RAPTOR RESEARCH
Vulumc ]7
Numher 1
Spring 1983
Raptor Research Foundation, Inc.
Fro v-o, Utah, LT.S.A.
Spring 1983
RAPTOR RESEARCH
Volume 17, Number 1, Pages 1-32
CONTENTS
SCIENTIFIC PAPERS
The Raptor Actigram: a General
Alphanumeric Notation for Raptor
Field Data — Hartmut Walter
Nest Box Use and Reproductive Biology
of the American Kestrel in Lassen
County, California — Peter H. Bloom
and Stephen J. Hawks 9* ;
Prey Weights for Computing Percent Biomass
in Raptor Diets — Karen Steenhof 15
Nest Site Selection by Peregrine Falcons —
David A. Ponton 27
Camus hemapterus Nitzsch from Swainson’s
Hawk — Richard E. Fitzner and Norman
E. Woodley 28
Three Adult Bald Eagles at an Active
Nest — James D. Fraser, L.D. Frenzel,
John E. Mathisen and Mark E. Shough 29
THESIS ABSTRACTS 30
ANNOUNCEMENTS 8,31
RAPTOR RESEARCH
Published Quarterly by the Raptor Research Foundation, Inc.
Editor Dr. Clayton M. White, Dept, of Zoology, 161 WIDB, Brigham Young Univer-
sity, Provo, Utah 84602 (801) 378-4860
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THE RAPTOR ACTIGRAM: A GENERAL ALPHANUMERIC
NOTATION FOR RAPTOR FIELD DATA
by Hartmut Walter
Ecosystems and Conservation Section
Department of Geography
University of California, Los Angeles (UCLA)
405 Hilgard Avenue
Los Angeles, CA 90024
“I don’t want to have pages and pages
of endless notes when we go home. ”
J.T. Harris (1979)
Abstract
Raptor actigrams are ethograms using an alphanumeric notation system that enhances the
efficiency of observing, recording, and analyzing behavioral dta of individual birds. The
actigram concept uses a small number of fixed elements, and a potentially large number of
observer-specific subelements that permits maintenance of basic notations but generates high
adaptability to different species and environments. Actigrams are therefore proposed for
general use to promote comparative and quantitative field studies.
Introduction
In the rapidly developing area of raptor behavior progress has been hampered by signific-
ant inefficiencies encountered in recording, storage, access, transfer and quantitative analysis
of data. The culprit is usually the familiar and indispensible notebook used by most observers
during field and laboratory research.
Following is a technique that can substantially increase the overall efficiency of recording,
using, and transferring data on raptor ecology and behavior. Departing from traditional
procedures in ethology (where almost everyone designs his/her own ethogram code, etc.), this
technique has been designed for general use. The two major reasons prompting this approach
are (1) the unusual homogeneity found in the ecology and behavior of th e Falconiformes and
Strigidae', this opens up the potential for the development of an information management
system that can be applied to all raptors and used by many researchers. And (2), we are
standing at the threshold of interspecific and intergeneric comparative raptor studies (Walter
1979a): a general notation system would be an obvious advantage for this developing field.
The Actigram Concept
The need for higher efficiency and general applicability to a wide range of objectives,
species, environments, and observers requires a work language that meets the following
criteria:
(1) comprehensive but not too sophisticated,
(2) detailed and specific yet flexible,
(3) logical and easy to teach, learn and use,
(4) capable of recording and retrieving qualitative and quantitative data,
(5) time- and space-saving yet high in information content, and
(6) useful at different technological levels.
1
Raptor Research 17(1): 1-8
2
RAPTOR RESEARCH
Vol. 17, No. 1
After several drafts and field tests by at least a dozen researchers a shorthand notation
system of letters, numbers, and symbols has been developed that can be used to construct
ethograms containing all recognizable “ethons” (Ellis 1979) exhibited by a raptor. Such
ethograms are termed raptor actigrams; they serve to replace or supplement other written,
verbal or mechanical records. The actigram notation achieves its general applicability by using
a limited number of fixed behavioral elements (Table 1), and by offering an unlimited number of
user-specific subelements. Data entries are ordered along a time gradient, and grouped into
segments of uniform time length. The use of the actigram concept is not only time- and
space-saving but promises to meet the other criteria listed above.
Table 1:
Actigram Elements
Individual Behavior
Social Behavior
P-Group
Physical Status
S-Group
Sexual/Territorial Behavior
PI
perched
SI
display from perch
P2
flying (beating wings)
S2
display in flight
P3
soaring, gliding
S3
other display
P4
other type of flight
S4
soliciting food
P5
climbing, hanging
S5
offering food
P6
hopping, walking
S6
copulation
P7
swimming
S7
physically harassing, attacking
P8
lying down
S8
defensive, evasive behavior
P9
other
S9
other
F-Group
Feeding fs? Body Care
N-Group
Nest-Related Behavior
FI
feeding self
N1
inspecting nest site
F2
drinking/bathing
N2
coll./carrying nest materials
F3
asleep
N3
building, repairing nest
F4
panting
N4
sitting on nest
F5
preening, cleaning
N5
serious incubation
F6
scratching
N6
turning, rolling eggs
F7
shaking feathers, sunning
N7
brooding, sheltering nest content
F8
pellet extraction/defecating
N8
feeding young
F9
other
N9
other
H-Group
Hunting & Prey Handling
User-defined groups
HI
prey search from air
A-Group
Acoustic Behavior
H2
other prey search behavior
H3
prey chase, pursuit
X-Group
Other Activities
H4
prey capture, in possession of prey
H5
prey transport
Y-Group
Environmental Elements
H6
prey transfer
H7
prey handling
Z-Group
Human Impact Elements
H8
prey storage, “caching”
H9
other
The Notation System
A literature search for all behavioral characters or ethons resulted in a list containing well
over 100 terms; many are closely related to each other while others are distinct but extremely
rare in occurrence. In order to achieve a simple and comprehensive notation only 45 ethons
were selected as actigram elements ; each represents at least several behavior patterns, displays,
Spring 1983
Walter — Raptor Actigrams
3
vocalizations, activities, etc. The elements are ordered into five groups (Table 1). The first
three groups (P, F, and H) contain behavioral elements of raptors that can be observed
year-round; the other two (S and N groups) are more often or always associated with
reproductive seasons.
Each element appears in the actigram with its code composed of a capital letter and a single
digit number (F4, P8, or N3). The ninth element in each group (i.e. P9, F9, H9, S9, and N9) is
“open” (unspecified); it must be defined by the observer who needs an extra element in a
particular group.
There are four additional groups listed in Table 1. Group A contains elements of acoustic
communication, usually vocalizations. They remain unspecified here as there are too many
vocalizations to permit a meaningful general definition of these elements. Group X is an entire
unspecified group that may only be used if certain observed phenomena cannot be placed into
any other group. Finally, group Y has been reserved for the listing of environmental “ele-
ments” (components of the bird’s physical and biological environment), and group Z is
comprised of human impact “elements” that we may wish to record.
Subelements do not appear in Tables 1 and 2 because they exist only after an observer has
created and defined them. As an example, a falcon may use four perch sites near its nest site.
We could simply write “PI” every time the falcon makes use of one of them. More accuracy can
be achieved by creating four subelements of PI (Pll =perchl,P12= perch 2, PI 3 = perch 3,
and P14 = perch 4). Should there be more than 9 subelements per element, a third numerical
digit (like PI 14 = perched on site no. 14) can be added.
Auxiliary symbols (Table 2) are a vital part of the actigram concept. They permit recording of
action-response sequences, of simultaneously occurring ethons, and of accurate time data.
Table 2: Auxiliary Symbols
Symbol Definition
1 . Independent Symbols
observed bird absent
! bird present but not recorded
? no data collected
/ end of time segment
+ repeat of last event
( ) inferred event(s), not directly observed or recorded
2. Element-dependent symbols
(To be used after the alphanumeric notation of element [and subelement]; followed by a numerical value)
* duration in minutes within one time segment
(“soaring for 3 minutes” — P3* *3; “soliciting food
for 1 5 seconds” — S4*0: 1 5)
# or @ position of activity in an action- response sequence
between individuals (male H4H5# 1H6#3P2; female
P1P2#2H5#4P2#5P1)
= value or size (Y3 was user-defined as “air temperature
in°C”; then Y3 = 27.5 means "air temp. 27.5°C.”)
3. Interactive Symbols
& or $ Simultaneous occurrence (P6&H4, F5&F7)
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RAPTOR RESEARCH
Vol. 17, No. 1
Observation time is divided into time segments of equal duration, determined by the observer
(usually from one to ten min depending on research design and/or raptor activity levels). An
example for a data sheet with six time segments reads:
P3P4P2P1F5/F5P2P3P1F5&6/P1P2-/-/P1F5/P1/
All segments must show a data entry (even if it should be + , — , !, ?). This encourages and
maintains the observer’s alertness and it generates data collections that can be quantitatively
analyzed.
Preparation and Use of Actigrams
Nearly all imaginable situations can be recorded with the help of the alphanumeric codes;
the observer must, however, possess a good command of the system. This requires some
practice, preferably a field test and the transcribing of longhand notes into the actigram mode.
Battery-operated “memoprinters” and electronic field recorders may also print or store the
actigram notation (Stephenson & Roberts 1977, Morris & Shaw 1978, Dawkins 1971). Some
can record an entire day’s field work, then feed it directly into a computer for analysis.
Programs for their quantitative and sequential analysis can be developed in different compu-
ter languages (BASIC, PASCAL, FORTRAN, etc.).
The actigram should never be regarded as the sole recording technique. Unexpected ethons
may occur from time to time requiring an instant decision on the need for additional
subelements; drawings need to be made of new postures or spatial features. Thus, pencil and
paper, tape recorders, etc. and other field techniques (Nelson 1973) will always be needed
during field work.
The definitions of subelements and other observer-specific coded information should be
written down before or during the observation period. They should be placed in front of the
observer at all times together with the actigram notation tables (Tables 1 and 2). Physical status
elements are recorded only when they first occur. The change from flying to perched has to be
P2P1 but if the bird then begins to preen we follow up with F5 (not P1&F5) as it is quite clear
that the bird is perched while preening, and that it will remain perched until the codes
P2,P3,P4, etc. indicate a change in physical status.
The final actigram should be preceded by a short paragraph containing the necessary
introductory data on species, date, location, time segment, and observer-specified codes.
A relatively simple actigram is shown in Table 3; this is a transformation of Brown’s (1980)
written account of eagle activities.
A more complex actigram contains data on the Sooty Falcon ( Falco concolor ) during the
nesting stage of the breeding season (Table 4), developed from many pages of notes taken in
longhand (see also Walter 1981b).
