- 
pers; deer  mice  were  next  in  importance.  Heint- 
zelman  (1964)  has  summarized  much  of  tlie  in- 
formation on  North  American  Sparrow  Hawk 
predation  and  indicates  that  murid  rodents  and 
grasshoppers  are  the  most  common  components 
of  the  Sparrow  Hawk  diet. 

Invertebrates,  particularly  grasshoppers,  com- 
prised the  majority  of  the  prey  taken  by  Bur- 
rowing Owls  on  the  study  area.  Scott  (1940) 
reported  Burrowing  Owl  populations  in  Iowa 
to  be  preying  primarily  on  locustids  and  scara- 
bids  and  noted  that  vertebrates  were  rarely 
taken,  in  agreement  with  the  findings  of  Bourdo 
and  Hesterberg  (1950)  in  Michigan.  Grant 
(1965)  and  Marti  (1969a),  however,  while  not- 
ing a  similar  heavy  utilization  of  invertebrates, 
also  found  that  murids  formed  a  conspicuous 
portion  of  the  total  prey  biomass. 

Suqjrisingly,  lagomoiphs  were  an  important 
element  of  the  Raven  diet  in  central  Utah,  but 
an  unknown  percentage  was  undoubtedly  car- 
rion. Deer  mice  were  next  in  importance  and 
were  the  most  fre<iuently  taken  prey  species. 
Nelson  (1934)  also  found  a  heavy  utilization  of 
lagomorphs  (51  percent  of  the  total  prey  taken), 
followed  by  invertebrates,  chiefly  insects. 

Prey  Species  Taken  Versus  AvailaJnlitij.  Many 
of  these  central  Utah  raptors  show  similarities 
in  their  food  habits,  particularly  when  compared 
within  their  rilative  size  classes.  Raptors  have 
been  shown  to  respond  to  temporarily  super- 
abundant foods,  but  are  also  considerably  op- 
portunistic and  will  apparently  take  whatever 
is  available  and  most  easily  and  efficiently 
caught.  Comparisons  between  the  total  number 
of  available  prey  species  (potentials  derived 
from  Fautin,  1946)  reveal  that  the  collective  rap- 
tor population  utilized  much  of  its  potential 
prey  base.  Thus  60.7  percent  ( 17  of  the  28 
species  listed  by  Fautin )  of  the  mammal  species, 
51.1  percent  (2.3  of  a  potential  45)  of  tlie  birds, 
70  percent  of  the  reptiles  (7  of  10  species),  and 
11.9  percent  of  the  available  invertebrate  fami- 
lies (8  of  67  plus  families)  were  utilized  by 
one  or  another  raptor  species. 

However,  the  food  habits  studies  were  des- 
ignated primarily  to  ascertain  major  predation 
trends  and,  although  sufficient,  are  not  exhaus- 
tive.   Hence,  these  raptors  almost  certainly  will 


take  more  prey  species  than  revealed  by  this 
study,  although  this  would  occur  only  rarely.  In- 
stead, only  a  few  species  were  heavily  utilized 
and  these  tended  to  be  the  most  common  ani- 
mals on  the  study  area. 

Lagomorphs,  primarily  the  black-tailed  jack- 
rabbit,  were  the  most  heavily  utilized  vertebrate 
prev  species  and  were  recorded  as  prey  more 
frecjuentlv  than  any  other  vertebrate  species. 
As  such,  and  in  some  fonn,  they  were  the  major 
prev  of  7  of  the  11  species  of  raptors  studied, 
including  the  5  large  raptor  species.  Only  the 
smaller  raptors  excluded  this  species  from  their 
diet.  Black-tailed  jackrabbits  were  also  the 
single  most  abundant  and  conspicuous  medium- 
sized  mammal  on  the  study  area.  All  of  the 
raptors  showed  great  efficiency  in  procuring 
the  \()ung  of  this  species,  and  as  many  as  nine 
immature  jackrabbits  were  recorded  in  a  Golden 
Eagle  nest  at  one  time. 

Other  mammals  of  particular  importance  as 
prev  iucludetl  the  anti'lope  ground  sf^uirrel,  two 
kangaroo  rat  species,  and  the  deer  mouse.  Ante- 
lope ground  sciuirrels  were  a  common  food  item  of 
the  large  raptors  and  most  of  the  medium-sized 
raptors,  but  failed  to  appear  in  the  diets  of  the 
smaller  raptors.  They  were  the  most  frequent 
mammalian  prey  of  the  Prairie  Falcon.  Kanga- 
roo rats  were  a  very  common  minor  penneant 
influent  and  were  significant  elements  of  the 
diets  of  all  of  the  owl  species  nesting  on  the 
study  area  and  also  the  crepuscular  Ferruginous 
Hawk.  Both  Ord"s  kangaroo  rat  and  the  chisel- 
toothed  kan:i;ar(io  rat  were  taken  b\'  Great 
Horned  Owls  and  Ferruginous  Hawks,  but 
only  the  former  was  taken  by  Burrowing  Owls 
aiul  Sliort-eared  Owls,  whose  home  ranges  were 
restricted  to  the  \allev  floor.  Deer  mice  were 
distributed  in  all  the  stud\  area  habitats  and 
were  fre(|uentlv  taken  by  four  raptors,  including 
the  Red-tailed  Hawk,  and  less  fre(juently  by 
Tuost  of  the  otliiT  raptor  species. 

Horned  Larks  were  the  most  prevalent  avian 
species  on  the  study  area  and  were  tlie  only 
bird  spi'cies  of  major  importance  as  prey.  They 
were  recorded  among  the  prey  of  10  raptor 
species,  being  excluded  only  from  the  Short- 
eared  OuTs  diet. 

Locustids  were  the  onlv  inxertebrates  taken 
in  large  numhiTS  and  were  included  in  the  diet 
of  four  raptor  species.  They  were  of  particular 
importance  to  both  Burrowing  Owls  and  Spar- 
row Hawks.  Interestingly  Fautin  (1946)  found 
Orthoptcraus  nuieh  less  common  than  at  least 
eiglit  otlicr  major  insect  orders,  which  suggests 
lliat  these  represent  a  lower  limit  of  efficient 
prey  size  available  to  the  raptors  on  tlu'  studv 


BiOLor.ic:Ai.  Series.  \'()i..   18,  No.  3       BuEEDiNt;  Ecology  of  Uiaii  HAProns 


67 


area  ( although  not  iicces.sariK'  representing  the 
smallest  prey  which  might  be  taken). 

Relationship  betiveen  Raptors  and  Their 
Preij.  In  examining  the  food  habits  of  raptors, 
the  frequency  percentage  of  prev  items  can  be 
considered  to  reflect  the  prey  species  which  the 
raptors  are  expending  time  and  energy  to  ob- 
tain, whereas  the  biomass  percentages  essentially 
reveal  what  prey  species  sustain  the  raptors. 
Logically,  raptors  will  be  most  efficient  if  they 
can  expend  their  energies  on  the  largest  prey 
species  which  they  are  able  to  safely  capture 
and  kill,  thereby  achieving  a  maximization  of 
the  ratio  between  the  food  biomass  necessarv 
for  their  daily  energy  budget  and  their  energy- 
expending  hunting  time.  An  analysis  of  the 
raptor-prey  size  relationships  on  the  study  area 
reveals  this  to  be  the  case  (Fig.  26),  and  a 
gradual  increase  in  mean  prey  weight  was  found 
to  correspond  with  an  increase  in  average  raptor 
species  weight.  The  regression  of  the  two  vari- 
ables results  in  a  positive  slope  of  0.601  ± 
0.221,  significantly  larger  than  zero  at  the  0.001 
level  (t  ^  4.92).  There  were  no  significant  vari- 
ations in  mean  prey  weight  between  raptors  of 
approximately  the  same  weight.  This  is  evident 
in  comparisons  of  mean  prey  weights  of  the  Ruteo 
hawks  and  Great  Horned  Owl  and  points  up 
the  fact  that  these  species  must  bv  directly  com- 
peting for  the  same  food. 

In  summary,   the  predatoiy  habits   of  these 
raptors  reflect  pre\    a\aiiabilitv  and  a  size  dif- 


i    1000 


Fig.  26.  Relationship  between  raptor  weiglit  and  mean 
weight  of  prey  .species  taken.  N'umhers  refer  to 
raptor  species  and  follow  standard  te.\t  numbers. 
The  number  1.3  refers  to  the  Long-eared  Owl,  in- 
cluded  in   this   correlation   analysis. 


ferential  selection  correlating  with  the  raptor's 
body  weight.  Although  apparently  no  available 
prey  species  was  too  small  to  serve  potentially 
as  a  food  source,  several  of  the  largest  mammals 
were  not  utilized,  including  the  mule  deer,  bad- 
ger, coyote  and  kit  fox.  These  species  are  ap- 
parently larger  than  the  maximum  prey  weight 
wliich  can  safely  and  efficiently  be  obtained  and 
are  thus  safe  from  avian  predation,  although 
infrequent  accounts  of  Golden  Eagles  attacking 
or  killing  mule  deer  (Craighead  and  Craighead, 
1956),  bighorn  sheep  lambs  (Kennedy,  1948), 
pronghorn  antelope  (Lehti,  1947),  and  white- 
tailed  deer  ( Willard,  1916 )  have  been  recorded. 
With  one  exception,  no  examples  of  raptor 
predation  on  game  or  domestic  species  were 
found  during  this  stud\-,  despite  the  fact  that 
the  valleys  served  for  sheep  range  and  lambing 
during  the  spring  months.  McGahan  (1968) 
also  reported  a  conspicuous  lack  of  predation  on 
domestic  sheep  and  lambs  in  Montana.  Ravens 
on  the  study  area,  however,  sometimes  lined 
their  nests  with  slieep  wool,  probably  taken 
from  carrion. 

The  Ferruginous  Hawk 

Ferruginous  Hawks  were  the  predominant 
raptors  on  the  study  area  and  also  the  domi- 
nant Buteos.  In  this  respect,  they  appear  to  dis- 
place the  Red-tailed  Hawk  and  Swainson's  Hawk 
and  limit  the  respective  populations  of  these 
species  within  the  study  area  habitats.  Allen 
(1874)  also  recorded  Ferruginous  Hawks  as 
the  most  numerous  raptor  in  Montana  with  the 
exception  of  the  Sparrow  Hawk,  and  recently 
Gra)son  (in  Adolphson  and  Jonkcl,  1969)  re- 
ported that  Ferruginous  Hawks  were  di.splacing 
Red-tailed  Hawks  and  occupying  their  former 
ni'sting  territories  in  the  Texas  panhandle.  The 
same  possibilit)-  exists  in  the  Utah  area  also,  as 
evidenced  by  the  fact  that  Behle  ( 1944 )  reported 
Swainson's  Hawks  to  In-  the  most  common 
hawks  of  the  central   I'tah  valleys. 

Yet  the  Ferruginous  Hawk's  dominance  and 
indeed  its  presence  is  highly  limited  by  its  nar- 
row breeding  habitat  recjuirements,  as  previously 
discussed.  In  faxorable  areas  it  consistently  pro- 
duces significantly  larger  clutches  than  any  of 
the  other  large  raptors  on  the  study  area  and 
also  succeeds  in  fledging  more  young  per  nest. 
In  these  areas  it  is  apparently  limited  only  by 
its  minimmn  interspecific  (nearest  neighbor) 
nesting  site  distances.  But  it  tends  to  be  en- 
tirely absent  from  unfavorable  habitats,  which 
stands  in  marked  contrast  to  the  relatively  ver- 
satile Great  Horned  Owl,  Red-tailed  Hawk, 
Raven,  and  e\'eii  Ciolden   Eagle,  which  may  on 


68 


limciiAM  Young  Univeksity  Science  Bulletin 


occasion  disphu'  a  surprisingly  wide  choice  of 
nesting  sites.  Its  absence  from  less  favorable 
areas  is  conspicuous  and  can  be  predicted  on 
the  basis  of  the  vegetational  and  topographic 
features  of  the  habitat.  Thus,  neither  steep- 
sided  canyons  nor  the  interiors  of  piuNon-juniper 
woodlands  were  utilized.  Neither  of  these  habi- 
tats support  the  high  lagomorph  populations 
which  constitute  the  chief  prey  of  the  Ferru- 
ginous Hawks.  Consequently,  these  habitats 
may  have  been  avoided  because  they  would 
necessitate  longer  flight  times  to  and  from  the 
more  favorable  sagebrush  and  grassland  hunt- 
ing areas,  and  additional  time  would  have  to  be 
.spent  in  food  procurement.  Instead,  the  Ferru- 
ginous Hawk  pairs  choose  to  nest  within  very 
short  distances  of  their  food  supply,  thereby 
lessening  the  problem  of  procuring  adequate 
food   for   their   large  l^roods. 

This  suggests  that  Ferruginous  Hawks  are 
dominant  in  numbers  because  they  find  suitable 
habitats  within  th(>  limits  of  the  study  area 
which  allow  a  maximization  of  their  productiv- 
ity. Undoubtedh',  their  status  as  the  largest  of 
the  North  American  Buteos  is  also  contributory. 

The  Long-eared  Owl 

The  status  of  the  Long-eared  Owl  in  this  area 
of  the  Great  Basin  is  uncertain.  Although  Hen- 
shaw  (1875)  and  Bee  and  Hutchings  (1942)  re- 
corded this  species  nesting  in  pinyon-juniper, 
only  one  nest  was  fomid  in  this  habitat  type 
during  the  present  study.  It  was  located  in  an 
old  Ferruginous  Hawk  nest  constructed  in  the 
top  of  a  juniper  and  within  a  dense  pinyon- 
juniper  stand  in  southwestern  Rush  \'alley  ( Fig. 
27).  The  nest  was  approximately  2.5  ft  x  3.0  ft 
and  almost  flat.  On  3  Ma)'  it  contained  three 
newly  hatched  young  and  three  eggs  and  on 
26  May  fi\e  nearly  full  grown  young  were 
present  and  sul)se(|ui'ntly  banded. 

Fifteen  p(>ll(ts  and  several  prey  remains  were 
removed  from  tlie  nest  and  analyzed.  The  re- 
sults are  presented  in  Table  40.  Mammals  com- 
prised 90.4  percent  of  tlie  total  prey  taken  and 


93.3  percent  of  the  total  prey  bioniass.  The  two 
principal  species  \\ere,  in  order  of  their  im- 
portance, Old's  kangaroo  rat  and  the  dei'r  mouse. 
The  mean  prey  weight  taken  by  this  species 
was  40.S  gms,  or  only  4.5  gms  higher  than  the 
in(\ui  prey  weight  taken  by  the  closely  related 
species,  the  Short-eared  Owl.  This  is,  however, 
three  and  four  times  larger  than  the  mean  prey 
weight  taken  by  Sparrow  Hawks  and  Burrowing 
Owls  on  the  study  area,  although  a  wide  over- 
lap within  the  variety  of  prey  taken  by  these 
four  raptors  is  evident. 

The  absence  of  Long-eared  Owl  nests  on  the 
study  area  invites  comment,  as  does  their  ap- 
parent scarcity  in  the  pinyon-juniper  community. 
.'\s  pre\i()usly  discussed.  Long-eared  Owls  com- 
prised a  sizeable  portion  of  the  wintering  owl 
populations  and  were  trapped  almost  three  times 
as  often  as  Great  Horned  Owls.  Yet  they  were 
virtually  absent  from  the  same  area  during  the 
breeding  season.  Although  both  Long-eared 
Owls  and  Great  Horned  Owls  prey  on  some 
similar  species,  their  prey  selection  differential 
is  great;  hence,  their  rare  breeding  status  can- 
not be  attributed  to  severe  competition  with  the 
larger  owl.  However,  the  combination  of  breed- 
ing habitat  recjuirements  and  potential  preda- 
tion  offers  another  possibility.  Long-eared 
Owls  do  not  construct  their  own  nests  but  rather 
utilize  abandoned  nests  of  a  wide  variety  of 
avian  and  mammal  species,  and  in  other  parts  of 
their  range,  sciuirrel  nests  and  Cooper's  Hawk 
nests  are  frequently  utilized  ( Bent,  1938;  Arm- 
strong, 1958;  Re)nolds,  1970).  In  addition, 
these  nests  are  nonnallv  placed  in  dense  conifer 
stands  ( Randle  and  Austing,  1952).  In  the 
pinyon-juniper  habitat,  however,  the  only  nests 
a\ailable  are  those  of  the  Ferruginous  Hawk, 
Red-tailed  Hawk,  and  Swainson's  Hawk.  All 
of  these  are  constructed  in  the  tops  of  junipers 
and  are  direeth  exposed  to  potential  predators 
from  aljove.  I'^irthermore,  probably  all  ot  the 
large  raptors  wliieli  nest  in  this  area  are  capable 
of  killing  Long-eared  Owls,  and  in  other  areas 
Golden  Fagles  ( McGahan,  196S),  Great  Horned 
Owls     (  l'",rringt()n,     Hamerstroiii,     and     Hamer- 


Table   40.     Food   liahils  of   Long-eared  Owls 


1970. 


No. 

% 

Approx. 

% 

Species 

Indv. 

Indv. 

Biomass 

Biuma.ss 

Dipo(lonu/s 

ordii 

10 

45.5 

680 

75.7 

Pcronu/scus 

inanictihitus 

7 

31.8 

119 

13.3 

Microlus  sp. 

2 

9.1 

24 

2.7 

Pero<inathu.s 

parvus 

1 

4.5 

15 

1.6 

Unident.  Passerine 

2 

9.1 

60 

6.7 

Totals 

22 

100.0 

898 

100.0 

BiOLOGiCAi,  Series,  Vol.  18,  No.  3       Bueedinc  Ecology  of  Utah  Raptors 


69 


Fig.  27.     Juniper    tree    nest    containing;    a    brood    of    five    voung    Long-eared    Owls    in    Rush    V'allev.    30    May, 
1969. 


Strom,  1940),  and  Red-tailed  Hawks  (Collins, 
1962)  have  been  recorded  as  preying  upon  this 
species.  B.  F.  Harrison  (personal  communica- 
tion) cites  a  specific  example  wherein  a  Long- 
eared  Owl  was  flushed  from  a  similar  juniper 
nest  (in  this  same  area)  containing  eight  well- 
developed  eggs.  When  rechecked  about  two 
hours  later,  both  eggs  and  adults  had  disap- 
peared. The  rapidity  of  their  disappearance  and 
the  absence  of  remains  of  either  the  eggs  or 
adults  suggests  that  the  predator  was  probably 
a  hawk  or  Raven. 

The  above  considerations  suggest  that  Long- 
eared  (>wls  recjuire  well-concealed  nesting  sites 
in  dense  cover  or  thickets,  all  of  which  are  lack- 
ing in  the  pinxon-juniper  commimity.  Hence, 
their  breetling  suec(\ss  is  rendered  uncertain  be- 
cause of  the  high  le\e]s  of  exposinc  of  the  only 
available  nesting  sites. 

Effect  of  the  Investigator 

The  effect  of  the  investigations  and  the  pres- 
ence of  the  investigators  are  difficult  to  evaluate 
except  where  such  presence  clearly  led  directly 
to  the  destruction  of  the  raptor's  nests,  eggs  or 


young,  or  resulted  in  adult  mortality.  The  effect 
of  the  investigators  on  raptor  nesting  activities 
was  often  deleterioiLS.  Despite  the  fact  that  nest 
visits  were  kept  short,  particularly  in  cold  weath- 
er, adverse  effects  occurred.  Most  commonly 
these  effects  took  the  fonn  of  nest  abandonment, 
with  loss  of  eggs  and  yoiuig  occurring  less  fre- 
(juently.  There  is  some  indication,  however, 
that  the  birds  adjusted  somewhat  to  the  investi- 
gators after  the  first  breeding  season,  and  several 
of  the  pairs  which  had  abandoned  their  nests 
in  1967  tolerated  similar  nest  visits  during  the 
subscciuent  breeding  seasons  and  nested  success- 
fully. However,  some— particularly  two  Golden 
Eagle  pairs— never  became  tolerant  of  human 
presence  and  activities. 

