Nat. Mus., 10; Philad. Acad., 2; Boston Soc., 2; Coll. R. Ridgway, 2.
Total, 16.
_Measurements._
+----+-----------+-----------+---------+---------+-----------+----------+
|Sex.| Wing. | Tail. | Culmen. | Tarsus. |Middle Toe.|Specimens.|
+----+-----------+-----------+---------+---------+-----------+----------+
| ♂ |15.90–17.00| 9.50–10.50|1.00–1.18|3.10–3.45| 1.40–1.50| 6 |
+----+-----------+-----------+---------+---------+-----------+----------+
| ♀ |17.00–17.60|10.50–11.00|1.08–1.20|3.20–3.40| 1.60–1.65| 6 |
+----+-----------+-----------+---------+---------+-----------+----------+
The variations in this species are very slight, and never sufficient
to mislead the student. One specimen (26,590, ♂; Fort Tejon, Cal.;
J. Xantus) differs from the adults described in having the abdomen
quite closely barred, the streaks on the breast distinct, the
rufous above tinging the secondary coverts, and spreading over the
upper tail-coverts, while the tibiæ and tarsi are of a very deep
ferruginous,—the bars black.
In a specimen from the Platte (5,577, ♂; W. S. Wood) white prevails on
the tibiæ, the bars being dark ferruginous upon a white ground; the
flanks are similarly marked, the other lower parts, however, immaculate;
there is much concealed white on the scapulars. The rufous tinge of the
tail is very deep, while there is a transverse series of black blotches,
indicating the course of a transverse band near the end.
HABITS. The California Squirrel Hawk appears to be an exclusively
western species, occurring as far to the east as Nebraska and Kansas,
and as far to the north as the Plains of the Saskatchewan and Washington
Territory. It occurs as far to the southeast as Texas, and has been
found also in New Mexico and in Arizona.
This species was first noticed and described in a paper on the natural
history of California published in the Transactions of the Royal Academy
of Berlin, in 1838, by Professor Lichtenstein, a Prussian naturalist. It
was first brought to the notice of American naturalists by Mr. Edward M.
Kern, of Philadelphia, who accompanied Colonel Fremont in his expedition
of 1846, and who brought home specimens.
Dr. Coues found it quite abundant about Fort Whipple, where it was
especially numerous in the winter, and where also he thinks it probable
that it is a permanent resident. He found it more generally frequenting
meadows, plains, and the more open woods. He usually found their
stomachs filled with arvicolæ and other small quadrupeds peculiar to
that country. It could always be readily recognized by its conspicuously
white under parts, contrasted with its dark chesnut tibiæ and reddish
back.
[Illustration: _Archibuteo ferrugineus._]
At San Pedro, on the southern coast of California, he again found this
Hawk very common. It there alights very freely on the ground, where he
often observed it. At Fort Whipple he only saw it on trees. At San Pedro
its choosing thus the bare plain may have been a matter of necessity.
Dr. Kennerly observed a single individual of this species in a
“prairie-dog-town” of large extent, near Fort Davis. It was intently
watching at the hole of one of these animals. While in this position,
it was observed to strike at the prairie-dog with its claw, when one of
these animals protruded its head. As it was very intently watching its
prey, it was easily approached and shot.
Dr. Heermann observed this Hawk in the valley of the Sacramento, where
he thought it rather rare, but afterwards, during his connection
with the government surveying party under Lieutenant Williamson, in
the southern part of the State, he found it very abundant. On one
occasion five or six individuals were in view at the same moment,
among the mountains, sixty miles east of San Diego. It was there much
more abundant than any other species. As large tracts of that country
frequented by these birds are entirely without trees, they alight on the
ground or on some slightly elevated tuft of grass, or a stone, where
they sit patiently for hours watching for their prey, which was always
found to consist of mice and other small quadrupeds. In one instance the
crop was found filled with the remains of a ground squirrel.
Dr. Heermann states that he found the nest and eggs of this bird on the
Consumnes River. The nest was in the fork of an oak, and was composed of
coarse twigs and lined with grasses; the eggs were two in number, white
with faint brown dashes. The nest was placed in the centre of a large
bunch of mistletoe, and would have escaped notice had not the Hawk, in
flying, betrayed her retreat.
The eggs, however, differ essentially in size from those mentioned
by Capt. Blakiston, and it is quite possible that Dr. Heermann was
mistaken in his identification. One of these eggs was figured in the
North American Oölogy, and resembles much more an egg of Swainson’s
Buzzard than any egg I have since seen of this species.
The specimens procured by Mr. Kerr were taken in the Tulare Valley,
in January, 1846, and are stated in his notes to have been remarkably
fat, and in excellent condition generally, so that some of his party
shot these birds whenever opportunity offered, for the mess-kettle, and
considered them very good eating.
Dr. Cooper states that in the spring and fall these Hawks abound in
Southern California, migrating in summer through the interior plains
of the Columbia and the Platte Rivers, at least as far north as the
Dalles. He found it in winter at Martinez, and is of the opinion that
few migrate beyond the State. It was usually to be seen slowly sailing
over the plains, sometimes in circles, and occasionally pouncing down
obliquely on its prey, which consists principally of the large ground
squirrel. It rarely, if ever, attacks poultry, and limits its prey to
wild animals, and is therefore a decided friend to the farmer.
Capt. Blakiston met with this bird breeding between the north and the
south branches of the Saskatchewan River, April 30, 1858. The nest was
placed in an aspen-tree, twenty feet from the ground, was composed
of sticks, two and a half feet across, and lined with buffalo wool.
The eggs were four in number. Those taken from another nest near the
same locality were five in number. This nest was in a tree, and was
only ten feet above a lake. Two eggs were taken by Mr. Bourgeau on
the Saskatchewan Plains, July 9. These differences in seasons, from
April to July, are suggestive either of great variations in the time of
nesting, or of there being two broods in a season. The eggs obtained by
Capt. Blakiston measured, one 2.60 by 2.00 inches, the other 2.50 by
1.95 inches, and are described as having been white with large distinct
blotches and smaller specks of two shades of brown. The other was more
obscurely blotched with a paler brown, and at the same time freckled all
over.
An egg of this species taken by H. R. Durkee near Gilmer in Wyoming
Territory, May 9, 1870, measures 2.43 inches in length by 1.95 in
breadth. The ground-color is a creamy white, over which are very
uniformly distributed on every part of the egg, in nearly equal
proportions, blotches, plashes, and smaller markings of a dark burnt
umber. The nest from which this egg was taken was composed of sticks,
and was placed among rocks. The nest contained but one egg. The parent
bird was secured, and there was no question as to identification.
Archibuteo lagopus, var. sancti-johannis (PENN.).