Discussion
The selection of elements (Table 1) as well as alphanumeric notation may not be everybody’s
first choice. The guiding principles in the selection of elements were (1) their presence among
most raptors, (2) the relative ease of recognizing these ethons in raptors, and (3) the need for
descriptive, non-interpreting definitions. Because of the addition and subdivision potential of
any actigram there should be few if any inconveniences in adhering to this structure.
The proposed notation itself was preferred over a part numeric or literary one. The latter
two are more difficult to read and memorize than the proposed scheme. The reverse (a single
digit number at the beginning of each element, the rest on letters) looks attractive as well but it
seems more logical to have a group with nine elements where numbers 1-9 are right behind the
capital letter.
Spring 1983
Walter — Raptor Actigrams
5
The actigram has a built-in potential that can only be realized by the user. It offers a solution
to a vexing problem: how to record and extract information in equally efficient ways. With the
actigram there is no longer a need to glean information from dust-covered notebooks which
often don’t lend themselves to any quantitative analysis due to their anecdotal or incomplete
nature.
In general, most raptor studies do not require the knowledge of exact minute and second
for each ethon’s occurrence; it is more important to record the context or behavioral sequence
associated with a particular ethon, and to register the temporal distribution of peaks and lows
in activity. This is accomplished with the use of uniform time segments; the duration of
individual elements can also be recorded by using the auxiliary symbol * (see Table 2).
One reviewer felt that Table 1 might lead inexperienced observers to look with great
determination for certain actigram elements, thereby overlooking other ethons, and perhaps
misinterpreting certain behavior. This danger certainly exists with behavioral observations in
general; the limited number of fixed elements tries, however, to avoid oversophistication and
bias. On the other hand, I hope that Table 1 will contribute to the discovery of actually existing
homologous and analogous ethons in different raptors.
The actigram concept should be of particular value for the behavioral studies of captive
raptors (e.g. Wrege Sc Cade 1977), and in the long-term monitoring of a raptor pair’s activities
at the nest site. A full day’s observations may fill only one or two pages of the finished actigram,
reducing the otherwise unmanageable paper stack of longhand notes at the end of the season
by a factor of 10 or more.
Acknowledgments
Quite a number of colleagues, students and friends have discussed the actigram concept
with the author. Others made helpful comments on an early draft. Particular thanks go to
R.W. Nelson for a very thoughtful letter; highly appreciated were the comments made by
D.W. Anderson, C.T. Collins, J. Mosher, B.J. Walton, G.R. Bartolotti, W.G. Hunt, T. Kaiser,
K. Garrett, D. Hector, and G. Lennon.
Table 3. African Fish Eagle (Haliaeetus vocifer)
Breeding pair with downy eaglet, Lake Naivasha, Kenya, 5 October 1971
Observer: Leslie Brown
Time segments: 10 minutes each
Adapted and transformed from field data (Brown 1980: 140-144)
See also graphical analysis (Brown 1977: 70, Brown 1980: 49)
Subelements: PI 1 perched on nest, Pill standing in nest (eaglet visible), P12 perched near nest, P13 behind nest, P14
west of nest, PI 5 east of nest, P16 perched near Colobus Monkey, PI 7 perched on papyrus edge of
lagoon, P31 soaring above nest, P32 soaring high above lake, P41 descends for attack; HI 1 hunting
sortie over water, H2 prey search from shore perch; S7 1 attacking strange, intruding ad. female, S72
forcing strange female down near shore; A1 male’s calls, A2 female’s calls, A3 duetting; Y1 sunrise,
Y5 calls from other eagles, Y6 several Colobus Monkeys in same tree, Y8 ad. eagle passing overhead;
symbol = gives distance in meters from nest (P14 = 80) or distance flown (HI = 200).
Table 3 continued on next page
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RAPTOR RESEARCH
Vol. 17, No. 1
Table 3 cont. . .
Time
Male
05:40
?*5 P16 Y5/A1A1/
06:00
A1 Y5 A1 Y5 A3 / P16 S22 P12*6 P2P1 = 20 / + /
06:30
+ *1 P2 HI 1*2 Pl = 30 Y1 Pl=30*6/ Pl = 30/ +*7 P2 H1P1P2 Pl-50/
07:00
+ /+*6 P2=40 P12 Y6 A1 / P12 /
07:30
P2=20 P12 / P2P3P14=70*7 P2 P3&H1 P15=200/+P2P/4 = 80*5P2P3&H1P14=80 /
08:00
+*4 P2 P14=30 H2 A1 + + +/ H2 / + /
08:30
+ *2 P2 & HI P13/ + / + /
09:00
P13 A1 P2P11*3 A3/+ P2 P12 / P2 P14=80/
09:30
+ *5 P2 P15=40 /+ *7 Y5 A1 + + + P2P3 / + /
10:00
P32*8 P2#1Y5#2P31 / + / + *9 P41 S71#l S72#3 P14=80/
10:30
+ *5 P2 P14 P2 Pll / + / P2P 13 A3 P2 P13=40/
11:00
+ / + / P2 P32 Al#l Y5#2 P32 /
11:30
+ *7 P2 Pll P2P1 / P2 Pll / + *4 P2 (PI) /
12:00
(Pl)*3 P2 P13 / + / + *8 Y8#l Al#2 /
12:30
P13 P2=30 (P13) A1 / (P13P2P13) AI / (P13) P2 =#40 P13 /
13:00
+ A1P13/ + /P2P13/
13:30
P13P2 (P2) H3 P2P12=30/P2(P2P12)A1 / (P12)*2 P2P1H2 /
14:00
H2 / + / + *8 P2 H3 P3 PI /
14:30
P1/ + / + /
15:00
+/Y8#1A1#2P2H31H4P2P12P2P15#1 (F1#S) / + *2P2P12(H6)/
15:30
P2 P3 HI P14=200 / P2 P12 / + *5 P2 P13 /
16:00
P13 / + / + *2 P2 P12=20 P2 P3 P16 /
16:30
+ / P2P1P2P3 H 1 = 200 P2P14=80 H2 / + /
17:00
H2*b P2 H1&P3 P14=80/ + *8 P2 P3 P17*l P2 (PI H2 )/-/
17:30
-/-/-/
18:00
- / P2 P3 *6 P13 / + /
Time
Female
05:40
? *5 Pll Y5/ Al + /
06:00
+ Y5 A2 Y5 A3/S22P11/ + /
06:00
+ Yl/Pll / + /
07:00
+1+1+1
07:30
+/+/+/
08:00
+/+/+/
08:30
+/+/+/
09:00
+/+/+/
09:30
+/+/+/
10:00
+ 1 + 1+ *9 P2 S71#2S72#3 P2#4P11#5/
10:30
P11/ + / + A3 Pll/
Table 3 continued on next page
Spring 1983
Walter — Raptor Actigrams
7
Table 3 cont. . .
Time
Female
11:00
+ / + /+* 5 P2 (P13) /
11:30
+/+/+/
12:00
P13 / + / +*8 Y8#l A2#2 /
12:30
P13 Y8#l A3#2 / (P2P13) A3 + / (P13) /
13:00
(P13J/ + / + *5 P2P11/
13:30
P11/ + / + /
14:00
+/+/+/
14:30
+/+/+/
15:00
+ / + *5 PI 1 1 A2 P2#2 P12 / P2 P12 A2 H4 FI P2 (PI) /
15:30
(PI = 300) A2 (FI) P2 (PI) / A2 P2P3P12P2P11 / + *5 N8 /
16:00
N8*9 Pll / + / + /
16:30
+/+/+/
17:00
+/+/+/
17:30
PI 1*5 Pill /+ / P2P3P1P2P1P2P3*3P2P11 /
18:00
+ /A2#2/P11 /
Table 4: Sooty Falcon (Falco concolor)
Breeding pair near Hawar Island (Bahrain) with three young.
3 October 1977 from 5:00 - 7:30 and 15:45 - 18:00 from a boat anchored in front of the low
breeding bluff. Shown here only period 06:00 ; 07:00 (local time).
Observer: H. Walter
Transformed from field notes and sketches. Five minutes per time segment. One line per time
segment.
Subelements :
Pll
perched at nest
A1
male’s call on arrival with prey
P13
perched in full sunlight
A2
female’s call of response to male
P14
perched in shade
A3
nestling’s call when female flew by nest
P20
flying around nest site
A4
nestling’s begging calls
P21
flying north
Y3
air temperature in the shade (°C.)
P24
flying southeast
Table 4 continued on next page
8
RAPTOR RESEARCH
Vol. 17, No. 1
Table 4 cont. . .
Time
Male
Female
Nestlings (3)
6:U0
— *1P2# 1 A1#3H5#5#5H6#6P13
P2A2#2P2#4H5#7
P13
P13
H7N8H7&N8P2P13
P13&F1
P2H2*4:30
P13
F4
6:15
-(H2)
P13P2&P3
F4P13
-P2*l
P2&P3
A3P13
P24*4— P2&H5# 1 H6#4P2 1 - H 1
P24*2P20P2#3P13#5
P13A4#2A4#6
6:30
-(HI)
P13P2P13F1F5F1
A4
-(HI)
P13P2&H5P13F1
P13
-(HI)
P13&F1P2P1 1N8
P13F1
6:45
-(HI)
N8P2P1*1
F1P13
-*3P2P1
P13
P13
P13Y3— 28.5
P13
P13*4P13&P14
Literature Cited
Brown L, 1977. Eagles of the World. New York.
Brown, L, 1980. The African Fish Eagle. Folkestone.
Dawkins, R. 1971. A cheap method for recording behavioral events for direct computer
access. Behavior 40: 162-173.
Ellis, D.H. 1979. Development of behavior in the Golden Eagle. Wildl. Monogr. 60:1-94.
Harris, J.T. 1979. The Peregrine Falcon in Greenland: observing an endangered species.
Columbia (Missouri) 8c London.
Morris, M. and E. Shaw 1978. A new decoding and transcription device (DTD) for SSR
Keyboard data Beh. Res. Meth. & Instr. 10:571-575.
Nelson, R.W. 1973. Field techniques in a study of the behavior of Peregrine Falcons, Raptor
Res. 7:78-96.
Stephenson, G.R. and T.W. Roberts 1977. The SSR System 7: a general encoding system with
computerized transcription. Beh. Res. Meth. & Instr. 9:434-491.
Walter, H. 1979a. Eleonora’s Falcon: adaptations to prey and habitat in a social raptor.
Chicago 8c London.
Walter, H. 1979b. The Sooty Falcon (Falco concolor) in Oman: results of a breeding survey,
1978. T. Oman Studies 5:9-59 (publ. 1982).
Wrege, P.H. and T.L Cade 1977. Courtship behavior of large falcons in captivity. Raptor
Research 11:1-27.
NEW RELEASE FOR THE WORLD WORKING
GROUP ON BIRDS OF PREY
The ICBP World Working Group on Birds of Prey published its first Bulletin in February.
This comprises 240 pages covering a wide range of current topics including population
censuses, conservation programmes, problems of protection, international smuggling, re-
ports of conferences, etc. from many different countries.
