For Reference
NOT TO BE TAKEN FROM THIS ROOM
CAT. NO. 1935 LOWE-MARTIN CO. LIMITED
UBfii*
aiBEfieiEMis
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THE UNIVERSITY OP ALBERTA
A PRELIMINARY STUDY
OP
THE GREAT GRAY OWL (Sc otla.pt ex nebulas a nebula sa) (Forster)
IN ALBERTA
WITH OBSERVATIONS ON SOME OTHER SPECIES OP OWLS
A DISSERTATION
SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE
OF MASTER OF SCIENCE
FACULTY OF ARTS AND SCIENCE
DEPARTMENT OF ZOOLOGY
by
Albert Frederick Oeming, B,Sc»
Edmonton, Alberta
September 1955
ABSTRACT
A paucity of scientific information concerning
this continent’s largest owl, the Great Gray, and the
known scarcity of this species in Alberta prompted
this investigation.
Two nests of this rare species were discovered
during the course of the study, one in the Edson area,
the other in the Rocky Mountain House region. This,
together with fourteen dead specimens and eight live
Great Gray Owls encountered, in the course of this
investigation, made possible a study of this species
with regard to the following: identification,
classification, plumages, sub-species, pterylography,
molt, eye-color, anatomy, distribution and movements,
courtship, nesting, reactions to intruders, voice,
activities of adult owls, description of young,
physical development of young, food habits, enemies,
parasites and diseases, and economic status.
No less than eleven new records for the Barred
Owl emerged in the course of this investigation. These
findings revealed, a hitherto unsuspected, established
population in Alberta.
Thirty-five Snowy Owls captured Airing the x^inters
of 1953-54 an<3“ 1954-55 for banding purposes were used
for a weight and plumage color study which proved
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conclusive in sex determinations. An extremely
interesting banding recovery was also recorded.
Observations were made on the distribution and
feeding habits of the ubiquitous Great Horned Owl.
Since the spring of 1951 an effort has been made to
gather data on the little known northern forest owls
of the province. Notes were made on the occurrences
and food habits of the Hawk Owl, Saw-whet and
Richardson* s Owl, to supplement information already
known about the birds.
The first Screech 0x^1 captured in Alberta was
taken in the Swan Hills. A second specimen from
Lesser Slave Lake was forwarded to Dr. Wm. Rowan of
the Zoology Department of the University of Alberta.
Although much remains to be learned about the
Great Gray Owl and the other northern forest owls of
Alberta, it is felt that this preliminary study has
laid the ground work for more extensive investigation
in the future
CONTENTS
Page
INTRODUCTION . . . . . 1
DESCRIPTION OF THE STUDY AREA. ..... . 7
THE GREAT GRAY OWL . . 11
IDENTIFICATION AND CLASSIFICATION . . 11
Taxonomic Position • • • . . ........ 11
Common Names . 13
Comparisons with the Great Homed Owl. ... 13
Feet and Tarsi ............... 13
Heads .................... II4.
Plumages of the Great Gray Owl. ....... 1 5
Adult Female ................ 15
Adult Male . . 1?
Immatiares ................. 17
Question of Subspecies • • • . ...•••• 20
PTERYLOGRAPHY . ......... 25
Feather Tracts ............... 25
Feather Structure . . 30
Molt .................... 31
EYE COLOR ....... ..... ....... . 33
ANATOMY ..................... 34.
Intestinal Tract .............. 34
Skeleton .................. 37
DISTRIBUTION AND MOVEMENTS ........... 40
Breeding Range . 4°
Winter Range . •••••• 41
Bandipg Recoveries . . br2
NESTING . . \i$
Type of Woods Preferred • • • • • . . 45
The Nest . . . 45
Position and Condition • . . . . l\.G
Selection of Site • • • . • . *4.6
Courtship ••••••••••••••••••• lj.7
Nesting Density , . , , , . I|9
Egg Dates . . . . . 49
Number ....... . •••••••49
Color . . . . .50
Shape and measurements . ...... 50
Incubation Period ••••••••• ...... 50
Nests of Other Birds Pound in the Vicinity
of the Nests . • . . ....... 5l
Reactions to Intruders . 52
Man . . . . . . . . . 52
Other Intruders • ••••.... . . . 54
VOICE . 55
Introduction 55
Voice of Adult Female . ••••••••55
Voice of Adult Male • ••...••• . 5&
Voice of Young . ••••••••••• $6
ACTIVITIES OP ADULT OWLS . . • . • 57
Activities of the Female on the Nest • • • • . 57
Activities of the Male about the Nest • . • • • 57
FEEDING TIMES AND PLACES OF ADULT AND YOUNG . ... 58
DESCRIPTION OF YOUNG ............ . . . 61
Page
RICHARDSON* S OWL . ........... 113
SAW-WHET OWL ........ . . . . . 111*.
SCREECH OWL .....•••••••. . 116
SUMMARY . ....... . . . 119
ACKNOWLEDGEMENTS .................. 123
REFERENCES .................... 125
PERSONAL CORRESPONDENCE . , ..... 129
LIST OP TABLES
TABLE I
TABLE II
TABLE III
TABLE IV
TABLE V
TABLE VI
TABLE VII
Page
MEASUREMENTS OP ADULT GREAT GRAY OWLS . • 19
MEASUREMENTS OF LAPP AND GREAT GRAY OWLS . 21
STOMACH ANALYSES OP GREAT GRAY OWLS . « . 8l
FISHER * S ANALYSES OF GREAT GRAY OWL
STOMACHS .............. . . 82
PELLET ANALYSES OP GREAT GRAY OWLS ... 83
SNOWY OWL WEIGHTS AND PLUMAGE COLOR ... 103
STOMACH ANALYSES OP GREAT HORNED OWLS , . 109
Pig.
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Pig.
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Pig.
LIST OF FIGURES
Page
Copy of Great Gray Owl Brochure • • • • 5>
Map of areas investigated 195>2-55 • • ♦ 6
Typical poplar growth frequented by
nesting Great Gray Owls, 9
Swan Hill forests * , • • • , , . • » 10
Muskeg frequented by Great Gray Owls
near Rocky Mountain House • «•»••• 10
Comparison of feet; Great Horned Owl &
Great Gray Owl ••,«••••••• , 1L».
Comparison of heads; Great Horned Owl &
Great Gray Owl , . , . . , . • • If?
Adult male Great Gray Owl ,«•••,, 17
Adult Female Great Gray Owl 18
Comparison of Great Gray and Lapp Owl
skins; Ventral aspects • • , • . , » , 23
Comparison of Great Gray and Lapp Owl
skins: Dorsal aspects, , , • • , • » , 2k
Pterylosis of Great Gray Owl; Ventral
aspect, . . • ••,.. . « 28
Pterylosis of Great Gray Owl; Dorsal
aspect, . . . . , 29
Dorsal view of molting Great Gray , . , 32
Intestinal tracts 36
, .
....
Page
Fig* 16.
Pig. 17.
Fig . 18 .
Fig. 19.
Fig. 20.
Fig. 21.
Fig. 22.
Fig. 23 .
Fig. 2 4*
Fig. 25.
Left Side of Great Gray skull showing
large ear aperture ........... 39
Right side of same skull indicating
smaller ear aperture ........... 39
Map showing breeding records and winter
range of Great Gray Owls in North America I4.3
Map showing nesting records for Great
Gray Owls in Alberta .......... I4J4.
Nest and eggs of Great Gray Owl .... 48
Typical position of nest in White Poplar
Female Great Gray Owl threatening to
attack investigator at the nest .... 53
Great Gray female in defensive attitude. 54
Female Great Gray Owl feeding young at
the nest . . 60
Female Great Gray in tree adjacent to
nest .................. 60
Fig. 26. Nest with young approximately ten days
old •* ««.***« ...... ... . 61
Fig* 27 • Nest with young approximately fourteen
days old 62
Fig. 28. Young Great Gray Owls approximately
twenty- one days old ........... 63
Fig. 29 • Young twenty- eight days old ...... 64
Fig. 39 • Great Gray Owls approximately forty days
old ............. ..... 65
Fig • 31®
Fig. 32.
Fig. 33«
Fig. 34*
Fig* 35*
Fig. 36.
Fig* 37*
Fig. 38.
Fig. 39.
Fig. )+0.
Fig. 4-1*
Fig. li.2.
Fig. 43 •
Fig. 44*
Page
Measurements of Great Gray Owl ..... 67
Great Gray twenty -ei$it days old being
weighed ............ .... 68
Graphs: Length of bill from commissural
point; Length of head and bill; Length
of cere .................. 69
Graphs: Weight; Length of Humerus;
Length of ulna ............. 70
Graphs: Wing spread; Length of middle
toe and nail .............. 71
Graphs: Length of tarsus; Total length
plus tail ..... .......... 72
Graphs: Length of tibio- tarsus; Length
of f emur .... .. ....... ... 73
Great Gray Owl forty days old* showing
aggressive tendencies ........ • 77
Male Great Gray hunting in muskeg north
of Corbett Creek ............ 79
Close-up of Great Gray in l?hunting muskeg” 80
Snared Red Squirrels. Trappers accuse
the Great Gray of destroying such catches 8 4
Typical pole trap set-up ..... ... 86
Feet taken from owls killed in pole trap
at Cross Lake .......... ... 86
Remains of Great Gray killed by Great
Horned Owl
87
Pag©
Pig. 45 • Remains of Barred Owl found near site
of Great Gray nest at Rocky Mountain
House • •••••• 96
Pig. 46. Mounted Barred Owls of specimens
collected in Alberta ..... .... 9&
Pig. 47 • Nest box set out for Barred Owls. ... 98
Pig. 4^ ® Map showing Barred Owl records for
Alberta ................ 100
Pig. 49 • Snowy Owl caught in specially designed
trap .... ............. 102
Pig. Female Snowy Owl showing darker plumage 106
Pig. 5l® Male Snowy Owl showing whiter plumage.. 106
Pig. 52* Young Saw -whet Owls .......... 11 5
Fig. 53® Screech Owl captured in Swan Hil3s • . . liy
Pig. 54® Map showing occurrences of Screech* Hawk*
Saw-whet and Richardson’s Owls from
1952-55 in Alberta ........... 118
A PRELIMINARY STUDY
OP
THE GREAT GRAY OWL ( Scotiaptex nebulosa nebulosa) (Forster)
IN ALBERTA
WITH OBSERVATIONS ON SOME OTHER SPECIES OP OWLS
INTRODUCTION
The first notes and photographs on the nesting of the
Great Gray Owl in Alberta were taken by A*D* Henderson of
Belvedere, Alberta in 1915® Never really common then,
these owls have now almost vanished*
Pew of America* s experienced ornithologists have seen
the Great Gray Owl in life and there has always been a dearth
of material in collections* Shortly after 1930* Red Squirrel
pelts in Alberta began to acquire some commercial value*
Hundreds of trappers then Invaded the great spruce forests
and at the same time declared war on all owls* Most trappers
are imbued with a universal prejudice against owls, feeling
that the birds prey heavily on marketable fur-bearing animals
and so seriously reduce the trapper’s potential profit*
The Great Gray Owl was condemned along with other species
of owls and not having the wary and suspicious nature of some
of these it offered an easy target for the trappers* guns*
The decline in numbers of Great Gray Owls was rapid, and in
less than ten years after the price Increase for squirrel
pelts, the birds became exceedingly rare in Alberta*
In December of 1951 I collected my first Great Gray Owl
in dense muskeg country west of Fawcett, Alberta*
2
Veteran oologist A.D. Henderson x^ras consulted on
suitable nesting areas of this species. He felt there
was still a chance of locating Great Gray Owls in the
more unsettled regions of heavy timber, north and west
of Edmonton*
The first area investigated during the spring and
early summer of 1952 covered the large poplar and muskeg
stands west of the village of Flatbush stretching to the
Athabaska River* This entailed working all suitable
timbered areas by horseback and on foot, north to Smith
and Fawcett Lake, south to the Vega Ferry Grossing on the
Athabaska, and west across the river to Tipi Lake and
Timeu. Ho Great Grays were discovered that year although
two dead specimens had been sent from the area the previous
itfinter* One nest of the American Hawk Owl ( Surnia ulula )
was found* Great Horned Owls ( Bubo virginianus ) were
relatively numerous owing to a high rabbit population*
Eight nests of this species were located.
In the spring of 1953 the search was again concentrated
in areas from which dead specimens of Great Gray Owls had
previously been sent. A juvenile female was shot by a
trapper near Sangudo in March 19 53 * and an adult male was
similarly disposed of by a trapper north of Timeu. Another
bushman working in an area north-west of Ft. Assiniboine
had shot no less than six during the winter and showed me
the evidence. In the Corbett Creek area west of Ft.
Assiniboine a nesting pair was shot.
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No nests of the Great Gray Owl were found but
thirteen nests of the Great Horned Owl were located in the
course of field work in these areas.
It became apparent that some form of publicity especially
directed to the trappers might prevent the needless slaughter
of these birds and also lead to the finding of a nest,
A seven page brochure (Pig, 1) asking for information
on the owl, complete with sketches comparing it with the
common Great Horned Owl was accordingly circulated through¬
out the northern part of the province. Every registered
trapper, logging camp and ferry operator, as well as all
northern school divisions and government forestry personnel
received a copy. More than 5# 000 were mailed. Various country
weeklies in Alberta and some of the farm publications which
have an enormous circulation in Western Canada carried an
appeal for Information. A national weekly paper published
a large picture of a Great Gray Owl with an accompanying
request for available data,
Numterous people responded to the appeal and many in¬
teresting Items on owls came to light. For instance, new
records for the Barred Owl In Alberta were sent in.
During the winter of 195>4 three dead Great Gray Owls
were sent In from Anzac, Rocky Mountain House and Ft.
Assiniboine respectively. Two live birds were also re¬
ceived. They had been trapped and slightly injured in
the process.
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One was taken north of Melfort, Saskatchewan, and
represents the fourth record for that province (Bard,
personal correspondence); the other came from Ft. Assiniboine.
The Saskatchewan bird still survives and provided the material
on feather sequence and molt. The remains of another Great
Gray Owl were found north of Ft. Assiniboine.
