246 NORTH AMERICAN BIRDS. 
Arctic America, from northern Labrador and coasts 
of Hudson’s Bay to Alaska........ 354a. F. rusticolus 
gyrfalco (Linn.). Gyrfalcon. 
jf’. Lower parts with dusky prevailing, sometimes entirely 
dusky, except on lower tail-coverts, which are always 
(?) spotted with white. Male: Wing 14.00-14.60 
(14.20), tail 8.20-9.40 (8.64), culmen .86-95 (.88), 
tarsus 2.38-2.45 (2.41), middle toe 1.90-2.00 (1.91). 
Female: Wing 14.75-16.25 (15.89), tail 9.60-10.00 
(9.85), culmen .98~1.05 (1.02), tarsus 2.55-2.70 (2.62), 
middle toe 2.05-2.15 (2.11). Eggs 2.26 1.77. Hab. 
Coast of Labrador; south, in winter, to Maine, Canada, 
and New York'.......... 354). F. rusticolus obsoletus 
(Guxzx.). Black Gyrfalcon. 
c’. Tarsus feathered for not more than upper half, the posterior side 
almost wholly naked. (Subgenus Gennaia Kavp.') 
Top of head grayish brown, streaked with dusky; outer web of 
tail-feathers without distinct lighter spots (usually quite plain), 
and outer webs of quills without trace of spots; secondaries 
with lighter spots on outer webs; under parts and nuchal collar 
white, the flanks heavily spotted or blotched with dusky, the 
under tail-coverts sparsely spotted with same. Adult male: 
Above pale grayish brown (usually tinged more or less with 
rusty), indistinctly but broadly barred with pale clay-color or 
dull grayish buffy anteriorly and pale bluish gray posteriorly. 
Adult (?) female: Above grayish brown, without distinct or 
well-defined lighter bars, but feathers margined with pale 
rusty brown or dull whitish, both the ground-color and these 
edgings paler on posterior portions; tail tipped with buffy 
whitish, the feathers edged with a paler tint of the ground- 
color. Young (both sexes): Above grayish brown, the feathers 
distinctly margined with light rusty; lower parts pale buffy or 
buffy whitish, with broader dusky streaks, the dusky flank- 
patch larger and more uniform than in the adult, and the ax- 
illars unbroken dusky. Young in first summer: Similar to the 
preceding stage, but ground-color above darker, with rusty 
margins to feathers more distinct, the ground-color of the lower 
parts light ochraceous or creamy buff. Male: Length about 
17.00-18.00 (weight about 14 pounds), wing 11.60-12.50, tail 
6.40-7.50, culmen .70-.75, tarsus 1.85-2.15, middle toe 1.60- 
2.00. Female: Length about 18.50-20.00 (weight sometimes 4} 
pounds), wing 13.25-14.30, tail 8.00-9.00, culmen .85-.90, tarsus 
2.05-2.40, middle toe 1.85-2.15. Nest usually on cliffs. Eggs 2-5, 
1 Gennaia Kavp, Isis, 1847, 69. Type, Falco jugger Gray. 