Whilst primarily intended to serve as a means of communication between members of the
Working Group, this Bulletin is available to anyone interested in birds of prey and copies can
be obtained at $7.00 or <£ 4.00 post free from the Working Group (Herbertstr. 14, D-1000
Berlin 33, Fed. Rep. of Germany) of from ICBP (do British Museum (Natural History),
Cromwell Road, London, S.W.7, England). It is hoped to publish further issues biannually.
NEST BOX USE AND REPRODUCTIVE BIOLOGY OF THE
AMERICAN KESTREL IN LASSEN COUNTY, CALIFORNIA
by
Peter H. Bloom 1
Department of Biology
California State University, Long Beach
Long Beach, California 90840
and
Stephen J. Hawks
Susanville District
Bureau of Land Management
P.O. Box 1090
Susanville, California 96130
Abstract
During 1976 we implemented an American Kestrel ( Falco sparverius ) nest box program in
the Great Basin of Lassen County, California. The primary goal was the creation of nesting
habitat where no habitat existed, and the reestablishment of such habitat where it had been
eliminated. Of 247 functional nest boxes examined between 1977 and 1980, 31% of these were
active and 82% of these were successful. 3.1 young were fledged per active nest box. With
careful placement of nest boxes, the percent active may be increased to more than 50%.
Introduction
Despite its widespread occurrence in California, the American Kestrel has received rela-
tively little study in the state. Except for the major ecological study by Balgooyen (1976) and on
seasonal weight variation (Bloom 1973), habitat partitioning (Koplin 1973), winter territorial-
ity (Cade 1955), and predatory efficiency (Collopy 1973), basic natural history information is
lacking for most of California.
In 1976 we implemented an American Kestrel management-study program in Lassen
County, California. The objectives were, 1) to determine if kestrels would nest in artificial nest
boxes in areas which lacked suitable natural nest sites, and 2) to investigate the species’
reproductive biology. Data were collected over 4 breeding seasons (1977 - 1980).
Study Area
The study area covered about 900 km 2 of the Great Basin in Lassen County, California. Elevadon ranged from 1,260 to
2,340 m. The dominant plant association was western juniper (Juniperus occidentalis) and big sagebrush (Artemesia
tridentala). Other sub-dominant plant associations included ponderosa pine (Pinus ponderosa), white fir (Abies concolor),
and the greasewood-shadscale complex (Sarcobatus vermiculatus, Atriplex confertifolia).
Address all correspondence to Peter H. Bloom. Current Address: National Audubon Soci-
ety, Condor Research Center, 87 N. Chestnut Street, Ventura, CA. 93001.
9
Raptor Research 17(1):9-14
10
RAPTOR RESEARCH
Vol. 17, No. 1
Methods
Nest box design followed Hamerstrom, et al. ( 1973), with modifications to meet dimensions of natural nest cavities (Fig.
1). Nest boxes were constructed of 1.9 cm thick pine and measured 18 cm deep, 20 cm wide and 33 cm tall inside. The hole
was 7.6 cm in diameter and located 7.6 cm from the top, in the middle of the front of the box. The back of the box
extended 5 cm above the top and 5 cm below the bottom and was fastened to the supporting structure by one nail through
each extension. Boxes were placed 2 to 6 m above ground and faced all directions.
The top of each nest box was completely removeable and fastened on by eye hooks. This was later modified by bending
the hook or by wiring the lid to the box since some nest boxes were later found without tops. Presumably they were blown
off or sun warped. Nest boxes without tops were rendered useless; no birds of any species ever used them.
The juniper-big sagebrush habitat was chosen as the primary habitat for nest box placement because kestrel nesting
densities were believed low and junipers made logical support structures for nest boxes. Junipers do not readily form
natural cavities by limb breakage or rot; thus, kestrels relied primarily on woodpeckers, particularly the Common Flicker
(Colaptes auratus ), to excavate their nest holes.
Much of the Great Basin juniper country is composed of relatively young trees (Burkhardt et al. 1976). Generally, if
large mature junipers are not present, Common Flickers are also limited in their choice of nest trees; thus, large areas may
be devoid of suitable nest trees for either species.
Although the majority of nest boxes were placed on western junipers some nest boxes were placed on white fir,
ponderosa pine, aspen ( Populus tremuloides), cottonwood (Populus trichocarpa), and telephone poles to determine site
preferences.
Figure 1. American Kestrel nest box in western juniper, Lassen County, California.
Spring 1983
Bloom and Hawks — Kestrel Nest Box Use
11
Results
Ninety-six nest boxes were erected during autumn 1976. Since this study was conducted
supplementary to a general wildlife inventory of Lassen County, it was not always possible to
check all boxes each year thereafter; 71 were checked in 1977, 67 in 1978, 49 in 1979, and 60 in
1980. Reproductive data are given in Table 1 . Of the 247 boxes examined in all years, 35 lost
tops, 1 had fallen from the tree, 2 had been vandalized (shotgunned), and the bottom of 1 box
was destroyed by a Common Flicker. These 39 boxes were considered nonfunctional and not
used in Table 1. Seven functional boxes were used by rodents, 5 by woodrats ( Neotoma spp.),
and 2 by Douglas squirrels ( Tamiasciurus douglasii).
TABLE I
American Kestrel Nest Box Use and Reproductive Biology
Lassen, County, California
1977
1978
1979
1980
TOTAL
Number of Boxes Examined
71
67
49
60
247
Number of Boxes Functional
65
53
40
50
208
Number (Percent) Active
14(%)
18 (34%)
14(96)
19(38%)
65(31%)
Number (percent) Successful
12(86%)
15(83%)
13(93%)
13(68%)
53(83%)
Average Clutch Size/
3.5
4.9
4.3
4.2
4.3
Box 1 /
6 boxes
14
7
11
38
Hatching Success 1 /
(81%)
(83%)
(83%)
(70%)
(79%)
17/21
52/63
25/30
30/43
124/157
Average Brood Size/
2.8
4.7
4.2
3.8
4.0
Box 1 /
6 boxes
11
6
8
31
Fledging Success
(88%)
(88%)
(100%)
(87%)
(90%)
15/17
46/52
25/25
26/30
112/124
Number of Young Fledged/
2.5
4.6
4.1
3.2
3.7
Successful Box 1 /
6 boxes
10
6
8
30
Number of Young Fledged/
2.5
3.5
3.6
2.6
3.1
Active Box 1 /
6 boxes
13
7
10
36
V Data not available from all nests in all years.
12
RAPTOR RESEARCH
Vol. 17, No. 1
An additional 33 nest boxes were occupied by other species of birds. These included
Bufflehead ( Bucephala albeola), Flammulated Owl ( Otus flammeolus), Common Flicker, Tree
Swallow (Iridoprocne bicolor ), Mountain Chickadee (Parus gambeli), House Wren ( Troglodytes
aedon), Mountain Bluebird ( Sialia currucoides) , Starling ( Stumus vulgaris) and House Finch
{Carpodacus mexicanus ).
A nest box was considered to be active (used by kestrels) if eggs, young, or evidence of
nesting (eggshells, etc.) were found. The box was considered successfuf if it fledged at least 1
young.
Reproductive Biology
Biases may be present in some reproductive data since most boxes were not observed during
the incubation period, and not all were reexamined to determine actual fledging success.
Clutch size may thus be biased on the low side, and fledging success on the high side. However,
20 nests contained the maximum clutch or brood size observed, and since clutch sizes larger
than 5 are rare, we believe that these represent complete clutches. Unhatched eggs were
frequently found in the boxes along with young, allowing original clutch sizes to be calculated.
For example, if an initial visit showed that 5 eggs were present, and on a later visit the box
contained 4 young, the mortality was attributed to the nestling stage. Although the remains of
some larger nestlings were found in the nest boxes, very small young may have disappeared
without a trace due to cannibalism, or being consumed by the dermestid beetle larvae which
often infest the box bottom. Although not documented, such losses would have similarly
biased clutch size on the low side and fledgling success on the high side.
Incubation period was assumed to be 30 days (Brown and Amadon 1968). Hatching success
was derived by dividing the number of eggs laid into the number that hatched and multiplying
by 100, while fledging success was determined by dividing the number of young fledged by the
number hatched and multiplying by 100.
Age of the young was estimated on the basis of body size and feather development. We
believe that ages assigned to young were accurate to within 3 days. Average egg laying and
hatching dates were derived by back dating from the estimated average age of the young in
each brood. The dates on which surviving young would have fledged were determined by
projecting forward from the estimated average age of the young in each brood at the last nest
box visit. Because the ages were not based on detailed measurements and the sample size was
small, we used median rather than mean to indicate central tendency of the data. However, in
1977 and 1978 mean and median were only different by one day and mean and median were
identical in 1 979 and 1980. The number of nest boxes in T able 2 is smaller than noted in T able
1 as the ages of the young in nine boxes were not recorded.
Kestrel use of boxes averaged 31%, and 82% of these fledged at least 1 young (Table 1). An
average of 3.1 young fledged per active box. The rate of productivity reported for other
studies of the American Kestrel ranged from 2.3 to 4.4 (Hamerstrom et al. 1973, Nagy 1963,
Smith et al. 1972, Craig and Trost 1979, and Stahlacker and Griese 1979). Of the 99 nestlings
that were old enough to be reliably sexed, 47 were females and 52 were males.
Because not all boxes were examined at fledging, we can only estimate number of young
actually fledged. However, based on the number of young known to have fledged per
successful box (3.7) and nest succes (82%) for the 65 boxes (Table l), we estimate that 197
nestlings were fledged over the four-year period.
Egg laying to fledging period spanned 112 days, between 6 May and 25 August for the 4
years (Table 2). Young fledged in 28-30 days. Nesting phenology was similar to that reported
in southeastern Idaho (Craig and Trost 1979). Median egg laying, hatching, and fledging
dates for the 4 years were 22 May, 21 June, and 21 July, respectively (Table 2).
Spring 1983
Bloom and Hawks — Kestrel Nest Box Use
13
TABLE 2
American Kestrel Laying-Hatching-Fledging Chronology, Lassen County, California
1977
n=7
1978
n= 1 1
1979
n=4
1980
n=5
All Years
n=27
Median Egg Laying Date
and Range
05/23
05/13-06-04
05/16
05/06-05/24
05/23
05/23-05/24
05/30
05/08-06/26
05/22
05/06-06/26
Median Hatching Date
and Range
06/22
06/12-07/04
06/15
06/05-06/23
06/22
06/22-06/23
06/29
06/07-07/26
06/21
06/07-07/26
Median Fledging Date
and Range
07/22
07/12-08/03
07/15
07/05-07/23
07/22
07/22-07/23
07/29
07/07-08/25
07/21
07/05-08/25
Unlike species that do not tolerate human disturbances (Fyfe and Olendorff 1976, Bloom
1974), we found that kestrels tolerated disturbance during the incubation period, if parents
were allowed plenty of notice of our approach, and were allowed to fly from the box. In one
instance, a nest may have failed due to an investigator who surprised an incubating female that
kicked her eggs while assuming a defensive posture on her back. However, not all incubating
adults responded this way, and some could be captured, banded, and replaced in the box
without any loss of eggs or young.
