246 NORTH AMERICAN BIRDS. 



Arctic America, from northern Labrador and coasts 



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



gyrfalco (Linn.). Gyrfalcon. 

 /". 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 2 . Tarsus feathered for not more than upper half, the posterior side 

 almost wholly naked. (Subgenus Gennaia Katjp. 1 ) 



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 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 4 J 

 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, 



l Gennaia Kaup, Isis, 1847, 69. Type, Falcojugger Gbay. 



