JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 621 



Genus IRIDOPROCNE Coues. 



285. Iridoprocne bicolor (ViEiLL.). 



TREE SWALLOW. WHITE-BELLIED SWALLOW. 



Tachycineta bicolor (Vieill.), A. O. U. Check List, 1895, p. 258. 



Distr.: Whole of North America, north to Ungava, Hudson Bay, 

 and Alaska, south in winter to Cuba and Central America; breeds 

 from Alabama and Texas northward throughout its range. 



Adult male: Upper plumage, glossy greenish blue or steel-blue, 

 showing a greenish gloss when held in the light; under parts, white; 



Tree Swallow. 



wings and tail, blackish, with faint greenish gloss; tail, slightly 

 emarginate, the outer feathers being only Y% of an inch or less longer 

 than the middle feathers. In fall plumage the inner secondaries 

 are edged and tipped with white. 



Adult female: Similar, but duller. 



Young birds in first plumage on leaving the nest have the upper 

 parts, including the wings and tail, slaty gray; under parts, white, 

 more or less washed with ashy; feet, yellow. 



Length (adult), about 6; wing, 4.50 to 4.90; tail, 2.50; bill, .28. 



The Tree Swallow is a common summer resident throughout 

 Illinois and Wisconsin from the latter part of April until September. 

 Late in August they congregate in large flocks preparatory to the 

 southern migration. 



. The -nest is usually in hollow trees, but sometimes in buildings 

 or on the sides of a cliff. The eggs are from 4 to 6, pure white, and 

 measure about .75 x .54 inches. 