Kestrels used only those nest boxes with unobstructed entrances and open to moderate, but
never dense canopy coverage. Dead snags or live trees with open trunks or large gaps in the
branches were most often used (Fig. 1). All types of supporting structures to which nest boxes
were fastened were utilized, including white fir, ponderosa pine, aspen, cottonwood, and
telephone poles.
Of 54 boxes used by kestrels where direction was recorded, 19 faced south, 17 north, 11
west, and 7 east. Failure rates for each direction were 10, 18, 36, and 14%, respectively. The
high failure rate of west facing nest boxes may be due to the intensity of the afternoon sun.
Discussion
American Kestrels readily accepted our nest boxes and fledged young in habitat that was
previously unoccupied. Although it was not possible to qualify the increased number of pairs
as a result of nest box installation, we are confident, because of earlier searches, that most areas
lacked nesting kestrels before we installed nest boxes.
Because many of the nest boxes were intentionally placed in less than optimum trees or
habitat conditions, we feel that the number of breeding attempts could be substantially
increased. Particularly important is the placement of the box on the edge of a forest or on a
lone tree and not deep inside the forest. Another important factor was unobstructed flight
paths to next boxes. The lower use of an artificial box in an earlier similar study, also in juniper
in the Great Basin of Utah (McArthur 1977), appears to be a result of the latter two variables
(C.M White pers. comm).
During our study kestrel use of nest boxes steadily increased from 20% in 1977 to 38% in
1980. We feel that with careful placement, nest box use by kestrels could easily reach 50% in the
Great Basin habitats of California.
14
RAPTOR RESEARCH
Vol. 17, No. 1
Acknowledgments
We thank Charles T. Collins, Richard R. Olendorff, Melinda Leach, and an anonymous
reviewer for comments on earlier drafts. Robert M. Walker assisted in installing boxes. Dean
K. Swickard provided initial impetus for this study by having the foresight to promote studies
of nesting raptors on public lands. This study was funded by the U.S. Department of the
Interior, Bureau of Land Management, Susanville District.
Literature Cited
Balgooyen, T., C. 1976. Behavior and ecology of the American Kestrel in the Sierra Nevada of
California, Calif. Publ. Zool. 103:1-83.
Bloom, P.H. 1973. Seasonal variation in body weight of Sparrow Hawks in California, West.
Bird Bander 48:4-5.
1974. Some precautions to be used in banding studies of nesting raptors. West. Bird
Bander. 49:4-5.
Brown, L. H., and D. Amadon. 1968. Eagles, hawks, and falcons of the world. 2 vols.
McGraw-Hill, New York. pp. 771-776.
Burkhardt, W. J., and E. W, Tisdale. 1976. Causes of juniper invasion in southwest Idaho.
Ecology 57:472-484.
Collopy, M. W. 1973. Predatory efficiency of American Kestrels wintering in northwestern
California. Raptor Res. 7:25-31.
Craig, H. C., and C. H. Trost. 1979. The biology and nesting density of breeding American
Kestrels and Long-eared Owls on the Big Lost River, southeastern Idaho. Wilson Bull.,
91:50-61.
Hamerstrom, Frances, F.N. Hamerstrom, Jr., and J. Hart. 1973. Nest boxes; an effective
management tool for Kestrels./. Wildl. Manage. 37:400-403.
Koplin, J.R. 1973. Differential habitat use by sexes of American Kestrels wintering in northern
California. Raptor Res. 8:39-42.
McArthur, L. B. 1977. Utilization of nest boxes by birds in three vegetational communities
with special reference to the American Kestrel (Falco sparverius). Abstract of theses, Raptor
Res. 11:80.
Nagy, A. C. 1963. Population density of Sparrow Hawks in eastern Pennsylvania. Wilson Bull.
75:93.
Smith, D. G., C. R. Wilson, and H. H. Frost. 1972. The biology of the American Kestrel in
central Utah. Southwest Nat. 17:73-83.
Stahlecker, D. W., and H. J. Griese. 1979. Raptor use of nest boxes and platforms on
transmission towers. Wildl. Soc. Bull. 7:59-62.
PREY WEIGHTS FOR COMPUTING PERCENT BIOMASS IN RAPTOR
DIETS
by
Karen Steenhof
Snake River Birds of Prey Research Project
Bureau of Land Management
3948 Development Avenue
Boise, Idaho 83705
Researchers have been assessing the relative importance of prey species in raptor diets for
many years. Early in this century, biologists attempted to document the number of pest species
consumed by raptors (e.g., Kalmbach et al. 1964). More recently, biologists have studied
raptor diets to understand the effects of land use changes and environmental contaminants
(e.g., Cade et al. 1968).
Frequency of an individual prey species in the diet is not always directly related to its
nutritional importance (Southern 1954, Morris 1979). Raptors may consume several small
items that provide less weight and energy than a single large prey item. To account for this,
raptor diets are now usually reported in terms of biomass: frequency of a prey item multiplied
by its average weight (e.g., McGahan 1966, 1967; Porter and White 1973; Smith and Murphy
1973; Marti 1974).
Accuracy of a biomass estimate depends on the accuracy of the weight assigned to a prey
item. To ensure accuracy, weights for each prey species should be categorized by age and sex
when appropriate. An average adult weight will distort relative importance of a prey species if
raptors are consuming juveniles. Similarly, an average weight will distort results if one sex of a
sexually diomorphic prey species is more vulnerable to raptor predation. Unfortunately, few
studies have considered size classes in computing biomass in the diet.
Prey weights can rarely be obtained directly from pellet remains, partially consumed prey,
or decomposed food items found in nests or under perches. Snout-vent lengths may be
reliable indicators of snake weights (BLM unpublished data), and Morris (1979) and Hamilton
(1980) reported a useful relationship between rodent jaw lengths and body weights. Unfortu-
nately, similar relationships are not available for most prey species, and in most cases, weights
of freshly collected animals or average weights reported in the literature must be used. During
studies of raptor ecology in the Snake River Birds of Prey Area in southwestern Idaho, I
compiled information on weights of 116 raptor prey species taken by 9 species of raptors
(Table 1). These weights may be useful to others investigating predator-prey relations.
When possible, I used prey weights obtained in the area by BLM research project personnel.
Nestling raptors and Common Ravens ( Corvus corax ) of various ages were weighted by BLM
researchers in the nests; live cottontails ( Sylvilagus nuttallii); woodrats ( Neotoma spp.), and
Townsend ground squirrels ( Spermophilus tovmsendii) were weighted during trapping activities
by BLM contractors from the University of Idaho; dead rodents captured in snap traps were
weighed by contractors from Utah State University; and reptiles were weighed by L. Diller,
University of Idaho. Weights of prey species not measured during the study were obtained
from published literataure. In addition, C. Robbins and M. Fuller kindly provided weights for
several birds from banding records, L.C. Stoddart provided weights for black-tailed jackrab-
15
Raptor Research 17(l):15-27
16
RAPTOR RESEARCH
Vol. 17, No. 1
bits (Lepus calif ornicus), and M.R. Browning provided Say’s Phoebe (Sayornis saya) weights from
files at the National Museum. I calculated weights for prey items that could be identified only
to class or genus by using the mean weight of identified individuals within that class or genus
that were taken by raptors.
Size classes of prey were assigned either at the time remains were collected or when they
were analyzed. Neonates included very small mammals just emerging from nests or burrows.
Most other young of the year birds and mammals that were smaller than adults were classed as
juveniles. An intermediate class was used for fledging-age birds, second year marmots ( Mar -
mota flaviventris ) and rabbits less than approximately 3 months old but older than 1 month.
Adults included any fully grown prey, and an average class was used for any prey item that
could not be aged. Averages were calculated using relative proportions of known size classes in
raptor diets. Juvenile weights for prey species that show large weight gains over a short period
of time (e.g., Canada Goose (. Branta canadensis ); badger ( Taxidea taxus), and mule deer
(Odocoileus hemionus)) were estimated by considering the typical size of a young animal available
to raptors during the nesting season. Because of large seasonal changes, weights assigned to
Townsend ground squirrels depended on the months ground squirrels were found in nests.
This paper is a contribution from the Bureau of Land Management’s Snake River Birds of
Prey Research Project. I thank M.J. Collopy and J.S. Marks for assistance in reviewing the
literature and G.W. Smith and N.C. Nydegger for assistance in tabulating rodent weights. This
compilation would not have been possible without the efforts of M.N. Kochert, A.R. Bam-
mann, J.H. Doremus and the many biologists and technicians who worked on the project. J.S.
Marks, M.Q. Moritsch and M.N. Kocher reivewed draft manuscripts and made helpful
suggestions. J. A. Gessaman kindly provided access to an unpublished compilation of literature
on bird weights.
Table 1. Weights of Prey Species Captured by Raptors
Species
Size Class & Sex
Wt(g)
N
Reference
MAMMALS:
Shrew-unid.
(Sorex spp.)
Average
6
(1)
BLM Data
Pallid Bat
(Antrozous pallidus)
Average
32
Burt & Grossenheider 1964
Bat-unid.
(Myotis spp.)
Average
10
(2)
Porter & White 1973
Long-tailed Weasel
Juvenile
85
Palmer 1954
( Mustela frenata)
Adult
178
Smith & Murphy 1973
Badger
(' Taxidea taxus)
Neonate
2833
Estimated
Coyote
( Canis latrans)
Juvenile
2043
Estimated
Domestic Cat
(Felis domesticus )
Average
1800
Estimated
Spring 1983
Steenhof — Prey Weights
Table 1. Weights of Prey Species Captured by Raptors (cont.)
17
Species
Yellow-bellied Marmot
(Marmot a flaviventris)
Townsend Ground Squirrel
(Spermophilus townsendii)
White-tailed Antelope
Squirrel
(Ammospermophilus leucurus)
Ground squirrel-unid.
Least Chipmunk
(Eutamias minimus)
Townsend Pocket Gopher
(Thomomys townsendii)
Great Basin Pocket Mouse
(Perognathus parvus)
Ord Kangaroo Rat
(Dipodomys ordii)
Harvest Mouse
( Reithrodontomys megalotis)
Deer Mouse
(Peromyscus maniculatus)
Size Class & Sex
Wt(g)
Neonate
500
Juvenile
1000
Intermediate
2346
c?
2530
9
2280
Adult
3222
S
3900
9
2800
Average
1808
Juvenile: April
79
Juvenile:May
120
c?
127
9
114
Juvenile:
199
June-July
<?
