246 NORTH AMERICAN BIRDS. 



Arctic America, from northern Labrador and coasts 



of Hudson's Bay to Alaska... 354rt. F. rusticolus 



gyrfalco (Linn.). Gyrfalcon. 

 p. 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 14.75-16.25 (15.89), culmen .98-1.05 (1.02), 

 tarsus 2.40-2.70 (2.47), middle toe 2.05-2.15 (2.11). 

 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 X 1-77. Hah. 

 Coast of Labrador; south, in winter, to Maine, Canada, 



and New York] 3546. F. rusticolus obsoletus 



(Gmel.). Black Gyrfalcon. 

 c^. Tarsus feathered for not more than upper half, the posterior side 

 almost wholly naked. (Subgenus Gennaia Kaup.^) 



Toj) 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 j)ale grayish brown (usually tinged more or less with 

 rusty), indistinctly but broadly barred with pale clay-color or 

 dull grayish buffy anteriorly tind 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 jjortions ; 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 1^ 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 4i 

 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 Kaup, Isis, 1847, 69. Type, Falco jugger Gray. 



