2-tl NOUTH AMEIUCAS ISiJWH. 



Ge.nls FALCO Li.nx.tus. (Page 224, pi. LXXII., fiys. 1-5 ; pi. LXXIII., fig.s. 1-3.J 



Species. 



a\ Only one quill (the outcrmo.sl) with inner web eniavginuted near tip; first quill 

 longer tliau fourth. 

 bK Tarsus decidedly longer than middle toe (without claw) ; first quill shorter 

 than third. 

 C^. Tarsus densely feathered in front and on sides for the upjK'r two- 

 thirds, the edges of the feathering meeting on the posterior side. 

 JYest usually on cliffs. Egys 2-4, about 2.30 X 1-'J'5, varying from 

 palo cinnamon or tawny to buffj-, more or less distinctly sprinkled, 

 speckled, or marbled witli deeper cinnamon-brown — sometimes 

 almost unilbrnily cinnamon-color. (Subgenus Ilierofalco Cuvier.) 

 d}. Lower tail-coverts immaculate white, the thighs also usually im- 

 maculate; prevailing color of whole plumage white. Adult: 

 Top of head and hind-neck usually narrowly streaked with 

 dusky, but often immaculate; rest of upper parts more or less 

 barred, or transverselj' 8])otted, with slate dusky; lower parts 

 usually immaculate, or without well-defined markings. Young : 

 Upper parts with longitudinal spots or stripes of dusky (this 

 less slaty than in adult) ; low.er parts usuallj- distinctly strijjed. 

 3Iah: Length about 21.00-22.50, wing 14.00-14.75 (14.49), tail 

 8.50-9.50 (8.94). culmen .90-.98 (.92), tarsus 2.30-2.50 (2.43), 

 middle toe 1.95-2.05 (1.98). Femuh- : Length about 23.00-24.00, 

 wing 15.50-16.50 (16.00), tail 9.00-10.00 (9.49), culmen .95-1.08 

 (1.03), tarsus 2.30-2.50 (2.47), middle toe 2.05-2.15 (2.09). Eggs 

 2.26 X 1-27. Hah. Circumpolar regions, breeding in Greenland, 

 northeastern (and other?) portions of Arctic America, Com- 

 mander Islands, etc. 



353. F. islandus Brunn. White Gyrfalcon. 

 cf. Lower tail-coverts alwaj's more or less marked vvitii dusky ; upper 

 parts with little if anj- white, except, sometimes, on top of head 

 and hind-nock. Adult with u])pcr parts banded with dusky 

 and bluish graj' (sometimes uniform duskj- anteriorly), the 

 flanks and thighs barred, banded, or transverselj' spotted with 

 dusk}-. Young without transverse bars on U])])er parts (ex- 

 cept sometimes on tail), and lower parts with all the markings 

 loni^itudinal. 

 e'. Lighter colored : To]) of head much stroalu'd with white, often 

 with white prevailing, the lighter tail-bands usually whitish 

 and near!}' as broad as the darker interspaces. Adult, with 

 anterior u])]ier parts everywhere more or less distinctly 

 barred with very pale grayish, grayish white, or huffy 

 whitish, these lighter bars sometimes nearly equal in 