In early May, 19 5k- 9 two nests of the Great Gray Owl
were located in widely separated areas. Both nests contained
two week-old young and these f5.nds provided. the basis for
this study. All nesting activities were recorded and a
photographic study was made. A good deal of original data
concerning these rare birds was gathered. This marked the
first substantial contribution towards a knowledge of the
life history of the species.
The spring of 1955 produced no nests of this species
but two more dead birds arrived, one from the Edson, and
the other from the Raven district west of Innisf ail, A
live bird sent from Raven subsequently died in captivity.
The four year investigation produced fourteen dead
Great Gray Owls, four live birds that were sent me, and
two nests each containing two young.
Further interesting observations were made on the
Hawk Owl, Snowy Owl (Bye tea nyctea). Barred Owl (Strlx
varia), Richardson* s Owl (Cryptoglaux funerea richardsoni) ,
Saw- whet Owl (Cryptoglaux acadia ) , Screech Owl ( Otus asio )
and the Great Horned Owl, A total of 36,000 miles was
covered during the search period from the spring of 1952 to
the summer of 1955 ty car, truck, jeep, canoe, on horseback
and on foot
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The Great Gray Owl
HAVE YOU SEEN THIS BIRD?
THE GREAT GRAY OWL
One of Alberta’s Rarest Bir ds
An amazing number of Albertans have never seen
this large and beautiful owl. It is in fact fast becoming one
of Alberta’s rarest birds and definitely in acute danger of
becoming extinct in the next few years.
It is the writer’s intention to attempt the writing of a
complete life history of this owl and Mr. Ed Jones, well known
bird expert of Edmonton, will endeavor to record much of the
bird’s life and activity on movie film. We have been engaged
in an intensive search over the past two years travelling more
than 10,000 miles for the nest of the Great Gray Owl and as
yet have been unsuccessful. For this reason, through the
medium of this pamphlet, I am extending this appeal for any
information that readers of this publication might be able
to forward.
DESCRIPTION OF THE GREAT GRAY OWL:
By measurement and appearance it is the largest of
all our owls but when it is stripped of all its feathers, it is a
surprisingly small bird. In color, this owl appears rather dark
and blackish rather than the light brown or dull gray of the
Great Horned Owl. Its body appears to be barred in tones of
black and white throughout. An easy way to identify this
owl is by its enormous saucer shaped face. The head appears
very large and is without horns and the face has very distinct
concentric circles of alternating black and white. The eyes
are quite small and yellow in color. When you see any large
owl, try to approach it as closely as possible and firstly de¬
termine whether it has tufts or horns on the head. If it has
these projections on the head it will undoubtedly be a Great
Horned Owl and if without these horns, and somewhat dark
in appearance and large in size with an enormous head it will
be the Great Gray Owl.
3
VOICE :
According to Mr. A. D. Henderson of Lac La Nonne,
who found several nests of the Great Gray Owl some 25 years
ago, this bird has a call somewhat different from the sound
made by the Great Horned Owl. Mr. Henderson describes the
hoot of the Great Gray Owl as more of a long drawn whistle
than a deep slow hoot.
HABITS AND CHARACTERISTICS :
This owl is extremely tame and very unsuspicious and
one can approach very close to it. For this very reason, these
birds have offered an easy target for the guns of trappers,
hunters, settlers and farmers and all others who happen to
be in the northern woods where this bird is found. Scientific
analysis of the stomach contents of this bird made on numer¬
ous dead specimens forwarded to the University have shown
that this owl is predominantly a mouse eater and seldom
bothers squirrels, game birds or even rabbits. Its feet are not
nearly as strong and powerful as those of the Great Horned
Owl. This is a valuable and rare owl and one that should not
be shot, and1 1 hereby request the assistance of all readers of
this publication to aid in the protection of this interesting
bird.
4
NEST AND WHERE TO LOOK FOR IT
The Great Gray Owl does not build a nest of its own
but makes use of an old hawk’s nest. These nests are usually
found in tall poplars, more commonly the white poplar and
occasionally in the tall balm of gilead or black poplar trees.
Nests have occasionally been found in spruces and pines so any
large old hawk’s nest shoud be checked from early March to
early June, the time of nesting for these birds. Groves of tall,
heavy poplars are the most likely areas for old hawk’s nests to
be found and here the owls will nest. These nests are easily
seen in the early spring before the leaves bud out on the trees
and a close look at the nests will soon reveal whether an owl
is sitting on it and by examination of the head you can readily
tell whether it is a Great Gray Owl.
If such a bird should be found nesting, please write
or phone as soon as possible to Mr. A1 Oeming, Sub. P.O. 23
Edmonton, Phone 392350. If these birds should be nesting in
an area where other settlers or trappers are living, please ask
them to afford the birds all the protection possible and notify
the writer (as above) immediately.
5
GREAT HORNED OWL (Compare with Cover Picture of Great Gray Owl)
The undersigned will grant a substantial reward to
any person providing him with information that will lead to
the nest of a Great Gray Owl.
REMEMBER TO WRITE, WIRE OR PHONE COLLECT TO :
AL OEMING, SUB. P.O. 23, EDMONTON, PHONE 392350,
if you have any information on this important bird.
6
The Great Gray Owl on the Nest in Early April
This investigation and study of the Great Gray Owl is
a University of Alberta Project supervised by Dr. Wm. Rowan,
head of the Zoology Dept. Your help in this scientific study is
earnestly requested and will be most appreciatively received.
Your information will assist greatly in this difficult and
valuable research. Please help us to save our few remaining
Great Gray Owls.
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SB
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DESCRIPTION OF THE STUDY AREA
The Great Gray Owl is a denizen of deep forests.
Henderson (1915) and Randall (1920) have hoth
emphasized the fondness of this species for heavy
stands of poplar fringing large muskegs.
The area covered during the spring and early summer
of 1952 contained many good stands of old black poplar
and several sizeable muskegs. Great tracts of this
region have been burnt over and only scrubby second
growth white poplar surrounds some of the muskegs*
Substantial stands of old white and black poplars were
encountered along the Pembina river west of Flatbush
and Fawcett. Particularly extensive muskegs were found
west of the village of Fawcett, but the area is
practically devoid of any substantial poplar growth.
The muskegs of this area are in the main tamarack and
black spruce associations and provide excellent nesting
locations for Hawk Owls.
Considerably less muskeg but more heavy white poplar
was encountered in the areas investigated in the spring
of 1953» The region north and west of Timeu contains a
mixed growth of huge black and white poplar, black spruce,
jack pine and tamarack. Some of the larger muskegs in
this area had little in the way of old stands of poplar
around them due to the fires that have swept the region
repeatedly in the past twenty years.
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North west of Ft* Assiniboine one finds the finest
big stands of white poplar in Alberta, the Corbett Creek
country having perhaps the largest growth with many
muskegs scattered throughout® This area appeared to
provide the ideal Great Gray habitat® Farther north of
Ft® Assiniboine the deciduous woods disappear and give
way to heavy and vast coniferous growth covering the
undulation called the Swan Hills® The Swan Hill forests
are composed in the main of lodgepole pine (Fig® >
balsam, jack pine and black spruce® The trees are among
the oldest in Alberta and no serious fire has ever
reduced the M green” of this magnificent forest. Undoubtedly
birds such as Great Gray Owls could spend much of their
lives undiscovered in this vast, dense solitude only
moving into the lower regions near Ft. Assiniboine during
the winter and nesting seasons. Almost complete absence of
poplar and a dearth of suitable nest sites would appear
to eliminate the possibility of nesting in the Swan Hills
proper.
The area north and west of Wandering River towards
Pelican Portage was covered in 195>ij-. This is a vast
region of black spruce growth and muskegs, although there
is an extensive poplar growth and some willow. Much of
the best available spruce in Alberta is now being logged
in this area, producing 1,000 board feet per tree®
The country north of Edson and west of Rocky Mountain
House also provides suitable Great Gray habitat. The
study area here consisted of large muskegs containing
(Fig. 5) willow, alders, black spruce and tamarack. Many
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9
are fringed with large black and white poplar (Fig* 3).
The spring of 1955 was spent checking the areas
already described. The map on page 6 (Fig. 2) will
serve to give some impression of the location of the
study area.
Fig. 3. Typical poplar growth
frequented by nesting
Great Gray Owls.
10
Fig. 4. Dense Lodgepole Pine Growth
in the Swan Hills.
Fig. 5. Muskeg frequented by Great Gray Owls
in the Rocky Mountain House area.
±1
THE GREAT GRAY OWL (Gcotiaptex nebulosa nebulosa(Forster )
IDENTIFICATION AND cLAbElFlOATlUN
Taxonomic Position
The Great Gray Owl belongs to the order Strigiformes
suborder Striges, family Strigidae, genus Scotiaptex,
species nebulosa and subspecies nebulosa. It was first
described by J.R. Forster (1772) from a juvenile specimen
collected near Severn River in north-western Ontario. The
type specimen is believed to be somewhere in England but
some doubt has been expressed that it still exists (Amadon,
personal correspondence). Forster's description translated
from the original in Latin by Dean Walter Johns is as
follows:
r,The Strix with smooth head, dusky colored body
with many white stripes. The sixth flight feather rather
long and with a dark colored crest. It lives around Hudson
Bay and feeds on hares, rabbits and mice. The beak is
dark yellow, the upper part more yellow than the lower.
The eyes are large with yellow irises. The head is greyish
in appearance from the feathers being striped with alter¬
nating dark and pale grey. Behind these feathers towards
the neck there is a line of small dark feathers toward
each cheek, producing a dark semicircle. The back of the
head to upper and lower parts is dusky with feathers spotted
with white on the margins. The breast is whitish with white
stripes running up and down and across. The abdomen is white
with longitudinal stripes above as on the breast, but
marked below with cross stripes. The back and entirely
.
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12.
covering the wings and tail are striped with covering
of dusky and white. The wings are dusky; the front
feathers dusky with cross bands of grey, and white with
cloudy cross lines. The sixth £L ight feather is longer
than the rest with the rest rather blackish • The rest
of the flight feathers are rather pale, striped with
darker colors. The tail is rounded with twelve tail
feathers with the two in the middle rather longer. The
whole with wavy stripes of ashy white and dark with
several dark double lines across. The rest of the tail
feathers slightly striped with dark and light. The feet
are covered with whitish feathers striped with dark. In
size it is almost the same as that of Strix nyctea. The
length is sixteen inches, the width four inches, and the
weight three pounds.”
When Forster described, the G-reat Gray Owl as Strix
nebulosa someone unfamiliar with the bird supposed he
referred to the Barred Owl ( Strix varia) and so con¬
sequently nebulo s a was applied to the latter for over a
hundred years. The name was later changed to the present
Scotiaptex nebulosa (Preble, 1902). It was then
transferred to the species Forster intended it for ( A.O.U
1912).
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Gommon Names
The Great Gray Owl is known by a variety of common
names such as spruce owl, cinereous owl, spectral owl,
saucer-faced owl, big-headed owl and the hornless owl*
Comparison between the Great Gray and the Great Horned Owl
Feet and Tarsi
Because of the availability of the Great Horned Owl
it is compared with the Great Gray, Both species belong
to the same family, Strigidae.
The feet of the two species display an interesting
difference* The feet of the Great Horned Owl are con¬
siderably stronger, with the middle claw measuring up to
l\2. mm. in length while that of the Great Gray seldom
exceeds 32 mm* (Fig* 6). There appears to be a correla¬
tion between relative length of the middle toe and the
prey preferred. The Great Grays feed principally on
small mammals such as mice and voles* Their feet would
appear unable to take large prey such as Snowshoe Hares
which the Great Horned Owls commonly feed on*
The extent of feathering on the tarsus is quite
similar in both species. Both species can voluntarily
assume a zygodactylous position of the toes and Great Grays
appear to adopt this placement more frequently than the
Great Horned Owl which usually places three toes ahead with
the first toe behind.
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Comparison of Heads
The heads of the two species show a marked
difference. The head of the Great Gray Owl appears
much larger than that of the Great Horned Owl and
lacks the ear tufts of the latter (Fig. 7). The eye
of the Great Gray is considerably smaller than that of
the Great Horned. This can be established by measuring
the eyes, length of beak from commissural point, and the
length of the head and beak of live birds (Meng, 195>1).
The typical ratios for the two species are as follox^s:
Beak to Eye Head to Eye
Great Gray . . 2 1 . b : 1
Great Horned . 1.2 -» 1 . 3*3 l 1
A.
Fig. 6. Comparison of feet.
B.
A. Foot of Great Horned Owl
B. Foot of Great Gray Owl
(-| actual size)
*
-
15*
A. B.
Fig. ?• Comparison of heads from life (1/3 actual
size) A. G-reat Gray
B. G-reat Horned
Plumages of the G-reat G-ray Owl
Adult plumages have "been previously described (Gladden
193b) and the description of the immature bird is original.
Adult Female : The general color of the upper parts is dusky,
dull, grayish brown or bluish-sooty color, broken by transverse
mottlings of whitish grey. The uniformly sooty centres of the
feathers produce an effect of irregular dusky stripes, most
conspicuous on the back and shoulders. The edges of the
feathers of the breast plumage are more regularly barred.
The mottling becomes more profuse on the rump and the upper
tail-coverts and produces a more greyish appearance. The
primary coverts are crossed with very dull or indistinct bands
of paler brown. The secondaries are crossed by about nine bands
(one terminal and three concealed by the greater covertsj.
16.
of light greyish- brown, becoming lighter on the edges
of the outer webs. The primaries are crossed by nine
transverse lines of square spots of mottled pale grey
on the outer webs. The spots nearer the tips are quite
indistinct except for the terminal bar. The middle
secondaries and tail feathers are coarsely mottled with
dusky brown or greyish- white and this color tends to
form irregular bars. The rest of the tail is dusky
and crossed by about nine paler bands that are marked
off by a narrow line or edging of grey that in turn
encloses a greyish-brown and sometimes slightly mottled
space. Towards the base of the tail feathers the
mottling is somewhat more confused and the bands are
broken up. The basic color of the underparts is
greyish- white. Each feather of the neck, abdomen,
chest and breast has a broad, irregularly saw-toothed
centre stripe of dusky brown or dull grey. The flanks,
anal region and under tail coverts are narrowly banded
with dull brown and greyish- white. The legs have
narrower, more irregular bars. The "eyebrows11 , lores
and chin are greyish-white with a dark space immediately
in front of the eye. The face is greyish- white with
distinct concentric semicircular bars of greyish-brown.