The  aggressiveness  of  the  adults  toward  the 
investigatois  varied  greatly,  both  among  species 
and  among  pairs  of  a  species  and  even  within  the 
members  of  a  pair.  Generally  Golden  Eagles 
and  Swainson's  Hawks  rapidly  departed  and 
did  not  reappear  during  nest  visits,  but  Ferru- 
ginous Hawks  and  Red-tailed  Hawks  always 
pressed  attacks  if  young  were  in  the  nest,  al- 
though terminating  them  before  actual  contact 
was  made.    Great  Horned  Owls  were  probably 


BiiioiiAM  Young  University  Science  Bulletin 


the  most  dangerous  raptors  in  the  study  area. 
Several  females  made  det(>rmhied  attaeks,  and 
three  made  actual  eontact,  two  knocking  one 
of  the  authors  out  of  the  nesting  tree,  and  the 
tiiird  lacerating  the  scalp  and  forehead  of  a 
colleague  ( Bruce  Arnell,  personal  communica- 
tion). Of  the  medium-sized  and  small-sized  rap- 
tors, Prairie  Falcons  were  the  most  aggressive 
and  Ravens  and  Sparrow  Hawks  the  most  vocal. 
None,  however,  made  serious  threats  or  dc- 
tennined  attacks  against  the  investigators. 


In  summary,  the  activities  of  the  investiga- 
tion did  apparentlv  provoke  the  nesting  raptor 
species  to  some  extent  and  apparently  resulted 
in  mortality  in  e.xtre'me  cases.  The  effect  of  this 
mortality  on  the  total  population  and  popula- 
tion trends  is  tmknown,  but  it  is  certainly  not 
as  drastic  as  the  sum  total  of  untoward  human 
actix'ities  directed  against  the  nesting  raptors, 
which  must  contribute  to  the  overall  low  raptor 
densit\'  of  this  area.  Only  additional  evidence 
will  permit  definite  conclusions,  however. 


SUMMARY 


A  studv  of  the  breeding  ecologv  of  raptorial 
birds  was  conducted  in  central  Utah  from  1967 
to  1970.  The  objectives  of  the  study  were  to 
provide  four  years  of  (juantitative  data  on  the 
breeding  raptor  populations  and  their  distribu- 
tion, their  habitat  utilization,  vearlv  productivity 
and  success,  territorialits ,  and  predation. 

The  study  area  supported  a  total  of  354  indi- 
viduals of  12  raptor  species  during  the  four  study 
years.  The  vearlv  raptor  population  varied 
from  8  to  11  raptor  species  and  from  32  to  46 
pairs.  Individuals  commonly  comprised  from 
9  to  13  percent  of  the  yearly  raptor  population, 
and  a  varying  percentage  of  pairs  did  not  at- 
tempt to  nest.  Ferruginous  Hawks  were  the 
predominant  raptor  species  and  comprised 
some  19  percent  of  the  total  yearly  raptor  popu- 
lation. Other  important  raptors  included  the 
CJolden    Fagle,    Red-tailed    Hawk,    and    Raven. 

Yearly  population  densities  averaged  0.5 
pairs  per  square  mile,  much  lower  than  raptor 
populations  found  in  Michigan  and  Wyoming 
((Iraigliead  and  Craigliiad,  1956).  However, 
much  of  the  area  was  not  utilized,  and  if  such 
areas  were  eliminated  from  the  calculations,  the 
raptor  population  densities  would  be  increased. 

The  breeding  activities  of  the  collective  rap- 
tor population  occurred  ovi'r  a  period  of  eight 
months.  Raptor  species  exhibited  a  definite 
breeding  sequence  relative  to  one  another,  and 
each  species  initiates!  its  nesting  activities  at 
slightly  different  time  periods,  although  some 
overlap  occurred  between  early  and  late  nesters 
of  different  species.  Cireat  Horned  Owls  and 
Colden  Eagles  were  the  first  raptors  to  initiate 
nesting  activities,  usuall\-  in  late  January  or  earh 
February.  Red-tailed  Hawks  were  the  first  of 
tlie  migratory  raptors  to  return  and  begin  nest- 
ing and  were  closely  followed  by  Ferruginous 
Hawks.  Swainson's  Hawks  were  the  last  of  the 
large  raptors  to  begin  nesting,  usuailv  in  lati' 
May   or  June,   and    at    approximately   the  same 


time  Cooper's  Hawks  and  Burrowing  Owls  ini- 
tiated tluMr  nesting  activities. 

The  raptors  exhibited  a  wide  range  of  nest 
site  selection  within  the  limits  imposed  by  the 
study  area  ]ial)itat.  The  large  raptors  nested 
primarily  in  cliffs  (including  ([uarries)  or  juni- 
pers; but  many  of  the  medium-  and  small-sized 
raptor  species,  such  as  the  Marsh  Hawk,  Short- 
eared  Owl,  and  Burrowing  Owl  were  ground 
nesters.  Obserxations  indicated  that  several  of 
the  raptor  species  exhibited  a  vertical  stratifi- 
cation of  nesting  sites.  Territories  and,  less  com- 
monly, nesting  sites  were  usually  reoccupied  by 
a  pair  of  the  sanie  species. 

The  fecundity  of  the  collective  raptor  popu- 
lation varied  between  years.  Specific  causes  of 
mortality  of  eggs  and  young  included  nest  de- 
sertion and  destruction,  predation,  apparent  egg 
infertilit\-,  and  accidents.  Human  interference 
was  the  probable  cause  of  most  of  the  observed 
nest  desertion  and  destruction.  Approximately 
6.5  percent  of  all  eggs  produced  were  apparent- 
ly infertile,  of  which  the  majority  were  from 
Ferruginous  Hawk  nests. 

The  observed  home  ranges  of  the  raptor 
species  were  a  function  of  their  relative  size 
and  breeding  status.  Thus,  nesting  pairs  main- 
tained larger  home  ranges  than  nonnesting  pairs, 
wliieh  in  turn  held  larger  home  ranges  than  in- 
dividuals Tlie  sizes  and  shapes  of  the  liome 
ranges  confonned  generally  to  the  topography 
of  the  nesting  Idcale  and  usualK'  ranged  widely 
into  the  surrounding  desert.  Distanci'S  bi'tween 
nearest  neighbors  of  closely  related  species  of 
similar  weight  were  greater  than  between  rela- 
ti\(l\  unrelated  species.  An  exception  occurs 
bi'twcen  species  witli  iliffering  acti\itv  pat- 
terns, such  as  tlu'  nocturnal  owls  and  the  diurnal 
hawks.  ( )verlapping  of  home  ranges  was  seldom 
substantial  between  pairs  of  the  same  species, 
but  it  was  somewhat  more  frecjuent  between 
pairs  of  diftereiit  species. 


Biological  Seiues.  \'oi,.  IS,  \o.  3       Bukkdinc  Ecology  of  Utah  Raptobs 


71 


Kach  of  the  raptor  species  maintained  defi- 
nite luinting  activity  periods.  The  ob\ious  dif- 
ferential occurred  between  the  diumal  hawks, 
eagles  and  ravens,  and  the  nocturnal  owls;  but 
at  least  one  species,  the  Ferruginous  Hawk,  ex- 
hibited a  crepuscular  hunting  activity  timetable. 

The  food  of  the  raptors  on  the  study  area 
included  at  least  55  different  prey  species,  but 
most  relied  hea\'ily  on  only  1  or  2  species.  The 
principal  prey  of  the  majority  of  the  large  rap- 
tors was  the  black-tailed  jackrabbit,  which  also 
figured  prominently  in  the  diets  of  some  of  the 
medium-sized  raptors.  Other  prey  species  of  im- 
portance to  one  or  more  raptor  species  included 


the  antelope  ground  scjuirrel,  two  kangaroo  rat 
species,  the  white-footed  deer  mouse,  and  the 
Horned  Lark.  Tlie  smaller  raptors  also  took 
large  numbers  of  invertebrates,  principally  or- 
thopterans.  Gencrallv  the  raptors  preyed  heavily 
upon  the  most  aliundant  potential  prey  species, 
and  a  correlation  of  predator-prey  size  was 
found,  indicating  that  the  various  raptor  species 
preyed  most  heavily  upon  the  largest  prey 
species  which  they  could  most  efficiently  cap- 
ture and  kill.  No  examples  of  raptor  predation 
on  game  or  domestic  livestock  were  found  dur- 
ing the  study  period. 


ACKNOWLEDGMENTS 


We  wish  to  express  our  sincere  appreciation 
to  Dr.  C.  Lynn  Hayward,  Dr.  Herbert  H.  Frost, 
and  Dr.  Glen  Moore  for  reading  and  criticizing 
an  earlier  version  of  this  manuscript.  Grateful 
acknowledgment  is  also  expressed  to  many 
others  who  contributed  to  the  successful  com- 
pletion of  this  work,  including  Dr.  Clyde  C.  Ed- 
wards for  his  assistance  in  the  field  from  1967- 
1970;  David  H.  Ellis,  Franz  J.  Camenzind,  and 
J.  Bradford  Weston  for  field  assistance  from 
1967-1968;  W.  Bruce  Arnell  for  field  assistance 
from  1969-1970;  and  Charles  R.  Wilson  for  field 


assistance  from   1969-1970. 

Miss  Nancv  Lee  Balan  typed  and  edited  the 
final  manuscript. 

We  express  gratitude  to  the  Southern  Con- 
necticut State  College  Computer  Center  for  its 
services  and  to  the  Brigham  Young  University 
Department  of  Zoology  for  furnishing  equip- 
ment and  transportation. 

Tliis  stud\  was  supported  in  part  by  a  Na- 
tion;il  Defense  Education  Act  Fellowship  and 
in  part  bv  a  research  grant  from  the  National 
Audubon    Societv. 


APPENDIX-WEIGHTS    OF    PREY    SPECIES  USED   IN  THE  BIOMASS   CALCULATIONS. 


Species 


MAMMALS 
Lepus  californicus 
Si/Ivilagus  sp. 
Spermopliilus  tDunsendi 
Ammospermophihis  leuctirus 
Eutcnnius  minimus 
TfioDuimyv  hotlac 
Perognathus  parvus 
Peroiinuthtis  formosus 
Dipodomtjs  microps 
Dipodomi/s  ordii 
Microdipodops  meii.acephalus 
Ontjchomijs  leucogaster 
Reithrodentomi/s  mcii.(dofis 
Peromiiscus  mitniculalus 
Neotoma  lepida 
Micruttts  sp. 
Mustehi  frenata 

BIRDS 

Btiteo  sitditisoui 


Appro.v.  wt. 

in  gms. 

Source 

2300 

Haskell  and  Reynolds  (1947) 

1000 

Seidenstickcr  (196S) 

191 

Cornish  and  Mrosovsky  (1965) 

145 

This  study 

78 

This  study 

170 

This  study 

15 

This  study 

19 

This  study 

65 

This  study 

68 

Desha  (1967) 

24 

This  study 

38 

Marti   (Unpubl  IBP  data) 

12 

Marti   (Unpubl  IBP  data) 

17 

Bee  (1947) 

217 

Marti  (Unpubl  IBP  data) 

38 

Bee  (1947) 

178 

Marti  (Unpubl  IBP  data) 

988 


Craighead    and    Craighead    (1956) 


72 


Brigham  ^■ouNc  University  Science  Bulletin 


Zetiaklura  macroura 

Ask)  flammeus 

Chordeiles  minor 

Phdlacnoptilus  nuttallii 

TijTdnnns  verticelis 

Sai/ornis  saija 

Olocoris  cdpestris 

Pica  pk;a 

Ctjanocephalus  ct/anocephalus 

Oreoscoptes  montamis 

Sialki  curnicokles 

Larius  hidovickimis 

Passer  domesticus 

Oherholseria  chlorura 

Calanwspiza  mchnocorijs 

Poecetes  graminetts 

SpizcUa  hreiceri 

Zo  not  rich  ia  leiicoph  n/s 

Stiirnis  vulgaris 

Sturnella  neglecta 

REPTILES 

Crotaphytus  collaris 
Ufa  sfanshuriana 
Sceloporus  graciostis 
Phrynosoma  platyrhinos 
Cncmidophorus  tigris 
Masticof)his  tacniatus 
Pituophis  melanoleucus 

INVERTEBRATES 

Curahidae 

Scarabidae 

Sdphidae 

Curcidionidae 

Tcnchrionidae 

Locustidae 

Aranae 

Scorpionidae 


153 

Hiitt  and  Hall  (19.38) 

340 

Craiglicad    and    Craifjhead    ( 

75 

Thi.s  .study 

62 

Thi.s  studs' 

36 

This  stud) 

28 

This  study 

28 

Bohlc  (1943) 

173 

SeidcnstickcT  (1968) 

108 

Foole  (1938) 

45 

This  study 

45 

Marti  (Unpubl  IBP  data) 

52 

Esten  (1931) 

25 

Poole  (1938) 

30 

This  study 

33 

Marti   (Unpubl  IBP  data) 

27 

Poolc  (1938) 

30 

This  study 

30 

Baldwin  and  Kendeigh  ( 1938 

84 

Poole  (1938) 

145 

Poole  (1938) 

30 

This  study 

4 

This  study 

13 

This  study 

9 

This  study 

24 

This  study 

169 

This  study 

372 

This  study 

0.23 

Marti  (Unpubl  IBP  data) 

0.3 

Marti  (UnpuhllBPdata) 

0.3 

Marti  (Unpubl  IBP  data) 

0.1 

Marti  (Unpubl  IBP  data) 

0.55 

Marti  (Unpubl  IBP  data) 

0.6.3 

This  study 

0.4 

Marti  (Unpubl  IBP  data) 

1.45 

This  study 

1956) 


LITERATURE    CITED 


Adoi.phson,   D.   and  C    |onkel.      1969.      Raptor  popu- 

iation.s  committee  report  for  1968.    Raptor  Research 

News   .3:4,3-57. 
Alcohn,  J.   R.      1942.     Notes  on  tlie  food  of  the  C;r(  at 

Horned  Owl  near  Fallon,  Nevada.    Condor  44:284- 

285. 
Allen,   J.   A.      1874.     Notes   on   the   natural   history   of 

portion.s   of   Dakota   and    Montana   territories.    .   .    . 

Proc.  Boston  Soc.  Natiir.  Hist.   17:33-86. 
Ancell,  T.     1968.     A  study  of  tlie  Ferruginous  Hawk: 

Adult     and     Brood     Behavior.      The     Living     Bird 

7:22.5-241. 
.'Vrmsthonc,    W.    H.      1958.     Nesting    ;ind    food    liabits 

of  the  Long-eared  Owl  in  Michigan.    Pnhl.  Michi- 
gan   St.    Univ.    Biol.    Series    1:61-96. 
Arnold,    L.    W.      1954.     The    Golden    Eagle    and    its 

economic    status.     U.    S.    Fish    and    Wildlife    Serv. 

Circular  No.  27:l-.35. 


AusriNc,  (...  n.  1964.  'Hit-  world  of  the  Red-tailed 
Hawk.     J.    B.    Lippincott    Co.     Philadelpliia. 

B.mi.ev,  A.  .\I.  and  R.  J.  Niedh.^ch.  1933.  The 
Prairie   Falcon.  American   Forests  39:356-358,   384. 

Bmdwin.  S.  p.  and  S.  C.  Kenoeigh.  1938.  Varia- 
tions in   the  weight  of  birds.    ."Vuk  55:416-467. 

Bai'mcvrtner,  F.  M.  1938.  Court.ship  and  nesting 
of  the  Creat  Horned  Owl.  Wilson  Bull.  50:274- 
285. 

liAUMGAitrNEH,  F.  M.  1939.  Territory  and  popula- 
tion in  the  Creat  Horned  Owl.    Auk  .56:274-282. 

Baumgahtneh,  a.  M.  and  F.  M.  Baumgartner.  1944. 
Ha«ks  and  owls  in  t)klahoma,  1939-1942:  Food 
habits  and  population  changes.  Wilson  Bull.  56: 
209-215. 

Bi:i;,  J.  1947.  Mammals  of  Utah  County.  Unpub- 
lished master's  thesis.  Department  of  Zoology,  Brig- 
ham  Young  University,  Provo,  Utah. 


Biol()gic:al  Seiues,  Vol.  IS.  No.  .'5       Bueedinc  Ecology  of  Utah  Raptors 


73 


Bee,  R.  G.  Unpublished  field  notes,  1932-1959.  Brigham 
Young  University  Life  Sciences  Museum,  Prove, 
Utah.' 
Bee,  R.  G.  and  J.  Hutchincs.  1942.  Breeding  rec- 
ords of  Utah  birds.  The  Great  Basin  Natur.  3:61- 
88. 
Behle,  VV.   H.   1944.     Check-list  of  the  birds  of  Utah. 

Condor   46:67-87. 
Behle,  W.  H.      1954.     Chiuiging  st;it\is  of  tlu-  .Starling 

in    Utah.     Condor   56:49-50. 
Bent,  A.   C.     1937.     Life  histories  of  North  American 
birds  of  prey.    Part  1.    U.  S.  Natl.  Mus.,  Bull.  167. 
Bent,  A.   C.     1938.    Life  histories   of  North  American 
birds  of  prey.    Part  2.    U.  S.  Natl.  Mus.,  Bull.  170. 
Bent,  A.  C.     1946.     Life  histories  of  North  American 
jays,    crows,   and   titmice.     U.    S.   Natl.    Mus.,    Bull. 
191. 
BissEL,  H.  J.,  J.  K.  RiGBY,  P.  D.  Proctor,  and  R.  W. 
Mayle.      1959.     Geology  of  the  Southern   Oquirrh 
Mountains     and     the     Five     Mile     Pass — northern 
Boulter  Mountain  area,  Tooele  and  Utah  Counties, 
Utah.  Guidebook  to  the  geology  of  LItah,   No.    14: 
1-254.  Utah  Geol.  Soc. 
BoEKER,   E.   L.   and  T.   D.   Ray.      1971.     Golden  Eagle 
population   studies   in   the   southwest.     Condor   73: 
463-467. 
Bond,  R.  M.      1939.     Observations  on  raptorial  birds  in 
the    Lava    Beds — Tule    Lake    region    of    northern 
California.     Condor   41:54-61. 
Bond,    R.    M.     1940.     Food   habits   of   homed   owls   in 
the    Pahranagat    Valley,    Nevada.     Condor    42:164- 
165. 
BoHREHO,    J.    I.     1962.     Notas    varias    sobre   Asia  flam- 
metis    bogotensK    en    Colombia    Rev.    Biol.    Trop. 
10:45-59. 
BouRDO,   E.   A.  and  G.   A.   Hesterburg.      19.50.     West- 
em     burrowing    owl    in     Michigan.      Wilson     Bull. 
62:214. 
Bowles,  J.  H.  and  F.  R.  Decker.      1930.     The  Ravens 

of  the  state  of  Washington.    Condor  32:192-201. 
Bowles,   J.    H.    and   F.    R.    Decker.      1931.     The    Fer- 
ruginous  Rough-leg   in   Washington.     The   Murrelet 
12:65-70. 
Bowles,   J.    H.   and   F.   R.   Decker.      19.34.     Swainson's 

Hawk    in    Washington   state.   Auk   51:446-4.50. 
Brecklnhidge,    W.    J.      1935.     An    ecological    study    of 
some  Minnesota  Marsh  Hawks.    Condor  37:268-276. 
Brodie,  E.  D.  and  C.  Maser.     1967.     Analysis  of  Great 
Homed  Owl   pellets  from  Deschutes  County,   Ore- 
gon.   The  Murrelet  48:11-12. 
liROWN,    J.    L.      1969.     Territorial    behavior   and   popu- 
lation   regulation    in    birds.     Wilson    Bull.     81:293- 
.329. 
Brown,    L.    H.      1966.     Observations    on    some    Kenya 

eagles.    Ibis   108:. 53 1-571. 
Brown,   L.   H.      1969.     Status  and  breeding  success   of 
Clolden    Eagles    in   north-west   Sutherland   in    1967. 
Brit.   Birds  62:34.5-363. 
Brown,    L.    H.      1970.     African   birds    of   prey.    Collins 

London. 
Brown,  L.  H.  and  D.  Amadon.      1968.     Eagles,  hawks 
and  falcons  of  the  world.  McGraw  Hill,  New  York. 
Brown,    L.    H.   and   A.    Watson.     1964.     The    Golden 
Eagle  in   relation   to   its  food  supply.    Ibis   106:78- 
1(K). 
Blllock,    K.    C.      1959.     Geology   of   the   Lake    Moun- 
tains,   Utah.    Utah   Geol.    and   Mineral    Surv.    Bull. 
41:1-48. 
Burns,  B.  J.      1952.     Food  of  a  family  of  Great  Homed 
Owls   in    Florida.     Auk   69:86-87' 


Cade,    T.    J.     1960.     Ecology    of    the    Peregrine    and 

Gyrfalcon   populations   in   Alaska.     Univ.   California 
Publ.   in   Zool.   63:151-290. 
Cahn,  a.  R.  and  J.  T.  Kemp.     1930.     On  the  food  of 

certain    owls   in   east-central    Illinois.     Auk  47:323- 

328. 
Cameron,   E.  S.      1905.     Nesting  of  the  Golden  Eagle 

in  Montana.    Auk  22:158-167. 
Cameron,  E.  S.      1908.     Changes  of  plumage  in  Buteo 

swainsonii.    Auk  25:468-471. 
Cameron,    E.    S.      1913.     Notes   on    Swainson's    Hawks 

Biiteo  swainsonii  in  Montana.  Auk  30:167-176,  381- 

394. 
Cameron,  E.  S.      1914.     The  Fermginous  Rough-leg  in 

Montana.   Auk  31: 1,59-167. 
Carnie,    S.    K.      1954.     Food   habits   of   Golden    Eagles 

in   the   coast    ranges    of    Califomia.     Condor   56:3- 

12. 
Christensen,    E.    M.    and    M.    A.    Hutchinson.      1965. 

Historical    observations    on    the    ecology    of    Rush 

and  Tooele  Valleys,   Utah.    Proc.   Utah  Acad.   Sci., 

Arts   and   Letters.    42:90-105. 
Collins,  C.  T.     1962.     Red-tailed  Hawk  attacks  Long- 
eared  Owl.    Wilson   Bull.    74:89. 
Cornish,  E.  and  N.  Mrososty.      1965.     Activity  during 

food    deprivation    and    satiation    of    si.\    species    of 

rodents.    Animal  Behavior  13:242-248. 
Cdulombe,     H.     N.      1971.     Behavior    and    population 

ecology    of    the    Burrowing    Owl    in    the    Imperial 

Valley  of  Califomia.    Condor  73:162-176. 
Craighead,    F.    C.    and    J.    J.    Craighead,    Jr.      19.56. 

