Jan., 1909. Birds of Illinois and Wisconsin — Cory. 



621 



Genus IRIDOPROCNE Coues. 



285. Iridoprocne bicolor (Vieill.). 



Tree Swallow. White-bellied Swallow. 



T-achycineta bicolor (Vieill.), A. 0. 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 % 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. 



