All the eggs of the several forms of Gerfalcon that I have seen present common characteristics, and do not differ from each other more than eggs known to belong to the same species of Hawk are frequently found to vary. One from Greenland, presumed to belong to the candicans, measures 2.37 inches in length by 1.71 in breadth. The predominant color of its markings is a deep reddish-brown, very generally and nearly equally diffused over its surface, concealing the ground-color, which is lighter and of a yellowish-brown shade.
An egg of the islandicus, from Iceland, has the same measurements, but is so slightly yet uniformly marked with light yellowish-brown as to seem to be of one color only,—a light brown, shaded with yellow.
An egg from Norway, of the form gyrfalco, is 2.42 inches in length, 1.71 in breadth, has a ground-color of a dirty yellowish-white, and is marked with spots, dottings, and confluent blotches of yellowish-brown, more so about the larger end.
The series of eggs of Falco sacer in the Smithsonian Collection exhibits the following range of variation in size, color, and markings: length, from 2.30 to 2.45 inches; breadth, 1.60 to 1.90 inches; ground-color usually a light reddish-ochre, varying to pinkish on the one hand, and to rufous on the other. They are usually sprinkled all over with small spots, which are sometimes not distinguishable from the ground-color when this is very deep, and again larger and quite conspicuous.
An egg of the variety candicans, from Greenland (No. 2,606, S. I.), measures 2.25 inches by 1.80. In color and in markings it is like the average eggs of variety sacer, namely, pale rufous, sprinkled over with a slightly deeper shade.
Falco lanarius.
Var. polyagrus, Cassin.
AMERICAN LANNER; PRAIRIE FALCON.
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.