JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 475 



Immature (second year) : General plumage, dark grayish brown, 

 the concealed bases of the feathers, white, and more or less exposed 

 in places; feathers on back of head, tipped with light brown; tail, 

 brownish black, the feathers more or less blotched and speckled with 

 white on the inner webs; bill, blackish; feet, yellowish. 



Male: Length, 37 to 38.50; wing, 22.50 to 24.50; bill, 2.50. 



Female: Length, 38 to 42.50; wing, 24 to 26.50; bill, 2.50 to 2.80. 



The Bald Eagle occurs more or less commonly throughout Illinois 

 and Wisconsin in the more unsettled localities, and breeds through- 

 out its range. Numerous nesting records. 



The location of the nest varies with different localities, either in 

 large trees or on rocky cliffs and even on the ground, according to Mr. 

 Harry C. Oberholser, who writes (Bull. U. S. Dept. of Agriculture, 

 1906, p. 9) : " Where there are no trees, a rock or a niche in a cliff 

 serves the purpose, while along the coast of Texas nests have been 

 found even on the ground of low islands." 



The eggs are usually two, dull white, and measure about 3 x 2.50 

 inches. Nidification commences late in February or in March in 

 this latitude. 



Subfamily FALCONING. Falcons, etc. 



Genus FALCO Linn. 

 Suhgenus HIEROFALCO Cuvier. ' 



167. Falco rusticolus LINN. 

 GRAY GYRFALCON. 



Distr. : Arctic America, accidental or casual in winter to northern 

 border of United States. 



Adult: Size, large; length, over 20 inches; wing, over 13; tar- 

 sus, feathered, at least half way down on front and sides; second 

 primary, longest; first primary, shorter than third; upper plumage, 

 mixed slaty brown and white, the feathers being barred and edged 

 with grayish white or buffy white; under parts, white, streaked and 

 marked with dusky; under tail coverts, spotted and barred with 

 dusky; tail with numerous bands. 



Male: Length, about 21; wing, 13.50 to 15; tail, 8 to 9; bill, 

 about .95; tarsus, about 2.35. 



Female: Length, 23; wing, 15 to 17; tail, 9 to 10; bill, about i; 

 tarsus, about 2.50. 