Hawks,   owls,   and  wildlife.    Stackpole  Co.    Harris- 
burg. 
Crawford,    R.    D.      1968.     Some    food    habits    of    the 

Great  Horned  Owl  in  north-central  Missouri.    Iowa 

Bird   Life   38:119-121. 
Gushing,   J.   E.      1941.     Winter  behavior  of   Ravens   at 

Tomales    Bay,    Califomia.     Condor   43:103-107. 
Decker,  R.   R.  and  J.  H.   Bowles.      1930.     The  Prairie 

Falcon  in  the  state  of  Washington.  Condor  47:25- 

31.  ^ 

Desha,    P.    G.      1967.     Variation    in    a    population    of 

Kangaroo   Rats    Dipodomijs   orii    media    (Rodentia: 

Heteromyidae)     from    the    high    plains    of    Te.xas. 

Southwestem   Natur.    12:275-290. 
Di.xon,    J.     B.      1914.     History    of    a    pair    of    Pacific 

Homed  Owls.    Condor  16:47-54. 
Dixon,  J.   B.      1937.     The  Golden  Eagle  in  San  Diego 

County,  Califomia.    Condor  .39:49-56. 
Di.xon,  J.  B.  and  R.  M.  Bond.      1937.     Raptorial  birds 

in  the  cliff  areas  of  Lava  Beds  National  Monument. 

Califomia.     Condor   39:97-102. 
Drinkwater,    J.      19.53.     Yomig    bluebird    taken    from 

nest-box  bv  Sparrow   Hawk  Fiiico  sparverius.    Auk 

70:215. 

Earhart,  C.  M.  and  N.  K.  John.son.  1970.  Size 
dimorphism  and  food  habits  of  North  American 
owls.    Condor  72:251-264. 

Edwards,  B.  F.  1968.  A  study  of  tlie  Prairie  Falcon 
in   southern   Alberta.    The   Blue   Jay   26:32-36. 

Edwards,  C.  C.  1969.  Winter  behavior  and  popu- 
lation dynamics  of  American  Eagles  in  western 
Utah.  Unpublished  Ph.D.  dis.sertation.  Department 
of  Zoology,  Brigham  Young  University,  Provo, 
Utah. 

Ellis,  D.  H.,  D.  G.  Smith  and  J.  R.  Murphy.  1969. 
Studies  on  raptor  mortahty  in  western  Utah.  Great 
Basin   Natur.   29:16.5-167. 

IvNDEiisoN,    j.    H.      I960.      A    population    study    of    the 


BiuciiAM  Young  Univehsity  Science  Bulletin 


Sparrow  Hawk  in  iMst-central  Illinois.    Wilson  Bnll. 

72:222-231. 
Endehson,  ].  H.      1964.     A  study  of  llv_>  Prairie  l'"alc-on 

in    the   central    Rocky    Ntonntain   region.     Auk    81: 

332-352. 
English,  P.  !■".      U)3t.     Some  i)l)ser\  ations  on  a  p.iir  ol 

Red-tailed  Hawks.    Wilson  Bull.    46:228-235. 
Eriuncton,    p.    L.      1930.     The   pellet   analysis   method 

of  raptor  food  habits  study-    Condor  32:292-296. 
Ehhingtcin,   p.   L.      1932a.     Techniques   of  raptor  food 

liahits  study.    Condor    34:75-86. 
Ehuington,  p.   L.      19321).     Studies  on  the  behavior  of 

the  Creat  Horned  Owl.    Wilson  Bull.    44:212-220. 
Ehiungton,    p.    L.      1932c.     Food    habits    of    southern 

Wisconsin  raptors.    Part  1.    Owls.    Condor  34:176- 

186. 
EnniNGTON,  P.  L.     1933.     Food  habits  of  southern  Wis- 
consin raptors.    Part  2.    Hawks.     Condor  35: 19-29. 
KniiiNGioN,     P.     L.      1938.     The     Cicat     Horned     Ou  I 

as  an  indicator  of  vulnerabilitv  in  prey  populations. 

J.   Wild!.   Mgmt.    2:190-20.5.  ' 
EnniNGTON,    p.    L.    and   L.    J.    Bennett.     1935.     Food 

habits   of    Burrowing   Owls    in   northwestern    Iowa. 

Wilson  Bull.  47:125-128. 
Ehuington.  P.  L.,  and  W.  |.  Bheckinhii)c:e.    1936.    Food 

habits    of    Marsh    Hawks    in    the    glaciated    prairie 

region  of  north-central   United  States.    Amer.   Mid- 
land  i\'atur.l7:831-848. 
EnniNGTON,    P.     L.    and    W.     J.    Bheckinkidge.      1938. 

Food  habits  of  Biitco  hawks  in  north-eentr:iI  I'liited 

States.  WiLson   Bull.  .50:113-121. 
EnniNGTON,  P.  L..  F.  Hameustrom  and  F.  H.  Hameh- 

siHOM.      1940.     The    Great    Horned    Owl    and    its 

prev    in    the    north-central    United    States.       Iowa 

State  College   Agri.    F,xp.   Sta.   Res.    Bnll.   277:757- 

850. 
EsTEN,  S.   R.      1931.      Bird  weights  of  birds  from  notes 

of   William    van    Corder.     Auk   48:.572-574. 
1'"autin,     R.     W.      1946,     Biotic     communities     of     the 

northern    desert    shrub    hiome    of    western     Utah. 

Ecol.    Mongr.    16:251-310. 
I'av,    I'.    H,    and    T.    J.    Cade.      1959.     An    analysis    of 

the  a\'i-fuana  of  St.  Lawrence  Island,  Alaska.  Uniw 

C;ilifornia   Publ.  in  Zool.  63:73-1.50. 
Fei.tis,     R.     D.      1967.     Ground     water     conditions     in 

Cedar    Valley,    Utah    Connt\',    Utah.      Utah    State 

Engineer  Tech.  Pub.  No.  16:'l-34. 
FiNLEY,    W.     L.      1906.     The    Golden    Eagle.     Condor 

8:.5-ll. 
FisciiEn,    R.    B.      1947.     Data    on    the    food    habits    of 

local   owls,    Proc'.    I.innean    Soc.    Nos.    46-48:58-62. 
Kisiieu,    a.    K.      1895.     The    hawks    and    owls    of    the 

United     States     in     relation     to     agriculture.     I'.S. 

Dept.    Agri.     Di\'.     Oiiiitliol.     and    Mammal.     Bull. 

3:1-210. 
Fiicii,     H.     S.      1940.     Some    ob.servations    on    horned 

owl    nests.     Condor   42:73-75. 
Fitch,   H.  S.      1947.     Predation  bv  owls  in  the  Sierr.m 

foothills    of    California.     Condor    49:137-151. 
Imtcii,  H.  S.,  F.  Swenson,  and  O.  F.  Tilloison      1946. 

Behavior  and  food  habits  of  the  Red-tailed  Hawk. 

Condor   48:205-2,37. 
Fowi.EH,  F.  H.      1931.     Studies  on  food  and  growth  of 

the    Prairie    Falcon.     Condor   32:193-210. 
FuEEMEYiat,    H.    R.      1966.     Nesting    Hed-tailed    Hawks 

in   Lvon   Co.,    Kansas.     Kansas   Ornithol.   Soc.   Bull. 
17:1.5-16. 
Gladi.ng,    B.,    D.    F.    Tillotson    and    D.    M.    Seli.kck. 
1943.     Raptor  pellets  as  indicators  of  food  habits. 

California   Fish   and   Game    Bnll,     29:99-121. 


(ii.ovi),  H,  K.  1925.  Field  studies  on  the  diurnal 
raptors  of  eastern  :nKl  central  Kansas.  Wilson  Bull. 
.37:1.33-149. 

GoDEBEY.  W.  F.  1966.  The  birds  of  Canada.  Natl. 
Mus.  Canada   Bull.   No.   203.    1-428. 

CIoEi.iTZ,  W.  A.  1918.  The  Short-eared  Owl  in 
Saskatchewan.    Condor  20:1-3. 

Goldstein,  A.  1964.  Biostatistics.  Macmillan.  New 
York. 

GoitooN,  S,  1927.  Days  with  the  Golden  Eagle. 
Willi, nils   and   Norgate.     London. 

GniuioN.  S,  1955,  The  Golden  Eagle:  King  of  birds. 
Collins,     London, 

GiiANr.  R,  A.  1965.  The  Burrowing  Owl  in  Minne- 
sota.    The    Loon.    37:2-17. 

IIagan,  Y,  1952,  Roufuglriic  og  \jllpltiiu,  Oslo, 
(iylcudal, 

llAGAn,  D.  C.  1957,  Nesting  populations  oi  Red- 
tailed  Hawks  and  Homed  Owls  in  central  New 
York   state.     Wilson   Bull.   69:263-272. 

IlAiMEiiSTHOM,  F.  1969.  A  harrier  population  study, 
pp.  .367-385.  In  ].  J.  Hickey,  Ed.  Peregrine  Falcon 
populations.    Univ.  Wisconsin  Press.    Madison. 

Hameustrom,  F.  N.  and  F.  Hamerstrom.  1951. 
I'ood  of  young  raptors  on  the  Edwin  S.  George 
Reserve.     Wilson    Bull.     63:16-25. 

ll\MMOND,  M.  C.  and  C.  J.  Henry.  1949.  Success 
of  Marsh  Hawk  nests  in  North  Dakota.  Ank  66: 
271-274. 

H\NN\,  W,  C,  19.30,  Notes  on  the  Golden  Eagle 
ill    southern   California.     Condor    32:121-123. 

Hmidv,  R.  1939.  Nesting  habits  of  the  western  Red- 
tiiled   Hawk.    Condor' 41 :79-80. 

Hardy.  R.  194.5.  Breeding  birds  of  the  pigmy  coni- 
fers in  the  Book  Cliffs  region  of  eastern  Utah. 
Auk   62:. 533-542. 

!Imu.'>w,  R.  C.  1922.  The  breeding  habits  of  the 
northern   Raven  in   Pennsylvania.    Auk  39:399-410. 

IIxsKELL,  H.  S.  and  H.  G.  Reynolds.  1947.  Growth, 
developmental  food  retiuiremen.s,  and  breeding  ac- 
livi  V  of  tl  e  California  |ackrabbit.  J.  Mammal. 
28:129-1.36. 

Hkin  i/ELMAN,  D.  S.  1964.  Spri'ig  and  summer  Spar- 
row  Hawk  food  habits.     Wilson  Bull.    76:323-330. 

HE'NrzEL.MAN,  D,  S.  and  A.  C.  Nagy.  1968.  Clutch 
sizes,  hatchability  rates,  and  ,scx  ratios  of  Sparrow 
Ihiwks  in  eastern  Pennsylvania.  Wilson  Bull.  80: 
.306-311. 

IIi.NsiiAW.  II,  W,  1875,  Report  upon  the  ornitho- 
logical collections  made  in  portions  of  Nevada, 
I'tah,  California,  Colorado,  New  Mexico,  and  Ari- 
zona during  the  years  1871,  1872,  1873,  and  1874, 
Wheeler's  Rept,  '  Expl,  Surv,  West  lOOth  Merid, 
5:131-507. 

Hi  HHEMi',  H,  A,  and  K,  ,\,  Herhert,  1965,  Behavior 
of  Percgiine  Falcons  in  the  New  York  City  region. 
Auk  82':47-56. 

lliiKiA.  |,  j,  1949,  Siirvi\;il  studies  of  banded  birds. 
I 'iipiililivluil  Ph.D.  Dissertation,  Dept.  of  Zoology, 
Uiii\.  ol   Michigan,  Ann  Arbor.  Michigan. 

IIkklv.  |,  j,  1969,  Peregrine  Falcon  populations. 
Univ.    WiMciiisin    I'ress.     Madison. 

IIoi.voAK,  D,  T,  and  D,  A,  Balcliffe,  1968.  The 
distribution  of  the  R:i\'cii  in  Brit:iin  and  Ireland. 
Bird  Study   15:191-197. 

lIoi'sioN.  C.  S.  1971.  Brood  size  of  the  C.n-.it  Homed 
Owl    in    Saskatchewan.     Bird-banding  42:103-105. 

Howard.  H.  E.  1"20  Terriio  v  -n  bird  life.  E.  P. 
Diitloii   and  Co.     New    ^'ork. 


Biological  Series,  \'ol.  18,  No.  3       Biieedinc  Ecology  of  Utah  Uaptors 


75 


HuTT,  F.  B.  and  L.  Ball.      1938.     Number  of  feathers 

and    body    size    in    passerine    birds.     Auk    .55:651- 

657. 
Jacot,   E.   C.      1934.     Arizona  nest  of  the   Ferruginous 

Rough-leg.     Condor    36:84-85. 
Johnston,     R.    F.     1956.     Production    by    Short-eared 

Owls  on  a  Salicomia  salt  marsh.    Wilson  Bull.  68: 

91-102. 
JoLLiE,   M.  T.      1943.     The  Golden  Eagle:    its  life  his- 
tory,   belwvior   and  ecologw     Unpublished   master's 

thesis.    University   of   Colorado,    Boulder,   Colorado. 
Kendeigh,  S.  C.     1961.     Animal  ecology.    Prentice-Hall. 

New  Jersey. 
Kennedy,    C.    A.      1948.     Golden    Eagle    kills    Bighorn 

Sheep.    J.   Mammal.    29:68-69. 
KiRKPATRiCK,  C.  M.  and  C.  H.  Conavay.     1947.       The 

winter   foods    of   some   Indiana   owls.     Amer.    Mid- 
land   Natur.    38:755-766. 
KiTCHiN,     E.     A.      1919.     Nesting    of    the     Short-eared 

Owl   in   western   Washington.     Condor  21:21-25. 
Krebs,    J.    R.     1970.     Regulation    of    numbers    in    the 

Great  Tit  (Aves:  Passerifornies ) .    J.  Zool.,  London. 

162:317-333. 
Lack,     D.      1954.     The    natural    regulation    of    animal 

numbers.   O.xford.    Clarendon  Press. 
LeDuc,  p.      1970.     The  nesting  ecology  of  some  hawks 

and    owls    in    southwestern    Minnesota.     The    Loon 

42:48-62. 
Lehti,    R.    W.     1947.     The    Golden    Eagle    attacking 

antelope.    J.    Wildl.    Mgmt.     11:348-349. 
LocKiE,   J.    D.     1955.     The   breeding   habits    and   food 

of    Short-eared    Owls    after    a    vole    plague.     Bird 

Study  2:5.3-69. 
LocKiE,    J.    D.     1964.     The    breeding    density    of    the 

Golden   Eagle   and  fo.\   in   relation   to   food   supply 

in  Western   Ross.   Scotland.    Scottish  Natur.  71:67- 

77. 
LocKiE,  J.  D.  and  D.  Stephen.      1959.     Eagles,  lambs, 

and   land    management    in    Lewis.     J.    Anim.    Ecol. 

28:43-50. 
LuTTicH,   S.   L..    L.   B.   Keith   and  J.   D.   Stephenson. 

1971.     Population  dynamics  of  the  Red-tailed  Hawk 

at  Rochester,  Alberta.    Auk  88:75-87. 
Ll'tticii,   S.,   D.   H.   Rllscii,   E.   C.   Meslow,   and   L.   B. 

Keith.      1970.     Ecology   of   Red-tailed   Hawk    pre- 

dation   in   Alberta.     Ecology   51:190-203. 
Marti,   C.    D.      1969.     Some  comparisons   of  the   feed- 
ing ecology  of  four  owls  in  north-central  Colorado. 

The  Southwestern  Natur.   14:163-170. 
M,\thisen,  J.  E.  and  A.  M.atiiisen.     1968.     Species  and 

abundance  of  diurnal   raptors   in   the  panhandle  of 

Nebraska.   Wilson   Bull.  80:479-486. 
McAtee,  W.  L.      1935.     Food  habits  of  common  hawks. 

U.S.  Dept.  Agri.  Circ.  No.  .370.    Washington,  D.C. 
McDowell,     R.     D.     1941.     The    Cooper's  "llawk    in 

Penn.sylvania.     Pa.    Game    News.    12:4. 
McGahan,    J.      1967.     Quantified    estimates    of    preda- 

tion  by  a  Golden  Eagle  population.    |.  Wildl.  M[;mt. 

31:496-501. 

McGahan,  J.  1968.  Ecology  of  the  Clolden  Eagle. 
Auk  85:1-12. 

Mendall,  H.  C.  1944.  Food  of  hawks  and  owls  in 
Maine.    J.   Wildl.   Mgmt.    8:198-208. 

Menc,  H.  1959.  Food  habits  of  nesting  Cooper's 
Hawks  and  Goshawks  in  New  York  and  Pennsyl- 
vania.   Wilson  Bull.    71:169-174. 

Meslow,  E.  C.  and  L.  B.  Keith.  1966.  Summer  food 
of  Red-tailed  Hawks  near  Rochester,  Alberta.  Can. 
Field-Natur.     80:98-100. 


Miller,  L.  1930.  The  territorial  concept  in  the 
Great  Homed  Owl.    Condor    32:290-291. 

Moon,  E.  L.  1949.  Notes  on  hawk  and  owl  peUet 
formation  and  identification.  Trans.  Kansas  Acad. 
Sei.  43:4.57-466. 

Monro,  J.  A.  1929.  Notes  on  the  food  habits  of  cer- 
tain raptors  in  British  Columbia  and  Alberta.  Con- 
dor   31:112-116. 

.\IuNYER,  C.  A.  1966.  Winter  food  of  the  Short-eared 
Owl  in  Illinois.  Trans.  Illinois  St.  Acad.  Sci.  59: 
174-180. 

MuRiE,  A.  1944.  The  wolves  of  Mt.  McKinley. 
Fauna  Nat.   Parks  of  U.S.,  Fauna  Series  No.  5. 