The facial circle is dark brown passing into a very
pronounced white band on the foreneck (Pig. 9), This
white band is in turn interrupted by a sizeable spot
of brownish-black on the throat. The bill is dull,
light-yellow and the iris lemon-yellow.
-
T;
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5
.
.
.
.
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.
17
Adult Male
Similar to the female but usually an over- all lighter
color. The white on the foreneck is less pronounced. (Pig. 8)
Immature
In the downy stage the young are an overall greyish-
white with the base of the down on the hind-neck, back,
shoulders and wings sooty brown. The tips of down are
pale dull buff. After the third week the immature birds
show faint traces of barring on the lower breast and the
semicircular rings about the eyes are pronounced. The
tail is then about two inches long and shows barring.
The feet are pale yellow with dark grey claws. The cere
is orange-yellow and the pupil dark grey with the iris
limpid yellow.
Pig. 8. Adult Male Great Gray Owl. (From life)
18
Pig. 9. Adult female Great Gray Owl
(Mounted specimen)
Measurements
Complete measurements of five adult Great Gray Owls
were recorded (Table 1). The metric system has been
adopted throughout except for weights which are in
ounces. Meng (1901) favors this procedure.
19
TABLE I
MEASUREMENTS OF ADULT GRMT GRAY OWLS
Specimen No.
1.
2.
3.
k.
5.
Sex
F
F
F
M
M
1. Length of bill from
commissural point
20
30
33
33
31
2. Length of head and bill
120
110
100
105
100
3. Length of cere
23
22
25
26
21
li. Weight (in ounces)
37
34
k3
33
46-*
5. Length of humerus
Length of ulna
125
llj.0
130
14.O
130
lk2
O 1A
_d-co
H (H
130
142
6. Length of Manus (Wing)
100
85
00
90
80
7. Total length plus tail
520
635
660
600
635
8. Wing spread plus featha?s
1066
1422
1400
1450
1270
9* Spread of foot
110
95
110
100
108
10* Length of middle toe
and claw
65
60
57
62
60
11. Length of tarsus, middle
toe and claw
125
120
127
122
120
12. Length of tibio- tarsus
120
120
125
120
121
13* Length of femur
100
90
85
90
90
IIl* Length of Tarsus
60
62
60
61
60
1$. Length from anterior part
of clavicle to end of
pygostyle 152
213
165
196
203
16. Width of eye
16
15
ill
14
16
^Specimen No* 5 was a captive bird* The weight was far
above average due to excessive eating in confinement.
-*Fig. 31 indicates hoitf the measurements were taken in
millimetres.
.
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*
20.
The Question of Subspecies
The species is circumpolar in distribution and
has presented difficulties to taxonomists in Europe
and America. It is locally variable, while marked
fading occurs in old skins, complicating the issue.
This is evident in the recorded descriptions and
attempted recognition of subspecies (Hartert 1920).
Hartert recognizes three races in Eurasia, but
later in his supplement (1932-33), repudiates them
and reunites all of them Into one Old World Race,
Scotiaptex nebulosa lapponica, the Lapp Owl.
The Lapp Ow l is remarkably similar to the Ore at
Gray in habitat, nesting, egg size, behaviour and
plumage and measurements (Hagen 1952).
Three skins on loan from the Chicago Natural
History Museums and one from the New York Museum of
Natural History were examined and compared wth G-reat
Gray skins. Dr. Rowan examined and measured a lengthy
series of Lapp and Great Gray Owl skins in the museums
of Helsinki, Lund, Stockholm and London in 1954. This
information has been Utilized in Table II, together
&ith other measurements taken personally.
Because of the value of the skins on loan and the
decrepit condition of these specimens, only those
measurements appearing in the table were possible.
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.
*
.
21
TABLE II
MEASUREMENTS OF LAPP AND
GREAT GRAY
OWLS
LAP!
> OWL
GREAT
GRAY
Male
Female
Male
Female
No. of facial rings 8
8
6
8
11
7
6-7
9
9-10
8
7
8
7-8
7
8
8
6-7
7-8
8
9
7
Length of left wing 1+30
in mm.
1+50
1+1+1
i+30
1+1+0
1+37
1+50
1+60
1+32
1+1+3
1+1+0
1+50
1+65
1+1+0
1+50
1+37
l+5o
1+60
1+50
Tail length 320
in mm.
320
301+
335
310
330
320
330
320
3ll0
31+0
310
320
330
320
330
330
Summary:
Because of an. insufficient number of male Great Gray Owl
skins, significant comparisons are restricted to the female
of the two forms.
1. Female Lapp Owls averaged 7*7 facial rings compared
with 7.5 for female Great Grays.
22
2# Female Lapp Owls averaged \\$ 1,6 mm, for length
of left wing compared to 446,1}. for female
Great Grays,
3* Tail length for female Lapp Owls averaged 328
mm,, compared with 333 for female Great Grays,
Conclusions
From the above limited comparisons, a close similarity
between the two races is obvious. This is further corrobor
ated by personal examination of such skins as have been
available of both forms. The Old World race is in general
paler and more conspicuously streaked on the breast (Figs,
10,11), No other significant differences could be detected
Dr, Amadon (personal correspondence). Curator of Birds in
the American Museum of Natural History in New York and
one of the leading taxonomists of the continent confirms
this opinion. It is also substantiated in observations
and measurements by Professor Rowan on a long series of
skins of both forms in 1954*
For thousands of years the Canadian and Eurasian
birds must have beoi separated (since the Pleistocene
period presumably) so that their striking similarity
thus offers a point of theoretical interest, since
isolation Is generally accepted as one of the chief
factors In species formation (Huxley, 1940)* From the
available facts one must assume that either a remarkable
genetic stability, or similarity of habitat, has failed
to Induce notable variation. It is interesting to note
a
.
'
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.
.
• : •
.
.
.
23.
that another owl with circumpolar distribution, the
Snowy Oi%rl (Nyctea nyctea), has not a single recognized
subspecies, However, nowhere does an isolated group exist*
Owing to isolation the G-reat Gray Owls have varied in
minor degrees from the Lapp Owl subspecies but their
striking likeness suggests this process has not gone far
(Ridgway, 1914) •
Pig. 10. Comparison of Great Gray skins (Top How)
and Lapp Owl skins (Bottom r^ow). All
ventral aspects. Great Gray skins appear
smaller due to photographic foreshortening,
under the circumstances inevitable due to
the length of the skins.
2k-
Pig. 11. Comparison of Lapp (Bottom How)
and Great Gray Owl skins (Top Bow)*
All dorsal aspects.
25.
PTERYLOGRAPHY
Feather Tracts
The contour feathers of the Great Gray Owl may
be divided into eight tracts; the capital, spinal,
femoral, humeral, alar, crural, ventral and caudal
tracts respectively (Figs. 12, 13). The boundaries
of these tracts are quite easily seal and each tract
may be divided into various subdivisions or regions.
These however, are difficult to define. A true lumber
tract is absent in this species.
Methods of Investigating the Feather Tracts
The various feather tracts were determined in three
ways. The first method was to examine nestlings that had
not yet grown contour feathers long enough to cover the
apteria. The second method was to pluck carefully a
dead adult bird and note the follicles from which the
contour feathers spring. The third method was to skin
an adult bird and carefully clean the skin and examine
it from the inside. Feather tracts show up remarkably
well in this manner.
Short Description of the Various Tracts
1. The C ap i tal Tr ac t- The feathers of the entire head
are included in this tract. It passes over directly
into the spinal and ventral tracts.
2. The Spinal Tract- This pteryla. extends posteriorly
from the capital tract to the upper tail coverts.
Along the neck it is bordered on each side by the
-
of.
.
■
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■
.
.
26
cervical apterium, and along the trunk it is
bordered on each side by a rather large lateral
apterium. This tract is divisible into four regions
which are identified mainly by their shape and
location* There is a narrow interscapular region
extending from the area between the shoulder blades
posteriorly; a saddle shaped dorsal region extending
from the shoulder region to a point approximately
halfway to the tail and a narrow pelvic region lying
between the hips and extending from the dorsal region
to the tail coverts*
3* The Humeral Tract- A short pteryla of strong growth
found on each wing running obliquely backward on the
brachium from the anterior end of the shoulder, where
it barely coalesces with the feather tract below*
The scapular feathers arise from this tract.
!+. The Femoral Tract- A narrow but well developed tract
on the upper outer surface of each femur, forming a
sort of breeches. This is the only tract in this
region, for a true lumbar tract is missing in this
specie s*
5* The Ventral Tract- This tract covers the lower surface
of the neck and extends posteriorly almost to the anal
ring* The outer branch of the inferior tract is free
posteriorly, thus differing from Nitzsch & Burmeister » s (l81|0)
description for the typical disc-faced ox^ls.
27
6. The C rural, Tr ac t - The remaining feathers of the legs
are separated from the femoral tract by a narrow
apterium*
7. The Caudal Tract- This pteryla includes the rectrices, .
and the upper and under t ail coverts® The rectrices
number twelve.
8. The Alar Tract- Includes all the feathers of the
wing except the humeral tract on which the scapulars
are carried. The remiges or flight feathers are
divided into three chief groups; the primaries ,
secondaries and tertiaries. There are 10 primaries
with 10 greater primary coverts. The 12 secondaries
are borne on the ulna. Secondary number five Is
missing but its covert Is present. A wing which
lacks the fifth secondary is said to show di as t ataxy
or acquintocubitalism. It Is met with in nearly all
the lie ogna thine birds save the Passeres (Pyeraft, 1910).
The first primary is emarginated on the inner vane near
the apex. The second primary is emarginated on the
inner goad outer vane near the apex; the third and
fourth are like the second: the fifth is slightly
emarginated on the outside of the vane with noticeable
emargination on the inside; and the sixth shows only a
very slight emargination on the outer vane.
The alula has four feathers, excluding the
coverts
.
.
.
.■
.
,
.
r -
Cr\{\T&\_ T« rtcl^
- CL \c.a\_
C <2u &&\_ '\&ac.<.
Fig. 12. Ptarylosia of the Ore at Gray Owl
Dorsal Aspect
C-£dvJltO
Ventral Aspect
30
Feather Structure
The Great Gray Owl is remarkable for the softness
and lightness of its plumage. It was thought of interest
to include a brief comparison of its feather structure
with that of the Great Horned Owl,
The feathers of chief interest are those from the
upper and lower breast and the upper back* These are
the fluffiest contour feathers in owls,
A careful examination of these feathers revealed
the following:
1* The feathers from both species possess only
vestigial barbicels as revealed under microscopic
inspection,
2, The average length of a Great Gray Owl upper
breast feather is 170 mm, and that of the Horned
110 mm. The Great Gray Owl upper back feathers
average 10 5 m* as compared with 80 mm, for the
Great Horned Owl.
3« The number of barbs on a typical Great Gray upper
back feather average 16 per cm.. The Great Horned
averages 21 per cm. , Breast feathers of the Great
Gray average 13 barbs per cm., the Great Horned 17 .
4-. The extreme lightness and softness of the Great Gray
contour feathers is further due to the extra length
and fewer barbules per barb.
31.
Molt
Only limited observations were available on
the molting process of this species. The observations
recorded here were obtained from a captive male, which
had been in confinement since the late summer of 1954-
(Fig. 14). Up to August 15th, 1955 the molt had
proceeded as follows:
The bird commenced molting during the latter
part of June and by August 15th had undergone these
plumage changes:
1. All the re ct rices have grown in with the
central two or deck feathers having been
the first dropped. Under and upper tail
coverts are now completely grown in.
2. Primaries 3,4, and 5 (counting from the
outside in) have been replaced on both
wings, and secondaries 1,4, 6, 7, 8 and 9
are newly grown in. Molt appears to have
been completed for the secondary coverts
which appeared to be lost simultaneously.
The alula has completed its molt. The
middle and lesser coverts appear to be
shed and replaced somewhat irregularly
with very few new feathers appearing thus
far.
*
.
.
, . . .
32
3. The lateral areas of the breast molt
first. The molt continues posteriorly,
I4., The part of the back to molt first is
the area between the shoulders, and the
feathers appear to be replaced in both
directions,
5>, The feathers as yet not molted are those
at the front of the head, back of neck,
centre of back, chin, tibio-tarsus and
tarsus.
Normal molting proceedure is often completely
upset in captive birds, so a detailed record of feather
sequence is thus of doubtful validity, .
Pig, 1 4* Dorsal view of molting Great Gray,
The new feathers appear darker than the
old ones.
33
Bye Color
When the young are less than ten days old the
iris is a very pale yellow and the pupil a greyish
blue* As the owls become older the yellow strengthens
and the pupil becomes a darker grey* By the time the
young are three weeks old the pupil has become a very dark
blue and at the end of the sixth week the young owls
possess dark pupils and the typical lemon-colored iris
of the mature bird* Compared with those of the Great
Horned Owl the eyes are considerably smaller*
ANATOMY
This being primarily a field study of the Great
Gray Owl, no detailed anatomical study of the species
has been attempted* In any case the paucity of material
has precluded any such undertaking* Since the anatomy
of the bird is virtually unknown hox-jever, the following
facts are recorded*
Intestinal tracts were taken from two adult, male
and female specimens of the Great Gray that had undergone
considerable disintegration after a lengthy period in
formalin preservative. A complete tract was also taken
from a freshly killed adult female Great Horned Owl. A
brief comparison of the intestinal tracts of both
species was thought to be of interest (Fig. 15>).
1* The caeca of the Great Gray measured 72 mm* in length
compared to 90 ram. for the Great Horned Owl.
2. The large Intestine of the Great Gray was Lj.2 mm.
in length; the Great Horned 70 mm.
3. The small intestine of the Great Gray exclusive of
the duodenum, appears larger in diameter.
II. The caecal diameter of the Great Gray is also
slightly larger.
5>. The pancreas of the Great Gray appears smaller than
that of the Great Horned*
.
.
*
„
-
35
6, The gizzard, gall bladder and kidney appear to
be of equal size in both species*
7* Better differentiation of the proventriculus from
the gizzard vr&s noticed in the Great Horned Owl,
8. The heart and liver of the Great Gray appear
larger than the same organs of the Great Horned.
The intestinal tract of the Great Gray presents
no remarkable difference from that of the Great Horned
Owl. Both species appear to conform to the general
anatomy of owls as outlined by Gadoxtf & Selenka (1891
and Pycraft (19 10).
