714 Field Museum of Natural History — Zoology, Vol. IX. 



Subfamily SIALIINiE. Bluebirds. 



Genus SIALIA Swainson. 



365. Sialia sialis (Linn.). 



Bluebird. 



Distr.: United States and southern Canada, west to the base of 



the Rocky Mountains; winters from the middle states to the Gulf 



coast (casual or accidental in Cuba) ; breeds nearly throughout its 



range. 



Adult male: Upper parts, bright blue; wings and tail, blue, the 

 former with the ends blackish; throat, breast and sides of body, chest- 



Biuebird. 



nut; belly and under tail coverts, white, some of the latter tinged with 

 grayish blue; bill and feet, black. 



Adult female: Similar, but blue of upper parts more or less tinged 

 with grayish brown, shading into bright blue on rump and tail, the 

 chestnut on under parts paler. 



Immature in first plumage: Upper parts, grayish brown ; wings and 

 tail, blue; the back with white streaks (caused by the white shaft 

 lines of the feathers) ; under parts, white; the feathers of the breast 

 and sides edged with grayish brown, producing an irregular streaked 

 appearance. 



Length, 6.80; wing, 3.90; tail, 2.65; bill, .45. 



The Bluebird is a very common summer resident in Illinois and 

 Wisconsin, the majority arriving from the south in March (earliest 

 Chicago record, February 22) and leaving again in September. 