184
9
164
Adult: April
205
8
254
9
178
Adult: May-June
222
8
277
9
188
Average: April
176
Average: May-July
177
Juvenile
40
Adult
106
8
111
9
101
Average
105
Juvenile
127
Adult
225
Average
181
Average
32
Juvenile
100
Adult
248
8
261
9
236
Average
200
Juvenile
10
Adult
17
Juvenile
28
Adult
53
Adult
11
Juvenile
10
Adult
19
N Reference
Armitage et al. 1976
(38)
" " "
(10)
" " "
(28)
" " "
(99)
" " "
(38)
" " ”
(61)
" " ''
(147)
BLM Data
(480)
BLM Data
(1282)
" "
(646)
" "
(636)
"
(1331)
" "
(751)
" "
(580)
" "
(1188)
"
(440)
" "
(748)
" "
(750)
" "
(285)
" "
(465)
" *
(3053)
" "
(4501)
Estimated
(12)
Hall 1946
(6)
" "
(6)
" "
(40)
BLM Data
Calculated
(108)
Schreiber 1973
Estimated
(4)
Hall 1946
(3)
" "
(1)
Calculated
Estimated
(508)
BLM Data
Estimated
(31)
Schreiber 1973
(43)
Schreiber 1973
Estimated
(145)
Schreiber 1973
18
RAPTOR RESEARCH
Vol. 17, No. 1
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species Size Class & Sex Wt(g) N Reference
Grasshopper Mouse
( Onychomys leucogaster)
Adult
26
(76) BLM Data
Mouse-unid.
Juvenile
10
Calculated
Adult
17
"
Desert Woodrat
Juvenile
75
Estimated
( Neotoma lepida)
Adult
124
(10) BLM Data
<?
137
(6) "
9
105
(4) "
Bushy-tailed Woodrat
Juvenile
155
(7) Martin 1973
(Neotoma cinerea)
Adult
338
(32)
c?
405
(16)
9
271
(16)
Average
277
" "
Woodrat-unid.
Juvenile
195
(45) BLM Data
(Neotoma spp.)
Adult
326
(87) "
<S
335
(70) "
9
275
(16) "
Average
281
" "
Muskrat
Juvenile
1065
Donahoe 1966
(Ondatra zibethica)
d
1097
"
9
1032
"
Adult
1277
"
d 1
1298
"
9
1256
" "
Average
1171
(1895)
House Mouse
(Mus musculus)
Average
19
(16) BLM Data
Montane Vole
Juvenile
15
*
(Microtus montanus)
Adult
50
"
c?
60
"
9
40
"
Average
35
"
Sagebrush Vole
(Lagurus curtains)
Average
30
Burt & Grossenheider 1964
Rodent-unid.
Juvenile
10
Estimated
Adult
50
Estimated
Average
50
*
Porcupine
(Erethizon dorsatum)
Adults
5800
Smith pers. comm.
Black-tailed jackrabbit
Fetus
20
(Lepus califomicus)
Neonate
100
Stoddart pers. comm.
Juvenile
500
" " "
Spring 1983
Steenhof — Prey Weights
19
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
Wt(g)
N
Reference
Black-tailed Jackrabbit
Intermediate
1000
Stoddart pers. comm.
( Lepus californicus)
Adult
2114
"
3
1885
" " "
9
2344
"
Average
1536
Calculated
Mountain Cottontail
Neonate
100
BLM Data
(Sylvilagus nuttalln)
Juvenile
215
" »
Intermediate
500
" *
Adult
650
(92)
"
3
590
(45)
«
9
720
(47)
" "
Pygmy Rabbit
Adult
340
Burt Sc Grossenheider 1964
(Sylvilagus idahoensis)
Rabbit-unid.
Neonate
100
Calculated
Juvenile
404
"
Intermediate
1087
"
Adult
1550
"
Average
927
"
Mule Deer
Juvenile
3780
McGahan 1966
(Odocoileus hemionus)
Pronghorn Antelope
Neonate
2700
Beuchner 1950
(Antilocapra americana)
BIRDS:
Great Blue Heron
Average
1905
(1)
Poole 1938
( Ardea herodias)
Canada Goose
Juvenile
450
Estimated
(Branta canadensis)
Mallard
Adult
1185
(3226)
Bellrose 1976
(Anas platyrhynchos)
3
1248
(1809)
" "
9
1107
(1417)
" a
Northern Pintail
Adult
976
(556)
Bellrose 1976
(Anas acuta)
3
1025
(390)
"
9
866
(166)
n n
American Green-winged
Adult
316
(192)
Bellrose 1976
Teal
3
322
(113)
n
(Anas crecca)
9
309
(79)
a a
Blue-winged Teal
Adult
395
(164)
Bellrose 1976
(Anas discors)
3
463
(35)
"
9
377
(129)
"
20
RAPTOR RESEARCH
Vol. 17, No. 1
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
Wt(g)
N Reference
Cinnamon Teal
Adult
347
(24) Bellrose 1976
(Anas cyanoptera)
340
(13)
9
354
(11)
Teal-unid.
Average
361
Bellrose 1976
American Wigeon
Adult
794
(152) Bellrose 1976
(Anas americana)
<?
821
(84)
9
767
(68)
Intermediate
751
(731)
<?
794
(358)
9
708
(373)
Northern Shoveler
Adult
658
(41) Bellrose 1976
(Anas clypeata)
<?
680
(21)
9
635
(20)
Duck-unid.
Nestling
100
Calculated
Juvenile
425
"
Adult
899
"
<?
1003
"
9
659
"
Average
767
"
Red-tailed Hawk
Juvenile
800
Estimated
(Buteo jmaicensis )
Adult
1049
(39) BLM Data
<?
957
(90) "
9
1154
(113) "
Ferruginous Hawk
Intermediate
1110
(49) BLM Data
(Buteo regalis)
<?
1040
(20) "
9
1228
(13) "
Prairie Falcon
Intermediate
701
(87) BLM Data
(Falco mexicanus)
J
570
(195) "
9
810
(172) "
American Kestrel
Juvenile
57
Estimated
(Falco sparverius)
Adult
114
(117) Craighead 8c Craighead 1956
Northern Bobwhite
Adult
171
(1591) Johnsgard 1973
(Colinus virginianus)
<?
173
(899)
9
170
(692)
California Quail
Juvenile
70
(54) Lewin 1963
(Callipepla californica)
Adult
170
(374)
Ring-necked Pheasant
Juvenile
600
Estimated
(Phasianus colchicus )
Adult
1138
(361) Robertson 1958
<f
1362
(77)
9
1078
(284)
Chukar
Juvenile
300
Estimated
(Alectoris chukar)
Adult
602
(50) Galbreath & Moreland 1953
Spring 1983
Steenhof — Prey Weights
Table 1. Weights of Prey Species Captured by Raptros (cont.)
21
Species
Size Class & Sex
Wt(g)
N
Reference
Gray Partridge
Adult
389
(144)
Nelson & Martin 1953
( Perdix perdix)
Domestic Chicken
Bantam
908
Estimated
Adult
3120
Welty 1962
Gallinceous bird-unid
Juvenile
444
Calculated
(Galliformes)
Adult
940
"
Average
727
Rail-unid.
Adult
70
(2)
Poole 1938
American Coot
Adult
654
(47)
Fredrickson 1969
{Fulica americana)
Killdeer
Adult
104
(2)
Robbins pers. comm.
(i Charadrius vociferus)
Shorebird-unid.
Adult
497
Estimated
(Charadriiformes )
Ring-billed Gull
Juvenile
497
(39)
Vermeer 1970
( Larus delawarensis)
Gull-unid.
Adult
633
(78)
(Larus spp.)
Rock Dove
Adult
332
(9)
BLM Data
(Columba livia)
Mourning Dove
Juvenile
131
(10)
Ivacic & Labisky 1973
(Zenaida mcroura)
Average
134
(10)
Common Barn Owl
Adult
525
(78)
Marti pers. comm.
f Tyto alba)
c?
461
(28)
" " "
9
561
(50)
Great Horned Owl
Adult
1310
(188)
Earhart & Johnson 1970
(Bubo virginianus)
4
1110
(94)
" " ” "
9
1509
(94)
Burrowing Owl
Average
170
(22)
Thomsen 1971
(Athene cunicularia)
Short-eared Owl
Juvenile
200
Clark 1975
(Asia flammeus)
Adult
348
(4)
" "
t?
304
(2)
" "
9
393
(2)
" "
Common Poorwill
Adult
43
(1)
Lasiewski et al. 1971
(Phalaenoptilus nvMallii)
Common Nighthawk
Average
83
(2)
Esten 1931
(Chordeiles minor )
22
RAPTOR RESEARCH
Vol. 17, No. 1
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
Wt(g)
N Reference
Say’s Phoebe
(Sayomis soya)
Adult
23
(16) USFWS files
Horned Lark
Juvenile
17
(14) Beason 8c Franks 1973
( Eremophila alpestris)
Adult
26
Trost 1972
Cliff Swallow
( Hirundo pyrrhonata)
Adult
25
(10) Withers 1977
Northern
Rough-winged Swallow
( Stelgidopteryx serripennis)
Adult
16
(2) Poole 1938
Swallow-unid.
Adult
25
(10) Withers 1977
Blue Jay
(Cyanocitta cristata)
Adult
74
(1) Esten 1931
Pinyon Jay
( Gymnorhinus cyanocephalus)
Adult
108
(1) Poole 1938
Black-billed Magpie
( Pica pica)
Adult
170
(28) Linsdale 1937
Common Raven
Adult
1234
White & Cade 1971
(Corvus corax )
Juvenile
650
BLM Data
Average
876
(175) "
Common Crow
( Corvus brachyrkynchos)
Adult
460
(6) Balwin & Kendeigh 1938
Red-breasted Nuthatch
(Sitta canadensis)
Adult
11
(19) Mugaas & Templeton 1970
Marsh Wren
( Cistothorus palustris)
Adult
11
(76) Robbins pers. comm.
Canyon Wren
(Cat herpes mexicanus)
Adult
10
(2) Johnson 1965
Rock Wren
(Salpinctes obsoletus)
Adult
17
(1) Easterla & Ball 1973
Sage Thrasher
(Oreoscoptes montanus)
Adult
37
(2) Killpack 1970
American Robin
( Turdus migratorius)
Adult
79 (1781) Robbins pers. comm.
Hermit Thrush
(Catharus guttatus)
Adult
31
(4) Baldwin & Kendeigh 1938
Mountain Bluebird
(Sialia currucoides)
Adult
35
Baida et al. 1972
Spring 1983
Steenhof — Prey Weights
23
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
Wt(g)
N
Reference
Water Pipit
(Anthus spinoletta)
Adult
19
(1)
Poole 1938
Loggerhead Shrike
( Lanius ludovicianus)
Adult
51
(4)
Robbins pers. comm.
European Starling
{Sturnus vulgaris)
Adult
79
(18)
Robbins pers. comm.