Murphy,  J.  R.,  F.  J.  Caminzind,  D.  G.  Smith  and 
j.  B.  Weston.  1969.  Nesting  ecology  of  raptorial 
birds  in  central  Utah.  BYU  Sci.  Bull.',  Biol.  Series 
10:l-.36. 

Nelson,  A.  L.  1934.  Some  early  summer  food  pref- 
erences of  the  American  Raven  in  southeastern 
Oregon.    Condor   36:10-15. 

Nice,  M.  M.  1941.  The  role  of  territory  in  bird  life. 
Amer.    Midland    Natur.     26:441-487. 

Nice,  M.  M.  1943.  Studies  in  the  life  history  of  the 
Song  Sparrow  1,  II.  Trans.  Linnean  Soc.  New 
York  4:1-247;  6:1-328. 

Noble,  G.  K.  19.39.  The  role  of  dominance  in  the 
life  of  birds.    Auk    56:263-273. 

OnEHHOLSEH,  H.  C.  1918.  The  common  Ravens  of 
North  America.    Ohio  J.  Sci.    18:213-225. 

OouM,  E.  P.  and  E.  J.  Kuenzler.  1955.  Measurement 
of  territory  and  home  range  size  in  birds.  Auk 
72:128-137. 

Orians,  G.  and  F.  Kuhlman.  1956.  Red-tailed  Hawk 
and  Horned  Owl  populations  in  Wisconsin.  Con- 
dor   .58:371-385. 

Packard,  R.  L.,  E.  G.  Bolen,  M.  K.  Rvlander  and 
F.  A.  Hudson.  1969.  Golden  Eagle-livestock  re- 
lationships. Int.  Center  for  Arid  and  Semi-Arid 
Land  Studies,  Te.xas  Tech.  College.  Lubbock, 
Te.\as. 

Parslow,  J.  L.  F.  1967.  Changes  in  status  among 
breeding  birds  in  Britain  and  Ireland.  Brit.  Birds 
60:273-274. 

Pearson,  O.  P.  and  A.  K.  Pearson.  1947.  Owl  pre- 
dation  in  Pennsylvania  with  notes  on  the  small 
mammals  of  Delaware  Co.   J.  Mammal.  28:137-147. 

Pitelka,  F.  a.,  p.  Q.  Tomich  and  G.  W.  Treichel. 
19.55a.  Ecological  relations  of  Jaegers  and  owls  as 
Lemming  predators  near  Barrow,  Alaska.  Ecol. 
Mongr.    25:85-117. 

PiTEi.KA,  F".  A..  P.  Q.  Tomich  and  G.  W.  Treichel. 
1955b.  Breeding  beha\ior  of  Jaegers  and  owls  near 
Barrow,  Alaska.  "Condor  57:3-18. 

Poole,  E.  L.  1938.  Weights  and  wing  areas  in  North 
American   birds.     Auk   .55:511-517." 

I'owKiis,  H.  W.  1966.  Bioloi^y  of  the  Mountain  Blue- 
bird in  Montana.    Condor  68:351-371. 

Handle,  W.  and  R.  Austing.  1952.  Ecological  notes 
on  Long-eared  and  Saw-whet  Owls  in  southeastern 
Ohio.   Ecology  .33:422-426. 

Katclufe,  D.  a.  1962.  Breeding  dcnsit\  in  the 
Peregrine  (Fiilco  percgrinus)  and  Raven ( Cori>i/.s 
corax).   ibis   l()4:1.3-.39. 

Reynolds,  R.  T.  1970.  Nest  obser\ations  of  the  Long- 
eared  Owl  in  Benton  Co.,  Oregon,  with  notes  on 
their    food    habits.     The    Muircret    51:8-9. 

Rhoades,  J.  N.  1892.  The  breeding  habits  of  the 
Florida  Burrowing  Owl.    Auk  9:1-8. 

RoEST,  A.  L.  1957.  Notes  on  the  American  Sparrow 
Hawk.    Auk  74:1-19. 


76 


BniGHAM  Young  Univehsitv  Science  Bulletin 


Salt,  W.  P.  1939.  Notes  on  recoveries  of  liaiided 
Ferruginous  Rough-legged  Hawks.  Bird  Banding 
10:80-84. 
Sani)em.\n,  p.  W.  1957.  The  breeding  success  of 
the  Golden  Eagle  in  the  southern  Grampians.  Scot- 
ti.sh  Natur.  69:148-152. 
Sciioener,    T.    W.      1968.     Sizes    of   feeding    territories 

among    birds.     Ecology   49:123-141. 
ScHBiVE«,  E.  C.     1969.     The  status  of  Cooper's  Hawks 
in    western    Pennsylvania,    pp.    356-359.    In    J.    J. 
Hickey,    Ed.    Peregrine    Falcon   populations.     Univ. 
Wisconsin  Press,  Madison. 

Scorr,  T.  G.  1940.  The  western  Burrowing  Owl  in 
Clay  Co.,  Iowa  in  1938.  Amer.  Midland  Natur. 
24:585-593. 

Sealev,  S.  C.  1967.  Notes  on  the  breeding  biology 
of  the  Marsh  Hawk  in  Alberta  and  Saskatchewan. 
The  Blue  Jay  25:63-69. 

Seujenstickeb,  J.  C.  1970.  Food  of  nesting  Red- 
tailed  Hawks  in  south-central  Montana.  The  Mur- 
relet  51:38-40. 

Shelford,  V.  E.  1963.  The  ecology  of  North  Ameri- 
ca.  Univ.  Illinois  Press,  Urbana. 

Sherman,  A.  R.  1913.  The  nest  life  of  the  Sparrow 
Hawk.  Auk  30:206-218. 

Short,  H.  L.  and  L.  C.  Drew.  1962.  Observations 
concerning  the  behavior,  feeding,  and  pellets  of 
Short-eared  Owls.  Amer.  Midland  Natur.  67:424- 
433. 

Simi'.son,  G.G.,  A.  Roe  and  R.  C.  Lewontin.  1960. 
Quantitative  zoologv.  Harcourt,  Brace  and  World. 
New  York. 

Slevin,  J.  R.  1929.  A  contril)ution  to  our  knowledge 
of  the  nesting  habits  of  the  Golden  Eagle.  Proc. 
California  Acad.   Sci.   Series  4.   18:45-71. 

Smh-h,  D.  C.  1968.  Vegetational  analysis  of  the 
Pinyon-Juniper  comniunity,  Tooele  Valley.  Unpub- 
lished  Manuscript. 

Smith,  D.  G.  1970.  Close  nesting  and  aggression 
contacts  between  Great  Homed  Owls  and  Red- 
tailed  Hawks.    Auk  87:170-171. 

Smith,  D.  G.  and  C.  R.  Wilson.  1971.  Tenacity  of 
nesting  Barn  Owls.    The  Murrelet  52:25. 

Snyder,  L.  L.  and  C.  E.  Hope.  1938.  A  predator- 
prey  relationship  between  the  Short-cared  Owl 
and   Meadow   Mouse.     Wilson    Bull.   .50:110-112. 

Southern,  H.  N.  1970.  The  natural  control  of  a 
population  of  Tawny  Owls  (Strix  aluco).  J.  Zool., 
London    162:197-285. 

Sprunt,  a.  1963.  Bald  Eagles  aren't  producing 
enough  young.    Aud.   Mag.    65:32-35. 

Stanford,  J.  S.  1929.  Swain.son's  Hawks  at  home. 
Proc.   Utah  Acad.   Sci.,  Arts,  Letters    29:289. 

Stoneh,  E.  a.  1932.  The  appro.vimate  louse  popula- 
tion of   a   Burrowing  Owl.     Condor   34:230-231. 

Stoner,  E.  a.  1933.  Burrowing  Owls  occupying  un- 
usual   (juarters.     Condor    35:36. 

Storer,  R.  L.  1966.  Sexual  dimorphism  and  food 
habits  in  three  North  American  accipiters.  Auk 
83:423-426. 

SucDEN,  J.  W.  1929.  A  nest  site  of  the  western 
Homed  Owl  in  Utah.    Condor  30:324-325. 

Swenk,  M.  H.  1937.  A  study  of  tlie  distribution  and 
migration     of     the     Great     Horned     Owl     in     the 


Missouri   Valley  region.    Nebra.ska  Bird  Rev.  5:79- 
105. 

Thomsen,  L.  1971.  Behavior  and  ecology  of  Bur- 
rowing Owls  on  the  Oakland  Airport.  Condor  73: 
177-192. 

Tyler,  H.  and  P.  Saetyeit.  1969.  The  ecology  of 
the  Red-tailed  Hawk.  S.  Dakota  Bird  Notes  21: 
77-84. 

Tyler,  J.  G.  1923.  Observations  on  the  habits  of 
the   Prairie    Falcon.     Condor   25:90-95. 

U iTENDORFER,  O.  1939.  Die  emahmng  der  deutschen 
Raubvogel  und  Eulen,  und  ihr  bedeutung  in  der 
hemischen    Natur.     J.    Neumann-Neudamm.    Berlin. 

X'Auc.nAN,  T.  A.  19.54.  Diurnal  foraging  by  tlic  Great 
Horned  Owl.  Wilson  Bull.  66:148. 

Watson,  A.  1957.  The  breeding  success  of  the  Gold- 
en Eagle  in  the  north-east  Higlilands.  Scottish 
Natur.   69:153-169. 

Webster,  H.  1944.  A  survey  of  the  Prairie  Falcon 
in   Colorado.    Auk  61:609-616. 

Weicand,  J.  P.  1967.  Ferruginous  Hawk  attacks 
Great    Horned   Owl.     Auk  84:4.33. 

Wellein,  E.  G.  and  T.  Ray.  1964.  Eagle  investiga- 
tion.s — New  Mexico  and  western  Texas.  Wildl.  Re- 
search Lab.,  Colorado. 

W^ESTON,  J.  B.  and  D.  H.  Ellis.  1968.  Ground  nest- 
ing of  Ferruginous  Hawks  in  west-  central  Utah. 
Great  Basin  Natur.  28:111. 

White,  C.  M.  1966.  Notes  on  the  food  of  the 
Swainson's   Hawk.    Kansas   Omithol.   Soc.   17:10. 

White,  C.  NL  1969a.  Population  trends  in  Utah 
raptors,  pp.  .3.59-362.  In  J.  J.  Hickey,  Ed.  Pere- 
grine Falcon  populations.  Univ.  Wisconsin  Press. 
Madison. 

White,  C.  M.  1969b.  Is  there  a  genetic  continuit\' 
concemed  in  eyrie  maintenance?  pp.  391-399.  lii 
J.  J.  Hickey,  Ed.  Peregrine  Falcon  populations. 
Univ.   Wisconsin  Press.    Madison. 

Whitfield,  D.  W.  A..  D.  W.  Davis,  J.  M.  Gerrard 
and  W.  J.  Mahen.  1969.  Golden  Eagles  in  cen- 
tral  Saskatchewan.   The   Blue  Jay  27:74-79. 

WiLLARi),  F.  C.  1916.  The  Golden  Eagle  in  Cochise 
County,  Arizona.    The  Oologist  33:3-8. 

WiLLorc;iinY,  E.  J.  and  T.  J.  Cade.  1964.  Breeding 
behavior  of  the  American  Kerstrel.  Living  Bird 
3:7.5-96. 

Wilson,  K.  A.  1938.  Owl  studies  at  Ann  Arbor, 
Michigan.    Auk  55:187-197. 

Wolf,  L.  R.  1928.  The  breeding  accipiters  of  Utah. 
Oologist's    Record,    London.     8:90-102. 

WoLUUTEH,  B.  1969.  Notes  on  a  Kansas  Great  Homed 
Owl    population.     Raptor   Research   News   3:23. 

Woodbury,  A.  M.  and  C.  Cottam.  1962.  Ecological 
studies  of  birds  in  Utah.  Univ.  Utah  Biol.  Series 
12:1-29. 

WooDOEBD,    W.      1952.     Food    habits    of    the    Golden 

E.igle.  J,  Wildl.  Mgmt.   16:4.57-4.59. 
Wynne-Edwards,  V  C.     1955.     Low  reproductive  rates 

in  birds,  especiallv  sea  birds.    Act  XI  Int.  Omithol. 

Congr.  .540-.570. 
Wynne-Edwabds,  V.    C.      1962.     Animal   dispersion  in 

relation   to  social   behavior.    Hafner  Pub.   Co.   New 

York. 


C)'.      '  r^Acifo 


Brigham  Young  University 
Science  Bulletin 

MUS.  COM^.  ZOOL. 

LtfiNARY  -J!lo1r-Bo'feat 

HOV    51973 

HARVARD  EFFECTS  OF  A  NUCLEAR 
uNiv^ONATION  ON  ARTHROPODS 
AT  THE  NEVADA  TEST  SITE 


by 
Dorald  M.  Allred 


BIOLOGICAL  SERIES  — VOLUME  XVIII,  NUMBER  4 
JULY   1973/ISSN  0068-1024 


BRIGHAM  YOUNG   UNIVERSITY   SCIENCE  BULLETIN 
BIOLOGICAL  SERIES 

Editor:   Stanley  L.  Welsh,  Department  of  Botany, 

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Joseph  R.  Murdock,  Botany 
WiLMER  W.  Tanner,  Zoology 

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Sciences 

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Brigham  Young  University 
Science  Bulletin 


EFFECTS  OF  A  NUCLEAR 

DETONATION  ON  ARTHROPODS 

AT  THE  NEVADA  TEST  SITE 


by 

Dorald  M.  Allred 


BIOLOGICAL  SERIES  — VOLUME  XVIII,  NUMBER  4 
JULY    1973/ISSN   0068-1024 


TABLE  OF  CONTENTS 

INTRODUCTION  1 

METHODS  1 

RESULTS  7 

BEETLES    7 

Araeoschizus  sulcicoHis  7 

Centrioptera  muricata  7 

Conibiosoma  elongatum 8 

Edrotes   orhiis    8 

Eleodcs   armata    8 

E.   grandicollis   8 

E.    hispilabris    9 

E.  longipilosa  9 

E.    nigrina    9 

Eupsophylus    castaneus    9 

Euschides   htctatus   9 

Eusatttis  agnatus  9 

Metoponium  convexicoUe  9 

Pelecijphorus  pantex  9 

P.   semilaevis   9 

Triorophus   laevis   9 

Trogloderus  castatus  10 

Changes  within  Sectors   10 

Grid  vs.  Transect  Extrapolation  11 

Crater   Occupants    12 

ANTS    12 

Aphaenogaster  megommattis  12 

Crematogaster  coarctata  12 

Iridomijrmex    pniinosum    12 

Mijrmecocijstus   mexicanus   12 

M.   mimicus  12 

Pheidole    bicarinata    13 

Pogonormjrmex   calif ornicus   13 

P.    nigosus   13 

Veromessor   lariversi   14 

V.  smithi   14 

Changes  within  Sectors   14 

Grid  vs.  Transect  E.xtrapolation  15 

ORTHOPTERANS    15 

Arenivaga    erratica    15 

Cetithophilus    fossor    15 

C.   kimellipes   15 

Litaneutria   minor   15 

Stenopelmatus  fuscus  15 

Changes  within   Sectors   15 

SCORPIONS    16 

Hadrurus  spadix   16 

Vaejovi^    becki    16 

V.    boreius    16 

V.   confusus  16 

Changes  within  Sectors   16 

Crater  Occupants    16 

Grid  vs.  Transect  Extrapolation  16 

SOLPUGIDS    16 

Bronchia   potens   16 


Eremobates  scopulatus  IV 

Eremorhax  pulcher  17 

Hemerotrecha  calif ornica  17 

H.    proxima    17 

H.    scrrata    17 

Changes  within  Sectors  17 

Crater   Occupants    17 

Grid  vs.  Transect  Extrapolation  17 

SPIDERS    17 

Calilena   restricta 17 

Gtuijilwsa   hirsutipes   17 

Iliipliidrassu.s-    cuiiii    17 

Ilirptjllus    hcspcwlus    17 

Loxosceles  unicolor  18 

Megamijrmecion    naturalisticum    18 

Ncuuntigraphis  chamherlini   18 

Orthonops   gcrtschi   18 

Physocijclus   tanneri    18 

Pailochorus    utahensbi    18 

St/.spira    cclectica     18 

Changes  within  Sectors  18 

Grid  vs.  Transect  E.xtrapolation  19 

SUMMARY    19 

LITERATURE    CITED  20 


EFFECTS  OF  A  NUCLEAR  DETONATION  ON 
ARTHROPODS  AT  THE  NEVADA  TEST  SITE' 


by 

Dorald  M.  Allred^ 


INTRODUCTION 


Allred,  Beck,  and  Jorgensen  (1963b,  1964) 
and  Jorgensen,  Allred,  and  Beck  (1963)  dis- 
cussed the  effects  of  the  nuclear  detonation 
"Sedan"  on  vegetation  and  rodents  at  the  Ne- 
vada Test  Site.  My  report  discusses  the  effects 
of  that  same  detonation  on  arthropods. 

Project  Sedan,  a  phase  of  the  Plowshare  pro- 
gram for  peaceful  uses  of  nuclear  energy,  was 
detonated  underground  at  a  depth  of  194m  on 


July  6,  1962.  The  thermonuclear  device  of  100 
short  kilotons  created  a  crater  98m  deep  and 
.390m  in  diameter  (Fig.  1).  Intense  radioactive 
fallout  was  generally  confined  within  an  area 
of  6.5km  by  9.7km.  Ecological  studies,  which 
utilized  the  techniques  described  by  Allred, 
Beck,  and  Jorgensen  ( 1963 )  for  trapping  ground- 
dwelling  arthropods,  were  made  before  and  af- 
ter the  detonation. 


METHODS 


Can  pit-traps  were  placed  at  intervals  be- 
tween 305m  (1000  ft)  and  2743m  (9000  ft) 
from  ground  zero  (GZ  =  the  center  of  the 
nuclear  detonation)  as  shown  by  the  circles  on 
Fig.  2.  One  year  after  the  detonation,  pit  cans 
were  also  arranged  in  three  grids  as  shown  on 
Fig.  2.  Each  grid  consisted  of  four  transects 
3m  apart,  each  transect  with  five  cans  6m  apart. 

Cans  along  the  main  transect,  which  was 
2438m  long,  were  open  for  the  capture  of  ani- 
mals from  June  17  through  July  5,  1962  (pre- 
test). Arthropods  were  removed  from  the  cans 
at  two-day  intervals  prior  to  the  detonation.  Be- 
ginning on  August  25  after  the  detonation,  which 
was  as  soon  as  safety  conditions  allowed  entry 
into  the  area,  the  cans  were  opened  and  left 
until  September  2.3,  1962  (posttest).  During 
this  latter  time,  collections  were  also  made  at 
two-day  intervals,  except  for  three  periods  when 
strong  winds  created  sufficient  movement  of 
radioactive  dust  to  create  a  safety  hazard.  Dur- 
ing this  period,  entry  into  the  area  was  not  al- 
lowed, and  collection  intervals  of  five  to  seven 
days  were  used.  A  year  later,  from  20  to  30 
June,  and  15  to  25  August  1963,  cans  were 
opened  and  visited  at  two-day  intervals. 

Pit  cans  on  the  three  grids  which  were  es- 
tablished in  1963  were  also  open  from  20  to 


30  June  and  15  to  25  August  1963,  and  visited 
every  second  day. 

Jorgensen,  Allred,  and  Beck  (1963:51)  des- 
ignated two  pretest  and  three  posttest  zones 
(Fig.  2).  On  the  basis  of  their  analysis  of 
vegetation  before  the  detonation  and  subse- 
quent effects  of  the  blast  (Ibid: 54),  I  desig- 
nated nine  sectors  for  analysis  of  the  arthropod 
populations  (Fig.  2).  The  major  vegetative 
types  according  to  sectors  are  shown  in  Table  1. 