36
Pig* 15* Intestinal tracts
A. Male Great Gray
B* Female Great Gray
C* Female Great Horned Owl
Cftec* .
37.
Skeleton
Only one complete
skeleton of an adult Great
Gray Owl was available
for study and the chief
structural differences
between this and the skeleton
of an adult G-reat Horned Owl were noted.
The feet afford a striking difference, those
of the G-reat Gray being half the size of the Homed
Owl’.s. The leg lengths of the two species are fairly
similar. Measurements
of the leg bones are as follows:
GREAT GRAY
GREAT HORNED
Femur 85mm.
85mm.
Tibio-tarsus 110mm.
120mm .
Tarsus 55mm.
60mm.
Middle toe 57mm.
and ©Idw
92mm.
Wing bones also show little difference in the
two species and are listed as follows:
GREAT GRAY
GREAT HORNED
Humerus 125mm.
140mm .
Ulna 130mm .
1 50mm .
Manus 100mm.
110mm.
Another outstanding difference between the two
skeletons lies in the sternum and rib structures and
correlated muscles. The G-reat G-ray possesses a smaller
sternum and lighter ribs. The sternum of the Great Gray
measured 50 mm. in length and that of the Horned Owl 70mm
38
The shoulder girdle, sternum and all correlated
muscles are so much lighter and weaker in the Great Gray
Owl as to prevent it from preying on anything but small
quarry*
Skull
The palate, desmognathous (indirect), is typical
of owls (Stresemann, 1934)* The eap apertures of the
Great Gray Owl show remarkable asymmetry. The aperture
on the left side of the skull is noticeably larger
than that of the right side (Pigs. 16,17). Fycraft
(1910) bas described this modification for TengmalraT s
Owl (Aegollus funereus) as follows:
!,0n the left side of the head the combined post¬
orbital process and tympanic wing of the exoccipital
forms a large outstanding shield extending downwards to
the level of the lower jaw so as to leave a narrow chink
between itself and the bony ring of sclerotic plates
surrounding the eye. The chink traced inwards gives way
to a large chamber, in the floor of which will be found
the passage to the middle ear. On the right side this
chamber is wholly exposed but for a tongue- shaped plate
of bone which, extending forward to the bony rim of the
eye, encloses the lower half, leaving a small triangular
space lying immediately above the lower jaw.”
The skull of the Great Gray Owl conforms very closely
to this modification. No special significance has been
attached to this asymmetry.
.
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39
Pig. 16 Left side of Great Gray skull
showing large ear aperture.
Pig. 17 Right side of same skull
indicating smaller ear aperture.
DISTRIBUTION AND MOVEMENTS
Breeding Range
Daring the nesting season this species is found as
far north as Alaska and south as far as the Yosemite
Valley in California (Bent, 1938)# Definite nesting
records for the latter region exist (Bleitz, personal
correspondence)* Two nests were recorded by Craighead
(personal correspondence) for Wyoming* Roberts (1932)
has found the birds nesting in (Fig. 18) northern
Minnesota* There are a few other observations that
suggest successful nesting in other locations. Among
these are the G-aspe country of Quebec, northern Ontario
(Taverner, 1912), northern Manitoba and northern
Saskatchewan, Alberta dnd British Columbia.
, No authentic nesting records have been established
for Saskatchewan or British Columbia (Bard, personal
correspondence; Munro & Cowan, 1947 )• Alberta has
yielded twenty- three established nesting records. They
Include thirteen nests found by Henderson in the Belvedere
area, five by Randall in the Athabaska country, two by
Twomey in the Fawcett district, one by Dippie (Macoun,
(1909) in the Red Deer district in 1896 and two found
by the author In the Edson and Rocky Mountain House
regions (Fig* 19).
Alaska and Arctic Canada have produced three further
nesting records. However, Cade (personal correspondence,
1953) states the bird is now extremely rare in Alaska.
..
.
*
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0
4i
McDonald (personal correspondence, 195>2) believes the
birds breed in various wooded sections of the North
West Territories being more common to the south and west
of Great Slave Lake and extending down the McKenzie
river to Fort Good Hope. Two nests have been noted by
McDonald in this region. He considers the species very
rare for the region.
Preble (1908) records one nest along the McKenzie
river and has a record of another nest with two eggs
taken at Fort Providence. McFarlane (1908) in a manu¬
script list, records a nest containing two fresh eggs
near Fort Good Hope. Apparently the breeding range for
this species is in the timbered regions of central and
northern Canada, from Hudson Bay west to Alaska and the
Pacific coast, and south in the mountains to central
California.
Winter Range
This species is not known to undertake regular
southward movements, but at times (possibly owing to a
food shortage) it extensively invades more southern (Bent,1938)
regions. In years past great numbers of these owls came
through southern Ontario and extended as far south as
Massachusetts, New York and Wisconsin, To the west they
have been recorded during the winter in Oregon, Iowa,
Indiana, Nebraska, Montana, Washington and southern
■
5 ' ' ■. : '
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42
British Columbia (Pig. 18 ) . Ontario, particularly the
Toronto area, had its last substantial invasion during
the winter of 1889-90. These flights continued until
the winter of IvlO-ll and then apparently ceased. Since
then four birds have occurred in the Toronto region (Baillie,
1947)* According to Dippie (Macoun, 19 09) during the
winter of lu9b, Alberta was alive x^ith owls of every
description. Great Grays being particularly abundant.
The great southward movements ceased in Alberta more
than thirty years ago. Wolf e 1 s (Edmonton) taxidermy
records bear this out. It is estimated that at least
half a dozen Great Gray Owls a.re shot each winter in
areas in Alberta where they normally do not occur.
Banding Recoveries
The U.S. Pish and Wildlife Service records reveal
that prior to this study only two Great Gray Owls
had ever been banded. These were adults taken at
Centre Island, Toronto, Ontario by H.H. Southam on
January 18, 1947.
Two young x*rere banded by the author In June 195>4 in
the Rocky Mountain House region and a third in June
of the same year in the Eds on area. No banding recoveries
have ever been reported (Duvall, personal correspondence).
.
'
. .
.
• •
.
.
43.
p5^
Fig. 18.
Range of Great Gray Owl.
Breeding Records
Winter Range ^
In North America.
60'
Fig. 19,
Nesting Records for
3 re at Gray Owls(x.)
ALBERTA
SCALE
50 MILES 100
45*
■NESTING
Type of' Woods Preferred
In Alberta the most frequently chosen nesting
territories appear to be the large white or black
poplar woods. These poplar stands may be lightly
mixed with either black spruce or jack pine. Nests
are preferably near a sizeable muskeg. These muskegs
are characterized by a variable mixture of trees,
shrubs, grasses, sedges, horsetails, mosses and
lichens. They conform in general to those described
by Moss (1953), for northwestern Alberta. This is the
hunting habitat for the male bird during the nesting
period. Great tracts of these heavy poplar woods were
once common throughout most of central and northern
Alberta but are now chiefly confined to areas in the
north- we st and northern parts of the province. The
typical Great Gray nesting woods are deep and secluded
and well removed from agricultural activities.
The Nest
Randall (op. cit.) and Henderson (op. cit.) believe
this owl does not build its own nest, feut prefers to
make use of those discarded by other raptors. In Alberta
the species has made use of the nests previously occupied
by Red Tailed Hawks, Goshawks, Great Horned Owls and
occasionally Grows. Twice Randall found the birds
nesting on the top of an old spruce stump.
The twenty-three nests found in Alberta were in
the following locations, with the height indicated
in feet*
Aspen poplar ( Fopulus tremuloides ) :- L}5,f?0,
^0 , 50 , 3 5 5 40 , Lj-5 , 45 ,45,^5,80,30,50,4.0, 45 .
Tamarack (Larix laricina):- f?0,10.
Black Spruce ( P i c e a mar lan a ) : - 4°*25,l8.
Balsam Poplar ( Populus balsamif era) I4.0 , 30 9
40*
Position and Condition
In the deciduous trees the site is usually in a
crotch formed by two or three main branches (Fig. 21).
Other nests found in coniferous trees were in heavy
branches near the trunk.
The birds will frequently use nests in such flimsy
and decrepit condition that the eggs are plainly
visible from beneath. Neither Henderson nor Randall
noticed any attempt by the birds to recondition the
nest. Twomey (Bent, 1938) noted that one nest he
discovered near Fawcett contained fresh tips of green
pine needles and some newly added twigs. Personal
observations agree with the findings of Henderson and
Randall.
Selection of the Nesting Site
Henderson (op. cit.) reports the birds are seen and
heard in the general vicinity of the nesting site
approximately three weeks prior to actual nesting. The
*
.
* * ”, s * t t ■ t ■ r
*
t
.
■ r.
,
47.
birds are then quite noisy and the long-drawn hoot of
the male is heard for some distance. The site is
usually selected by the first week in April adid
frequently the birds return to the nest of a previous
year. The birds remain vociferous until well after
the nesting has commenced.
Courtship
In the early summer of 1954 I observed a pair of
captive G-reat G-ray Owls undergoing what appeared to
be a form of courtship activity.
The male would fly to the female’s stump and face
her. Standing face to face with breasts touching, he.
would commence rubbing his beak over hers, at the same
time uttering a faint droning or humming sound. Often
he would circle her face with his beak in a similar
manner. This was observed regularly for eight days
and would occur at anytime during the day or night.
The female died a short time after this activity
was observed and a post mortem examination revealed
slight ovarian development, while the oviduct appeared
more enlarged than one would expect in the quiescent state.
The ovary was approximately three times the size of an
inactive organ, which would suggest that she was at
least partially in breeding condition.
A similar courtship has been recorded for Barred
Owls (Bent 1936)
.
.
.
.
Pig. 20. Nest and eggs of Great Gray Owl
Pig. 21 Typical position of nest in
White Poplar.
Nesting Density
An accurate estimate of the nesting density of this
species is extrenely difficult to determine owing to the
small number of nests located. The fact that the
brochure circulated throughout northern Alberta revealed
only two nests is some indication that this species does
not have a heavy nesting density in the province. Whan one
considers that trappers cover every square mile of
Alberta* s remaining wilderness at a time when the birds
are most conspicuous and noisy, it may be assumed that
the birds are, in fact, very scarce.
THE EG-G-S
Egg Dates
The earliest Alberta record for a complete clutch
is March 23* The majority of nests have complete sets
by the 15th of April. Dates for complete sets in the
province are as follows:
March 23, March 30, April 1, April 6, April 10,
April 11, April 20, April 22, April 25>, April 27,
April 29 , May 1, May 5, May 7 , and June I}.*
These are not first egg dates, but when egg collectors
happened to find the nest.
Number
The number of eggs laid varies from two to five with
three per clutch being the most common (Pig. 20) and two
5o
the next. Of the tx^enty- three nests for which records
have been obtained, three contained five eggs, five had
four eggs, nine contained three, and six two eggs.
Color
The color is dull white and there appears to be no
visible difference in this respect from the color of the
eggs of other owls (Henderson, op. cit.).
Shape and Measurements
The eggs are small for the size of the bird, and
are not so round as the eggs of most other owls, being
between oval and elliptical- oval in shape (Henderson,
op. cit.). The shell is not glossy but is rather roughly
granulated. Measurements of twenty-four eggs from Alberta
nests average 54*3 mnu by . ip mm.. The eggs showing the
four extremes measure 63. 5 by IjJB, 52 by 43 • 9 , and 55 by
40«8. BentTs measurements for 52 eggs are as follows
Average, 54*2 by 43*4 extremes 58 « 7 by ^9, k8 by 42,
and 53 • 4 by 41 mm.
The type specimen egg (TfolO 277 ) was collected from a
set of two by Mr. J. Sibbiston near Pt. Yukon, Alaska
in April, 1864 (Bendire, 1892).
Incubation Period
Unfortunately the nests found in the course of this
investigation both contained newly hatched young and no
incubation data are available. An exhaustive check of all
other available literature on this species has revealed nothing.
.
■
.
.
51.
Henderson (op. cit.) and Randall (op. cit.) consider
all the incubation to be performed by the female. She
does not leave the nest even to eat as the male brings
her the food which she devours on the spot. Of the
several nests that Henderson ooserved, he never once
saw the male incubating.
Nests of Other Birds Found In theVlcinit y of 3- re at
dray uwis* Nests.
The following is a list of the nests of other
birds found near or in the general vicinity of the
Great Gray nests, during the spring of 1954- •
Red-tailed Hawk (Buteo borealis)
Ruffed Grouse (Bonasa umbe 11 us )
Myrtle Warbler (Dendroica coronata)
Slate “Colored Junco ( Junco hy emails hy emails )
Spruce Grouse ( Canachites canadensis )
Other birds' believed to be nesting in the general
area of the owls9 nests because of their almost constant
presence are as follows:
Ruby Crowned Kinglet ( Corthyllo calendula.)
Golden Crowned Kinglet ( Re gulus satrapa olivaceus )
White throated Sparrow ( Zo not rich la albicollls )
Hudsonian Chieadee (Penthestes hudsonicus )
Black Capped Chieadee (Pentheste s atricapillus )
Red-breasted Nuthatch ( Sltta canadensis)
Canada Jay ( Perlsoreus canadens is)
.
-
-
52
It is interesting to note that the remains of a
dead Barred Owl (Strix varia) were found quite near the
base of a Great Gray!s nesting tree near Rocky Mountain
House* The body was too decomposed to enable a determina¬
tion as to cause of death* A Barred Owl was also heard
hooting in the Edson area very close to the site of
another Great Gray nest* The little SIhte-colored Junco
was the only bird that was noticed objecting vigorously
to the presence of the owls* The owls paid no attention
to the smaller birds*
Reactions to Intruders
Man
I can think of no Alberta bird which is less wary
of man than the Great Gray Owl. The female will
normally sit very tight if she is on eggs or small
young and often it requires strenuous pounding of the
nest tree to force her off. Henderson and Randall (op.
cit. ) recall several occasions when the female almost
allowed herself to be touched by the investigator
climbing the tree. The male is invariably some distance
from the nest and will call repeatedly in a low, long-
drawn hoot. When the female does leave the nest she will
commence regular hooting of a short, plaintive nature
(Pig. 25) while perched in an adjacent tree.
