_Falco polyagrus_, CASSIN, B. Cal. & Tex. 1853, 88.—IB. P. A. N. S.
1855, 277; B. N. Am. 1858, 12.—HEERM. Pacific R. Rep’t, II, 1855,
31.—KENNERLY, P. R. R. III, 1856, 19.—COOP. & SUCKL. P. R. R. XII,
1860, 143.—COUES, P. A. N. S. 1866, 7.—STRICKL. Orn. Syn. I, 1855,
85.—DRESSER, Ibis, 1865, 323.—GRAY, Hand List, I, 1869, 20. _Falco
lanarius_, var. _mexicanus_, RIDGWAY in COUES’ Key, 1872.
SP. CHAR. _Adult_ (♂, No. 59,063, Wahsatch Mountains, Utah, May 23,
1868; parent of eggs; L. E. Ricksecker). Above cinereous-drab, becoming
gradually paler and more bluish posteriorly, barred, indistinctly,
everywhere with a more dusky tint, the shafts of all the feathers
blackish; anteriorly the darker shade predominates, while posteriorly
the bluish prevails; on the anterior portions the light bars are much
restricted in width, and of a more ochraceous tint. Tail plain, very
pale ashy-drab, narrowly tipped with reddish-white, this changing to
pale rusty on the middle pair; the concealed portion of the feathers
outside the shaft show obsolete, or faint traces of, darker bars, which
on the middle pair are apparently about eleven in number. On the inner
webs the paler bars become broader than the darker ones, and incline
to ochraceous in tint, the lateral feather being edged externally with
this color. Primaries plain ashy-drab, with a hoary tinge, growing
insensibly darker terminally, and with a slightly paler apical margin.
Head and neck above, dark umber-brown, with conspicuous shaft-streaks
of black. Lores, a broad superciliary stripe (somewhat interrupted
above the eyes), white, finely and sparsely streaked, the two stripes
confluent across the occiput; a broad heavy “mustache” from the lores
and rictus downward and obliquely backwards, across the maxilla, and a
wider postocular stripe, like the crown. Beneath continuous white, with
a faint ochraceous tinge on the abdomen and crissum; abdomen and sides
of the breast with a few scattered, small, ovate spots of vandyke-brown;
sides transversely spotted with vandyke-brown, the spots coalesced into
a broken patch on the flanks; outside of the tibiæ with transverse spots
of the same. Axillars plain, clear vandyke-brown, with a few nearly
obsolete rusty specks near their ends; lining of the wing clear white,
the feathers with central spaces of dusky-brown, which toward the edge
become aggregated into a longitudinal patch; inner webs of the primaries
with broad transverse spots of white, which reach nearly to the shaft;
they are about thirteen in number on the longest quill. Feet yellow;
base of the bill tinged with the same. Wing-formula, 2, 3–1, 4. Wing,
12.00; tail, 7.50; tarsus, 1.90; middle toe, 1.70; outer, 1.22; inner,
1.12; posterior, .77.
♀ (not _adult?_ 18,258, Fort Buchanan, New Mexico; Dr. Irwin). Above
continuous umber-drab, growing gradually lighter posteriorly, the tail
being pale drab; no transverse bars (except a few concealed obsolete
ones on back and secondaries), but all the feathers faintly bordered
with paler rusty-brown, these edgings being on upper tail-coverts almost
white. Tail tipped with creamy-white, and with many transverse spots or
broad bars of the same on inner webs, outer feather irregularly skirted
with the same, and all decidedly paler than the ground-color along
their edges. Head as in the male, but forehead white, and superciliary
stripe more continuous. Breast and abdomen with longitudinal lanceolate
or cuneate streaks of dark vandyke-brown; patch of same on flanks
more continuous than in the male; axillars unvariegated clear dark
vandyke-brown; longest primary with eleven transverse spots of white;
posterior outer face of tibiæ with sagittate spots of dark brown.
Wing-formula, 2, 3–1, 4. Wing, 14.25; tail, 8.00; tarsus, 2.10; middle
toe, 2.00.
