A History of North American Birds, Land Birds. Volume 3. Robert Ridgway

      Sp. Char. Adult (♂, 51,689, Yukon, mouth of Porcupine River; Strachan Jones). Whole upper surface with numerous transverse bands of brownish-plumbeous and ashy-white. Anteriorly the light bars are about half the width of the dark ones; posteriorly they gradually increase, the bands of the two colors being about of equal width on the upper tail-coverts and tail; with the increase of the lighter bars, they become more ashy, and, correspondingly, the darker ones are more plumbeous; on the rump there is but little contrast between the bands of the two, causing a prevalent bluish cast. The bands are everywhere continuous, the light ones being interrupted only by the black shaft; there are generally on the anterior portions about three light bars on each feather, the last always terminal. Tail tipped with white, and crossed with equal continuous bands of hoary-plumbeous and ashy-white; the latter eleven in number, and finely sprinkled with deeper ash. Primaries brownish-plumbeous, plain past the middle portion, but on the anterior half with quadrate spots of creamy white on the outer web. Head above brownish-plumbeous, this prevailing; but along the median line the feathers are edged with buffy white; forehead dull white, this continuing back in a streaked superciliary stripe to the occiput; cheeks very thinly marked with fine streaks of dusky, this prevailing along the upper border of the ear-coverts; a deeper dusky suffusion beneath the anterior angle of the eye. Lower surface pure white; chin and throat, only, immaculate; jugulum with very sparse, narrow longitudinal streaks of blackish; sides with scattered cordate or nearly circular spots, these larger and transverse on the flanks and tibiæ; abdomen with scattered minute elliptical spots; lower tail-coverts with minute irregular sagittate or transverse spots of dusky. Under surface of the wing white; each feather of the lining with a medial tear-shaped streak of dusky; primaries crossed with narrow bars of dusky, fifteen in number on the longest. Wing-formula, 2–3–4–1–5. Wing, 13.50; tail, 8.60; culmen, .90; tarsus, 2.15; middle toe, 1.87.

      ♀ (43,139, Fort Anderson, May 24, 1864, “♀ and two eggs”; R. MacFarlane). Generally similar to the male. Head above conspicuously streaked, but the dusky prevailing. Above the transverse bands are less regular and continuous, anteriorly the plumbeous largely prevailing; posterior portions, however, as in the male, but on the rump the bands are more distinct. Beneath, the markings are more numerous, larger, and broader; those on the jugulum linear; those of the abdomen medially elliptical; laterally they are transversely cordate, and on the flanks in form of broad transverse spots, or broad bars; on the tibiæ and lower tail-coverts they form regular transverse bars,—on the latter, quite distant. Wing-formula, 2–3–4, 1. Wing, 15.50; tail, 9.50; tarsus, 2.15 and .80; middle toe, 1.95.

      Juv. (♂, 55,400, Alaska, Nulato, February 10, 1868; W. H. Dall). Above plumbeous-umber, precisely as in young of islandicus, but on the rump having a decided ashy cast. No white edges to the feathers, as in islandicus, but, instead, numerous irregular transverse spots or obsolete ragged bars of cream-color or pale ochraceous-buff; the whole upper surface is quite thickly variegated with these irregular markings. Tail crossed with thirteen narrow bands of creamy-white, these so thickly mottled with dusky on the outer webs as to be obscure, but on inner webs they are regular and sharply defined; the last is terminal. Primaries plain dusky, skirted obscurely with paler, and marked toward bases with obsolete mottled spots of cream-color. Head streaked with dusky and creamy-white, the former predominating on upper surface, along upper edge of ear-coverts, and across the cheeks, on the latter forming a mustache; the white prevails over the ear-coverts in a broad supra-oral stripe, and on the forehead and lores. Beneath, soft dull white; chin and upper part of throat, only, immaculate; each feather with a broad medial stripe of clear dark plumbeous-brown, on the flanks and tibiæ prevailing, the whitish assuming the form of roundish spots; lining of the wing similarly marked; prevailing aspect of under surface of primaries white, crossed with narrow bars of ashy, fifteen in number on the longest. Wing-formula, 2, 3–1=4. Wing, 14.00; tail, 8.40.

      Hab. Interior regions of Arctic America; Anderson River, McKenzie, Yukon, and Severn River regions. Breeding abundantly in the former district, whence numerous specimens of skins and eggs have been received by the Smithsonian Institution.

      In the young specimen described, there are one or two new feathers appearing on the rump and upper tail-coverts, precisely as in the blue plumage, and proving conclusively their relationship. The species is as different from the Iceland bird in the young stage as in the mature. The most readily apparent differences are, lack of sharp white edges of feathers above, and in their stead numerous ragged transverse spots of yellowish; dark aspect of head above, etc.

      Specimens vary considerably in the shades of color and distribution of the markings, but the types of the above descriptions are the lightest of the series. The darkest example is No. 43,144½ (“♀ and eggs”), Fort Anderson, May 22, 1864. In this the whole head and neck (except underneath) are continuous blackish-plumbeous, only the middle of the auriculars being faintly streaked; the back is nearly plain dusky, and even on the wings the bars are very obscure and much reduced in width. The rump is plain ashy-blue, the darker bars being nearly obsolete. The longitudinal markings on the pectoral region are enlarged into conspicuous stripes, while on the sides and flanks the transverse bars form heavy spots. The transverse bars on the tibiæ are ashy-blue; those on the crissum clear plumbeous, and regularly transverse. Wing, 15.75; tail, 9.30. Upon comparing this specimen with the figures of a pair of var. gyrfalco, by Wolf, in Newton’s Oötheca Wolleyana, I can discover no difference at all; thus it would seem that our bird occasionally closely approaches in tints and markings this race of Continental Europe, of which I have seen only one immature example, and no adults.

      I cannot agree with Mr. Newton in considering the Gerfalcons of the interior of Arctic America as identical with the Iceland form, though that distinguished ornithologist considers them so in his paper in the Proceedings of the Philadelphia Academy for July, 1871, basing his conclusion upon the specimens from which the above descriptions were taken, which had been sent over to England for comparison. I have never yet seen a specimen of islandicus which could not be distinguished, by the characters given in my synopsis, from these examples, while they can be separated from that race by the characters which Mr. Newton himself gives, in his diagnostic table in the paper above cited, for distinguishing the adults of islandicus and gyrfalco.

      The var. sacer is evidently separable from both islandicus and gyrfalco, and about as much related to one as to the other; combining the size and proportions of the former with the colors of the latter, while in the wide amount of individual variation of plumage its lighter extreme approaches one, while its darkest phase approximates as closely to the average plumage of the other.

      National