For  purposes  of  comparative  populations  be- 
tween the  2438m  transect  and  the  grids,  I 
grouped  those  sectors  of  similar  vegetative 
types  and  damage  with  the  specific  area  of  the 
grid.  The  grid  closest  to  GZ  (lOt)  is  compared 
to  the  section  of  the  transect  within  sectors  1 
to  3,  the  second  grid  (lOu)  with  sectors  4  to 
6,  and  the  grid  farthest  from  GZ  (lOw)  with 
sectors  7  to  9. 

In  order  to  extrapolate  population  indices 
from  other  areas  of  similar  vegetative  types  of 
the  test  site  to  those  expected  in  the  nine  sec- 
tors of  the  Sedan  experiment,  relative  popula- 
tion factors  were  determined  for  four  major 
types  which  correspond  to  the  zones  and  vege- 
tative analysis  as  designated  by  Jorgensen,  All- 
red,  and  Beck  (1963:51,  54),  and  the  nine  sec- 
tors as  used  in  my  report  (Table  2).   These  are 


■BYUAEC   Report  C00-78(i  fin 

denier     for     Health     and     Environmental     Studies,     Brigham     Youni;   Univ,,    Provo,    Utah   84h02. 


Bhioham  Young  Univkhsitv  Scienck  Bulletin 


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Brigham  Young  Uniyehsity  Science  Bulletin 


TABLE  1.     Principal   vegetative   types   and   conditions   in  nine  sectors  before  and  after  the  detonation  of  Sedan. 


Sector 


Feet 

from 

GZ 


Pretest 


Posttest 


1 
2 
3 
4 

5 
6 

7 
8 
9 


0-1500 
1500-2500 
2500-3500 
3500-4500 

4500-5500 
5500-6500 
6500-7500 
7500-8500 
8500-9500 


Salsola-Grass 

Sahola-Grass-Hymenoclea 
Hijmenoclca-Grmjia-Grass 
Coleogtjnc-Grm/ia-GjTass 

Coleog,ijiic-Gr(itii(i 

Coleogijnc-Graijia 

Coleogyne-Grayia 

Coleogtjne-Grayia-Lycium 

Coleogyne-Grayia 


Covered  with  soil 
Covered  with  soil 

ditto 
Vegetation  destroyed;  partly  covered 

with  soil 
Vegetation    damaged;    layer    of    dust 
No  change;  layer  of  dust 
No  change;  layer  of  dust 
No  change;  layer  of  dust 
No  change;  layer  of  dust 


TABLE    2.     Relative    abundance    factors" 
1959-1963. 

of    arthropods    in    four    vegetative    types    at    the    Nevada    Test    Site, 

Plant    Commvmity""' 

Group  and  species 

Gr  Ly                 Co  Gr  Ly               Co  Gr  Ly 

Sa                          (dis)                       (dis)                      (undis) 

Tenebrionid  Beetles 


Araeoshiztis  sulcicoUis 

1 

48 

56 

46 

Centrioptera  imiricata 

1 

39 

25 

5 

Conibiosoma  cloi}gatum 

1 

39 

25 

7 

Edrotes  orbus 

3 

8 

5 

1 

Eleodes  aniiata 

1 

7 

6 

5 

E.  grandicoUis 

1.4 

8 

4 

1 

E.  his  p  Hal  iris 

12 

34 

17 

1 

E.  longipilosa 

0 

0 

0 

1 

E.  nigrina 

0 

0 

0 

0 

Eupso])hyhis  castaneus 

0 

2 

1 

4 

Euschides  btctatufi 

0 

1.3 

1.3 

1 

Eusattus  agnattts 

1 

2.6 

0 

0 

Metoponium  eonvexicoltc 

1 

2.5 

1.3 

2 

Pelecyphonis  pantex 

1 

3 

1.6 

3 

P.  semilaevin 

0 

1.5 

1 

2 

Triorophus  laevis 

1 

32 

18 

5 

Trogloderus  costatus 

4 

18 

9 

1 

Ants 

Aphaenogaster  megommatus 

0 

2 

1 

2 

Crematogaster  eoarctata 

1 

1 

1 

1 

Iridomynnex  pruinosum 

1 

2 

7 

9 

Mynnecoeystus  mexicanus 

1 

9 

8 

12 

M.  mimints 

1 

2 

2 

2 

Pheidole  bicarinata 

1 

2 

1 

1 

Pogonoimjrmex  californiciis 

1 

1.5 

1 

1 

P.  rugosus 

1 

121 

86 

129 

Veromessor  lariversi 

7 

4 

3 

1 

V.  smithi 

0 

0 

1 

2 

(Jrthopterans 

Arenivaga  erratica 

0 

1 

2 

3 

Ceuthophibis  fossor 

1 

1.5 

1 

1 

C.  lamcUipes 

1 

1 

1 

2 

Litaneiitria  vunor 

1 

1.5 

4 

6 

Stenopelmatus  fuscus 

1 

5 

4 

5 

Biological  Series,  Vol.  18,  No.  4       Effects  of  Nuclear  Detonation  on  Arthropods 

Table  2  (Continued) 

Scorpions 

Hadriirus  spadix 

Vaejovis  hecki 

V.  horeus 

V.  conftisus 
Solpugids 

Bronchia  potens 

Eremohates  scopulatus 

Eremorhax  pulcher 

Hemerotrecha  californica 

H.  proximo 

H.  serrata 
Spiders 

Calilcna  rcsfricta 

Gnaphosa  hirsiitipes 

Haplodrassus  eunis 

Herpt/Uus  hesperolus 

Loxoscclcs  itnicoJor 

Megoimjnnecion  naturolis- 
ticitm 

Neoonagrophis  chamberlini 

Orthonops  gertschi 

Physoctjchis  tanneri 

Psilochoriis  utahensis 

Syspiro  eclectica 

*.Mi  numbers  are  i-elated  to  the  factor  of  "1"  which  represents  the  least  abundant,  "0"  indicates  not  found  Factors  are  not  compar- 
able  between   species. 

••Sa  =  Salsola;  Gr  Ly  (dis)  =  Grayia-Lycium  disturbed,  Co  Gr  Ly  (dis)  =  Coleogyne-Grayia-Lycium  disturbed;  Co  Gr  Ly  (undis) 
=    Coleogyne-Grayia-Lycium    undisturbed. 


1 

3 

3 

4 

1 

2 

2 

2 

0 

.5 

.3 

.5 

1 

3 

2 

3 

0 

.5 

2 

3 

1 

1.5 

1 

1.5 

1 

1 

.5 

.5 

0 

3 

3 

5 

0 

2 

1 

2 

1 

1 

1 

1 

0 

3 

2 

3 

1 

4 

6 

9 

1 

5 

9 

14 

1 

3 

5 

7 

0 

0 

0 

0 

0 

0 

1 

2 

1 

1.5 

2 

2.5 

0 

1 

1 

1.5 

0 

0 

0 

0 

1 

1 

1 

1 

0 

.5 

1 

1 

(1)  Salsola.  (2)  disturbed  Grayia-Lycium,  (3) 
disturbed  Coleogyne-Grayia-Lycium,  and  (4) 
undisturbed    Coleogyne-Grayia-Lycium    (Table 

2). 

Similar  factors  were  determined  for  the 
seasonal  occurrence  and  abundance  of  each 
species  of  arthropod  in  other  areas  of  the  test 
site  not  affected  by  the  Sedan  experiment  so  as 
to  determine  the  expected  species  and  their 
populations  during  the  different  sampling  peri- 
ods in  the  environs  of  project  Sedan  (Table  3). 
Factors  of  adjustment  were  used  to  standardize 
sectors  and  grids,  as  well  as  other  areas  and 
seasonal  collecting  at  the  test  site,  to  the  number 
of  stations  and  collections.  Five  equations  were 
used  as  follows. 

For  pretest  and  posttest  populations  of  each 
sector  and  vegetative  type, 

FN,  =  N,:  X  Ts 
where 

PNa  =  number  of  animals  collected  adjusted 
to  the  number  of  collecting  attempts, 

Nc  =  actual  number  of  specimens  collected, 
and 

Ts  =  adjustment  factor  of  the  number  of 
traps   in   a   given  sector  or  vegetative  type,   as 


determined  by  the  greatest  number  of  traps 
used  in  any  of  the  vegetative  areas  or  sectors, 
divided  by  the  number  of  traps  in  the  specific 
sector  or  vegetative  type  considered. 

Seasonal  adjustment  factors  were  determined 
by  Sp  =  Ph 

Pi. 
where 

Sf  =  the  seasonal  adjustment  factor, 
Ph  =   the  greatest  population  collected  in 
one  of  the  four  months,  June  through  Septem- 
ber, over  the  whole  test  site,  and 

P,,  =  the  lowest  population  as  above. 
The  base  factor  for  determining  the  expected 
population   of   a    given   species    for   a   specific 
vegetative  type  and  month  was  calculated  as 
Bp  =^       PNa 

SJuf  +  SJyp 
where 

Bp  =r  the  base  factor, 
PNa  =  as  explained  above, 
SJup  =  the    seasonal    adjustment    factor    for 
June,  and 

SJyp  =  the  seasonal  adjustment  factor  for 
July. 


6 


Brigham  Young  Univebsiti-  Science  Bulletin 


The    posttest    expected   population    was    de-  period  considered, 
fomiined  by  If  the  period  considered  was  more  than  one 

Fx  =  Bf  X  Sf  month,  then  tlie  etjuation  should  read: 
where  Px  =  Bk  x  (Sif  +  Sjf) 

Px  =  the  expected  population  for  a  given  where 

period,  Sik  =  the  first  seasonal  adjustment  factor, 

Bf  ^  the  base  factor  as  explained  above,  and 
and  Slf  =  the  second  seasonal  adjustment  factor, 

Sf  ^=  the  seasonal  adjustment  factor  for  the  and  so  on. 


TABLE    3.     Relative    abundance    factors"     of    arthropods   related  to  above-ground   activity   during  four  months 
at  the  Nevada  Test  Site,  1959-1963. 


Month 

Group  and  species 

June 

July 

Aug. 

Sept. 

Tenebrionid  Beetles 

Araeoshiziis  sulcicollis 

1.6 

1 

2.2 

3 

Centrioptera  nniricata 

37 

22 

4 

1 

Conibiosoma  elonp^atiim 

1 

2 

1 

1 

Echofes  orbtts 

1 

2 

10 

9 

Eleodes  armata 

1 

1.2 

3.2 

8.8 

E.  grandicoUis 

1 

2 

7 

8.5 

E.  hispiUiljris 

3 

1 

1.4 

1.4 

E.  loriiiipilosa 

0 

1 

1 

0 

E.  nigrina 

0 

0 

3 

0 

Eupsopliyhis  ca.staneus 

18 

1 

0 

0 

Euschides  luctatus 

0 

0 

0 

3 

Eusattus  agnatus 

0 

0 

2 

0 

Metoponitim  convexicolle 

1.5 

1 

1 

1.5 

Pelectjphorus  pantex 

0 

1  ' 

76 

30 

P.  semilaevls 

0 

1 

20 

10 

Triorophus  laevis 

17 

7     . 

2.4 

1 

Trogloderus  costatus 

1.4 

1 

3.6 

1.2 

Ants 

Aphaenogaster  megommatus 

1 

122 

133 

0 

Crematogaster  coarctata 

8 

,  17 

21 

1 

Iridomtjrmex  pruinusum 

27 

14 

3 

1 

Mtjrmecociistus  niexicanus 

1 

1 

2 

2 

M.  mimicus 

1 

2 

2 

1 

Pheidole  bicarinata 

6 

7 

3 

1 

Pogonomtjrmex  califoniicus 

.3 

5 

3 

1 

P.  rugosus 

1.5 

1 

2 

1.5 

Veromessor  lariversi 

6 

10 

1 

0 

V.  smithi 

1 

0 

0 

0 

Orthopterans 

Arenivaga  erratica 

15 

1 

3 

0 

Ceuthophilus  fossor 

79 

34 

1 

2 

C.  lamellipes 

0 

1 

5 

6 

Litaneutria  minor 

3 

4 

3 

Slenopehnatus  fu.scus 

4 

7 

5 

Scorpions 

Hadrurus  spadix 

1 

2 

1 

Vaejovis  becki 

2 

2 

2 

V.  horeus 

1 

2 

2 

V.  confusus 

3 

2 

2 

SolpuRids 

Bronchia  potens 

7 

11 

0 

Biological  Serifs,  Vol.  18,  No.  4       Effects  of  Nuclear  Detonation  on  Arthropods 
Table  .3  ( Continued ) 


Eremohates  scopulafus 

2 

1 

0 

0 

Eremorhax  pulcher 

1 

1 

0 

0 

Hemerotrecha  californica 

65 

20 

2 

1 

H.  proxima 

0 

0 

0 

0 

H.  serrata 

1 

5 

6 

2 

Spiders 

Calilemi  restricta 

3 

4 

1 

1 

Gnaphosa  hirsittipes 

14 

11 

1 

7 

Haplodrassus  ctmis 

1 

0 

1 

2 

HerpijUus  Iiesperohis 

2 

1 

0 

4 

Loxosceles  unicolor 

5 

9 

7 

1 

Megamiirmecion  naturalistictim 

3 

3 

2 

1 

Neoancti^raphis  chamherlini 

1 

1 

1 

2 

Orthonops  p,ertschi 

7 

6 

0 

1 

Pht/soctjchis  tanneri 

0 

0 

1 

0 

Psihchonis  titahensis 

5 

5 

4 

1 

Syspira  eclectica 

5 

6 

4 

1 

'All  numbers  are  related  to  the  factor  of  "1"  which 

represen 

,ts  the    least    abundant.      " 

0"    indicates    not    found. 

Factors    are    not    com- 

parable  between  si)ecies. 


RESULTS 


Beetles 

Araeoschizus  sulcicoUis.  Beetles  of  this  spe- 
cies were  present  in  all  sectors  except  number 
8  before  the  detonation,  and  most  densely  con- 
centrated in  sectors  5,  6,  7,  and  2,  respectively 
(Table  4).  One  and  two  months  after  the  deto- 
nation, populations  were  86  percent  below 
the  e.vpected  normal,  and  somewhat  evenly  dis- 
tributed between  all  sectors  except  number  8, 
where  none  were  found.  In  June  1963,  popula- 
tions were  62  percent  below  the  expected  nor- 
mal and  occurred  in  only  four  sectors,  including 
number  8,  but  none  were  closer  to  GZ  than 
1067m.    In  August   1963,  populations   were  93 


percent  below   the   expected  normal   and  were 
found  only  in  sector  8. 

Ecologically,  significant  differences  in  popu- 
lation occurred  from  the  expected  normal  in  all 
sectors  except  numbers  1  and  2.  The  pretest 
population  in  sector  2  was  considerably  higher 
than  the  nomi,  whereas  the  posttest  population 
was  not  significantly  different.  In  sectors  3  to 
9,  pretest  and  posttest  populations  were  signifi- 
cantly lower  than  the  expected  norm. 

Centrioptera  muricata.  Beetles  of  this  species 
were  present  in  only  four  sectors  before  the  det- 
onation and  were  most  densely  concentrated  in 
sectors  7  and  8  ( Table  5 ) .   One  and  two  months 


TABLE   4.     Effects   of  a  nuclear   detonation   on  populations   of  beetles  of  the  species  Araeoschizus  sulcicoUis. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept. 

1962 

J' 

ine  1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Expected 

1 

3 

o 

0 

0 

2 

0 

3 

2 

11 

o 

• 

0 

7 

0 

9 

3 

4 

1 

8 

0 

2 

0 

3 

4 

1 

4 

2 

5 

1 

0 

1 

5 

28 

5 

56 

6 

17 

0 

24 

6 

18 

4 

36 

0 

11 

0 

15 

7 

14 

4 

28 

7 

8 

0 

12 

8 

0 

0 

0 

2 

0 

5 

0 

9 

7 

2 

14 

0 

4 

0 

6     . 

Total 

86 

20 

144 

20 

52 

5 

73 

"Colleclion  attempts  not  made. 


8  Bricham  Young  Univehsiti-  Science  Bulletin 

TABLE   5.     Effects  of  a   nuclear  detonation   on   populations  of  beetles  of  the  species  Centrioptera  muricata. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept.  1962 

June  1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Expected 

3 
6 

7 
8 

1 
4 
9 
9 

0 
0 
2 
0 

0 
0 

1 
1 

0 
0 
0 
0 

1 

3 
6 
6 

0 
0 
0 
0 

0 
0 

1 
1 

Total 

23 

2 

2 

0 

16 

0 

2 

after  the  detonation,  populations  were  not  re- 
duced from  the  e.xpected.  None  were  found  in 
sectors  3  and  6  immediately  after  the  detona- 
tion, and  in  1963  none  were  found  in  any  sector. 
Ecologically,  pretest  populations  were  not 
significantly  different  from  the  e.xpected  nonn 
in  any  sector  except  numbers  3  and  4,  where 
they  were  lower.  Similarly,  posttest  populations 
were  also  significantly  lower  than  the  norm  in 
these  two  sectors,  whereas  in  other  sectors  pop- 
ulations were  as  expected. 

Conibiosoma  elon<^(itum.  One  specimen  was 
taken  in  sector  9  before  the  detonation;  none 
were  taken  after.  Elsewhere  on  the  test  site 
beetles  of  this  species  were  relatively  abundant 
in  Coleogtjne  and  Grciyia-Lijcitim,  but  not  in 
Salsola.  Seasonally  they  were  common  from 
June  to  September. 

Edrotes  orhtis.  Animals  of  this  species  were 
present  only  in  sector  6  before  the  detonation. 
One  and  two  months  after  the  detonation  they 
were  densely  concentrated  in  sectors  3,  4,  and 
5,  whereas  none  were  foimd  in  sector  6.  Post- 
test  populations  occuned  in  six  of  the  sectors. 
One  and  two  montiis  after  the  detonation,  the 
population  actually  increased  over  the  expected 
by  64  percent.  In  June  1963  the  population 
showed  an  increase  of  300  percent,  whereas  in 


August  1963  a  decrease  of  100  percent  from  the 
expected  occurred. 

Ecologically,  pretest  populations  were  not 
significantly  different  from  the  expected  nonn, 
except  in  sector  3  where  they  were  lower.  Post- 
test  populations  were  significantly  higher  than 
expected    in    sectors   3,   4,    and   5. 

Eleodes  armata.  Beetles  of  this  species  were 
present  in  all  sectors  except  numbers  1  and  8 
prior  to  the  detonation  (Table  6).  Greatest 
concentrations  were  in  sectors  7,  6,  and  5,  re- 
spectively. One  and  two  months  after  the  det- 
onation they  were  not  found  in  sectors  2,  3,  and 
6,  but  were  still  most  densely  concentrated  in 
st'ctors  5,  6,  and  7.  Populations  immediately 
after  the  di'tonation  were  dimiiiislied  by  74  per- 
cent. In  June  1963,  beetles  were  found  only 
in  tiiree  sectors,  and  their  populations  were  66 
percent  iiiglier  than  expected.  In  August  1963, 
the  population  iiad  diminished  from  the  ex- 
pected norm  by  SO  percent. 

Ecologically,  these  beetles  were  significantly 
more  abundant  in  sectors  5,  6,  and  7  before  the 
detonation  tlian  was  expected. 

Eleodes  grandicoUis.  Beetles  were  found 
only  in  sectors  1  and  4  before  tlie  detonation. 
One  and  two  montlis  after  the  detonation  l)eetles 
were  present  in  sectors  3,  4,  5,  and  7,  l)ut  not 


TABLE   6.     Effects   of   a   nuclear   detonation   on    populalioiis  of  hcitlt's  ol  the  species  Eleodes  armata. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept 

.  1962 

June  1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Ex 

pected 

Actual 

Expected 

2 

4 

D 

e 

1 

0 

0 

1 

3 

4 

0 

2 

0 

0 

0 

1 

4 

2 

1 

1 

2 

0 

0 

0 

5 

12 

4 

7 

0 

1 

0 

2 

6 

14 

0 

8 

0 

1 

0 

2 

7 

19 

2 

10 

2 

1 

2 

3 

9 

7 

2 

4 

0 

0 

0 

1 

Total 

62 

9 

32 

5 

3 

2 

10 

'Collertion  allcmpts  not  made. 


