1921 BIRDS OF MONTANA 99 



records, Shields River, Park County, August 8, 1908, and Teton County, August 

 13, 1911. Another August date on record is Chief ^Mountain Lake, August 

 26, 1874 (Coues, 1874b, p. 600). 



The only nesting records in the state are from the vicinity of Lewistown. 

 where a nest containing three eggs of the Bobolink and two of the Cowbird was 

 found June 14, 1904, and other nests containing seven Bobolink eggs were found 

 later (Silloway, 19()4b, p. 150). 



193. Molothrus ater ater (Boddaert) 



Cowbird 



An abundant summer resident throughout most of the state, probably most 

 numerous eastward, though it is decidedly common in the extreme western part 

 also. Practically all observers report the species as common in prairie and valley 

 regions. It is said to be rare at Flathead Lake, but should not be expected to be 

 common on the heavily wooded shores there. In my experience it is conmion 

 about Kalispell, north of the lake, and on the Flathead Reservation south of it. 

 The Cowbird is found chiefly in open grass country, feeding in such places, and 

 laying its eggs in the nests of species that nest there or in neighboring cotton- 

 wood groves, or clumps of bushes. In the evergreen forests of the mountains the 

 Cowbird is absent, and the nests of small songbirds are free from its persecu- 

 tion. 



The Cowbird arrives in spring in the early part of May, and probably leaves 

 in September, though I can find little data to show just when it leaves in fall. 

 Spring dates are as follows: Great Falls, May 9, 1887 (Williams, 1888a, p. 15) ; 

 Bozeman, May 9, 1909; Silver Bow, May 20, 1910; Anaconda, May 12, 1911; 

 Choteau, May 10, 1912 ; Bitterroot Valley, May 18, 1910, May 14, 1911, May 9, 

 1912, and May 7, 1913 (Bailey, MS). Fall migration dates are almost missing. 

 The only date I can find among my own records is from Choteau, September 

 8, 1911, and I can find nothing whatever from other sources. 



Although Cowbird eggs have been taken very frequently in the state, but 

 few dates of their finding are published. Most of them are found in June or 

 late May. I have found them in May in the nests of the Brewer Blackbird, in 

 June in nests of various species, and in July in nests of the Cedar Waxwing and 

 Black-headed Grosbeak. The latest found were laid July 8 and 9 in the nest of 

 a Cedar Waxwing. The eggs are very commonly laid in the nest of the Brewer 

 Blackbird, and record of this fact is made by most writers on the nesting of 

 this species in ]Montana. It seems unusual, however, because the Blackbird is a 

 larger species with a larger egg. Cowbird eggs have also been found in the nests 

 of Western Vesper and Chipping sparrows, Arctic Towhee, and Long-tailed 

 Chat (Cameron, 1907, p. 397); Bobolink (Silloway, 1904b, p. 150); Yellow 

 Warbler, Black-headed Grosbeak, Slate-colored Fox Sparrow, and Cedar Wax- 

 wing (Saunders, 1911a, p. 40, and 1914a, p. 136) ; and Lazuli Bunting, Vesper 

 Sparrow, Western xMeadowlark, Western Yellowthroat, and Yellow Warbler 

 (Bailey, MS). 