Yellow Warbler
( Dendroica petechia)
Adult
10
(366)
Robbins pers. comm.
Yellow-breasted Chat
( Jcteria virens)
Adult
26
(4)
Stewart
Western Meadowlark
Juvenile
40
Estimated
{Stumella neglecta)
Adult
95
(11)
Lanyon 1962
Yellow-headed Blackbird
Adult
74
Willson 1966
( Xanthocephalus xanthocephalus)
<?
91
"
9
56
Red-winged Blackbird
Adult
48
(203)
Robbins pers. comm.
(Agelaius phoeniceus)
&
62
(28)
" " "
9
42
(18)
" " "
Northern Oriole
Adult
33
(7)
Baldwin & Kendeigh 1938
(Icterus galbula)
Brewers Blackbird
(Euphagus cyanocephalus)
Adult
65
(10)
Balph 1975
Brown-headed Cowbird
(Molothrus ater)
Adult
41
(25)
Robbins pers. comm.
Lazuli Bunting
(Passerina amoena)
Adult
15
Bock & Lynch 1970
House Finch
(Carpodacus mexicanus)
Adult
22
(32)
Robbins pers. comm.
Rufous-sided Towhee
(Pipilo erythrophthalmus )
Adult
41
(1116)
Robbins pers. comm.
Grasshopper Sparrow
( Ammodramus savannarum)
Adult
16
(2)
Stewart 1937
Vesper Sparrow
(Pooecetes gramineus)
Adult
27
(1)
Poole 1938
Lark Sparrow
(Chondestes grammacits)
Adult
28
(1)
Robbins pers. comm.
24
RAPTOR RESEARCH
Vol. 17, No. 1
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
(Wt(g)
N
Reference
Sage Sparrow
Juvenile
10
Estimated
( Amphispiza belli )
Adult
18
(77)
Moldenhauer 8c Wiens 1970
White-crowned Sparrow
(Zonotrichia leucopkrys)
Adult
27
(90)
Morton et al. 1973
Song Sparrow
(Melospiza melodia)
Adult
21
(1553)
Baldwin & Kendeigh 1938
Sparrow-unid.
Juvenile
10
Calculated
Adult
26
"
Passe rine-unid.
Juvenile
28
Calculated
Adult
56
AMPHIBIANS:,
Spadefoot Toad
( Scaphiopus intermontanus)
Adult
12
Seymour 1973
Woodhouse’s Toad
(Bufo woodhousei)
Adult
20
Diller pers. comm.
Toad-unid.
Adult
20
Diller pers. comm.
Leopard Frog
( Rana pipiens)
Adult
38
Seymour 1973
Bullfrog
Juvenile
250
Diller pers. comm.
{Rana catesbeiana)
Adult
500
"
Frog-unid.
Average
30
Estimated
REPTILES:
Collared Lizard
Adult
34
(18)
BLM Data
{Crotaphytus collaris )
Average
23
(38)
" "
Leopard Lizard
Adult
26
(31)
BLM Data
{Gambelia wislizenii)
Average
23
(38)
" "
Western Fence Lizard
Adult
18
(40)
BLM Data
(Sceloporus occidentals )
Average
17
(44)
Side-blotched Lizard
{Uta stansburiana)
Average
4
(69)
BLM Data
Horned Lizard
Adult
24
(42)
BLM Data
{Phrynosoma platyrhinos)
Average
18
(77)
" "
Whiptail Lizard
Adult
17
(39)
BLM Data
(Cnemidophortis tigris)
Average
15
(44)
" ''
25
Spring 1983 Nest Site Selection by Pregrine Falcons
Table 1. Weights of Prey Species Captured by Raptors (cont.)
Species
Size Class & Sex
Wt(g)
N
Reference
Lizard-unid.
Juvenile
8
Calculated
Adult
21
"
Average
17
"
Racer
(Coluber constrictor)
Average
77
(24)
BLM Data
Striped Whips nake
Adult
111
(223)
BLM Data
(Masticophis taeniatus)
Average
102
(246)
Gopher Snake
Juvenile
19
BLM Data
(Pituophis melanoleucus)
Adult
226
(355)
"
Average
202
(405)
"
Long-Nosed Snake
Adult
85
(29)
BLM Data
(Rhinocheilus lecontei)
73
(35)
" "
Garter Snake
(Thamnophis elegans)
Average
109
(8)
BLM Data
Ground Snake
Juvenile
2
BLM Data
( Sonora semiannulata )
Adult
9
(26)
"
Average
8
(31)
ft ft
Nightsnake
Adult
15
(45)
BLM Data
( Hypsiglena torquata)
Average
14
(52)
"
Western Rattlesnake
Juvenile
19
BLM Data
(Crotalus viridis)
Adult
425
(319)
" "
Average
393
(352)
„
Snake-unid.
Average
190
Calculated
Reptile-unid.
Average
111
Calculated
* Weight values derived from a variety of sources including Hall (1946), Frenzel (1979), Marti (pers. comm,), unpub-
lished BLM data and specimens examined at Boise State University.
Literature Cited
Armitage, K.B., J.F. Downhower, and G.E. Svendson. 1976. Seasonal change in weights of
marmots. Am. Midi. Nat. 96:36-51.
Baida, R.P., G.C. Bateman, and G.F. Foster. 1972. Flocking associates' of the Pinyon Jay. Wilson
Bull. 84:60-76.
Baldwin, S.P. and S.C. Kendeigh. 1938. Variations in the weight of birds. Auk 55:416-467.
Balph, M.H. 1975. Development of young Brewer’s Blackbirds. Wilson Bull. 87:207-230.
Beason, R.C. and E.C. Franks. 1973. Development of young Horned Larks. Auk 90:359-363.
Bellrose, F.C. 1976. Ducks, geese, and swans of North America. Harrisburg, PA.:Stackpole
Books. 543 pp.
Beuchner, H.K. 1950. Life history, ecology, and range use of the pronghorn antelope in
trans-Pecos Texas. Am. Midi. Nat. 43:257-354.
Bock, C.E. and J.F. Lynch. 1970. Breeding bird populations of burned and unburned conifer
forest in the Sierra Nevada. Condor 72:182-189.
26
RAPTOR RESEARCH
Vol. 17, No. 1
Burt, W.H. and R.P. Grossenheider, 1964. A field guide to the mammals. Boston: Houghton
Mifflin Co. 289 pp.
Cade, T.J., C.M. White, and J.R. Haugh. 1968. Peregrines and pesticides in Alaska. Condor
70:170-178.
Clark, R.J. 1975. A field study of the Short-eared Owl Asio flammeus Pontoppidan in North
America. Wildl. Monogr. 47:1-67.
Craighead, J .J. and F.C. Craighead, Jr. 1956. Hawks, owls, and wildlife. Dover Public., New
York, N.Y. 443 pp.
Donahoe, R.W. 1966. Muskrat reproduction in areas of controlled and uncontrolled water-
level units./. Wildl. Manage. 30.320-326.
Earhart, C.M. and N.K. Johnson. 1970. Size dimorphism and food habits of North American
owls. Condor 72:251-264.
Easterla, D.A. and R.E. Ball. 1973. The Rock Wren in Missouri. Wilson Bull. 85:479-480.
Esten, S.R. 1931. Bird weights of 52 species of birds (taken from notes of Wm. Van Gorder).
Auk 48:572-74.
Fredrickson, L.H. 1969. Mortality of coots during severe spring weather. Wilson Bull. 81 :450-
453.
Frenzel, R.W. 1979. The effects of prescribed burning on small mammal communities in Lava
Beds National Monument, California. M.S. Thesis. Oregon State Univ., Corvallis. 79 pp.
Galbreath, D.S. and R. Moreland. 1953. The Chukar Partridge in Washington. Wash. State
Game Dept. Bio. Bull. 11. 54 pp.
Hall, E.R. 1946. Mammals of Nevada. Berkeley: Univ. Calif. Press. 710 pp.
Hamilton, K.L. 1980. A technique for estimating Barn Owl prey biomass. Raptor Res. 14:52-55.
Ivacic, D.L. and R.F. Labisky. 1973. Metabolic responses of Mourning Doves to short term
food and temperature stresses in winter. Wilson Bull. 85:182-196.
Johnsgard, P.A. 1973. Grouse and quails of North America. Lincoln: Univ. Nebraska. 553
pp.
Johnson, N.K. 1965. The breeding avifaunas of the sheep and spring ranges in southern
Nevada. Condor 67:93-124.
Killpack, M.L. 1970. Notes on Sage Thrasher nestlings in Colorado. Condor 72:486-488.
Kalmbach, E.R., R.H. Imler, and L.W. Arnold. 1964. The American eagles and their
economic status. U.S. Dept. Inter. Fish and Wildl. Serv. Circ. 27 & 30.
Lanyon, W.E. 1962. Specific limits and distribution of meadowlarks on the desert grassland.
Auk 79:183-207.
Lasiewski, R.C., M.H. Bernstein, and R.D. Ohmart. 1971. Cutaneous water loss in the Rbad-
runner and Poor-will. Condor 73:470-471.
Lewin, V. 1963. Reproduction and development of young in a population of California Quail.
Condor 65:249-272.
Linsdale, J.M. 1937. The natural history of magpies. Cooper Ornithological Club, Pacific Coast
Avifauna No. 25. 234 pp.
Marti, C.D. 1974. Feeding ecology of four sympatic owls. Condor 76:45-61.
Martin, R.J. 1973. Growth curves for bushy-tailed woodrats based upon animals raised in the
wild./. Mammal. 54:517-518.
McGahan, J. 1966. Ecology of the Golden Eagle. M.S. Thesis. Univ. of Montana. 78 pp.
McGahan, J. 1967. Quantified estimates of predation by a Golden Eagle population./. Wildl.
Manage. 31:496-501.
Moldenhauer, R.R. and J.A. Wiens. 1970. The winter economy of the Sage Sparrow, Amphis-
piza belli nevadensis. Condor 72:265-275.
Morris, P. 1979. Rats in the diet of the Barn Owl (Tyto alba).J. Zool. Lond. 189:540-545.
Morton, M.L., J.L. Horstmann, and C. Carey. 1973. Body weights and lipids of summering
mountain White-crowned Sparrows in California. Auk. 90:83-93.
Mugaas, J.N. and J.R. Templeton. 1970. Thermoregulation in the Red-breasted Nuthatch.
Condor 72:125-132.
Nelson, A.L. and A.C. Martin. 1953. Gamebird weights./. Wildl. Manage. 17:36-42.
Palmer, R.S. 1954. The mammal guide. Garden City, NY: Doubleday and Co. 384 pp.
Poole, E.L. 1938. Weights and wing areas in North American birds. Auk 55:51 1-517.
Porter, R.D. and C.M. White. 1973. The Peregrine Falcon in Utah, emphasizing ecology and
competition with the Prairie Falcon. Brigham Young Univ. Sci. Bull. 18:1-74.