Biological  Series,  Vol.  18,  No.  4       Effects  of  Nuclear  Detonation  on  Arthropods 


in  sector  1  as  previously  found.  A  decrease  of 
30  percent  from  the  expected  population  oc- 
curred. In  June  1963,  no  beetles  were  found, 
and  in  August  1963,  tlie  population  was  75 
percent  lower  than  the  expected  norm. 

Ecologically,  pretest  populations  were  not 
significantly  different  from  the  expected  in  any 
sector,  except  number  3.  Likewise,  the  post- 
test  population  in  sector  3  was  the  only  one 
that  differed  significantly  from  the  expected 
norm. 

Eleodes  hispilabris.  Beetles  of  this  species 
were  found  only  in  sectors  1  to  5  before  the 
detonation,  and  only  in  sectors  1,  2,  3,  6,  and 
7  after  detonation.  In  no  sector  were  they 
densely  concentrated.  One  and  two  months  af- 
ter the  detonation  the  population  had  diminished 
from  the  expected  norm  bv  34  percent.  In  June 
1963,  the  population  was  the  same  as  expected, 
and  in  August  1963,  it  had  increased  over  the 
norm  by  50  percent. 

Ecologically,  pretest  populations  in  sectors 
1  to  4  were  significantlv  higher  than  expected, 
and  posttest  populations  in  sectors  2,  3,  4,  and 
6  were  significantlv  lower  than  the  norm. 

Eleodes  longipilosa.  One  specimen  was  taken 
in  sector  3  after  the  detonation  in  June  1963.  In 
other  areas  of  the  test  site,  these  beetles  were 
taken  in  similar  vegetative  types  in  May,  July, 
and  August,  but  only  in  small  numbers. 

Eleodes  nigrina.  Two  specimens  were  taken 
in  sectors  3  and  4  in  August  and  September 
1962,  immediatel)  after  the  detonation,  but 
none  at  any  other  time.  In  other  areas  of  the 
test  site  these  beetles  were  taken  only  in  the 
Pinvon-Juniper  conimunitv,  mainly  in  .August. 
Their  occurrence  in  the  disturbed  Grat/io-Li/citim 
and  Coleogyne  near  the  Sedan  crater  was  unex- 
pected. 

Eitpsophijlus  castoneus.  Eight  beetles  of 
this  species  were  taken  in  sectors  3,  4,  and  5 
after  the  detonation  in  June  1963.  None  were 
taken  at  other  times.  In  other  areas  of  the  test 
site  these  beetles  were  most  common  in  vege- 
tati\e  types  other  than  those  near  the  Sedan 
crater  and,  seasonally,  were  most  abundant  in 
Mav  and  June. 

Euschides  Itictcitus.  Two  specimens  were 
taken  in  sector  4  immediately  after  the  detona- 
tion in  .August  and  September  1962.  None  were 
found  at  other  times.  In  other  areas  of  the  test 
site  these  beetles  were  relatively  common  in 
vegetative  types  similar  to  those  which  surround 
the  Sedan  crater,  but  the\'  were  essentially  ab- 
sent between  May  and  September. 


Eusattus  agnattis.  Thirteen  beetles  of  this 
species  were  taken  in  sectors  1  to  4  in  August 
1963;  none  were  taken  at  other  times.  In  other 
areas  of  the  test  site  these  beetles  were  most 
abundant  in  the  same  vegetative  types  that 
surround  the  Sedan  crater,  but  they  were  ab- 
sent from  June  to  September. 

Metoponium  convexicoUe.  Four  specimens 
were  found  in  sectors  3,  5,  6,  and  9  after  the 
detonation  in  June  1963.  None  were  found  at 
other  times.  In  other  areas  of  the  test  site 
these  beetles  were  most  abundant  in  the  same 
vegetative  types  as  in  the  Sedan  environs,  but 
their  populations  were  at  a  minimum  in  August, 
with  an  increase  in  September. 

Pelecyphoms  pantex.  None  were  found 
prior  to  the  detonation  or  in  June  1963.  Im- 
mediatclv  after  the  detonation  in  August  and 
September  1962,  46  specimens  were  found  in 
sectors  3  to  7.  In  August  1963,  1.30  beetles 
were  found  in  all  sectors  except  number  1.  In 
other  areas  of  the  test  site  these  beetles  were 
relatively  abundant  in  the  same  vegetative  types 
as  occur  around  the  Sedan  crater.  Seasonally 
in  other  areas,  thcv  were  most  abundant  in 
August  and  September  and  essentially  absent 
at  other  times.  This  explains  their  absence  in 
June  and  July  before  the  detonation,  as  well  as 
in  June  1963. 

Felecijphorus  semUaevis.  Beetles  of  this 
species  were  not  found  in  the  Sedan  area  prior 
to  the  detonation.  After  the  detonation  in  Au- 
gust and  September  1962,  three  specimens  were 
found  in  sectors  4,  5,  and  7.  None  were  found 
in  June  1963,  but  in  August  1963,  16  beetles 
were  found  in  sectors  1  to  7  and  in  9.  In  other 
areas  of  the  test  site  these  beetles  were  common 
in  the  same  vegetative  types  that  surround  the 
Sedan  crater.  Seasonally,  however,  they  oc- 
curred almost  exclusixelv  in  August  and  Sep- 
temlier.  This  explains  their  absence  in  June 
and  Jul\'  in  the  Sedan  area. 

Triorophus  laevis.  Before  the  detonation 
these  beetles  were  present  in  everv  sector  ex- 
cept numbers  7  and  8  (Table  7).  They  were 
most  densely  concentrated  in  sector  6.  One  and 
two  months  after  the  detonation  tliey  were 
found  only  in  sectors  3,  4,  5,  and  7,  and  most 
denseiv  concentrated  in  sectors  3  and  4.  At 
tliat  time  the  population  was  1000  percent 
greater  than  the  expected  norm.  In  June  1963, 
these  beetles  were  found  onlv  in  sectors  5  to 
S,  and  their  population  was  29  percent  less  than 
the  expected  norm.  In  August  1963,  beetles  were 
not  found  in  any  sector. 

Ecologically,  pretest  populations  were  signif- 


10 


BlUGHAM    VoUNG    UNIVERSITY    SCIENCE    BULLETIN 


TABLE   7.     I 

Effects   of   a   nil 

clear   detonation 

oil    popiil;i 

itioiis  of  bee 

ties 

of  the  species  ' 

iriorophus  I 

aevis. 

No. 

specimens 

Pre- 
test 

Posttest 

Aug.-SepI 

:.  1962 

J' 

jne 

1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Expected 

1 

1 

o 

o 

0 

1 

0 

0 

2 

4 

« 

0 

0 

3 

0 

0 

3 

1 

20 

0 

0 

1 

0 

0 

4 

2 

15 

0 

0 

1 

0 

0 

5 

1 

5 

0 

5 

1 

0 

0 

6 

11 

0 

2 

4 

8 

0 

1 

7 

0 

4 

0 

4 

0 

0 

0 

8 

0 

0 

0 

2 

0 

0 

0 

9 

9 

0 

1 

0 

6 

0 

1 

Total 

29 

44 

3 

15 

21 

0 

2 

•Collection  attempts  not  made. 


icantlv  lower  in  sectors  3  and  4  and  higher  in 
sector  6  than  was  expected.  After  the  deto- 
nation, the  only  significant  difference  was  a  de- 
crease in  the  population  below  that  expected  in 
sector  3. 

Trogloderus  costatus.  Beetles  of  this  species 
were  present  only  in  sectors  1  and  2  before 
tiic  detonation.  {)ne  and  two  months  after  the 
detonation  they  were  found  only  in  sectors  3, 
4,  and  5.  In  that  period  their  populations  were 
only  23  percent  less  than  the  e.xpected  norm. 
In  June  1963,  the  populations  were  100  percent 
above  the  norm  and,  in  August  1963,  307  per- 
cent above  the  expected. 

lilcologicallv,  these  beetles  had  a  lower  pre- 
test population  in  sectors  3  and  4  than  expected, 
but  after  the  detonation  their  populations  in 
sectors  1  to  4  were  significantly  iiigher. 

Changes  trithin  Sectors.  Some  significant 
differences  occurred  between  the  population 
trends  in  different  sectors  during  the  posttest 
recover)'  time.  Populations  generally  and  con- 
sistently were  less  than  tlie  expected  normal  but 
for  few  exceptions.  In  August  1963,  the  popu- 
lation in  sector  2  was  13  percent  above  the 
expected,  whereas  in  sector  8  it  was  400  per- 
cent higher.  At  other  posttest  times  in  tiiese 
two  sectors  the  populations  were  considerabh' 
less  than  the  expected  normal.  However,  sectors 
3  and  4  had  posttest  population  increases  dur- 
ing eaeli  sampling  date  except  one,  June  1963. 
when  the  population  was  only  7  percent  less  than 
e.xpected.  At  other  times  the  population  was 
from  125  percent  to  291  percent  above  the  ex- 
pected nonnal.  As  indicated  by  analysis  of 
the  vegetation,  sector  3  was  in  tlie  fringe  area 
where  tiie  plants  were  desl roved  and  or  cov- 
ered bv  a  shallow  layer  of  soil  throw-out.  Si-ctor 


4  was  typified  by  a  removal  of  most  of  the 
vegetation  by  flying  debris,  with  a  small  amount 
of  throw-out  deposition.  Pretest  populations 
in  sectors  1  and  2  were  moderate  and  in  sectors 

5  and  9  generally  were  high.  Except  for  sec- 
tor 8,  pretest  populations  of  sectors  3  and  4 
were  lowest  of  all  sectors.  The  hypothesis  is 
presented  that  the  unexpected  increase  in  post- 
test  populations  in  sectors  3  and  4  may  have 
been  due  to  piiysical  transport  by  the  force 
of  the  detonation  of  beetles  from  sectors  1  and 
2  to  sectors  3  and  4.  Furthermore,  as  a  result 
of  reverse  air  movement  immediately  after  the 
detonation,  some  beetles  may  have  been  car- 
ried back  towards  sectors  3  and  4  from  the 
more  outh  ing  sectors  where  populations  were 
higiiest.  Because  of  the  tough  protective  exo- 
skeleton  and  nature  of  these  beetles,  one  may 
assume  that  thev  were  able  to  withstand  the 
shock  and  buffeting.  This  hypothesis  is  sup- 
ported by  a  change  of  species  distribution  in 
tile  sectors.  In  sector  3  in  August  and  Sep- 
tember 1963,  four  species  were  present  that 
were  not  taken  in  this  sector  before  the  deto- 
nation. Two  of  tiiese  were  present  before  the 
test  in  sectors  1  and  2,  one  was  present  in 
sector  4,  and  tiie  other  was  not  found  prior 
to  tlie  test.  In  sector  4,  six  species  were  found 
posttest  tliat  were  apparently  not  there  pre- 
test. Two  of  these  were  present  in  adjacent 
sectors  hi^fore  tiie  detonation,  l)ut  tiie  other 
four  were  not  found  prior  to  tiie  detonation. 

Complete  or  ncariv  complete  elimination  of 
tile  population  occurred  in  five  of  tiic  sectors 
at  some  period  after  detonation.  A  reduction 
of  100  percent  occurred  in  August  and  Septem- 
i)er  1962  in  sectors  2  and  8,  and  June  and  .Au- 
gust 1963  in  sector  9.  Ninet\-foiir  percent  re- 
diution     was     noti'd     in     sector    6     in     August 


Biological  Series,  Vol.  18,  No.  4       Effects  of  Nucle.^r  Detonation  on  Arthropods 


11 


and  Soptcmber  1962,  and  96  percent  in  sector 
5  in  August  1963. 

Total  populations  of  all  species  of  tenebrio- 
nid  beetles  were  5S  percent  lower  than  the  e.K- 
pected  normal  in  August  and  September  1962, 
61  percent  lower  in  June  1963,  and  58  percent 
lower  in  August  1963. 

Beetles  of  eight  species  were  found  both 
before  and  after  the  detonation.  Six  other 
species  were  found  after  the  test  that  apparently 
were  not  present  before  (Table  8).  Seasonally 
and  ecologically,  four  of  these  should  have  been 
present  before  the  detonation,  whereas  the  other 
two  were  not  expected.  However,  five  of  the 
species  were  expected  to  be  present  after  the 
test,  but  one  species  found  after  was  unexpected. 
Heretofore  Eleodes  nigrina  was  found  only  in 
the  Pinyon-Juniper  community,  and  its  occur- 
rence in  the  Grmjia-Lijchim  and  Coleogyne  com- 
munities was  unforseen. 

Species  stabilization  in  the  sectors  was  great- 
ly upset  during  the  postshot  periods  of  August 
and  September  1962  and  June  1963  (Table''9). 
By  August  1963,  the  numbers  of  kinds  of  spe- 
cies had  become  somewhat  stabilized,  but  in 
lower  numbers  than  during  the  predetonation 
time. 


Conibiosoma  elongatum  was  taken  before 
the  detonation  in  sector  9  but  not  after  in  any 
sector.  This  species  was  taken  from  June  to 
September  in  similar  \egetative  types  in  other 
areas  of  the  test  site;  so  its  disappearance  was 
unexpected. 

Grid  vs.  Transect  Extrapolation.  Results  be- 
tween the  main  transect  stations  and  the  grids 
could  not  be  correlated  relative  to  the  numbers 
of  beetles  captured.  On  the  basis  of  adjustment 
to  the  number  of  can  traps  used  in  each  grid 
and  the  respective  sectors  of  the  main  transect, 
considerable  differences  were  noted.  In  June 
1963,  the  transect  cans  caught  190  percent  and 
55  percent  more  beetles,  respectively,  than  did 
the  grid  cans  in  regions  1  and  3.  At  the  same 
time  in  region  2,  the  transect  cans  caught  9 
percent  less  than  did  the  grid  cans. 

In  August  1963,  the  grid  cans  consistently 
caught  more  beetles  than  did  the  transect  cans— 
20  percent,  57  percent,  and  37  percent  more  in 
regions  1,  2,  and  3,  respectively. 

In  Julv  and  August  1963,  when  the  grids 
and  transect  were  utilized  simultaneously, 
beetles  of  19  species  were  collected.  Six  of  these 
were  found  only  in  those  cans  arranged  as  a 
grid,  whereas  13  were  captured  in  cans  on  the 


TABLE  8.     Species  of  tenebrionid  beetles  found  after  but  not  prior  to  a  nuclear  detonation. 


Species 


Eleodes  nigrina 
Eup.mphyhis  castaneus 
Euschides  luctatus 
Metoponium  convcxicoUe 
Pelcciiphoriis  pantex 

Pelecijphorus  semilaevis 


Sector 

where 

Presence 

found 

Date 

Expected 

4 

Aug.-Sept.  1962 

no 

3,4,5 

June  1963 

yes 

4 

Aug.-Sept.  1962 

yes 

3,5,6,9 

June  1963 

yes 

2  to  9 

Aug.-Sept.  1962 
Aug.  1963 

yes 

1  to  7,9 

Aug.-Sept.  1962 
Aug.  1963 

yes 

TABLE 

9. 

Number 

of 

speci 

ies    of    tenebrionid 

beetles  found  in 

speci 

ific 

sectors  pretest 

and 

posttest 

Sedan. 

Sector 

Posttest 

Pretest 

Aug.-Sept. 

1962 

June  1963 

Aug.  1963 

1 

2 
3 
4 
5 
6 
7 
8 
9 


5 
5 
5 
5 
4 
5 
3 
1 
3 


6 

10 
7 
2 
8 
0 
3 


3 
2 
4 
5 
6 
3 
3 
2 
1 


3 
4 
3 
3 
3 
3 
3 
2 
2 


'Collettion    attempts   not   made. 


12 


Bmgham  Young  Uniyersity  Science  Bulletin 


main  transect  and  on  tlie  grid.  None  were 
taken  on  the  transect  that  were  not  also  taken 
on  the  grids. 

Crater  Occupants.  Minimal  populations  of 
beetles  of  five  species  were  found  in  the  bottom 
of  the  Sedan  crater  in  July  and  August  1963, 
one  year  after  the  detonation.  These  were 
Centrioptera  muricata,  Chilometopon  abnorme, 
Coelocnemus  sulcata.  Eleodes  armata,  and 
Eleodes  hispilahris.  Three  of  these  were  previ- 
ously taken  in  the  environs  of  the  Sedan  crater. 
Coelocnemus  sulcata  was  not  reported  from  the 
test  site  heretofore,  whereas  C.  abnorme  was  re- 
ported previously  from  other  areas  of  the  site. 
Centrioptera  muricata  was  taken  before  the  test 
on  transect  F  in  sector  2,  approximately  488m 
from  the  lip  of  the  resulting  crater.  Eleodes 
armata  was  taken  before  the  detonation  within 
488m  of  the  crater  and  E.  hispilabris  within  183m 
of  the  crater. 

Ants 

Aphaenogaster  meg,ommatiis.  Ants  of  this 
species  were  not  found  prior  to  or  immediately 
after  the  test,  but  a  single  specimen  was  taken 
in  June  1963  in  sector  7.  The  usual  habitat  of 
this  species  is  not  the  vegetative  types  that  oc- 
cur in  the  environs  of  the  Sedan  crater  but 
is  commonly  the  Larrea-Frameria  commimity. 
Seasonally  these  ants  were  most  active  above 
ground  in  July  and  August,  and  only  one  speci- 
men was  taken  elsewhere  on  the  test  site  in 
June. 

Crematogaster  coarctata.  Two  ants  of  this 
species  were  taken  in  sectors  3  and  9  prior  to 
the  test,  and  only  one  was  taken  on  the  grid 
in  sector  2  in  August  1963.  This  species  was  not 
commonly  found  elsewhere  at  the  test  site  in 
the  vegetative  types  peculiar  to  the  Sedan  crater 
environs,  although  seasonally  it  was  abundant 
from  June  to  August  in  other  areas. 


Iridomyrmex  pruinosum.  Animals  of  this 
species  were  present  in  small  numbers  in  sectors 
1,  2,  5,  8,  and  9  prior  to  the  test.  After  the  test 
in  June  1963,  three  specimens  were  found  in 
sector  7.  Elsewhere  on  the  test  site  this  species 
was  common  in  the  same  vegetative  types  as 
those  which  surround  the  Sedan  crater.  Sea- 
sonalh'  it  was  most  common  in  Jime  and  July, 
but  rapidly  diminished  in  above-ground  activity 
in  August. 

Myrmecocystus  mexicanus.  Ants  of  this 
species  were  present  in  sectors  4  to  9  prior  to 
the  detonation  (Table  10).  One  and  two  months 
after  the  detonation  none  were  found  in  any 
sector  except  4  and  9.  In  June  1963,  ants  were 
found  in  sectors  5  to  7.  In  sector  6,  175  percent 
more  ants  were  found  than  expected.  In  Au- 
gust 1963,  ants  were  found  in  sectors  3,  7,  and 
8;  none  were  expected  in  sector  3.  In  other  sec- 
tors, except  7,  fewer  animals  were  found  than 
expected.  An  increase  of  175  percent  occurred 
in  sector  7.  Considering  all  sectors  at  the  period 
of  one  and  two  months  after  the  detonation, 
populations  were  94  percent  less  than  expected; 
in  June  1963,  42  percent  more;  and  in  .\ugust 
1933,  55  percent  less. 

Ecolo'jjieallv,  pretest  and  posttest  popula- 
tions were  significantly  lower  than  expected 
in  all  sectors  except  numbers  1  and  2. 

Mt/rmecocystus  mimicus.  Ants  were  present 
in  sectors  2,  5,  7,  8,  and  9  before  the  detonation 
(Table  11).  One  and  two  months  after  the 
test,  specimens  were  found  only  in  sector  9. 
In  Juni-  1963,  ants  were  present  in  sectors  5,  7, 
and  8,  and  in  sectors  5  and  7  in  August  1963. 
In  sector  S  in  June  1963  twice  as  many  ants 
were  present  as  expected,  and  in  August  1963 
in  sector  5,  A'A  times  more  ants  were  present 
than  expected.  One  and  two  months  after  the 
detonation,  populations  in  all  sectors  had  di- 
minished from  the  expected  by  84  percent.    In 


TABLE    10.      Effects    of   a   nuclear   detonation   on    popui.itions  oi  ants   ot   the  species   Mijrmrcpcij.stua  tiwxicauus. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept. 

