244 NORTH AMERICAN BIRDS. 
Grnus FALCO Linyaus. (Page 224, pl. LXXII,, figs. 1-5; pl. LX XIII, figs. 1-3.) 
Species. é 
a’. Only one quill (the outermost) with inner web emarginated near tip; first quill 
longer than fourth. 
6. Tarsus decidedly longer than middle toe (without claw) ; first quill shorter 
than third. 
c. Tarsus densely feathered in front and on sides for the upper two- 
thirds, the edges of the feathering meeting on the posterior side. 
Nest usually on cliffs. Eggs 24, about 2.30 x 1.75, varying from 
pale cinnamon or tawny to buffy, more or less distinctly sprinkled, 
speckled, or marbled with deeper cinnamon-brown—sometimes 
almost uniformly cinnamon-color. (Subgenus Hierofalco Cuvizr.) 
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 transversely spotted, 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); lower parts usually distinctly striped. 
Male: 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). Female: Length about 23.00-2+.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 1.27. Hab. Circumpolar regions, breeding in Greenland, 
northeastern (and other?) portions of Arctic America, Com- 
mander Islands, ete. 
353. F. islandus Brinn. White Gyrfalcon. 
d*, Lower tail-coverts always more or less marked with dusky ; upper 
parts with little if any white, except, sometimes, on top of head 
and hind-neck. Adult with upper parts banded with dpsky 
and bluish gray (sometimes uniform dusky anteriorly), the 
flanks and thighs barred, banded, or transversely spotted with 
dusky. Young without transverse bars on upper parts (ex- 
cept sometimes on tail), and lower parts with all the markings 
longitudinal. 
ée. Lighter colored: Top of head much streaked with white, often 
with white prevailing, the lighter tail-bands usually whitish 
and nearly as broad as the darker interspaces. Adult, with 
anterior upper parts everywhere more or less distinctly 
barred with very pale grayish, grayish white, or buffy 
whitish, these lighter bars sometimes nearly equal in 