Robertson, W.B., Jr. 1958. Investigations of Ring-necked Pheasants in Illinois. 111. Dept.
Conserv. Tech. Bull. 1. 137 pp.
Schreiber, R.K. 1973. Bioenergetics of rodents in the northern Great Basin desert. Ph.D.
Thesis. Univ. of Idaho. 133 pp.
Seymour, R.S. 1973. Physiological correlates of forced activity and burrowing in the spadefoot
toad Scaphiopus hammondi. Copeia 1973:103-1 15.
Smith, D.G. and J.R. Murphy. 1973. Breeding ecology of raptors in the eastern Great Basin of
Utah. Brigham Young Univ. Sci. Bull. Biol. Ser. 18:1-76.
Southern H.N. 1954. Tawny Owls and their prey. Ibis 96:384-410.
Stewart, P.A. 1937. A preliminary list of bird weights. Auk 54:324-332.
Thomsen, L. 1971. Behavior and ecology of Burrowing Owls on the Oakland Municipal
Airport. Condor 73:177-192.
Trost, C.H. 1972. Adaptations of Horned Larks Eremophila alpestris to hot environments. Auk
89:506-527.
Vermeer, K. 1970. Breeding biology of California and Ring-billed Gulls. Can. Wildl. Serv.
Rep. 12. 52 pp.
Welty, J.C. 1962. The life of birds. Philadelphia: W.B. Lander Co. 546 pp.
White, C.M. and T.J. Cade. 1971. Cliff-nesting raptors and ravens along the Colville River in
Arctic Alaska. Living Bird 10:107-150.
Willson, M.F. 1966. Breeding ecology of the Yellow-headed Blackbird. Ecol. Monogr. 36:51-77.
Withers, P.C. 1977. Energetic aspects of reproduction by the Cliff Swallow. Auk. 94:718-725.
NEST SITE SELECTION BY PEREGRINE FALCONS
by
David A. Ponton
Los Alamos National Laboratory
P.O. Box 1663
Los Alamos, New Mexico 87545
The Peregrine Falcon {Falco peregrinus) is known to use different nest sites (nest ledges) at a particular cliff, either in
successive years, or in response to the loss of a clutch of eggs (Herbert and Herbert, 1965; Porter and White, 1973;
Ratcliffe, 1980). In Great Britain, at least 4 alternative nest sites are used at most eyries, and one had 8 (one involving a
repeat clutch) in 9 seasons (Ratcliffe, 1980).
A peregrine eyrie in northern New Mexico is unusual in that 10 different nest sites were used in 10 consecutive seasons.
The nest sites are eroded potholes in volcanic tuff along 1 km of cliff, where approximately 1 50 similar holes are available.
27
Raptor Research l7(l):27-28
The large availability of suitable sites apparently facilitated non-repetitive selection. In the 11th and 12th years, the
female apparently failed to lay eggs. A new female appeared in 1976 and laid eggs in 1977, 1978, and 1979, continuing
the pattern of selecting new nest sites each year. However, two second (repeat) clutches were laid in previously used sites.
Specifically, the 1978 second clutch was laid in the 1977 nest site, and the 1979 second clutch was laid in the site used for
the first clutch in 1978. This pattern, i.e., the second choice of nest site having been the first choice the year before, I have
termed the “fall-back-one” behavior.
The only historical event common to both second clutch sites is egg laying. I suggest that preference for location of
the second clutch is for a site where egg laying and associated behavior have been ritualized in the nearest past. Previous
nesting success at that site is incidental. If the “fall-back-one” behavior pattern is, in fact, common in peregrines, it should
aid in predicting the location of second clutches.
I thank Wayne Hanson for locating nest sites in 1978, and John Hubbard and Wayne Pilz for reviewing earlier drafts.
Literature Cited
Herbert, R.A. and K.G.S. Herbert. 1965. Behavior of Peregrine Falcons in the New York City Region. Auk 82:62-94.
Porter, R.D. and C.M. White, 1973. The Peregrine Falcon in Utah, Emphasizing Ecology and Competition with the
Prairie Falcon. BYU Science Bulletin, Bio. Series, Volume XVIII, No. 1. 74 pp.
Ratcliffe, D. 1980. The Peregrine Falcon. Buteo Books, USA and T. & A.D. Poyser Ltd., Great Britain. 416 pp.
Camus hemapterus NITZSCH FROM SWAINSON’S HAWK
by
Richard E. Fitzner
Ecological Sciences Department
Battelle, Pacific Northwest Laboratory
Box 999
Richland, WA 99352
and
Norman E. Woodley
Museum of Comparative Zoology
Harvard University
Cambridge, MA 02138
The wingless ectoparasitic fly ( Camus hemapterus, Nitzsch) was first reported on North American birds by Bequaert
(1942) although in Europe, C. hemapterus seems to be fairly generally distributed. Bequaert (1942) identified the fly from
2 birds, a nestling flicker ( Colaptes cafer) collected at Penn Yann, New York and a Screech Owl (Asia otus) taken in Florida.
Capelle and Whiteworth (1973) have since reviewed the distribution ofC. hemapterus in North America, siting records for
9 host species, including 3 woodpeckers, starling ( Sturnus vulgaris), Black-billed Magpie {Pica pica) and American Kestrel
(Falco sparverius). Main and Wallis (1974) found C. hemapterus on nestling Osprey (Pandion haliaetus) in Massachusetts and
Wilson (1977) found Pileated Woodpecker (Dryoco pus pile atus) nesting material to contain the parasites. These records,
seem to indicate that Camus is widespread in the United States. Its distribution, however, will be unclear until there is a
systematic study of bird ectoparasites in this country.
Bequaert (1942) reports the C. hemapterus has been observed on 12 families and 26 species of birds in Europe. Seven
raptor species, White-tailed Eagle (Haliaeetus albicilla). Imperial Eagle ( Aquila heliaca), Peregrine Falcon (Falco peregrinus).
Kestrel (F, tennunculus), Saker ( F . cherrug), Barn Owl ( Tyto alba), and T engmalm’s Owl (Aegolius funereus) have been noted
as host.
In July of 1980, while examining nestling Swainson’s Hawks (Buteo swainsoni), we found that 12 of the 15 nestlings we
studied were parasitized by C. hemapterus. The flies occurred in groups of 3 to 5 and were found only in the axillary region
of the hawks. No flies were attached and on being disturbed they moved from the bare axillary region to nearby feathered
areas. The exact nature of the diet of C. hemapterus is unknown. Noller (1920) reports that the fly sucks blood from its host,
while Hendel (1928) felt that Camus feeds most probably on skin secretions. We observed dried blood spots on the hawks
axillary region which is supportive of Noller’ s (1920) claim. The true diet of the fly is presently in question, but the fly
could act as a vector of certain avian blood parasites.
Our findings are of interest, since few records have been reported for C. hemapterus in non-cavity nesting birds or from
long-distance migrants like the Swainson’s Hawk. Our report is also the first record of this dipteran parasite on the
Swainson’s Hawk.
Raptor Research 17(l):28-29
28
Literature Cited
Bequaert, J. 1942. Camus hemapterus Nitzsch, an ectoparasitic fly of birds, New to America (Diptera). Bull. Brooklin Ent.
Soc. 37:140-149.
Capell, K.J., and T.L. Whiteworth. 1973. The distribution and avian hosts of Camus hemapterus (Diptera: milichiidae) in
North America./. Med. Ent. 10:525-526.
Hendel, F. 1928. Zweiflugler order Diptera. II. Allgemeiner Teil. in F. Dahl, Die Tierwelt Deutschlands, XI, Dipt,, Pt. 2,
pp. 1-135.
Main, A.J., and R.C. Wallis. 1974. Primary records of two vertebrate ectoparasites in New England (Acarina-.Argasidae
and Diptera: Milichiidae). Proc. Entomol. Soc. Washington 76:427.
Noller, W. 1920. Die Ergebnisse der Hemoptroteus-Forschung. Zugleich vorlaufige Mitteilung fiber Zuchtungsversuche
an einigen anderen Try panosomen. Arch. F. Protistenk., 41:149-168.
Wilson, N. 1977. Ectoparasites found in the nest cavities of Pileated Woodpeckers in Oregon. Bird-Banding 48: 171-1 73.
THREE ADULT BALD EAGLES AT AN ACTIVE NEST 1
by
James D. Fraser^
L.D. Frenzel
Department of Entomology, Fisheries, and Wildlife,
University of Minnesota, St. Paul, MN 55108
John E. Mathisen
Chippewa National Forest
Cass Lake, MN 56633
and
Mark E. Shough
Bemidji Aviation Inc.
Bemidji, MN 56601
Although Bald Eagle ( Haliaeetus leucocephalus) trios have been observed at nests in Alaska (Sherrod et al. 1976, Heglund
and Reiswig 1980), we are unaware of similar reports in the coterminous United States. Here we describe 4 observations
of 3 adult eagles at a nest on the Chippewa National Forest, north central Minnesota. The nest was observed 93 times
between March and October in 1976-1978. All observations were made from fixed-wing aircraft.
On 7 April 1976, an adult eagle was observed in the nest in incubating posture; 2 others, 1 in adult plumage and 1 with
an off-white head similar to Southern’s ( 1 967) plumage F, were perched next to the nest. On 22 June 1 977, an adult with a
nearly white head was in the nest with 2 nestlings, another adult was in the nest tree, and a third adult was in a tree
approximately 100 m to the south. On 7 April 1978, an adult was in incubating posture while 2 others were perched
together in the nest tree. On 30 June 1978, 2 adults and 1 nestling were in the nest and a third adult was perched 200-300
m to the north. One fledgling was produced in 1976, 2 in 1977, and 1 in 1978. Because our observations were brief, we
were unable to determine the nature of interactions among the eagles involved. It is not clear to us, therefore, what role, if
any, the 3rd adult played in the nesting effort.
Sherrod et al. (1976) reported 3 sites occupied by trios on Amchitka Island, Alaska. Three Amchitka nests were also
occupied by trios in 1980 and one of these contained 4 eggs (Heglund and Reiswig 1980). Both Herrick (1934: 106) and
Bent (1937:325) reported 4-egg clutches for the Bald Eagle, and Bent suggested that the eggs may have been produced
by more than 1 female.
The data suggest that Bald Eagles are occasionally poly gynous. Detailed behavioral observations of trios are required to
test this hypothesis, however.
The Amchitka population apparently has not experienced the level of reproductive failure reported for eagle
populations elsewhere (Sprunt et al. 1973, Sherrod et al. 1976) and the Chippewa population appears to be recovering
rapidly from effects of contamination (Fraser 1981). The 4-egg clutches reported by Herrick (1934) and Bent (1937)
were laid well before the earliest report of widespread Bald Eagle nest failures (Broley 1950). Perhaps trios occur most
frequently at nests in healthy Bald Eagle populations. If so, trios may become more common in the coterminous states if
Bald Eagle reproduction and survival improve.