1962 

June  1963 

Aug. 

1963 

Sector 

Actual            Expected 

Actual 

E.X 

pected 

Actual 

Expected 

3 

0 

0 

0 

0 

0 

1 

0 

4 

2 

1 

4 

0 

2 

0 

2 

5 

9 

0 

17 

4 

5 

0 

9 

6 

7 

0 

12 

11 

4 

0 

7 

7 

5 

0 

8 

2 

3 

11 

4 

8 

2 

0 

2 

0 

1 

2 

2 

9 

7 

2 

12 

0 

4 

0 

7 

Total 


32 


55 


17 


19 


14 


31 


Biological  Series,  Vol.  18.  No.  4       Effects  of  Nuclear  Detonation  on  Arthropods 


13 


TABLE    11.     Effects   of   a   nuclear   detonation   on   populations  of  ants  of  the  species  Myrmecocystus  mimicus. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept. 

1962 

June  1963 

Aug. 

1963 

Sector 

Actual            Expected 

Actual 

E.xpected 

Actual 

Expected 

2 

1 

o 

• 

0 

3 

0 

1 

5 

4 

0 

4 

1 

1 

9 

2 

7 

18 

0 

16 

2 

5 

4 

11 

S 

5 

0 

5 

2 

1 

0 

3 

9 

7 

5 

6 

0 

2 

0 

4 

Total 

35 

5 

31 

5 

12 

13 

21 

'('ollection  attempts  not  niade. 


June  1963  the  population  wa.s  58  percent  lower, 
and  in  August  1963,  38  percent  lower  than  ex- 
pected. 

Ecologically,  pretest  and  posttest  popula- 
tions were  not  significantly  different  from  the 
expected  nonn,  except  in  sector  7,  where  the 
population  before  the  test  was  higher  than  e.x- 
pected. 

Pheidole  hicarinata.  Before  the  detonation, 
ants  were  found  in  all  sectors  except  number  9 
(Table  12).  None  were  found  one  and  two 
months  later.  In  June  1963,  ants  were  found 
only  in  sectors  4  and  5  and  none  were  found 
in  any  sector  in  August  1963.  A  100  percent 
reduction  from  the  e.xpected  occurred  one  and 
two  months  after  the  detonation,  whereas  the 
populations  in  June  1963  were  75  percent  lower, 
and  in  August,  100  percent  lower  than  expected. 

Ecologically,  the  only  significant  deviation 
from  the  expected  norm  was  in  sector  2  before 
the  detonation,  when  populations  were  higher 
than  expected. 

Pogonomyrmex  californicus.  Ants  of  this  spe- 
cies were  found  in  everv  sector  except  number 
9  before  the  detonation   (Table  13).  One  and 


two  months  after  the  detonation  they  were 
found  in  sectors  4,  5,  6,  and  9.  In  June  1963, 
they  were  foimd  in  all  sectors  except  numbers 
7  and  8,  but  in  August  1963,  only  in  sectors 
1  to  5.  One  and  two  months  after  the  detona- 
tion the  population  was  only  23  percent  less 
than  expected,  in  June  1963  it  was  46  percent 
less,  and  in  August  1963  it  had  diminished  by 
76  percent. 

Ecologicall}',  populations  in  most  sectors  be- 
fore the  test  were  significantly  different  from 
the  e.xpected  norm.  In  sectors  1,  2,  and  9 
they  were  lower  than  expected,  whereas  in  sec- 
tors 3  and  5  they  were  higher.  After  the  det- 
onation, populations  in  all  sectors  except  5  and 
6  were  lower  than  the  expected  norm,  whereas 
in  sector  5  the  population  was  higher.  No  sig- 
nificant change  from  the  expected  occurred  in 
sector  6. 

Pogonoinijrmex  rtigosus.  Only  one  specimen 
of  tiiis  species  was  found  before  the  detonation 
in  sector  9.  One  and  two  months  after  the  deto- 
nation, two  specimens  were  found  in  sector  9. 
None  were  found  in  June  and  August  1963.  In 
other  areas  of  the  test  site  ants  of  this  species 


T.^BLE    12.     Effects    of   a    nuclear    detonation    on    populations  of  ants  of  the  species  Pheidole  hicarinata. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept 

.  1962 

J' 

ane  1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Ex 

pected 

1 

1 

o 

o 

0 

1 

0 

0 

2 

7 

o 

e 

0 

3 

0 

1 

3 

2 

0 

1 

0 

1 

0 

0 

4 

1 

0 

0 

1 

1 

0 

0 

5 

5 

0 

1 

2 

2 

0 

1 

6 

4 

0 

1 

0 

2 

0 

1 

7 

2 

0 

1 

0 

1 

0 

0 

8 

2 

0 

1 

0 

1 

0 

0 

Total 

24 

0 

5 

3 

12 

0 

3 

"Collection  attempts  not  made. 


14 


Bricham  Young  University  Science  Bulletin 


TABLE    13.     Effects   of   a   nuclear   detonation   on   populations  of  ants  of  the  species  Pogononnjrmex  californicus. 


No. 

specimens 

Pre- 
test 

Posttest 

Aug.-Sept.   1962 

J> 

uie  1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Expected 

1 

4 

0 

e 

1 

3 

3 

3 

2 

3 

e 

s 

3 

1 

1 

1 

3 

40 

0 

22 

5 

13 

3 

17 

4 

14 

6 

9 

1 

5 

1 

7 

5 

28 

25 

18 

6 

10 

4 

14 

6 

7 

14 

4 

4 

3 

0 

3 

7 

5 

0 

4 

0 

3 

0 

3 

8 

5 

0 

4 

0 

3 

0 

3 

9 

0 

2 

0 

2 

0 

0 

0 

Total 

106 

47 

61 

22 

41 

12 

51 

•Collection  attempts  not  made. 


were  most  abundant  in  the  Coleogijne  and 
Grayia-Lijchim  communities,  where  seasonally 
their  above-ground  activity  was  greatest  from 
June  to  September. 

Veromessor  lariversi.  Seven  ants  of  this  spe- 
cies were  found  in  sector  5  before  the  detona- 
tion. None  were  found  after  the  tests  e.xccpt 
on  the  grid  in  sector  2,  where  two  specimens 
were  taken  in  June  1963.  In  other  areas  of  the 
test  site,  ants  of  this  species  were  inhabitants 
principally  of  Piinon-Junipcr  areas  and  were 
most  active  in  June  and  July. 

Veromessor  smithi.  Five  ants  of  this  species 
were  found  onlv  in  June  1963  after  the  deto- 
nation in  sectors  5  and  6,  and  on  the  grid  of 
sector  8.  In  other  sections  of  the  test  site  these 
ants  were  taken  infrequentlv  in  few  numbers 
only  in  the  Coleogyne  community  in  June. 

Changes  within  Sectors.  In  August  and  Sep- 
tember, 1962,  populations  in  all  sectors  were 
consistently  less  than  the  expected  nomial,  ex- 
cept in  sector  6  where  they  were  the  same  as 


expected.  In  June  1963,  all  populations  were 
less  than  the  expected  normal,  except  in  sector 

6  where  they  were  200  percent  higher.  All  pop- 
ulations in  August  196.3  were  less  than  the  ex- 
pected nonn. 

Pretest  populations  were  lowest  in  sectors 
1  and  2  and  higliest  in  sectors  3  and  5. 

No  significant  changes  in  species  composi- 
tion occurred  in  the  sectors  by  August  and 
September  immediately  after  the  test.  How- 
ever, in  sector  9  one  species  was  found  after  the 
detonation  that  was  not  taken  prior  to  the  test. 
Most  changes  were  noted  in  June  1963,  when 
three  species   were  found   in  sectors   5,  6,   and 

7  that  had  not  been  found  there  previously. 
Similarly,  two  species  were  found  in  August 
1963,  in  sectors  2  and  3.  Eight  species  were 
found  before  the  detonation,  only  four  in  Au- 
gust and  September  immediately  after  the  det- 
onation, seven  in  June  1963,  and  only  four  in 
August  1963  (Table  14).  One  species,  Vero- 
messor lariversi,  taken  in  sector  5  before  the 
detonation,  was  never  taken  subsequently,  and 


TABLE    14.     Number   of   species   of   ants    found    in   specific   sectt>rs    pretest   and   posttest    Sedan. 


Sector 


Pretest 


Posttest 


Aug.-Sept.  1962 


June  1963 


Aug.  1963 


1 

2 
3 
4 
5 
6 
7 
8 
9 


3 
4 
3 
3 
6 
3 
4 
5 
5 


0 
2 
1 
1 
0 
0 
4 


1 
1 
1 

2 
5 
2 
4 
1 
1 


1 
2 
2 
1 
2 
0 
2 
1 
0 


*Colle«"ti<)n    attempts    not    ni.idc. 


Biological  Sekies,  Vol.  18,  No.  4       Effects  of  Nuclear  Detonation  on  Ahthropods 


15 


two  species,  Aphaenogaster  megommatus  and 
Veromessor  sniithi  in  sectors  5  and  7,  taken  in 
June  1963,  were  not  found  at  any  other  time. 

Complete  or  nearly  complete  elimination  of 
the  population  occurred  in  eight  of  the  sectors 
at  some  period  after  the  detonation.  A  reduc- 
tion of  100  percent  occurred  in  August  and 
September  1962  in  sectors  1,  2,  3,  7,  and  8, 
and  in  August  1963  in  sectors  6  and  9.  Ninety 
percent  reduction  was  noted  in  sector  4  in  Au- 
gust 1963.  In  June  1963,  populations  in  general 
were  not  reduced  as  drastically  as  at  other  times. 
In  fact,  in  sector  6  in  June  1963,  a  200  percent 
increase  in  population  occurred  when  compared 
to  the  expected  norm.  Similarly,  the  popula- 
tion in  sector  6  in  August  and  September  1962 
was  the  same  as  anticipated. 

Total  populations  of  all  species  of  ants  were 
64  percent  lower  in  August  and  September 
1962  than  the  expected  normal,  only  30  percent 
lower  in  June  1963,  but  69  percent  lower  in 
August  1963. 

Grid  vs.  Transect  Extrapolation.  One  speci- 
men of  Mynnecoct/stus  mexicanus  was  taken  on 
the  grid  in  sector  8  in  June  1963  and  one  on 
the  grid  in  sector  4  in  August  1963,  although 
beetles  of  this  species  were  not  taken  on  the  main 
transect  in  that  sector.  Similarly,  other  species 
taken  on  the  grids  but  not  on  the  corresponding 
transect  in  1963  are  Crematogastcr  coarctata 
and  M.  mimicus  in  sector  2  in  August,  Pheidolc 
hicarinata  in  sector  2  in  June,  and  Veromessor 
smithi  in  sector  8  in  June.  None  were  found 
on  the  transect  that  were  not  also  taken  on  the 
corresponding  grid. 

Orthopterans 

The  few  specimens  of  this  group  collected 
in  June  and  August  1963  have  not  as  yet  been 
identified  to  species.  Consequently,  effects  of 
the  detonation  on  these  insects  are  discussed 
only  for  the  immediate  posttcst  period  of  Au- 
gust and  September  1962. 

Arenivaga  erratica.  Roaches  of  this  species 
were  found  in  all  sectors  except  5,  8,  and  9  be- 
fore the  detonation.  After  the  test,  the  specimens 
which  were  found  onlv  in  sectors  3,  4,  5,  and 
9  represented  a  450  percent  increase  above  the 
number  expected.  In  other  areas  of  the  test 
site  roaches  of  this  species  were  abundant  in 
the  same  vegetative  tvpes  as  those  which  occur 
in  the  environs  of  the  Sedan  crater.  Seasonally, 
however,  populations  of  these  roaches  were  at 
low  levels  during  August  and  September. 

Ceuthophihis  jossor.  Crickets  of  this  species 
were  found  in  sectors  1  to  7  (except  6)  before 


the  detonation.  After  the  test  they  were  found 
only  in  sector  9  in  small  numbers.  In  other  areas 
of  the  test  site  these  insects  were  most  common 
in  the  same  vegetative  types  that  occur  around 
the  Sedan  crater.  Seasonally  they  were  most 
abundant  from  March  through  July,  and  in  few 
numbers  in  August  and  September.  This  sea- 
sonal variation  likely  accounts  for  the  few 
numbers  found  immediately  after  the  detona- 
tion in  the  Sedan  area. 

Ceuthophihis  lameUipes.  These  crickets  were 
found  in  all  sectors  except  numbers  2  and  7 
before  the  detonation.  Afterward,  they  were 
found  in  all  sectors  except  number  6.  Their 
numbers  after  the  test  were  diminished  by  97 
percent  from  the  expected  normal.  In  other 
areas  of  the  test  site  these  crickets  were  most 
abundant  in  the  same  vegetative  types  that  oc- 
cur in  the  environs  of  the  Sedan  crater.  Season- 
ally they  were  most  abundant  from  August  to 
November.  Consequently,  such  few  numbers 
after  the  detonation  seem  significant. 

Litaneutria  minor.  Three  praying  mantids 
were  found  only  in  sectors  1,  5,  and  6  before 
the  detonation;  none  were  found  after.  In  other 
parts  of  the  test  site  these  insects  were  most 
abundant  in  Coleogyne,  which  also  occurs  in  the 
area  of  the  Sedan  crater.  Seasonally  they  were 
relatively  abundant  during  August  and  Septem- 
ber. Their  apparent  absence  after  the  test  likely 
was  due  to  normal  low  populations  in  this  par- 
ticular area. 

Stenopelmatus  fuscus.  Before  the  detona- 
tion, Jerusalem  crickets  were  found  only  in  sec- 
tors 1  to  5.  After  the  test  they  were  taken  in 
sectors  3  to  9,  except  7  and  8.  In  all  sectors 
except  3  and  5  the  numbers  found  were  greater 
than  expected.  Considering  all  sectors,  popula- 
tions increased  by  36  percent  over  the  expected. 
In  other  areas  of  the  test  site  these  crickets 
were  most  abundant  in  Graijia-Lijcium  and 
Pinyon-Juniper  areas.  Tlieir  populations  were 
low  in  other  vegetative  types.  Seasonally  they 
were  most  abundant  from  May  to  August  and 
in  October.  Consequently,  their  high  popu- 
lations in  the  environs  of  the  Sedan  crater  in 
August  and  September  were  expected. 

Changes  within  Sectors.  In  August  and 
September  1962,  populations  in  all  sectors  ex- 
cept number  7  were  considerably  less  than  the 
expected  normal.  In  sector  7  an  increase  in 
numbers  occurred.  Considering  all  species  and 
all  sectors,  a  93  percent  reduction  in  popula- 
tion occurred  after  the  detonation. 

Before  the  detonation,  species  distribution 
was  about  equal  between  all  sectors  except  num- 


16 


Bricham  Young  Univehsity  Science  Bulletin 


bers  8  and  9,  which  had  only  one  species 
present.  After  the  detonation,  numbers  of  spe- 
cies were  concentrated  in  sectors  3,  4,  5,  and 
9.  Three  of  the  four  species  in  sector  9  after 
the  test  were  found  no  closer  than  sectors  5 
and  7  prior  to  the  test. 

Scorpions 

Hadriiius  spadix.  Scorpions  of  this  species 
were  found  in  few  numbers  and  only  in 
sectors  1,  4,  and  5  before  the  detonation.  In 
August  and  September  1962  (after  the  test) 
they  were  found  in  greater  nimibcrs  than  ex- 
pected and  only  in  sectors  3  and  5.  In  June 
and  August  1963,  they  were  found  in  few  num- 
bers in  sector  7.  In  no  sector  did  the  numbers 
deviate  significantly  from  the  expected,  either 
before  or  after  the  detonation.  In  other  areas 
of  the  test  site  these  scorpions  were  most  abun- 
dant in  the  Artemisia  and  Mixed  plant  associ- 
ations, types  which  were  not  common  in  the 
environs  of  the  Sedan  crater.  Seasonally  over 
the  test  site  these  animals  were  active  from 
April  to  October,  predominantly   in  July. 

Vaejovis  becki.  Before  the  detonation  these 
scorpions  were  found  in  sectors  3  to  9,  except 
4.  After  the  test  in  August  and  September 
1962,  the  scorpions  were  found  only  in  sectors 
3,  4,  5,  and  7.  In  June  1963,  they  were  found 
only  in  sector  7,  and  in  August  1963,  only  in 
sector  8.  In  no  sector  did  the  numbers  found 
deviate  significantly  from  the  expected,  either 
before  or  after  the  detonation.  In  other  areas 
of  the  test  site  these  scorpions  were  abundant 
in  the  same  vegetative  types  that  occur  in  the 
environs  of  the  Sedan  crater.  Seasonally  they 
were  collected  from  March  to  September,  pre- 
dominantly from  June  to  August. 

Vaejovis  boreus.  Scorpions  of  this  species 
were  not  found  in  the  Sedan  area  prior  to  the 
detonation.  In  August  and  September  1962  they 
were  found  in  sectors  3,  4,  and  5,  but  none  were 
found  in  June  or  August  1963.  The  numbers 
present  in  the  sectors  did  not  deviate  signifi- 
cantly from  the  expected,  either  before  or  after 
the  detonation.  In  other  areas  of  the  test  site 
these  scorpions  were  not  abundant  in  the  Grat/ia- 
Ltjcium  community  and  were  not  found  at  all 
in  the  Coleoi^ijne  and  Salsola  communities.  Sea- 
sonallv  tliey  were  taken  from  June  to  Septem- 
ber, and  predominantly  from  JuK-  to  September. 

Vaejovis  confusus.  Before  the  detonation 
these  scoipions  were  found  in  all  sectors  except 
numbers  6  and  8.  In  August  and  September 
1962  they  were  found  in  sectors  3,  4,  5,  and 
7.     In    that   latter   period,    populations    had    in- 


creased bv  438  percent  above  the  expected.  In 
June  1963,  scorpions  were  found  in  sectors  2  to 

7  (except  number  6),  and  in  August  1963  only 
in  sectors  1,  2,  5,  and  9.  Significant  differences 
from  the  expected  occurred  in  sectors  1  and 
2  before  the  detonation  and  in  sectors  3,  4,  5, 
and  7  after  the  detonation,  when  more  scorpions 
were  found  than  expected.  In  other  areas  of  the 
test  site,  scorpions  of  this  species  were  moder- 
ately abundant  in  the  similar  vegetative  types 
that  occur  in  the  environs  of  the  Sedan  crater. 
Seasonally,  specimens  were  taken  from  March 
to  November,  predominantly  from  June  to  Au- 
gust. 

Changes  iiithin  Sectors.  Significant  differ- 
ences occurred  in  populations  in  sectors  6,  8, 
and  9  in  August  and  September  1962,  when 
numbers  were  reduced  by  100  percent.  Simi- 
lar reductions  occurred  in  sectors  1,  6,  8,  and 
9  in  June  1963  and  in  sectors  3,  4,  6,  and  7  in 
August  1963.  Significant  changes  occurred  in 
sectors  3,  4,  5,  and  7  in  August  and  September 
1962,  with  increases  of  575  percent,  950  per- 
cent, 350  percent,  and  125  percent,  respectively. 
Only  one  significant  increase  occurred  in  June 
1963— sector  7  with  166  percent.  No  increases 
were  noted  in  August  1963.  Considering  all  sec- 
tors, populations  in  August  and  September  1962 
increased  160  percent  but  decreased  liy  50  per- 
cent and  72  percent  in  June  and  August  1963, 
respectivelv,  from  the  expected  nomial. 

Species  composition  in  the  sectors  before 
the  test  vaiied  from  one  to  three.  In  August 
and  September  1962,  sectors  3  and  5  contained 
all  four  species,  but  in  June  and  August  1963,  no 
sector  contained  more  than  one  species,  except 
sector  7,  which  had  three  in  June. 

Crater  Occupants.  One  specimen  of  Had- 
ruriis  spadix  was  found  in  the  bottom  of  the 
crater  in  July  1963. 

