JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 457 



white; throat, whitish, narrowly streaked with dusky; rest of under 

 parts, barred with pale rufous brown and white, the shafts of the 

 feathers dusky, showing fine hair-like lines; under tail coverts, white. 



Male: Length, n; wing, 6.70; tail, 5.60; tarsus, 1.90. 



Female: Larger; length, 12.50 to 13.50; wing, 6.50; tarsus, 2.05. 



Immature: Upper plumage, fuscous brown, the feathers often 

 edged with rufous; wings and tail marked as in the adult, but of a 

 more brownish tinge; under parts, whitish, streaked with brown, 

 the shafts of the feathers dusky, showing hair-like lines. 



The "square" tail and smaller size will always distinguish this 

 species from the Cooper's Hawk. 



A common species during the migrations in April, May, Septem- 

 ber and October. The majority of them go farther north, although 

 a few are summer residents in Illinois and probably breed. In Wis- 

 consin it is more common in summer. Kumlien and Hollister have 

 found it nesting at Milton in two instances and have breeding records 

 from many localities throughout the state. 



The nest is built in a tree (sometimes on a ledge of rocks) and is 

 composed of sticks, moss, and grass. The eggs are usually four or 

 five, pale bluish white or buffy white, blotched and washed with vari- 

 ous shades of brown. They measure about 1.50 x 1.20 inches. The 

 nesting season lasts from April until June. 



156. Accipiter cooperii (BONAP.). 

 COOPER'S HAWK. 



Distr. : North America and Mexico, breeding throughout its range. 



Special characters: Fourth primary, longest; tail, rounded, the 

 outer tail feather being three-quarters of an inch or more shorter than 

 the middle feather. 



Adult and immature birds of this species resemble the Sharp - 

 shinned Hawk, but may easily be distinguished by the larger size 

 and more rounded tail. In the adult the crown is usually darker. 



Male: Length, 14.25 to 16.75; wm > 8.90 to 9.40; tail, 7.75 to 

 8.25; tarsus, 2.30 to 2.50. 



Female: Length, 17.50 to 19.50; wing, 10 to n; tail, 9 to 10.30; 

 tarsus, 2.60 to 2.80. 



The Cooper's Hawk is a common summer resident in Illinois and 

 Wisconsin. It is commonly known as Hen Hawk or Chicken Hawk, 

 and .undoubtedly deserves the name more than several other species 

 to which it is applied. Dr. A. K. Fisher states that "of 133 stomachs 

 examined, 34 contained poultry or game birds; 52, other birds; n, 

 mammals; i, frog; 3, lizards; 2, insects; and 39 were empty." 



