FALCO. 245 



■width to tho darker ones; darker and lighter bands on tail 

 usually very sharply contrasted, the former often slate- 

 gray, the latter pale ash-ijraj- or dull whitish ; flanks and 

 thighs never very heavily banded or spotted with slaty, 

 but alwaj'S more or less marked with this color. Young : 

 Dark stripes of lower parts usually decidedly narrower than 

 white intei-sijaces ; upper parts in general usually much 

 spotted with whitish or light buflPy, in addition to the 

 lighter margins (often conspicuous) to the feathers; outer 

 webs of quills more or less distinctly spotted with whitish 

 toward base. Male: Length about 20.00-21.00, wing 

 13.40-15.00 (14.10), tail 8.00-9.30 (8.51), culmen .S8-.98 

 (.90), tarsus 2.10-2.G5 (2.40), middle too 1.80-2.20 (1.9C). 

 Female: Length about 22.00-24.50, wing 15.25-16.50 

 (15.76), tail 9!^10-10.50 (9.72), culmen .95-1.10 (1.01), tar- 

 sus 2.30-2 60 (2.46), middle toe 1.98-2.15 (2.08). Bugs 

 2.37 X l-'<'2. Hah. Extreme northern portions of Europe 

 (except Scandinavia), Asia, and North America, including 

 Iceland and southern Greenland ; south, in winter, to 

 northern border of United States. 



354. F. rusticolus (Linn.). Gray Gyrfalcon. 

 Darker colored : Top of head usuallj' with dusky prevailing, 

 often uniform dusky, lighter tail-bands bluish gray, and 

 usually narrower than dusky interspaces. Adxdt with an- 

 terior upper- parts (back, scapulai-s, and wing-coverts) 

 rather indistinctlj- barred with bluish gray, often nearly 

 plain dusky ; flanks heavily banded or spotted with dusky, 

 and thighs heavily baiTed with slaty (the white ground- 

 color tinged with bluish gray posteriorly). Young : Dark 

 stripes of lower parts usually about equal in width to 

 ■white interspaces, sometimes much broader (under parts 

 sometimes plain dusky); upper surface of tail never (?) 

 continuouslj- banded with whitish, sometimes almost plain, 

 or, if barred at all, the bars intciTupted, much narrower 

 than the dark interspaces, and never (?) approaching white 

 in color; upper parts usuallj' plain gi^iiyish brown, the 

 feathers more or less distinctly margined with paler, but 

 usually with little if any whitish spotting. 

 /'. Lower parts with white provailini;, or at least equal in 

 extent to the dusky. Male : Wing 13.35-14.25 (13.54), 

 tail 8.00-9.00 (8.49), culmen .86-.93 (.90), tarsus 2.30- 

 2.50 (2.35), middle toe 1.90-2.00 (1.96). Female: AVing 

 15.25-16.00 (15.52), tail 0.00-10.50 (9.82), culmen 1.00- 

 1.10 (1.03), tarsus 2.25-2.65 (2.48), middle toe 2.05-2.15 

 (2.10). Eggs 2.34 >< 1.77. Hab. Northern Europe and 