After the eggs have hatched, the female becomes
.
»
.
•
,
■
.
-
.
.
i :
.
,
.
•
53
more solicitous about the nest, and beak-snapping
and more excited calling will result if the young
in the nest are handled. When the young have
reached the age of three weeks, the female becomes
even bolder, and on one occasion at the Rocky Mountain
House nest site, flew menacingly at the author. She
continued vigorous beak- snapping and would often
perch a foot from the nest, while the young were
being examined (Pig, 22.),
Pig, 22, Fema.le Great Gray threatening
to attack investigator at the
nest .
*
*
• ■ ’ ,
1 0 .
.
Other Intruders
Pig* 23 Great Gray female In defensive
On one occasion a Red- tailed Hawk was seen diving
at a female Great Gray Owl* The owl immediately
assumed a defensive attitude, hunching the shoulders
and fluffing out the feathers (Pig. 23)* She made no
attempt to fly at the hawk, which in turn made no
further assaults.
The presence of dogs near the nest always caused
the female owl to adopt the same defensive pose.
attitude
55.
VOICE
Introduction
Randall (personal correspondence) notes that the
chief obstacle to observing the owls out of the breeding
season is their remarkable quietness, an observation
corroborated by three captive birds kept over the past
two years. These birds only became vocal with the advent
of the mating season, and when assuming a defensive pose.
During the breeding season the male emits a very long-
drawn call which lacks the depth and throatiness of the
common Great Horned Owl# The female !s response is always
a shorter and somewhat screechier note and again bears no
resemblance to the deep hooting of the Horned Owl,
Henderson (1923) was the first to draw attention to the
remarkable differences in the quality of sounds produced
by the Great Gray Owl and the Great Horned Owl.
In the following list the various notes the owls
utter and the circumstances under which each call is
given, are described.
Voice of Adult Female
1# A soft, dove-like ooh-ah, at times very weak and
more like a coo than a hoot# The sound is not loud
and carries no great distance, usually tapering to a
high raspy note at the end# It is repeated at irregular
intervals throughout the day when the bird sits on the
nest or perches in adjacent trees (Fig# 25)#
-
,
♦
.
.
.
.
56
2. An excited, intense hooting like ooh-uh repeated
quickly and loudly. This was the signal that the
male was arriving with food and she would immediately
begin to hunch on the nest and continue to call until
she had taken the food from him.
3. A fast repeated but faint who -who -who -who - , uttered
by the female when assuming a defensive attitude. This
note and attitude has also been recorded in captive
birds when alarmed by people or cats prowling nearby.
Voice of Adult Male
1. A long-drawn hoot rather like a whistle, whoo-oo-oo
uttered near the nest, and often heard when the male
could not be seen. It was often emitted when the
bird if as hunting in the muskeg.
2. A steady rumbling or pumping noise like oom-ah, 00m-
ah, repeated for a minute or two and then started
again whenever the male came close to the nest and
the young were being handled. The throat of the male
could be observed to maintain a pump-like motion and
the beak appeared not to open.
3. A screechy whistle-like ee-ah, eee-ah has been
recorded only from captive birds and is uttered at
any time throughout the day most frequently in the
spring and early summer.
Voice of the Young
1. When still in the nest, the young would emit a very
raspy screech, appearing to indicate hunger. These
sounds would subside as the young were being fed and
give way to a soft, chirp- like utterance.
.
-
57
2, A much louder, screech-like noise, eee-ih, emitted
by the young after they had left the nest. An
imitation of this sound proved the best way to locate
the adults after the young had entered the hunting
muskeg.
Some authors attribute a tremulous, vibrating noise
to this species (Bendire, 1892$ • I have never heard it
and Henderson and Randall have never recorded it.
Activities of the Female on the Nest
During the incui.bation period the female sits very
quietly on the nest. She arises occasionally to preen
herself and to turn the eggs. The bird is most attentive
to all movements, and watches all actions with great
curiosity (Henderson, op.cit.). The female was observed
sleeping beside two-week -old young at which time they
presumably no longer required brooding. The mother will
continue to remain near the nest at all times until the
young are old enough to leave. She shades them during
excessively hot weather and often sits with them after (Pig. 2l±)
a meal. After the young are three weeks old, the female
spends very little time about the actual nest, though
remaining always in the immediate vicinity.
Activities of the Male About the Nest
Henderson and Randall ( op.cit. ) never saw the male
bird incubating. He visits the female at the nest
regularly with food and spends almost all his time hunting,
never lingering about the nest after offering her the food.
As the young become older, the female will fly from the
nest to meet the male for the food exchange.
*
.
-
,
,
58
He usually approaches the nest from the same
direction and leaves by the same route.
Feeding Times and Places of Adults and Young
Before the Nesting Season
Great Gray Owls do most of their hunting prior
to the nesting season in the late afternoon. Their
activities during this period will only be sufficient
to allay their own hunger, when prey will be eaten on the
handiest stump. With the advent of the family the
male inevitably increases his hunting activities, he
being the sole provider.
During Incubation
No personal observations were made at this time
but Henderson* s notes describe the activity as similar
to that carried on after incubation.
After Incubation
During the first ten days of the life of the
young owls the male is making rapid and frequent trips
with food to the nest. A typical feeding schedule for
a day during this period is as follows:
May . 9/glj. ist Feeding
2nd M
3rd "
4th "
5th ”
6 th "
7th "
8th
9th "
9.35 AM
10.30 AM.
12.25 EM
12.45 "
1.10 "
2.10 M
3.10 f?
4.10 "
4.30 "
.
1
!
.
59
A typical schedule for a day during the second week
is as follows:
May l6/54lst Feeding 9^15 AM
2nd " 11*30 "
3rd !t 12.30 PM
4th " 5.30 n
5th " 5.50 "
During the third and fourth weeks the visits became
less frequent with not more than three trips per day
recorded. The infrequency of daytime feeding despite
numerous fresh pellets or castings, suggested supplemen¬
tary feed.ing by night. A typical schedule for a day
during this period is as follows:
May 23/54 1st Feeding 8.00 AM
2nd " 11.30 "
3rd ” 3.40 PM
The fourth week’s daily feeding schedule was more
difficult to determine for the young were away from the
nest and continually shifting location. Night feeding was
again indicated. As the trips by the adults with food
became less frequent, the young birds also became more
silent in contrast to their earlier behaviour.
Food was always transferred from the beak. Never
was the male observed to carry prey in his claws and
the female always accepted it from the male with her
beak.
*
«-
.
■
-
60
Pig. 2 4. Female Great Gray Owl feeding
young at the nest.
Pig. 2^. Female Great Gray in tree adjacent
to nest, emitting soft dove-like call.
61
Description of the Young
Ten Days Old (Approximately)
The young are still covered in downy feather
growth, that appears greyish, ashy white (Pig* 26).
The bill is yellow with darkish-blue in front of the
nares. The pupil is bluish with the iris greenish
yellow. The cere is yellowish orange.
Fourteen Days Old (Approximately)
The downy feathering has acquired a distinct
asny grey throughout. Faint barrings are visible in
the scapular region (Fig* 27). The breast is lighter
and more creamy grey, the cere greenish yellow
with a very pronounced centre piece, orange in color.
Fig. 26. Nest, with young approximately ten
days old
62
Fig, 27. Nest, with young approximately
II4. days old.
Twenty- one days old
Quite a number of feathers can now be seen pro¬
truding through the dense dox^n. A faint tint of brown
around the eyes and the first semblance of a facial
disc-ring is noted developing about the eyes (Fig, 28).
The hindneck has become more brownish while the back and
wings show signs of feather growth. Barring over the back
is noticeable with alternating dark and light coloring
of an ashy brown. The tarsus is well covered
.
-
.
63*
in ashy grey down, bristle-like feathers around the
cere are black and approximately half an inch in length.
The pupil is darkish blue and the iris a weak limpid
yellow. Joint of the tarsus and the metatarsus is pale
orange in color.
Pig. 28. Young Great Gray Owls, approximately
21 days old.
Twenty- eight Days Old
By this time the owls are almost completely covered
with feathers except for the down of the head, legs and
abdomen (Pig. 29). The rectrices are developing
64
well and showing signs of barring. The facial
rings about the eyes are getting conspicuous, with
a more pronounced brown color.
Fig. 29* Young twenty-eight days old.
Forty Days Old
The back is now well feathered with no traces
of remaining down. The (first remiges are well
developed with some downy growth still near the
rectrices (Fig. 30). The head is still downy but
65-
feathers are beginning to cover the tarsi and feet.
Feathers are also developing on the abdomen. The
head has a frosty appearance of greyish-brown with
white. There is a better development of the facial
rings about the eye. The joint between tarsus and
tibio-tarsus is bare and orange in color. The bill
is green with a yellow tip. The cere is less orange
and somewhat greener. The iris remains pale
yellow with the pupil a bit darker blue than
previously noted.
Fig. 30. Great Gray Owls forty days old.
66
(The age of the young from both nests is assumed on the
basis of information provided by trappers residing in
■the study areas.)
Physical Development of the Young
Explanation
Complete measurements for four young owls were obtained
at the age of fourteen days, for three young at twenty-one,
twenty-eight and forty days. Sixteen different measurements
were taken and included the following (Pigs. 31*32):
1. Length of bill from Commissural Point
2. Length of head and bill
3* Length of cere
I].. Weight
5>. Length of humerus and ulna
6. Length of manus (wing)
7. Total length plus tail
8. Wing spread plus feathers
9. Spread of foot
10. Length of middle toe and claw
11. Length of tarsus, middle toe and claw
12. Length of tibio-tarsus
13* Length of femur
Up. Length of tarsus
15. Length from anterior part of clavicle to
py go style
16. Width of eye
.
..
.
-
A. Length of Head and
Bill
B. Width of Eye
C • Length of Gere
D. Length of Bill from
Commissural Point
E* Length of Humerus
F. Length of Ulna
G. Length of Manus
H. Length of Ant. Part
of Clavicle to End
of Pygostyle
I. Length of Femur
J. Length of Tib io- Tarsus
K. Length of Tarsus
L. Length of Middle Toe
and CLaw
M. Spread of Foot
Fig» 31 • MEASUREMENTS - Great Gray Owl
68
Granhs
The following graphs (Fig. 33® “37) summarize
the data secured from the young owls during their
available period of development. All measurements
were taken on live birds and therefore the figures
cited will not represent actual bone length but a
figure eorriextfhat greater. Fig, 3^ indicates how
the measurements were taken.
Fig. 32. Great Gray twenty -eight days old
being weighed,
mm •
-20-
_ 10~.
LENGTH OF BILL
COMMISSURAL POINT
DAYS
14
21 28
40
_
H — I — I — 1 4-
LENGTH OF: HEAD AND BILL
400
mm •
-50-
■ -s
i — f— I — r
-rttt
tttt-hH-H-
i — — i — r — i — i — j — f — f~
DAYS
14 21
28 |
40
mm •
-20-
LSNGTH OF CERE
—
_
DAYS
14 21 28
40
Fig, 33»
4-4-
[
50
LENGTH OF TI5IC - TARSUS
74'
Summary
1. Length of Bill From Commissural Point
At fourteen days of age the bill is approximately
half grown. There is a gradual increase until at
forty days of age the beak is very close to full sixe.
2. Length of Head and Bill
From a length of 77 mm. at ten days the head and
bill grow rapidly, almost attaining full length
at 28 days and reaching maximum length at forty days.
3 • Length of Gere
From the tenth day on there was no change in length
of cere. It measured 20 ram. throughout the study
pe riod. The adult measurement averages 23 mm.
4* Weight
After the twenty-eighth day the weight increases from
twenty to twenty- six ounces. After the twenty-
eighth day the young are moving more, making the
first attempts at flapping their wings and muscle
development is gradually taking place. The average
weight for adult males is thirty- two ounces and
forty for females.
3?. Length of Humerus and Ulna
At fourteen days the ulna is 70 ram. long and at
twenty-one and twenty-eight days it measures 100
ram. On the fortieth day it measured 128 mm. The
humerus measured 73 ram. at ten days, and at
75
twenty-one and twenty-eight it measured 87
and 108 mm. respectively. It is now about 8mm.
longer than the ulna but by the fortieth day the
ulna exceeds the humerus by 6-7 mm. Meng (1951)
found a similar variation in Coopers9 Hawks at
twenty-e ight day s .
6 . Wing Spread
The greatest period of growth for the wing .spread
occurs between the fourteenth and twenty-first
days with the increase from 4 30** to 645 mm.,
7 • Length of Middle Toe and Nail
Very little difference is shown in this measurement
from 38 mm. at fourteen days, to 45 mm. at forty
days. Adult average is 60 mm.,
8 . Length of Tarsus, Tibio-tarsus and Femur
The tarsus also shows very little increase from
37 mm. at fourteen days to 50 mm. at forty days.
(Adult birds average 60 mm.) The Tibio-tarsus
measured 75 mm. at fourteen days and 105 mm. at
forty days, the femur 65 and 90 mm.. Adults
average 122 mm. for tibio-tarsus and 91 for the
femur.
9. Width of Eye
This measurement proved interesting with 8 mm.
recorded for the fourteenth day and 14 mm. for
the fortieth, which is the adult average.
76.
Behavior Development of Youn^c
At ten days of age the young reach up eagerly
for the small pieces of meat the female feeds them.
The female holds these pieces lightly in her beak
and the young snatch and swallow them.
The nest is kept quite clean since the young,
when defecating, will back to the edge of the nest
and discharge over the side. At this time they are
not in the least aggressive but remain quiet when
handled either in or out of the nest. From the
twenty-first day on they begin to show increasing
signs of Aggressiveness (Fig. 38). They are now
standing up in the nest and show interest in moving
objects about them such as flies. When handled they
indulge in beak snapping and clawing. After the
twenty-eighth day the young are out of the nest and
attempt short flights but seldom more than a few feet.
They are surprisingly agile and climb and flap their
way up leaning poles and limbs. When they have reached
their fortieth day they may be as far as a mile from
the nest, making excellent headway with short flights.
They are still moving as a family group.
' .
*
-
.
77
Fig.
38. Great Gray Owl Forty Days old
showing aggressive tendencies*
78.
FOOD HABITS
Intro duct ion
ureat u-ray owls like all other members of the
Strigidae capitalize on their silent flight and acute
sense of hearing' and sight. Their flight is not swift
and the birds rely on accuracy of location and a noiseless
approach rather than speed.
