134 U.S. NATIONAL MUSEUM BULLETIN 233 



Rusty Blackbird 



Euphagus carolinus (MixUer) 



The rusty blackbird has been recorded as a host of the north- 

 western race of the brown-headed cowbird, M.a. artemisiae, in Alberta. 

 T. E. Randall informed me many years ago that he had found two 

 parasitized nests of this blackbird; A. D. Henderson also wrote me of 

 similar observations. 



In a commercial price list of November, 1947, the natm-al history 

 dealer, C. H. Gowland of Wirral, England, listed two sets of eggs of 

 the rusty blackbird, each with eggs of the cowbird. No locality or 

 date was given for either set, and correspondence failed to obtain 

 either the specimens or further data about them. 



The Alberta records refer to the typical race of the host. Because 

 the parasite does not breed in the range of the Newfoundland race 

 nigrans, the Gowland sets presumably also involve the nominate race 

 of the host. 



Brewer's Blackbird 



Euphagus cyanocephalus (Wagler) 



Brewer's blackbird frequently is imposed upon by the brown-headed 

 cowbii'd in Alberta and Montana, and it also has been noted as a 

 cowbird host in British Columbia, Saskatchewan, Colorado, Minne- 

 sota, and California. In the Rowan collection at the University of 

 Alberta there are seven parasitized sets of eggs which were taken in 

 Alberta. Other Alberta records have come to my attention from 

 T. E. Randall and A. D. Henderson. 



In Gallatin County, Montana, A. A. Saunders (1911, p. 40) found 

 cowbird eggs more often in nests of Brewer's blackbird than in nests 

 of any other species; he wi'ote that a large percentage of the blackbird 

 nests were parasitized. Cameron (1907, pp. 396-397) found the bird 

 parasitized in Custer and Dawson Counties, Montana, and Rust (1917, 

 p. 37) found a parasitized nest in Fremont County, Idaho. At St. 

 Vincent, Minnesota, Peabody (1909b, pp. 15-20) concluded that few 

 nests of this blackbkd seemed to escape the visitation of the cowbird. 

 More recent observers (Hayward, 1950; Mierow, 1949; Warner, 1951) 

 also have reported this blackbird as a regular host of the cowbird in 

 Minnesota. Belts (1912, p. 204) found it imposed upon in Boulder 

 County, Colorado. Mrs. K. Baton has informed me of at least three 

 parasitized nests at Oxbow, Saskatchewan. 



As many as 3 cowbird eggs have been found in one nest of this black- 

 bird; in fact, 4 eggs of the parasite have been found in a single nest 

 together with 7 of the owner — a crowded nest indeed. 



All the records, with the exception of one from California, refer to 

 the northwestern race of the cowbird, M.a. artemisiae. The south- 

 western race, obscurus, is involved in the record of a parasitized nest 