_Juv._ (♂, 32,207, South Fork of the Platte River, July 19, 1838; C. S.
McCarthy). Above darker umber than the last, each feather distinctly
bordered terminally with rusty-ochraceous. Beneath with a deeper
cream-colored tinge, streaks blacker; flank-patch more conspicuous and
uniform; axillars unvariegated dusky. Wing-formula, 2, 3–1=4. Wing,
13.25; tail, 7.25.
HAB. Western division of North America, eastward to Illinois; Oregon to
Lower California, and Texas. Localities: Texas, San Antonio and Eagle
Pass (DRESSER); Arizona (COUES).
The different stages of plumage are in this by no means so well defined
as in other species, there being nearly the same general appearance in
all. There is, also, very little variation in different specimens of
the same age. No. 8,504, (♀, Dalles, Oregon; Dr. George Suckley) has
the black markings on the sides of the breast more circular, and the
vandyke-black of the axillars with a few circular white spots on the
edges of the feathers. Wing, 14.50; tail, 8.40. Nos. 17,204 (♀, San
José, Lower California; John Xantus, January, 1860) and 18,258 (♂ ? Fort
Buchanan, N. M.) have the upper surface almost perfectly continuous
grayish-drab, the first absolutely unvariegated by markings, though the
feathers fade a little on edges. Beneath, the white is very pure; the
streaks are numerous, sharply defined and longitudinal. Wing, 13.25;
tail, 7.50 (17,204).
The American Lanner Falcon is so very closely related to the Lanners
of Europe and Asia (var. _lanarius_ and var. _jugger_) that it is very
difficult to indicate the differences which separate them. The two Old
World forms above named are more unlike each other than they are from
the two American races; the var. _jugger_ differing from _mexicanus_
apparently only in larger size; and the var. _lanarius_, more like
_polyagrus_ than it is like either _jugger_ or _mexicanus_, differs
from _polyagrus_ mainly in the greater amount of white on the plumage,
this imparting a lighter aspect to the pileum, and causing a greater
development of the light spots on the outer webs of the primaries and
rectrices.
[Illustration: _Falco polyagrus._]
The var. _polyagrus_, compared with var. _lanarius_, is much darker,
having, at all ages, the crown uniformly brown, with darker streaks,
instead of having these streaks upon a white ground. The “mustache” is
more distinct in the American bird, while in the European the bands on
the tail are much more distinct, and the spots forming them are on the
outer webs, as well as on the inner, instead of on the latter alone; the
dark bars between the light spots are in the American bird much narrower
and more numerous, and in the young the light ones come to the edge of
the web, instead of being enclosed within the dark color. Two very young
birds (i.e. in first perfect plumage) appear almost identical until
closely examined, the chief differences being a lighter tint to the
crown in the European, and heavier dark stripes on the breast, besides
the peculiar character of the tail-spots, which are always distinctive.
In shades of color, there is not the slightest difference.
I have seen no specimen of any of the Old World forms in the plumage
corresponding to that transversely barred above, described here as the
adult, though figures of the adult _lanarius_ indicate a very similar
plumage. The series of the latter race at my command is unfortunately
limited to a very few immature specimens. One marked “ad.” (56,051,
Hungary; Schlüter Coll.) measures as follows: Wing, 14.50; tail, 8.00;
culmen, .83; tarsus, 1.90; middle toe, 1.80. Its colors are as described
in the synopsis (p. 1429) for the young bird.
The var. _mexicanus_ and var. _jugger_, which are both much darker, and
more uniform in the coloring of the upper parts, than var. _polyagrus_,
are more nearly alike; in fact, the only tangible difference that I
can find between a specimen of the former in the Museum of the Boston
Society of Natural History (No. 1,438, ♂, Juv. Lafr. Collection;
“Mexico”) and two examples of the latter in the New York Museum,
consist in the larger size of the var. _jugger_ (see synopsis),
besides its whiter cheeks and more isolated and distinct “mustache.”
A direct comparison of these two races may show other tangible points
of distinction, or, on the contrary, may show even these slight
distinguishing features to be inconstant. The former result is, however,
most reasonably to be expected.