Method of Hunting
This species prefers to hunt in muskeg country.
Except at the nesting period when the male hunts by (Fig.
39.) day, these owls are crepuscular. At dusk these
birds are seen perched high on old tamarack stubs waiting
to make a floating swoop at their prey, invariably mice or
voles. The birds have been observed performing a gliding
series of flights from stub to stub throughout a muskeg
and occasionally stooping to pick up quarry. The flight
is soft and measured and appears much slower than that
of the Great Horned Owl. Infrequently the birds hunt in
the heavy spruce and poplar woods where the method is
to sit and wait for some form of prey that will be seen
and heard. When perched, the owls assume a face down
attitude (Fig. Li_0 . ) as if listening and watching for
what may move on the ground. They then seem so intent on
their task that they can always be approached with ease.
'
.
'
.
.
♦
79
Fig® 39® Male Great Gray hunting in
muskeg north of Gorbett Creek®
These owls possess none of the pursuit-persistence
of the fiercer raptors such as the Great horned Owl,
Goshawk and Snowy Owl® Their disposition is mild at
all times and shows no variance in the hunting field®
80
Prey
Over a four year period a study has been made
of the stomach contents from all available specimens
collected in Alberta (Table III). Further study was
made on pellets collected at the nest under observation
(Table V). Identification of all the remains was based
mainly on skull characteristics. This work was kindly
carried out by Dr. J.E. Moore.
An exhaustive search of the literature reveals
only one other listing of stomach contents for this
species. It is quoted in Table IV, (Fisher, 1893).
Fig. i|.0. Close-up, showing characteristic
posture of male Great Gray Owl
when perched on dead stub in
"hunting muskeg".
'
*
.
*
* * » *
, : , - ,
< -
STOMACH ANALYSES OP GREAT GRAY OWLS
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83.
Bent (1938) records that Dr.W.H. Hall took no
less than thirteen skulls and other remains of Arctic
Red Polls (Ac ant his hornemannl) , from the crop of a
single bird. Bent also states that Swart h
found in the stomach of one an adult Red Squirrel.
TABLE V
PELLET ANALYSES OF GREAT GRAY OWLS
Date Locality Contents
Microtus
Clethrionomys
Synaptomys
ifc —
pennsylvanicus
gapperi
borealis
May
9 to
June
3/54
Ed son 26
4
1
May
9 to
June
3/54
Rocky Mt. 46
1
House
Summary
Tables III, IV, and V indicate that this species
feeds almost entirely on small mammals. The Northern
Bog Lemming ( Synaptomys borealis) , twice recorded from
Great Gray Owl stomach contents and pellets, is rarely taken
by Alberta mammal collectors.
Evidence of Spruce and Ruffed grouse feathers near
the nests at Eds on and Rocky Mountain House suggest
that if driven by hunger, these birds can take larger
quarry than usual. The fact is significant however,
that although Red Squirrels (Tamlasc lurus hudsonicus)
a/bounded in both nesting areas, no evidence that they
were being preyed upon came to light. Red Squirrels
are common throughout the range of the Great Gray Owl,
. . .
, ;
'
-
,
.
'
I • • ■
8Lj-
but the evidence to date lends no support to the
constant charge of the trapping fraternity that this
species preys habitually on them* It is the argument
put. forth by most trappers who doubtless have had Red
Squirrels at some time torn from their snares (Pig* Lpl )
by owls of the northern forests, that all of the specie
are guilty of this action. Pew trappers are able to
accurately identify the culpable species*
Pig* lj.1. Snared Red Squirrels. Trappers accuse
the Great Gray of destroying such catches
Some sources (Bendire, 1892) maintain that the
Snowshoe Hare ( Lepus ame r 1c anus ) is the principal
quarry of the Great Gray Owl, but no evidence to this
effect was uncovered in this study*
85.
ENEMIES
Mam
Without question man is the prime destroyer of Great
Gray Owls and predatory birds in general. Trappers,
poultry-men, and sportsmen are the die-hard enemies of all
owls. This species always allows a close approach and
presents an easy target to thoughtless people with guns,
and as a consequence its numbers have declined to one
point where its very existence is threatened.
Pole traps are perhaps the most viciuus and deadly
set-up that man has devised to kill predatory birds, and
owls in particular. A number of pole traps around a pheasant
enclosure near Barrhead took a constant toll of owls in¬
cluding such rare species as Richardson* s and Great Grays
during the winters of I9I18 to 1953* Personal investiga¬
tion of this farm revealed the numbers of raptors taken
to be past counting. During the winter of 195>2 and part
of 1953 a pole trap device near Gross Lake (Figs. Lj_2,!f3)j
Alberta was investigated. The toll of birds for that
period amounted to 92 dr eat Horned Owls, three Great Grays
and one Barred Owl. The feet were identified and counted
by the author.
Black Bears
This species lives in black bear country. Numerous
trees containing unu.s.e d - raptors* nests bear the claw
marks of black bears, suggesting that they have at some
time climbed to the nest either for eggs or young.
86
Henderson (1920) believes this is a common occurrence
when bears1 smell or hear young birds at the nest*
Pig. 42. Typical Pole Trap Set-up,
& *? ■** *$■*- 5 t *
, i/m ■tv st
i ... ;Vv’ :
& f S - : t i A *
* * ■ . * - - £ *
'><* sr '
^ %
Pig. 43. Peet taken from Owls killed in Pole
Traps at Gross Lake. (Dark feet are
those of Great Gray Owl^*
37
G-reat Homed Owls
In the Corbett Creek district evidence was
uncovered that the Great Gray does fall victim to
this powerful bird. A trapper had reported seeing
a Homed Owl fly at a bird he thought might be a
Great Gray Owl. An inspection of the area revealed
a freshly killed Great Gray (Fig. 44) and the
remaining evidence was characteristic for the
predation of the Great Homed Owl. Otto Borg, a
veteran trapper in the Ft. Assiniboine country reports
that he saw three instances of this action during the
winter of 1954. In years of low Snow shoe Hare
populations the Homed Owl is doubtless driven to
taking what it can.
Fig. 44. Remains of Great Gray killed by Great
Horned Owl in Corbett Creek area.
88
DIFFERENTIAL WHITE CELL COUNT AND RHP CELL COUNTS ON
GREAT GRAY OWLS
Thred captive birds were submitted to Dr. C. Bigland
of the Provincial Veterinary Laboratory in order that a
fed cell count and a white cell differential could be
performed. The birds were identified in this manner.
#1 Male Very weak and thin
#2 Female Quite thin and losing both weight and
appetite .
#3 Male Normal and robust
Red Sell Count
#1 Male
1,160,000
per cu. mm.
#2 Female
1,710,000
per cu. mm.
#3 Male
2,010,000
per cu. mm.
The specimens in poorest condition showed
cell count.
White Cell Differential
the lox-jest
Male #1
Female #2
Male #3
Heterophils
70 %
86%
19%
Basophils
1 %
2%
6%
Eosinophils
8%
0%
1%
Lymphocytes
& Monocytes
21 %
12%
lk%
A total white cell count is not included as this is
most difficult to do in birds because of the existence of
nucleated red cells (Sturkie, 1954)*
-
*
■ ' ' '
.
.
89
PARASITES AND DISEASES
Parasites
1* Two well preserved specimens of feather lice
(Mallophaga) were taken from the body of a bird
shot at Anzac, Alberta, Provincial entomologist
J, H, Brown kindly forwarded the specimens to Dr,
K, C, Emerson, University of Oklahoma, Stillwater,
Oklahoma, for identification. His determination
was the genus Kurodaia with no species as yet
named. Of the several Great Gray Owls examined
for this parasite, only the bird from which these
specimens were taken possessed any,
2, Seventeen round wormd were taken from the abdominal
cavity and the small intestinal tract of a Great
Gray Owl shot at Sangudo, Alberta, The round wormd
were identified by Dr, L,P,E, Ghoquette, Institute
of Parasitology, Ottawa, as of the genus Porroc caecum
spp. They have been reported from species of owls
from many parts of the world. The bird was in poor
condition*
3, Blood smears from a deceased captive specimen
revealed a number of letikocytozoons • At certain
stages in the development of these parasites there is
considerable amount of liver damage. This particular
bird revealed a much distended gall bladder and numerous
03 O'
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90.
hemorrhages in the liver tissue. A few coliform
bacilli, Staphlococcus gibus, and an ft 3$ negative
paracolon bacillus were isolated during the post
mortem examination of this bird, kindly conducted
by Dr. Bigland of the Provincial Veterinary
Labo ratory .
4. While performing a red cell count on a live G-rsat
Bray Owl, Dr. Bi gland noted that a large number of
inclusion bodies could be seen within some of the
red blood cells. These were believed to be parasites,
either Haemoproteus or an avian form of Plasmodium
spp . .
Disease s
1. Microscopic examination of the faeces from a bird
shot near Sangudo , Alberta, revealed several coccidial
oocysts. Goccidiosis is a disease infecting the small
intestine caused by the Coccidium sp. .
2. Post-mortem examination of a captive bird revealed
that death was due to Aspergillosis. This disease is
caused by a common fungus, Aspergillus f um la at us .
The symptoms are a shortness of breath and a quick
heaving of the body, especially the lower part of
the abdomen. If the mouth is examined a white cheese¬
like deposit may be seen. It is interesting to note
that almost every Goshawk ( Astur atricapillus ) kept
by the author for falconry, eventually has succumbed
to this disease. The fungus is apparently already
9
■
.
'
.
Ut t •
/'■'■> 1 .1
■
J
.
• . i i '
91.
active internally at the time of capture. The
time for its advance through the bird's internal
system varies. This particular owl had been in
captivity for a month and was eating well but Dr.
Bigland believes the bird had been infected for some
time prior to capture. A dose of four grains of
phenothiazine for each pound of body weight has
met with some success in treating this disease in
Goshawks .
ECONOMIC STATUS
G-ene rally the Great Gray Owl remains in wilderness
regions where its small mammal eating habits will have
no direct effect on agricultural activities. However,
its quite evident 'bousing" habits would make the birds
desirable even in settled fanning areas. No substantial
evidence has yet been unearthed to convict these birds
as Red Squirrel killers. The few game birds such as
Ruffed and Spruce Grouse that the owls may take, makes
not the slightest difference to the over-all game bird
population, especially when considered in the light of
the cyclic fluctuations of game bird numbers.
CONCLUSION
The Great Gray Owl is now so rare a species that
it deserves protection under all circumstances, regardless
of its habits. It is harmless and interesting and much
remains to be learned about it. This task becomes
.
.
.
.
■
92
increasingly difficult with the numbers steadily
diminishing. The owls still have a vast breeding
range left, and only complete protection through
enforced legislation will ensure the survival of
America1 s largest but least known owl.
On the basis of the material presented in this
study it is evident that this bird is primarily a
small mammal feeder, and as such should be encouraged
as a beneficial, species.
The limited data offered in this investigation
would suggest that predation by man is the critical
factor endangering the population of this species in
the province, illthough vulnerable to other forms of
predation and disease, the birds do not appear to be
seriously threatened by these factors.
It is suggested that only complete protection
for all birds of prey, including the common and the
rare, will ensure a population of the Great Gray Owl
in Alberta
,
5
*
*
.
-
93
OBSERVATIONS ON OTHER SPECIES OF OWLS IN ALBERTA
The .oar red Owl ( Strlx yaria. )
This species has always been considered as an
accidental in Alberta, In the course of this investi¬
gation enough records of the Barred Owl have emerged to
suggest that it is a resident species, ^ilk*s (personal
correspondence) collected records show only four
previous occurrences in Alberta, They include a bird
collected from Kvass Creek, near Smoky River about 120
miles north of Jasper, on August 9bh, 194-5 by the
Twomey-Mellon party, Preble (194-1) beard one near Pt.
McMurray, May 1934-5 bhe basis for Bentfs Ft, McMurray
record in his volume on the owls of America, There is
a specimen in Cornell University taken at Calgary
February 12th, 1912, Barney Hamm of Sexsmiti; in th©
Peace River country reports that a neighbor shot a
Barred Owl in the fall of 1952, Hamm saw the bird and
is familiar with the species.
The following records must now be added to the
Alberta list (Fig, 4-8*)
1, May 11th, 1953- A single feather from the breast
of a Barred Owl was found in an area of dense
muskeg approximately fifteen miles north-west of
Corbett Creek,
♦
.
,
,
.
. <
. ■
.
94*
2# December 18 th, 1953® A dead male Barred Owl was
brought to me by Indian trapper John S# Jacobs of
Calling Lake, The bird had perished in a weasel
set. The mounted specimen is now in my possession
(Pig# l\h) » Weight, measurements and stomach contents
were as follows:
Weight
2? o z s ♦
Length 5 02# 2 5 mm#
Wing " 339*75 wni.
Wing Span 1004*5 mm#
Stomach Contents 3 Bed-backed Mice
( C 1 e thr 1 onomy s gar>p eri )
1 Cinereus Shrew ( Sorex
clrereus )
3# March 27 th, 1954® H#E* Junck of Grosmont forwarded
a dead female which had been shot by a trapper twenty
miles west of Fawcett# The mounted ecimen. is now
in the collection of E#T# Jones, Edmonton# Weights,
measurements and stomach contents were as follows:
Weight 26 ozs *
Length 490 mm#
Wing 441# mm.
Wing Span 1053 « 5 mra.
Stomach Contents Remains of one Plying
Squirrel ( Glaucomys sabrinus )
4# March 1954® A pair of Barred. Owl feet were discovered
in the collection of a pole trapper near Cross Lake,
east of Fawcett#
.
„
95
The bird had been taken in a trap set on a pole
near a runway housing tame rabbits and pigeons, (Pig. 4-2) •
5« April 11th, 1954-* While cruising heavy t.imber country
in the search for Great Gray Owls, about 39 miles
west of the village of Platbush, a Barred Owl was
observed in heavy black spruce timber along the
Akuinui Greek* Mr* E.T. Jones, E&nonton was able
to obtain several feet of colored movie film of the
bird. Dr.O. Hohn and Mr* William McKay of Edmonton,
also observed the bird.
