Var. islandicus, Sabine.
ICELAND GERFALCON.
Accipiter falco islandicus, Briss. Orn. I, 336, 1763. Falco islandicus, Sab. Linn. Trans. XII, 528, 1818.—Temm. Man. Orn. pt. x; 17, pt. iii, p. 9; Tab. Meth. p. 2, 1836.—Faber, Prod. Island. Orn. 1822, p. 2; Isis, 1827, 62.—Rich. & Swains. F. B. A. II, 27, 1831.—Hoy, Mag. Nat. Hist. Ser. 1, VI, 107.—Hancock, Ann. Nat. Hist. II, 247; Rev. Zoöl. 1839, 123.—Bonap. Consp. Av. p. 24.—Strickl. Orn. Syn. I, 77, 1855.—Cassin, Birds N. Am. 1858, 13. Hierofalco islandicus, Gray, Gen. B. p. 3 (ed. 2, p. 4), 1844; Hand List, I, 18, 1869. Falco candicans islandicus, Schleg. Krit. übers, p. 1, 1844. Falco lanarius, Faber, Isis, 1827, 68. Falco gyrfalco, Keyserling & Blasius, Wirbelth. Eur. p. 135, 1840.
Sp. Char. Adult (♂, Iceland; No. 12, Coll. Geo. N. Lawrence). Ground-color of the plumage dull white, gradually becoming somewhat bluish posteriorly, this color especially noticeable on the tail. Whole upper parts crossed with broad transverse bands of dark plumbeous, these bands continuous, and more than twice as wide as the pale ones, except on the upper tail-coverts and tail, where the bands of the two colors are more regularly defined and about equal; in addition to the transverse bands, the feathers anteriorly have narrow borders of white. Tail with the dark bands twelve in number; the terminal pale band is purer white than the others. The dusky plumbeous prevails on the primaries, and is unvariegated beyond the middle portion; the anterior half, however, is marked with quadrate ragged spots, of a slightly yellowish-white; all are margined terminally with purer white. Each feather of the head and neck with a narrow medial streak of dusky, but the general aspect abruptly lighter than the back; the streaks are more condensed along the upper and terminal portion of the ear-coverts. Jugulum and breast with a medial narrow streak on each feather; abdomen with more elliptical streaks; sides with circular and cordate spots, and flanks and tibiæ with transverse spots; lower tail-coverts with narrow shaft-streaks of dusky. Lining of the wing with sparse narrow streaks of dusky; under surface of primaries with white prevailing, this, however, crossed by narrow bars of dusky, these numbering about sixteen on the longest. Wing-formula, 2–3–1. Wing, 14.60; tail, 7.80; culmen, 1.00; tarsus, 2.30; middle toe, 2.00.
Juv. (No. 20,344, Iceland). Ground-color of head, neck, and lower parts, white. Upper surface grayish umber-brown, becoming paler and more grayish on the tail; each feather above sharply bordered (both webs, all round) with dull white, producing a somewhat squamate appearance; in places, a few obsolete hidden spots of yellowish-white. Tail ashy-drab (feathers somewhat paler along edges), crossed with about eleven transverse series of spots of ochraceous or creamy white; these very obsolete on middle feathers, and sharply defined only on inner webs; the last is terminal. Primaries plain brown, somewhat darker than the back, and becoming insensibly darker terminally; skirted with white, and somewhat mottled or irregularly spotted toward their bases with yellowish-white. Head and neck, each feather, with a medial streak of dusky, but white the prevailing aspect; these streaks condensed and somewhat suffused along upper border of ear-coverts, and from the lores along cheeks, forming an obsolete “mustache”; every feather beneath (including lining of wings) with a medial broad stripe of clear plumbeous vandyke-brown, the shaft pure black; under surface of primaries with transverse spaces of white, these numbering thirteen on the longest. Wing-formula, 2–3, 1. Wing, 15.00; tail, 9.20.
Hab. Iceland and Southern Greenland. Northeastern North America in winter, straggling accidentally south to the New England States; Rhode Island (Museum, Cambridge); Norway, Maine “not uncommon” (Verrill); Massachusetts (Peabody & Jillson); Long Island (Cab., G. N. Lawrence).
Falco islandicus.
No. 56,050, Greenland (Schlüter Collection), is moulting, and assuming the adult dress; the adult and young stages above described being nearly equally combined. No. 56,055, from Greenland, differs from the other young individuals which I have seen in being considerably darker. The feathers of the upper surface are not bordered with whitish, but are merely paler on their edges, along which are specks of yellowish. On the head and neck the dark streaks predominate, while the stripes below are very broad. It approaches quite nearly toward the young of var. sacer.
The only specimen of this race which I have seen from Continental North America, is a young individual, obtained during the winter of 1864–65, near Providence, R. I., taken by Mr. Newton Dexter, and now in the Cambridge Museum, where I had the pleasure of seeing it.