_Falco æsalon_, RICH. & SWAINS. F. B. A. II, pl. xxv, 1831.—NUTT.
Man. Orn. II, 558.—COUES, P. A. N. S. Philad. 1866, p. 42 (in text).
_Falco_ (_Hypotriorchis_) _richardsoni_, RIDGWAY, P. A. N. S. Philad.
Dec. 1870, 145. _Falco richardsoni_, COUES, Key, 1872, p. 214.
SP. CHAR. Adult male like the female and young? The known stages of
plumage more like the adult female and young of var. _lithofalco_ (_F.
æsalon_, AUCT.) than like var. _columbarius_.
_Adult male_ (Smithsonian, No. 5,171, mouth of the Vermilion River, near
the Missouri, October 25, 1856; Lieutenant Warren, Dr. Hayden). Upper
plumage dull earth-brown, each feather grayish-umber centrally, and
with a conspicuous black shaft-line. Head above approaching ashy-white
anteriorly, the black shaft-streaks being very conspicuous. Secondaries,
primary coverts, and primaries margined terminally with dull white; the
primary coverts with two transverse series of pale ochraceous spots;
outer webs of primaries with spots of the same, corresponding with those
on the inner webs. Upper tail-coverts tipped, and spotted beneath the
surface, with white. Tail clear drab, much lighter than the primaries,
but growing darker terminally, having basally a slightly ashy cast;
crossed with six sharply defined, perfectly continuous bands (the last
terminal) of ashy-white. Head, frontally, laterally, and beneath,—a
collar around the nape (interrupting the brown above),—and the entire
lower parts, white, somewhat ochraceous, this most perceptible on the
tibiæ; cheeks and ear-coverts with sparse, fine hair-like streaks of
black; nuchal collar, jugulum, breast, abdomen, sides, and flanks with
a medial linear stripe of clear ochre-brown on each feather; these
stripes broadest on the flanks; each stripe with a conspicuously black
shaft-streak; tibiæ and lower tail-coverts with fine shaft-streaks of
brown, like the broader stripes of the other portions. Chin and throat,
only, immaculate. Lining of the wing spotted with ochraceous-white
and brown, in about equal amount, the former in spots approaching the
shaft. Inner webs of primaries with transverse broad bars of pale
ochraceous,—eight on the longest. Wing-formula, 2, 3–4, 1. Wing, 7.70;
tail, 5.00; culmen, .50; tarsus, 1.30; middle toe, 1.25; outer, .85;
inner, .70; posterior, .50.
_Adult female_ (58,983, Berthoud’s Pass, Rocky Mountains, Colorado
Territory; Dr. F. V. Hayden, James Stevenson). Differing in coloration
from the male only in the points of detail. Ground-color of the upper
parts clear grayish-drab, the feathers with conspicuously black shafts;
all the feathers with pairs of rather indistinct rounded ochraceous
spots, these most conspicuous on the wings and scapulars. Secondaries
crossed with three bands of deeper, more reddish ochraceous. Bands
of the tail pure white. In other respects exactly as in the male.
Wing-formula, 3, 2–4–1. Wing, 9.00; tail, 6.10; culmen, .55; tarsus,
1.40; middle toe, 1.51.
_Young male_ (40,516, Fort Rice, Dacotah, July 20, 1865; Brig.-Gen.
Alfred Sully, U. S. A., S. M. Rothammer). Differing from the adult
only in minute details. Upper surface with the rusty borders of the
feathers more washed over the general surface; the rusty-ochraceous
forms the ground-color of the head,—paler anteriorly, where the black
shaft-streaks are very conspicuous; spots on the primary coverts and
primaries deep reddish-ochraceous; tail-bands broader than in the adult,
and more reddish; the terminal one twice as broad as the rest (.40 of
an inch), and almost cream-color in tint. Beneath pale ochraceous, this
deepest on the breast and sides; markings as in the adult, but anal
region and lower tail-coverts immaculate; the shaft-streaks on the
tibiæ, also, scarcely discernible. Wing, 7.00; tail, 4.60.
HAB. Interior regions of North America, between the Mississippi Valley
and the Rocky Mountains, from Texas to the Arctic regions.