6. April 28th, 19 54-* The bodies of two dead Ba.rred Owls
were seen hanging from the back porch of Mr. Guy
Miller* s cabin in the Obed Lake area. They had bem
partly skinned in an amateur attempt at taxidermy.
Both skins were secured. One bird was determined to
be a female and the mount is now in the collection
of W.R, Salt of Edmonton (Pig. 4-6), Sex determination
of the other bird was impossible but a presentable
mount is now in the collection of M. Houle of Edmonton
(Pig. 4-6 )« Both were taken in weasel sets north of
Obed. Lake ,
7® May l^th, 1954-* A dead Barred Owl was found in the
Saunders area west of Rocky Mountain House (Pig. 4-5) ,
not less than forty-five feet from the base of a
large black poplar containing a nest of Great Gr§>r
Owls, The bird was too badly decomposed to enable
a sex determination or cause of death.
.
' , ■
.
■
♦
*
, •
96
Pig* 45. Remains of Barred 0x^1 found near site
of Great Gray nest at Rocky Mountain House.
Pig. 46. Mounted Barred Owls of specimens
collected in Alberta.
97
8. February 1955* Mr, Helge Carlson, a trapper at
Goose Lake, west of Ft, Assiniboine reported catching
alive, in a weasel set, an owl with dark eyes and
without horns or ear tufts. The owl was taken to
Carlson* s cabin on the lake and left over-night, in
a state of exhaustion, in an open roofed fox pen. The
bird had disappeared by morning but feather traces
were unmistakably those of a Barred Owl,
9. April, 1955* I received from Mr, Guy Miller at
Obed Lake another skin of a recently trapped Barred
Owl, The raw skin was sent to Mr, Earl Godfrey of
the National Museum, Ottawa, in fulfi lment of a
request for such material in order that the subspecific
status of these birds might be determined, Mr, Godfrey
subsequently wrote to inform that the owl was a
Northern Barred Owl ( Strlx varia varla Barton). The
skin showed no difference from the northeastern
subspecies, and one skin from British Columbia proved
to be the same (Godfrey, personal correspondence).
The stomach yielded remains of a Snox^shoe Hare.
10. May l8th, 1955* A Barred Owl was observed three
hundred yards from the very area where the first
feather of uhis species nad. been found in 1933*
11. May 20th, 1955* The call of this species x^as heard
in the vicinity of the Great Gray nesting site near
Edson
98
Pig *[{-7. Nest box set out for Barred Owls,
Nest Boxes
In an attempt to produce the first nest of this
species for Alberta, a total of twenty-two nest boxes
(Pig, !l7 ) , were set up in the various areas where the
birds had been recorded. Barred Owls have been
successfully induced to nest in such boxes in eastern
Canada and the United States (Bent, 1938).
The first check revealed no nesting Barred Owls but
four had been inhabited by Yellow- shafted Flickers, two
by Mountain Bluebirds, three by Red squirrels, one by a
Plying squirrel, and four had. been torn down by inquisitive
99
black bears. Five had succumbed to the elements
and three remained untenanted and undisturbed.
Conclusion
Reports continue to be received from observant
woodsmen i^ho describe an owl answering to the description
of this species, from many areas throughout northern
Alberta. Many have accurately described its voice,
and there is no reason to doubt, especially on the
evidence already outlined, that the species has a
general distribution throughout northern Alberta.
With the advent of more, competent field observers,
there is reason to believe a nest will be discovered
for the first time in Alberta. Its preference for
heavy timber in remote .areas has undoubtedly been
the major reason for the fact that the bird has
hitherto almost totally escaped observation and may
yet prove to be a relatively common bird in the
province.
-
*
«■
I ■
'
-
100
101
The Snowy Owl (Nyctea nyctea)
This species is a winter visitor to Alberta, arriving
as early as September and remaining as late as May,
The chief concern with Snowy Owls was banding. Very
few of these birds have ever been banded during their
winter movements and consequently little is known of
their routes to and from the Arctic breeding grounds.
In the interest of banding as many birds as possible,
none were collected for stomach analyses although a
thorough study of the bird*s food habits in the province
is badly needed to ascertain its economic status and
supposed game depredations. Food analyses for this species
from castings or pellets are difficult for the reason that
fresh or drifting snow makes recovery of sufficient pellets
uncertain. Furthermore, the majority of birds are
Incessantly moving about.
Prior to release after banding, the birds were
weighed (Table VI) and the color of the plumage noted.
This was an attempt on the basis of weight to corroborate
a sex identification long since determined by field
collectors from sexed skins; that the light plumaged
birds were males, and the dark birds females (Gladden, 193^ ) *
As with most raptors the female is always considerably
larger than the male.
Method of Trapping
A special trap (Fig. 49) was designed, which facili¬
tated capture of the birds wl thout injury. An owl was
approached, normally within four hundred yards and while
*
■
*
t
*
'
*
*
102.
an assistant set up the trap which was baited with a
dead pigeon, a live pigeon was allowed to flutter
while attached to a thirty foot cord. When satisfied
that the owl had seen the fluttering bird a hasty
withdrawal was made with the live pigeon. The owl, if
hungry, would fly immediately to the spot and pounce
upon the dead pigeon, thus releasing the spring action
of the trap and instantly throwing both meshed sides
over.
Fig. 49. Snowy Owl caught in specially
designed trap.
SNOWY OWL WEIGHTS AND PLUMAGE COLOR
103
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Summary
1# Twenty- three birds weighed four pounds or over
and averaged four pounds eleven and one half
ounces. These were all of dark plumage and
considerably darker than the (Fig. £0) twelve
remaining birds which weighed under four pounds
each. It may thus be assumed on the basis of
xtf eight that the birds were females,
2, Twelve birds weighed under four pounds and
averaged three pounds ten ounces. These were
all of lighter plumage and in three cases (Fig.
51) almost totally white. The weight difference
would suggest that these x^ere the male birds.
3. The average weight difference between males and
females is 15>.8 ounces, .with the female the
heavier bird,
Lj.. Additional measurements of Snowy Owls were
unobtainable due to all work being done in the
field. The severity of the weather and the
combativeness of the species combined to make the
task of taking accurate measurements impossible.
Four Year Cycle of Snowy 0x4 Mo vernal ts
In reviewing the literature of Snox^ry Owl southward
movements it is seen that in many instances peak numbers
have followed, intervals of four to five years or
*
.
-
»
105
multiples of that length of time. Gross ( 19 27- 31“ 47 )
states that this cyclic periodicity is correlated with
the established periodic abundance of Arctic Fox (Elton,
1942) and lemmings in the north. Gross recorded peak
numbers for Snowy Owls during migration in 1945 and
allowing an average of four years for the build-up of
another peak this should have occurred in 1949 and
again in 1953® This was confirmed from personal
observation in northern Alberta for those years. Snowy
Owls were exceptionally numerous throughout the winter
of 1949-50 and again in the winter of 1953-54* when as
many as twenty-eight were observed in one day in the
Morinville area,
A congregation of numbers for a return movement
has been observed in Alberta, From the middle of March
until their departure for the north, these owls gather
in certain areas in such numbers as to become up to
three times as numerous there as in previous months.
The Morinville area north of Edmonton is particularly
notable in this respect. An almost daily check of this
area during March and April, since 19 4^* offers evidence
that a build-up for a return movement takes place during
that period. Gross (1947) suggests the build-up for
the return movement as a possibility, and the above
observations seem to establish this as a fact.
106.
Pig. £l« Male Snowy Owl showing whiter
plumage. (Prom Life)
Pig. 50. Female Snowy Owl showing darker
plumage. (Mounted Specimen)
107
Banding Recoveries
On January 10, 1955> a female owl wearing band
No. 509-02669 was captured in the Morinville area, at
a weight of 4 lbs. 10 ozs.. A check of records revealed
the bird had been banded exactly one mile from the spot,
on March [}_, 19 and the weight was identical.
The Greet Horned Owl ( Bubo virgin! anus )
Introduction
This bird is still very common in the province,
although its numbers vary noticeably from year to year.
Detailed studies have been made on this species in many
parts of its North American range (Bent, 19 38; Errington,et al,
1946) but no extensive investigations have as yet been
made in Alberta. Again a much broader study of food
habits is necessary before 'the controversy over its
economic status can be cleared up.
The observations of this p ecies during the present
study (1952-55) Provided the following information.
Eight nests found in 1952 in the FI at bush district,
all contained the remains of Snow shoe Hares. Thirteen
nests discovered in 1953 similarly provided exclusively
Snowshoe Hare remains. These nests were all in the
northern part of the province in heavy timber. Six nests
found in 1954 contained a variety of contents. Two were
located west of Edmonton and had remains of Pheasants
and Ruffed G-rouse. White-footed Deer Mice and Short¬
tailed Meadow Voles were collected from all six. A
Pocket Gopher occurred in two others.
.
'
.
.
108.
This was a "minimum" year for Snowshoe Hares and very
few remains were found in any of the nests •
Five nests located in 1955 were all in the Edmonton
district, and as is common for this species in low Snowshoe
Hare years, the owls were feeding on a variety of quarry, A
list of food remains found in or near these nests on a
single trip in which all were visited is as follows:
3 Mallard Ducks ( Anas platyrhynchos )
3 Coots ( Fulica airier ic ana)
2 Pheasants ( Phasianus colchicus )
1 domestic chicken
Several Short- tailed Meadow Voles ( Micro tus
pennsylvanicus )
2 Pocket gophers ( Thomomys t alp o ides )
2 Short- tailed weasel ( Mustela ermine a)
In contrast, pellets taken from a single nest in the
Flatbush area In 1953 contained parts of the following:
4 Adult Snowshoe. Hares ( Leo us am eric anus )
14 immature Snowshoe Hares
1 Red Squirrel ( T ami a s c luru s lands onic us )
2 Short-tailed Meadow Voles (Micro tus pennsylvanicus )
1 White-footed Deer Mouse ( Peromyscus manlculatus )
Stomach Analyses
A report or stomach contents for ten birds examined
between 1952-55 is listed in Table VII,
T OMAGH ANALYSES OP GREAT HORNED OWLS
109
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110
Conclusion
The diet of the Great Horned owl is largely determined
by availability depending on its range, the phase of the
rabbit cycle, and the abundance of "buffers” • Of the ten
stomachs examined, six contained mammal remains, two had
bird remains and two contained unidentifiable remains.
This list is far too limited to permit any definite con¬
clusions as to actual food preferences.
Unlike so many of the other owls, this bird is
comparatively wary and appears to be maintaining a sub¬
stantial population in Alberta.
Ill
The Hawk Owl ( Surnla ulula)
This species is now extremely rare in Alberta. Thirty
years ago the bird was relatively common in all the muskeg
areas of Alberta (Henderson, 1919)* Its decline since that
lime has baffled ornithologists (Beebe, personal correspon¬
dence). Some lay the blame on failing mouse and vole
numbers, while others attribute it to persecution by man.
The birds have the same trusting nature of the Great Gray
Owls, and doubtless many are wantonly shot. However, the
Hawk Owl lacks the conspicuous size of the Great Gray Owl,
making it less liable to predation by man. It would seen
that some other explanation for the scarcity of this
species seems probable.
In 195>1 Hawk Owls x^ere again noted in limited numbers
in many of the muskeg regions north and west of Edmonton.
By 1954 they had virtually disappeared and at the present
time are once more scarce throughout Alberta.
The following are records for this species made in
the course of this study:
1. April 2l}.th, 1952. A nest containing six eggs was
discovered west of F3a tbush. E.T. Jones of Edmonton
procured considerable color film footage of the birds
at the nest and reported that they preyed exclusively
on small mammals.
2. July 20 th, 1952. Two Hawk Ox-7 Is xjere observed in a
large muskeg near Chisholm, Alberta.
-
„
, *
112.
3* December, 1953* A single male bird was collected in
the Rocky Mountain House district by Ranger J.
Williams and forwarded to the University of Alberta
Zoology Department.
hr, February, 1954* A pair were brought to the local
taxidermy shop. the birds were diot in muskeg
southwest of Grande Prairie and were in breeding con¬
dition.
5* March, A single bird was observed twenty miles
north of Ft. Assiniboine on the edge of a large muskeg.
6. January, 195b* A specimen was sent from Whitecourt,
having been shot on the outskirts of the village, ‘^he
stomach contained two Short- tailed Meadow voles.
7® February, 1955* A single bird was again observed in
the same location as noted in report No, 5> .
8. February, 1955* Another specimen was forwarded to the
local taxidermy shop after being shot near the town of
Slave Lake.
9» April, 195>5>® A pair of breeding birds were shot in
muskeg country near the village or Wandering River,
Alberta, by a. local trapper.
0 one Ins ion
The extreme scarcity of this species in Alberta and
its habit of preying on small mammals make it a. desirable
species and worth protecting.
-
.
*
.
-
*
-
,
...
,
*
,
.
*
.
113
Richardson1 s Owl ( Crypt oglaux f unarea richardsom )
Introduction
This species has never been abundant in Alb erta.
Henderson (1931) found only four nests, Randall (19 29)
one, and Rowan (1929) another* In the course of this
study five occurrences of this bird were noted as
foil ows :
1* January 1953* A male bird was killed in a pole
trap near Barrhead*
2* March 19 54* A female was sent from Anzac, Alberta
having been shot by an Indian trapper*
3* March I95>ll-* A single specimen was observed in
heavy spruce woods north of Spruce Grove, Alberta*
It held a partly eaten Redpoll in Its claws.
4* April 195b* Another dead female specimen was sent
from Anzac .
5* July 1st, 1955* An immature bird was captured near
the Tamarack Creek in the Swan Hills. The bird
appeared almost blind in the bright sunlight and
easily allowed, itself go be snared with a nylon
noose on the end of a fishing pole. The bird was
taken unharmed and thrust into a knapsack but
unfortunately escaped. Pellets collected from
this specimen contained parts of the follox^ing:
1 Pigmy Shrew (Micro sorex hoyi)
1 Saddle- back Shrew (Sorex arc ileus )
2 Red-backed Mouse ( C 1 e t hr 1 onomy g gapperl )
m
It is interesting to note that the Pigmy Shrew
is rarely collected, particularly in Alberta.
Conclusion
Although the rarity of this species makes its economic
influence insignificant, it should be regarded as a bene¬
ficial type. Its inability to see well enough to capture
food in daylight, and its small size discount it as a
menace to game birds.