1 Paper No. 12,049, Scientific Journal Series, Minnesota Agricultural Experiment Station, University of Minnesota, St.
Paul, MN 55108
2 Present Address: Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061.
29
Raptor Research 17(l):29-30
30
RAPTOR RESEARCH
Vol. 17, No. 1
We acknowledge financial support from the Caleb Dorr Fund, the Hunt-Wesson Corporation, the Minnesota
Agricultural Experiment Station, the National Wildlife Federation, and the Herz Foundation.
Literature Cited
Bent, A.C. 1937. Life histories of North American birds of prey. Part I. U.S. Natl. Mus. Bull. 167. Dover Publ., New York.
409 pp.
Broley, C.L. 1950. The plight of the Florida Bald Eagle. Audubon 52:42-9.
Fraser, J.D. 1981. The breeding biology and status of the Bald Eagle on the Chippewa National Forest. Unpubl. Ph.D.
Diss., Univ. of Minnesota, St. Paul. 236 pp.
Heglund, P.J., and B. Reiswig. 1980. 1980 Raptor survey, the breeding Bald Eagle population, Amchitka Island, Alaska.
Unpubl. rep., U.S.D.I. Fish and Wildl. Serv., Aleutian Islands National Wildlife Refuge. 19 pp.
Herrick, F. H. 1 934. The American eagle: a study in natural and civil history. Applet
Sherrod, S.K., C.M. White, and F.S.I. Williamson. 1976. Biology of the Bald Eagle on Amchitka Island, Alaska. Living
Bird 15:143-182.
Southern, W.F. 1967. Further comments on subadult Bald Eagle plumages. Jack Pine Warbler 45:70-80.
Sprunt, A., IV, W.B. Robertson, Jr., S. Postupalsky, R.J. Hensel, C.F. Knoder, and F.J. Ligas. 1973. Comparative
productivity of six Bald Eagle populations. Trans. N. Arner. Wildl. Conf. 38:96-106.
ABSTRACTS OF THESES AND DISSERTATIONS
ARTIFICIAL PERCH USE BY RAPTORS ON RECLAIMED SURFACE
MINES IN WEST VIRGINIA
Raptor use of 24 artificial perches on 4 reclaimed surface mines in West Virginia was studied
from May to October, 1980. Each perch had crosspieces at heights of 3 and 6 m. Perch use was
documented by direct observations and use of 24 automatic event recorders. More than
99% of total use by raptors was made by American Kestrels (Falco sparverius.) Red-tailed
Hawks ( Buteojamaicensis ) and, as indicated by the event recorders, possibly Great Horned Owls
(Bubo virginianus ) made relatively small use of the perches. The 6-m crosspieces were used
substantially more than the lower heights and this choice was independent of topography.
Relationships among perch use, prey abundance, and vegetational structure were evaluated
and, based on these variables, models were generated to predict perch use by the 3 raptor
species. Vegetational structure appeared to be important in determining perch use by all 3
species but use by kestrels may be determined more by insect prey.
Forren, John D. 1981. Artificial perch use by raptors on reclaimed surfce mines in West
Virginia. M.S. Thesis, West Virginia University, Morgantown. 199 pp.
KESTREL USE OF NEST BOXES ON RECLAIMED SURFACE MINES
IN WEST VIRGINIA AND PENNSYLVANIA
Kestrel (Falco sparverius) use of mines with boxes (treatment) and without boxes (control) was
studied in a 4-county area in northern West Virginia and southern Pennsylvania during
March to August of 1980 and 1981. Kestrels did not nest on nor was any breeding activity
observed at 6 control mines during either year of the study. In contrast, Kestrels accepted 14 of
Spring 1983
Announcements
31
60 (23%) boxes on 10 of 18 (56%) treatment mines in 1980, and accepted 33 of 91 (36%) boxes
on 19 of 24 (79%) treatment mines in 1981. During the 2-year study, 122 young fledged from
these boxes. Of 14 boxes accepted by Kestrels in 1980, 13 (93%) were reoccupied in 1981.
Nesting chronology, clutch sizes, and productivity were comparable to published studies of
kestrels on unmined areas.
A search of the mines and adjacent woods borders revealed that natural cavities were absent
on 20 of 30 (67%) sites. Kestrels nested in 1 natural cavity, on a treatment mine, and nested in
boxes on 14 mines that lacked natural cavities.
To examine the relationship among box use, mine, and site characteristics, the following
information was recorded: individual box use by Kestrels, site characteristics for individual
nest boxes, vegetation characteristics for each mine, and insect and rodent abundance.
Stepwise discriminant analysis of 10 nest box location variables revealed that a single variable,
the distance of a box to a woods border was the most important for classifying box use by
Kestrels during each year of the study. Group means of this variable were significantly higher
for used boxes than unused boxes, indicating that used boxes were farther from a woods
border. Only 10 of 65 (15%) availble woods border boxes were used during the study period
while 47% of all boxes erected 50 m or more from a woods border were used. Effective
management of kestrels involves erecting boxes on isolated trees that are at least 50 m from a
woods border.
Mines where boxes were used were characterized by a significantly lower percent of bare
ground and a deeper litter depth than unused mines. Unreclaimed or marginally reclaimed
mines with excessive bare ground may be unsuitable Kestrel habitat even if boxes are pro-
vided. Recommendations for managing Kestrels on reclaimed surface mines are provided.
Noteworthy behavioral observations were made during the study period. Vigorous defense
of a nest box containing 3 downy eyasses by 4 fully-feathered Kestrels was observed during
July at 1 mine. Ground-perching on barren spoil areas was noted during both years of the
study. In 1981, this habit was observed on 11 mines, and involved as many as 14 individuals on
a single mine. Nearly all ground-perching was observed during July of both years.
Examination of prey remains found in boxes used by Kestrels revealed 4 species of birds not
previously recorded as prey items. Incubation by male Kestrels was observed at 6 boxes. With 1
exception, males were found incubating after 1800 hr.
Wilmers, Thomas J. 1982. Kestrel use of nest boxes on reclaimed surface mines in West
Virginia and Pennsylvania. M.S. Thesis, West Virginia University, Morgantown. 182 pp.
ANNOUNCEMENTS
SECOND SYMPOSIUM ON AFRICAN PREDATORY BIRDS
The Natal Bird Club, a branch of the Southern African Ornithological Society, will be
holding a symposium on African Predatory Birds from 22-26 August 1983. The first sym-
posium on this topic was held in Pretoria in August 1977.
Four sessions are planned: The role of captive breeding in conservation; The effects of
pesticides, particularly in the 3rd World; The energetics of large predators, and; The biology
of rare and poorly known species.
32
RAPTOR RESEARCH
Vol. 17, No. 1
The meeting will be held at the Golden Gate National Park in the Orange Free State.
Further information and application forms are obtainble from Dr. John Mendelsohn, Durban
Museum, P.O. Box 4085, Durban, South Africa 4000.
REQUEST FOR INFORMATION
The Marsh Hawk ( Circus cyaneus) is a commonly-observed bird of prey of grasslands and
marshes throughout California. It feeds largely on rodents, but is opportunistic in hunts on
other avian, mammalian, and occasionally reptilian and amphibin species. Sexes are identifi-
able in adult plumage due to color dimorphism. Nests are on the ground; large broods are
common.
Although Marsh Hawk wintering habitat in California is extensive, breeding habitat (largely
marshes or some other natural grasslands situation) is severely reduced. Some estimate marsh-
land habitat has been reduced in terms of acreage in excess of 90% since the early 1900s.
Coastal bay and estuary and Central Valley habitats are continuing to decline.
The Marsh Hawk is a Species of Special Concern for the state of California (Remsen, 1982).
Unfortunately funds are not available for studies by California Department of Fish and Game
(CDFG) at this time. As a result, the Santa Cruz Predatory Bird Research Group (SCPBRG) is
attempting to establish baseline information on this species to provide to CDFG, U.S. Fish and
Wildlife Service (USFWS), and other government agencies who have management responsi-
bility for birds of prey or habitat protection.
We are requesting information from all sources regarding Marsh Hawk natural history
observation. Of special importance are observations of breeding attempts, both successful and
failing; and also both current and historic. Information on Marsh Hawk breeding in areas no
longer suitable is equally important to observatios in areas remaining habitable.
Should you be able to provide observations or have opinions or comments on any aspect of
Marsh Hawk ecology in California, please respond.
Send responses to:
Santa Cruz Predatory Bird Research Group
Room 231 Clark Kerr Hall, University of California
Santa Cruz, CA 95064 (408) 429-2466
Information obtained in this project will be provided in the form of a report to Ron Schlorff,
Non-Game Wildlife Management Section, California Department of Fish and Game, 1416
Ninth Street, Sacramento, CA 95814.
THE RAPTOR RESEARCH FOUNDATION, INC.
OFFICERS
President Dr. Jeffrey L. Lincer, Office of Environmental Management, 2086 Main
Street, Sarasota, Florida 33477
Vice-President Dr. Richard Clark, York College of Pennsylvania, Country Club
Road, York, PA 17405
Secretary Ed Henckel, RD 1, Box 1380, Mt. Bethel, PA 18343
Treasurer Dr. Gary E. Duke, Department of Veterinary Biology, College of Veteri-
nary Medicine, University of Minnesota, St. Paul, Minnesota 55108
Address all matters dealing with membership status, dues, publication sales, or other
financial transactions to the T reasurer . See inside front cover.
Send changes of address to the Treasurer.
Address all general inquiries to the Secretary.
See inside front cover for suggestions to contributors of manuscripts for Raptor
Research, Raptor Research Reports, and special Raptor Research Foundation publica-
tions.
BOARD OF DIRECTORS
Eastern Dr. James Mosher, RT 2, Box 572-D, Frostburg, Maryland 21532
Central Dr. Patrick Redig, Department of Veterinary Medicine, 295K AnSci /
Veterinary Medicine Bldg., University of Minnesota, St. Paul, MN 55108
Pacific and Mountain Dr. Joseph R. Murphy, Department of Zoology, 167 WIDB,
Brigham Young University, Provo, Utah 84602
Canadian Eastern Dr. David Bird, Macdonald Raptor Research Center, Macdonald
College. Quebec, H9X ICO, Canada
Canadian Western Dr. R. Wayne Nelson, 42 1 8-63rd St., Camrose, Alberta T4V 2W6,
Canada
At Large #1 - Dr. Lynn Oliphant, Universty of Saskatchewan, Veterinary Anatomy,
Saskatoon, SA Canada S7N OWO
At Large #2 - Dr. Tom Dunstan, Biology Science, Western Illinois University,
Macomb, Illinois 6 1455
At Large #3 - Dr. Mark R. Fuller, Migratory Bird Lb, U.S.F.W.S., Patuxent Research
Center, Laurel, Maryland 2081 1
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