552 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. IX. 



a common summer resident in northern Illinois and Wisconsin, breed- 

 ing in open meadows. It arrives from the south about the first of 

 May and nidification commences the latter part of May or early in 

 June. The song of the Bobolink is a delightful medley impossible to 

 describe and is often uttered while the bird is poised high in the air 

 or slowly descending to the ground. 



The nest is of grass, built on the ground or in a tussock of grass 

 in fields and meadows. The eggs are 4 to 7, dull white or buffy 

 white, thickly blotched and spotted with dark brown and a few lines 

 and spots of blackish, and measure about .82 x .62 inches. 



The Field Museum collection contains a number of sets of eggs of 

 this species taken in the vicinity of Joliet and Chicago, 111., between 

 May 28 and June 8. 



Genus MOLOTHRUS Swainson. 

 224. Molothrus ater (BooD.). 



COWBIRD. 



Distr. : Whole of the United States, and north to southern British 

 America; south to Mexico in winter. 



Adult male: Head, neck, and breast, seal brown; rest of plumage, 

 bluish black, with purplish and greenish reflections; bill and feet, 

 black. 



Adult female: General plumage, brownish gray, darker above than 

 below; throat, pale ashy gray, decidedly lighter than rest of under 

 parts; wings and tail, dark brown. 



Length, 7.85; wing, 4.28; tail, 3; bill, .62. 



Cowbird (male). 



