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 

 S. sialis, female." 