Grid  vs.  Transect  Extrapolation.  Scorpions 
of  lladrunts  spadix  were  found  on  the  grids  in 
sector  2  in  August,  sector  4  in  June  and  August, 
and  sector  8  in  June,  but  not  on  the  correspond- 
ing parts  of  the  main  transect.  Those  belonging 
to  Vaejovis  becki  were  found  on  the  grids  in 
sectors  2  and  4  in  August,  but  not  on  the  tran- 
sect. Scorpions  of  V.  confusus  were  taken  on 
the  grids  in  sector  S  in  Jime  and  sectors  4  and 

8  in  August,  but  not  on  the  corresponding 
transect. 

Solpugids 

Ihunchia  potens.  These  solpugids  were 
found  in  few  numbers  and  only  in  sector  8  be- 
fore   the    detonation.     None    were   found    after. 


BiOLOCiCAL  Series,  Vol.  18,  No.  4       Effects  of  Nucxear  Detonation  on  AnTHROPODS 


17 


In  otlier  areas  of  the  test  site,  these  organisms 
were  found  in  the  Coleogijne  and  Graijia-Lijc'mm 
communities  in  relative  abundance  from  June 
to  September,  predominantly  in  June  and  July. 
Their  seasonal  limitations  likely  explain  their 
absence  in  August  and  September,  but  not  their 
absence  in  June  1963. 

Eremohates  scopulatus.  These  specimens  were 
found  only  in  sector  1  before  the  test;  none 
were  foimd  after.  In  other  areas  of  the  test  site 
these  animals  were  present  in  the  similar  vege- 
tative types  that  occur  in  the  area  of  the  Sedan 
crater,  found  predominantly  in  May,  but  also 
present  in  June  and  July.  This  seasonal  limita- 
tion likelv  explains  their  absence  in  June  and 
August  after  the  test. 

Eremorhax  piilcher.  This  solpugid  was  found 
only  in  sector  4  prior  to  the  detonation;  none 
were  found  after  except  on  the  grid  in  sector 
2.  In  other  areas  of  the  test  site  this  new  spe- 
cies, described  bv  Muma  in  1963,  was  taken  in 
few  numbers  in  the  Grayia-Lycium  and  Sahola 
communities  in  June  and  July. 

Hemerotrecha  californica.  Solpugids  of  this 
species  were  foimd  before  the  detonation  in  sec- 
tors 2,  3,  5,  6,  and  7.  None  were  found  after 
the  test.  In  other  parts  of  the  test  site  these 
animals  were  most  abundant  in  the  Coleogyne 
and  Grayia-Lycium  communities,  but  none  were 
found  in  Sahola.  Seasonally  they  were  taken 
from  April  to  September,  predominantly  in  June. 
Their  absence  in  the  sectors  in  June  1963  was 
unexpected. 

Hemerotrecha  proximo.  This  species  de- 
scribed as  new  by  Muma  (1963)  was  repre- 
sented by  specimens  found  in  sector  8  after  the 
test,  but  only  in  August  and  September,  1962. 
In  other  areas  of  the  test  site  the  few  speci- 
mens of  this  species  that  were  taken  were  pre- 
dominantly in  the  Grayia-Lycium  community 
in  October.  Their  occurrence  in  sector  8  was 
expected,   but   not   so   early   in   the  season. 

Hemerotrecha  scrrata.  A  single  specimen 
was  found  in  sector  2  before  the  test,  but  none 
after.  In  other  areas  of  the  test  site  these  sol- 
pugids were  commonly  found  in  the  same  vege- 
tative t\pes  that  occur  in  the  environs  of  the 
Sedan  crater.  Seasonally  they  were  found  from 
June  to  September,  predominantly  in  July  and 
August. 

Changes  within  Sectors.  The  almost  com- 
plete absence  of  solpugids  in  any  of  the  sectors 
after  the  detonation  is  indicative  of  the  tre- 
mendous influence  of  the  detonation  on  sol- 
pugids,  although   seasonal   differences   must  be 


considered  as  somewhat  influential  also  on  their 
occurrence. 

Crater  Occupants.  Specimens  of  two  spe- 
cies taken  from  the  crater  in  August  1963  were 
not  found  on  the  main  transect,  but  one  of  the 
species  was  taken  on  the  grids  in  sectors  2 
and  4.  One  specimen  each  of  Eremohates  zinni 
and  Therobates  cameronensis  was  found  in  the 
crater  in  August  1963.  In  other  areas  of  the 
test  site  E.  zinni  was  the  most  abundant  in  the 
Grayia-Lycium  community  and  was  also  found 
in  Sahola;  none  was  taken  in  Coleogyne.  Sea- 
sonally this  species  was  found  only  in  July  and 
August.  Therobates  cameronensis  was  found 
in  moderate  abundance  in  Coleogyne  and 
Grayia-Lycium  but  not  in  Sahola.  It  occurred 
from  May  to  July. 

Grid  vs.  Transect  Extrapolation.  Only  one 
species  of  solpugids  was  taken  on  the  grids  but 
not  on  the  main  transect— Eremohates  zinni,  taken 
in  sectors  2  and  4  in  August  1963.  A  specimen 
of  Eremorhax  piilcher  was  taken  from  the  grid 
in  sector  2  in  August  1963,  but  not  on  the  cor- 
responding parts  of  the  transect. 

Spiders 

Calilena  restricta.  A  single  specimen  was 
taken  in  sector  6  before  the  test.  None  were 
taken  after.  In  other  areas  of  the  test  site  these 
spiders  were  only  moderately  abundant  in  the 
Grayia-Lycium  community.  They  were  active 
from  February  to  December,  predominantly 
from  June  to  November. 

Gnaphosa  hirsutipes.  Only  three  spiders  of 
this  species  were  taken  before  the  test,  all  in 
sector  7.  None  were  taken  after.  In  other  areas 
of  the  test  site  these  spiders  were  relatively 
abundant  in  the  same  vegetative  types  that  oc- 
cur in  the  environs  of  the  Sedan  crater.  They 
were  active  from  Febraary  to  November,  pre- 
dominantly in  June  and  July. 

Haplodrassus  eunis.  Three  specimens  of  this 
spider  were  taken  in  sectors  2  and  3  before  the 
detonation.  None  were  found  after.  In  other 
areas  of  the  test  site  these  spiders  were  com- 
mon in  undisturbed  vegetation  of  the  types 
that  occur  in  the  environs  of  the  Sedan  crater. 
Tiiey  were  active  all  months  of  the  year,  but 
in  predominant  numbers  only  in  the  nonsum- 
mer  months  of  October  to  April. 

Herpyllus  hesperolus.  A  single  spider  of 
this  species  was  taken  in  sector  8  before  the 
test,  and  one  specimen  was  taken  after  the 
detonation  in  sector  7  and  in  August  1963.  One 
specimen    was    taken   on    the   grid    in   sector   2 


18 


BuicuAM  Young  University  Science  Bulletin 


in  June  1963.  In  other  areas  of  the  test  site 
these  spiders  were  rehitively  abundant  in  un- 
disturbed vegetation  of  the  types  which  occur 
in  the  area  of  the  Sedan  crater.  Seasonally  they 
were  active  the  year  around,  but  predominantly 
in  April.    Few  were  taken  from  June  to  August. 

Loxosceles  ttnicolor.  Spiders  of  this  species 
were  not  found  prior  to  the  detonation.  After 
the  test,  a  single  specimen  was  found  in  sector 
8  in  June,  and  two  in  sectors  2  and  7  in  August 
1963.  These  spiders  were  not  found  in  other 
areas  of  the  test  site  in  the  same  vegetative 
types  that  occur  near  the  Sedan  crater.  Thev 
were  found  predominantly  in  the  Mixed  type  of 
vegetation  from  April  to  September,  predomi- 
nantly in  July  and  August. 

Me<iamyrmecion  naturalisticum.  Spiders  of 
this  species  were  found  before  the  test  in  sec- 
tors 2  and  7.  None  were  found  after.  In  other 
areas  of  the  test  site  these  spiders  were  most 
common  in  the  Coleogyne  community  from  April 
to  September,  predominantly  in  June  and  July. 

Neoanaiiraphis  chamberlini.  Spiders  of  this 
species  were  taken  before  the  test  in  all  sectors 
except  number  9.  The  only  ones  found  after  the 
test  were  taken  in  sectors  2,  6,  and  8 
in  June,  and  in  sector  4  in  August  1963. 
In  other  areas  of  the  test  site  these  spiders 
were  common  in  the  Coleogyne,  Grayia-Lychtm, 
and  Salsola  communities.  They  were  active 
from  February  to  October,  predominantly  from 
June  to  October. 

Orthonops  gertschi.  These  spiders  were 
found  before  the  test  in  sectors  5,  7,  and  9.  None 
were  found  after.  In  other  areas  of  the  test 
site  spiders  of  this  species  were  not  abundant 
in  the  vegetati\e  tvpes  common  to  the   Sedan 


area.     They   were   acti\e   from    March   to    Sep- 
tember, predominantly  from  April  to  July. 

Physocyclus  tanneri.  Only  one  specimen  of 
tliis  species  was  taken  before  the  test,  in  sector 
6.  None  were  found  after.  In  other  areas  of 
the  test  site  these  spiders  were  not  abundant 
and   were   found   onlv   in   August. 

Psilocliorus  utahensis.  Spiders  of  this  spe- 
cies were  the  most  abundant  ones  represented 
in  the  Sedan  area.  They  were  found  before  the 
test  in  all  sectors,  predominantly  in  sectors  6 
and  7  (Table  15).  One  and  two  months  after 
the  detonation  they  were  not  found  at  all.  In 
June  1963,  they  were  found  in  all  sectors  except 
numbers  1  and  2,  and  in  August  1963,  they  were 
found  on  the  grids  in  sectors  2  and  8.  Considering 
all  sectors,  their  100  percent  reduction  in  numbers 
from  the  expected  norm  in  August  and  Sep- 
tember 1962  and  in  August  1963  is  significant. 
Likewise,  in  June  1963  their  populations  were 
reduced  b\'  50  percent.  In  other  areas  of  the 
test  site  these  spiders  were  predominant  in  the 
same  vegetative  types  that  occur  around  the 
Sedan  crater.  Seasonally  they  were  active  all 
vear,  predominantly  from  June  to  August.  Eco- 
logicalh',  before  the  test,  in  all  sectors  popula- 
tions of  this  spider  were  higher  than  expected. 
After  the  detonation,  populations  were  not  gen- 
erally different  from  the  expected. 

Syspira  eclectica.  Spiders  of  this  species  were 
found  before  the  test  only  in  sectors  8  and  9. 
None  were  found  after.  In  other  areas  of  the 
test  site,  these  spiders  were  not  common  in  the 
same  vegetative  types  that  occur  around  the 
Sedan  crater.  They  were  active  from  April  to 
November,  predominantly  from  May  to  August. 

Changes  tcithin  Sectors.  Significant  differ- 
ences from  the  expected  occurred  in  August  and 


TABLE    15.     E 

ffects   of   ;i 

I   nuclear   deton 

ation 

on    populations  of  s 

piders  of  the  species 

Psilochon 

ts  utahensis. 

No 

.  specimens 

Pre- 
test 

Posttest 

Aug.-Sept. 

1962 

J 

une 

1963 

Aug. 

1963 

Sector 

Actual 

Expected 

Actual 

Expected 

Actual 

Expected 

1 

8 

a 

e 

0 

4 

0 

2 

2 

4 

e 

» 

0 

2 

0 

1 

3 

7 

0 

3 

1 

4 

0 

2 

4 

8 

0 

3 

0 

4 

0 

2 

5 

7 

0 

3 

4 

4 

0 

2 

6 

21 

0 

9 

4 

10 

0 

7 

7 

19 

0 

8 

5 

9 

0 

6 

8 

7 

0 

3 

/ 

4 

0 

2 

9 

7 

0 

3 

2 

4 

0 

2 

Total 

90 

0 

32 

23 

36 

0 

26 

*Collcclion  allcnipts  n»l  made. 


BioLOGicAi,  Series,  Vol.  18,  No.  4       Effects  of  Nuclear  Detonation  on  Arthhopods 


19 


September  1962  in  sectors  6  and  7,  where  a  100 
percent  reduction  in  population  occurred.  In 
June  1963,  reductions  of  100  percent  occurred 
in  sectors  1  and  4,  whereas  in  sectors  5,  6,  and 
8  populations  were  much  higher  than  expected. 
In  August  1963,  100  percent  reductions  from 
the  expected  occurred  in  all  sectors  except  2 
and  7,  where  the  actual  numbers  were  equal 
to  the  expected.  Considering  all  sectors,  popu- 
lations in  August  and  September  1962  decreased 
by  100  percent,  increased  33  percent  in  June 
1963,  then  decreased  by  80  percent  in  August 
1963  from  the  expected  normal. 

Species  composition  in  the  sectors  before 
the  test  varied  from  2  to  5.  In  June  1963,  sec- 
tors  3,   5,   7,   and  9  each  contained   only  one 


species,  whereas  sectors  6  and  8  each  contained 
two.  In  August  1963,  sector  7  contained  two 
species. 

Grid  vs.  Transect  Extrapolation.  Spiders  of 
Herpyllus  hesperolus  were  not  found  on  the 
main  transect  in  sector  2  in  June,  but  were 
found  on  the  corresponding  grid.  Those  of 
Loxosceles  unicolor  were  not  found  on  the  tran- 
sect in  sector  2  in  August,  but  were  found 
on  the  grid.  Spiders  of  'Neoanagraphis  chainher- 
lini  were  not  found  on  the  transect  in  sectors 
2,  4,  and  8  in  June  and  August,  but  were  found 
on  the  grids.  Psilochorus  utahensis  was  not 
found  on  the  transect  in  sectors  2  and  8  in  Au- 
gust and  sector  4  in  June,  but  was  found  on 
the  corresponding  grids. 


SUMMARY 


Fifty-three  arthropod  species  were  studied 
in  an  area  affected  by  an  underground  nuclear 
detonation.  These  were  represented  by  10  spe- 
cies of  ants,  17  beetles,  5  orthopterans,  4 
scorpions,  6  solpugids,  and  11  spiders  (Table 
16).  Relative  populations  were  dctcnnined  prior 
to  the  detonation  and  at  three  periods  after  the 
detonation— (1)  one  and  two  months  after  (Au- 
gust and  September  1962),  (2)  11  months  after 
(June  1963),  and  (3)  13  months  after  (August 
1963).  One  and  two  months  after  the  detona- 
tion, the  number  of  species  was  reduced  from 
the  expected  b\'  48  percent,  by  52  percent 
after  11  months,  and  by  66  percent  after  13 
months.  Greatest  reduction  of  specimens  oc- 
curred with  spiders,  followed  by  ants  and  bee- 
tles. Fewest  changes  occurred  in  the  number  of 
scorpions. 


Populations  of  each  group  changed  signifi- 
cantly in  each  period.  Reductions  from  30  per- 
cent to  100  percent  occurred  in  all  groups  in  all 
periods  after  the  detonation  except  for  the  scor- 
pions one  and  two  months  after,  when  an  in- 
crease of  160  percent  was  noted.  After  11 
months  spiders  had  increased  33  percent  ( Table 
17). 

Within  specific  sectors,  populations  did  not 
vary  significantly  from  the  expected  except  in 
a  few  instances.  In  August  and  September  1962, 
immediately  after  the  detonation,  populations 
of  arthropods  in  sectors  3,  4,  and  5  were  much 
higher  than  expected.  This  represented  the 
area  from  approximately  65m  to  140m  from 
ground  zero.  The  increase  may  have  been 
due  primarily  to  the  physical  transport  and 
initial  survival  of  those  arthropods  living  closer 


TABLE  16.     Effects  of  a  nuclear  detonation  on  species  occurrence  of  arthropods  in  the  disturbed  area. 


No. 

Species 

Category 

Ants 

Beetles 

Orthoptera 

Scorpions 

Solpugids 

Spiders 

Total 

Total  no.  involved 

10 

17 

5 

4 

6 

11 

53 

Pretest 

Expected 
Present 

10 

8 

14 
9 

5 

5 

4 
3 

5 
4 

10 
10 

48 
39 

Posttest  Aug.-Sept.  1962 
Expected 
Present 

9 
4 

16 
12 

5 

4 

4 
4 

3 
1 

11 

0 

48 

25 

Posttest  June  1963 
Expected 
Present 

10 

7 

11 

8 

4 

o 

4 
3 

5 
0 

10 
3 

44 
21 

Posttest  Aug.  1963 
Expected 
Present 

9 

3 

15 

8 

5 

0 

4 
2 

2 
0 

9 

2 

44 
15 

•Ilata     nut     available. 


20 


BnicHAM  Young  University  Science  Bulletin 


to  ground  zero  than  65ni.  Similarly,  slight  in- 
creases were  noted  in  sectors  7  and  9,  but  these 
likely  were  not  significant.  In  June  1963  in 
sector  5  and  in  August  1963  in  sector  3,  slight 


increases  in  populations  were  noted.  These  may 
have  been  due  to  seasonal  differences  correlated 
with  vegetative  type,  and  are  also  not  consid- 
ered   significant. 


TABLE     17.     Population    trends    of    arthropods    affected  by  a  nuclear  detonation. 


Group 


Percent  change  from  expected  normal 


Aug.-Sept.  1962 


June  1963 


Aug.   1963 


Ants 

Beetles 

Orthoptera 

Scorpions 

Solpugids 

Spiders 


-  64 

-  58 

-  93 
+160 

-  90 
-100 


-  30 

-  61 

O 

-  50 
-100 

-f  33 


-  69 

-  58 

o 

-  72 
-100 

-  80 


'Data    not    available. 


LITERATURE  CITED 


Allbed,  D.  M.  and  D  E.  Beck.  1967.  Spiders  of  tlie 
Nevada  Tost  Site.  Great  Basin  Natur.,  27(  1 ):  11-2.5. 

Allred,  D.  M.,  D.  E.  Beck,  and  C.  D.  Jorcensen. 
1963-a.  Biotic  communities  of  the  Nevada  Test 
Site.  Brigham  Young  Univ.  Sci.  Bull.  Biol.  Ser., 
l(2):l-52. 

Allred,  D.  M.,  D  E.  Beck,  and  C.  D.  Jorcensen. 
1963-1).  Close-in  effects  of  an  underground  nuclear 
detonation  on  small  mammals  and  selected  inver- 
tebrates. (Preliminary  Report)  Operation  Sedan, 
PNE-226  (P),  Project  62.87,  Office  Tech.  Services, 
Oept.    Commerce,    Washington,    D.C. 

Allred,  D.  M.,  D  E.  Beck,  and  C.  D.  Jorcensen. 
1964.  Close-in  effects  of  an  underground  nuclear 
detonation  on  small  mammals  and  selected  inver- 
tebrates. (Final  Report)  Project  Sedan,  PNE  226F, 
Project  62.87,  Office  Tech.  Services,  Dept.  Com- 
merce,   Washington,    D.C. 

Barnum,  a.  H.      1964.     Orthoptera  of  the  Nevada  Test 


Site.  Brigham  Young  Univ.  Sci.  Bull.  Biol.  Ser., 
4(3):1-134. 

Cole,  A.  C.  1966.  Ants  of  the  Nevada  Test  Site. 
Brigham  Y'oung  Univ.  Sci.  Bull.  Biol.  Ser.,  7(3): 
1-27. 

Certsch,  W.  J.,  and  D.  M.  Allred.  1965.  Scorpi- 
ons of  the  Nevada  Test  Site.  Brigham  Young  Univ. 
Sci.    Bull.   Biol.   Ser.,   6(4):1-15. 

Jorcensen,  C.  D.,  D.  M.  Allred,  and  D  E.  Beck. 
1963.  Some  effects  of  an  underground  nuclear 
detonation  on  biotic  communities  at  the  Nevada 
Test  Site.  Proceedings  Utah  Acad.  Sci.  Arts  and 
Letters,  40(1):49-61. 

.\IuMA,  M.  H.  1963.  Solpugida  of  the  Nevada  Test 
Site.  Brigham  Young  Univ.  Sci.  Bull.  Biol.  Ser., 
3(2);  1-13. 

Tanner,  V.  M..  and  W.  A.  Packham.  196.5.  Tene- 
brionidae  beetles  of  the  Nevada  Test  Site.  Brig- 
ham Young   Univ.   Sci.   Bull.   Biol,   Ser.,  6(1):  1-44. 


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