Jan., 1909. Birds of Illinois and Wisconsin — Cory. 715 



The breeding season lasts from April until the middle of June. The 

 nest is in hollow trees and stumps or about buildings. The eggs are 

 from 4 to 7, very pale blue or bluish white, rarely white, and measure 

 about .83 X .64 inches. 



The Field Museum collection contains a series of sets of eggs taken 

 in northern Illinois between April 25 and June 10. The song of the 

 Bluebird is a pleasing whistle, usually a single note repeated two or 

 three times. 



The Mountain Bluebird, Sialia arctica, was included by Mr. Nel- 

 son on the authority of Dr. Hoy. He states: "Dr. Hoy informs me 

 that he has seen a specimen of this species in a collection at Dubuque, 

 Iowa, which was taken late in the fall upon the east side of the Missis- 

 sippi River near that town." (Birds N. E. 111., 1876, p. 95.) But Mr. 

 Ridgway says (Birds North and Middle America, 1907, p. 145, foot- 

 note) : "I have examined the specimen upon which the above record 

 was based and it proves to be a somewhat discolored example of 

 5. sialis, female." 