I he S aw- t ~ he t Gw 1 (Cryptoglaux acadia)
No new information on this species can be contributed
in this study to the extensive existing knowledge, the
bird cannot be considered rare In Alberta but its
nocturnal habits and small size make it a difficult species
to encounter, much less to study. During the course of this
study on owls generally, it was noticed that Saw- whets have
been on the increase since 195>2.
The following records x^ere obtained from 1952 to
1955:
1. February 1, 1953* A live male was sent from Westloek
where it had been captured in a barn. It subsequently
died in captivity.
2. March, 1954* A live bird was sent from Stony Plain,
having been picked up on a road near the town. This
specimen, like most Saw-whets captured alive, ate well
but was dead within a week. Rowan says this is
115
characteristic of Saw-whets that have allowed an easy
capture. Post-mortem analysis by Dr. Bigland revealed
nothing conclusive.
3. July 1, 1955. A nest containing four eggs was located
near Beaumont, Alberta. This is an extremely late
nesting date for the species. No detailed study of the
nest was undertaken. Pour young from the nest are
shown in Fig. 52.
Fig. 52. Young Saw- whet Owls
116
Conclusion
This species apparently fluctuates in numbers
from year to year. It is not known to be migratory.
The comparative rarity and diminutive size make it
a negligible threat to game. Studies elsewhere (Bent,
1938) indicate that it is predominantly a small
mammal feeder and this is apparently also the case
in Alberta. The species should be considered beneficial.
The Screech Owl ( Otus asio )
Introduction
Only two previous records for the species
existed in Alberta prior to this study. These were
sight records by A.D. Henderson, the veteran oologist
of Belvedere, Alberta (I9I4.I, 1955)*
The following new records are herewith submitted:
1. October 21, 1954* A live specimen was captured
(Pig. 53) in the Swan Hill country north of Ft.
Assiniboine, The skin was forwarded to the
National Museum for subspecific identification.
.Mr. Godfrey was unable to name the specimen but
felt that an undescribed race might be involved.
2. August, 1955* On. Win. Rowan received another
specimen found dead on the highway near Lesser
Slave Lake. The bird was a juvenile male, red phase.
'
*
,
* .
-
.
.
.
V
117
Cone lus Ion
With only four authentic records to date, for
the species in Aluerta, it would be premature to
assume that the Screech Owl has established itself
in the province. Further investigation with additional
records is required before an accurate assessment can
be made •
Fig. $3* Screech Owl captured in Swan Hills
118.
119
SUMMARY;
1. The Great Gray OxYL ivras first described by J.R. Forster
from an immature bird collected near Severn River,
Ontario, in 1772.
2. A recognized Old World subspecies, the Lapp Owl, differs
only slightly from the Great Gray in being lighter in
color and with more noticeable longitudinal markings
on the breast,
3* A four year study of the Great Gray Owl in Alberta,
from. 1952 - 55* produced fourteen dead specimens,
four live birds shipped to the author, and two nests
each containing two young which provided the basis for
the study,
4. When compared with the Great Homed Owl it was seen that
the Great Gray possessed considerably smaller and weaker
feet, a larger head, but a very similar intestinal tract.
5* The sternur^ shoulder girdle and correlated muscles of
the Great Gray Owl are much smaller than corresponding
structures in the Great Horned Owl.
6. The extreme softness of the Great Gray Owl*s breast
plumage and upper back feathers is due to the length of
these feathers and the f ewer b arbs and barbules as com¬
pared with those of the Great Horned Owl,
7. The feather tracts are described. The inferior branch
of the ventral tract differs from the typical arrangement
for disc-faced owls as described by Hitzsch & Burmeister
(I8I4.O).
'
, -
.
*
. ■ I
■ .
.
.
.
.
rt ft
120
8. The molt observed on a captive bird commenced in late
June and the feathers appear to drop in a definite
sequence. The Great Gray Owl lacks the fifth secondary
and is said to show diastataxy or acquintocubitalism.
9. Great Gray Owls have been recorded nesting from Alaska
to the Yosemite Valley of California and east to
Northern Quebec and Ontario.
10. Winter movements have been recorded for the species but
any regular movements ceased to be noted from 1900
onwards .
11. Three young Great Gray Owls were banded in 1954* Only
two previous banding records for this species are
recorded in the files of the U.S. Pish and Wildlife
Services.
12. There is no information to indicate that Great Gray Owls
build their own nests. They prefer to use a structure
previously built by some other species of raptor.
13. Great Gray nesting sites are in heavy poplar woods and
invariably near an extensive muskeg.
1L}_. The birds become quite vociferous during the nesting
season and the male emits a droning noise when rubbing
his bill with that of the female during their courtship.
l^. An average clutch numbers three and the eggs are laid in
late March or April.
16. The birds will assume the defensive attitude and
threateningly hunch their backs and call faintly
but rapidly when reacting to intruders. They have not
been known to attack at the nest.
121.
17. Both adults and young have distinctive calls which
are only uttered under certain conditions.
18. The male appears not to share any of the incubation
duties but is occupied in obtaining food for the
incubating female and later for the young.
19. At twenty- one days the young stand up in the nest and
are becoming active. At forty days they have left the
nest.
20. In graphing the measurements of young Great Gray Owls,
the length of the cere remains almost constant for the first
four weeks. An other measurements show a gradual, but
variable increase.
21. This species preys principally on small mammals, particu¬
larly mice and voles.
22. Man is the chief enemy of the Great Gray Owl. Great
Horned Owls will attack and kill the lighter Great Gray
Owls .
23. The birds possess a number of parasites including feather
lice, round worms, leukocyte zoons and malarial protozoa.
Coccidiosis and aspergillosis were also discovered in
this species.
2I4.. Owing to its scarcity, food habits and general inoffensive¬
ness, the Great Gray Owl merits full protection.
Other Owls
25. Snowy Owls are common winter visitors in Alberta with
years of varying numbers. The males are approximately
a pound lighter than the females and much whiter in color.
122
26, Alberta appears to have an established Barred Owl
population. Eleven new records for the species,
uncovered in this study are evidence of this.
27* The Great Horned Owl’s economic status in this province
is still open to debate. Its food habits are apparently
determined by its range, the availability of quarry,
particularly the cyclic phase shoe s .
28. Haw’.: Owls, Richardson's Owls and Saw- whet Owls offered
only very limited opportunities for observation and
study in the course of this investigation. It was
evident that they are relatively rare birds with the
Hawk Owl particularly so.
29, Two new records for the Screech Owl were also added to
the Alberta list. Both are the first specimens procured
in the Province
123
ACKNOWLEDGEMENTS
I should like especially to express my sincere
appreciation to Dr. Wm. Rowan for his supervision,
advice and kind assistance in securing essential
reference material.
To Mr. E.T. Jones I owe a particular note of
thanks for his invaluable assistance in the field
throughout most of this study.
Special thanks are due to Dr. C. Eigland and
staff of the Provincial Veterinary Laboratory for
numerous pathological studies and post-mortem
examinations on material submitted. Dr. Bigland
kindly assisted on all problems of anatomy.
I am thankful for the financial assistance
rendered by the National Research Council in helrjing
to defray the travelling costs of this investigation.
To veteran oologists A.D. Henderson and T.
Randall, I am most indebted for the kind use of their
excellent notes and advice; to Dr. Heinz Meng f©r
valuable suggestions on the outline; to the Edmonton
Bird Club for financial aid in the printing of the
brochures; to Mr. K. Hutchinson, Provincial Film
Commissioner for placing the services of his highly
trained staff and equipment at my disposal; to Mr.
Hugh HaLliday of the Toronto Star for his timely
newspaper appeals; to Dr. J.E. Moore for countless
hours spent in stomach and pellet analyses, go my
humble thanks and appreciation.
Finally, I wish to acknowledge the fine companion¬
ship and superb field assistance of Mr. Wm. McKay,
particularly in the task of banding Snowy Owls which was
often painful and tedious.
125.
REFERENCES
1. Allen, F.H., 19 OLj_, The Great Gray Owl Near
Boston, Auk, Vol. 21, p 278.
2. Baillie, J.L., 1947* Largest Owl a Visitor,
Excerpt Toronto Evening Telegram,
3. Bent, A.C., 1938, Life Histories of North American
Birds of Prey, Part 2, Orders Falcon if ormes
and Strigiformes. Bull, U.S. Nat. Museum
No. 170.
4-. Bendire, C., 1892, Life Histories of North
American Birds, Smithsonian Inst., Spec.
Bull. No. 1, pp 345-348.
5. Cones, E. , 1903* Key to North American Birds.
Two Volumes, Dana Estes & Co., Boston,
6. Elton, E. , 1942* Voles, Mice and Lemmings, Oxford
at the Clarendon Press.
7. Errington, P.L., Hamerstrom F. and Hamerstrom F.N.
Jr,, 1940* The Great Horned Owl and Its
Prey in North-Central United States, Res.
Bull., State College, Ames, Iowa,
8. Fisher, A.K., 1893* Hawks and Ox^ls of the U.S,,
U.S® Govt. Biol. Survey, pp 157-158,
9* Forster, J.R», 1772, ( S tr lx nebulo s a ) Philos, Trans.
LXII, Art. 29, p 424
'
126
10. Gadow, H. and Selenka, E. , 1891* Anatomie der
V6*gel, Leipzig, C.F. Wintersche Verlagshandlung.
11. Gladden, G. , 193&* Color of Great Gray and Snowy
Owl in Birds of America, edited by G.T.
Pearson, Garden City Publishing Co., Garden
City, N.Y., pp 105-106, p 115.
12. Gross, A.O., 1927* Snowy Owl Migrations, Auk, Vol.,
44* PP 479-493*
13* > 1933* Snowy Owl Migrations, Auk, Vol.,
48, pp 501-511*
14* * 1947* Snowy Owl Migrations, Auk, Vol.,
64, pp 584-599.
15. Hagen, Y. , 1952, Rovfuglens og Viltpleien, Oslo
Gyldendal Norsk For lag, pp 399-410.
16. Hartert, E. , 1920, Die Vo*gel der palaarktischen
Fauna, Band 2, pp 1014-101?* ( Erganzungsband
Heft 1), p 392, 1932.
I?. Henderson, A.D. , 1915* Nesting of the Great Gray
Owl in Alberta, Oologist Vol., 32, pp 2-6.
18. , 1919* Nesting of the American
Hawk Owl, Oologist Vol., 36, pp 59-63.
19. * 1923* Further Notes on the Nesting
of the Great Gray Owl, Oologist Vol., 40*
pp 126-127 •
20. , 1931* Richardson* s Owl, Unpublished
Field Notes.
, 1941* Screech Owl in Alberta,
21
127
Cano Field Nat., VoL, 5>8, No. 4, p D.l2.
22* Holstein, V. , 1942* Duehogen, Astur gentlllis
dubius (Sparrman), H. Hirschsp rungs Forlog.
Kobenhave (Life History).
23. Huxley, J.S., 19 14.O , The New Systematic s, Oxford,
Clarendon Press.
2l|« Macoun, J. and J.M., 19 09, Catalogue of Canadian
Birds, Can., Dept, of Mines, pp 295-296.
25# Meng, H., 195>1> The Cooper* s Hawk, Ph. D. Thesis,
Cornell University, Ithaca, N.Y.
26. McFarlane, R. , 1908, Notes on the Mammals and Birds
of Northern Canada, Wm. Briggs, Toronto, p 41^6.
27. Moss, E.H. , 19 53 i Marsh and Bog Vegetation In
Northwestern Alberta, Vol., 31, No. J4, Can.
Journal of Botany, pp 448-470.
28. Munro, J., and Cowan, J.M., 1947> The Bird Fauna
of B.C., B.C • Prov. Museum, pp 127-131.
29. Nitzsch, C.L., and Burmeister, C.C.H., 1840, System
der Pterylographie. (English Translation by
P.0. Sclater in 1867* Hay Soc., London.)
30. Preble, E.A., 1902, North American Fauna, No. 22,
P 109.
31. , 1908, North American Fauna, No. 27 ,
Washington Govt. Printing Office, pp 388-369.
32. , 19 41* Barred Owl on Athabaska River,
Alberta, Auk, Vol., 58, No. 3, pp 4°7-4°8.
128
33* Pycraft, W.P., 1910, A History of Birds, Methuen
and Co., London.
34-. Randall, T. , 1920, Great Gray Owl, Unpublished
Field Notes.
35* _ _ , 1929* Richardson1 s Owl, Unpublished
Field Notes,
36. Ridgway, R. , 1914? The Birds of North and Middle
America, Vol., 6, U.S. Nat. Mus., pp 635-
636.
37* Roberts, T.S., 1932* The Birds of Minnesota, Vol.,
1., University of Minnesota Press, pp
624-626.
38. Rowan, ¥. , 1929* Richardson1 s Owl, Unpublished
Field Notes,
39* Streseman, E, , 1934? Vol., Aves of Eukenthal und
Erunibach, Handbuch der Zoologie, Walter
de Gruyter, Berlin.
40. Sturkie, P.D*, 1954? Avian Physiology, Comstock
Publishing Associates, ithaca, N.Y.
41. Taverner, P.A., 1912, Great Gray Owl Breeding in
Chisholm, Nipis sing District, Ontario,
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129
PERSONAL CORRESPONDENCE
1. Amadon, D. , New York City, N.Y. Curator of Birds,
The American Museum of Natural History,
New York,
2, Bard, P, , Regina, Saskatchewan. Curator, Provincial
Museum of Natural History, Regina.
3* Beebe, P, , Victoria, B.C. Chief Illustrator,
Provincial Museum, Victoria, B.C.
4* Bleitz, D. , Los Angeles, California, President,
Bleitz Wildlife Foundation.
5>. Cade, T. , Glendale, California. Research Biologist,
State Game Commission.
6, Craighead, J., Missoula, Montana. Director, Montana
Cooperative Wildlife Research Unit.
7* Duvall, A., Laurel, Maryland., Research Biologist,
Patuxent Research Refuge, Laurel, Md.
8. Godfrey, W. , Ottawa, Ontario. Biologist, National
Museum of Canada,
9. McDonald, W. , Yellowknife, N.W.T, Amateur Ornithologist.
10, Randall, T., Brooks, Alberta. Veteran Oologist.
11, Wilk, A.L., Camrose, Alberta* Recognized authority
on Alberta birds.
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