HOST RELATIONS OF PARASITIC COWBIRDS 105 



egg but, unfortunately, he gave neither locality nor data of collection. 

 On June 28, 1952, at Pontiac Lake, Michigan, a female cerulean war- 

 bler was observed feeding a recently fledged cowbird along with a 

 fledghng warbler (Detroit Audubon Soc, 1953, p. 72). The southern- 

 most record comes from southwestern Virginia, where Jones (1936, 

 p. 88) found a parasitized nest. The nominate race of the cowbird is 

 involved in all these records. 



Blackburnian Warbler 



Dendroica fusca (Mxiller) 



This is a very uncommon host of the brown-headed cowbii'd. In 

 my first account of the bird (1929, p. 245), I listed four cases; in more 

 than 30 years since then, I have learned of only six others — testimony 

 in itself, to the very slight incidence of parasitism on the blackburnian 

 warbler. The records are from New York, Michigan, Minnesota, and 

 Ontario. 



Apparently on the basis of a note from Dr. Brewer, Audubon (1839, 

 p. 491) was the first to record this warbler as a victim of the cowbird. 

 Brewer (in Baird, Brewer, and Ridgway, 1874, pp. 154-157) included 

 this bu'd in a list of species in whose nests he had found cowbkd eggs. 

 Merriam (1885, p. 103) reported a nest, 84 feet from the ground in a 

 tall tree in the lower Hudson Valley, New York, containing 4 eggs of 

 the warbler and 1 of the cowbu'd. This is the "altitude record" for a 

 cowbird's egg. 



According to Roberts (1932, pp. 229-231), S. A. Grimes found a nest 

 in Cass County, Minnesota, on June 22, 1929, with 2 eggs of the warbler 

 and 2 of the cowbird, and another nest with 3 eggs of the host and 1 of 

 the parasite. Another Minnesota record (from a note in files of U.S. 

 Fish and Wildlife Service) states that E. D. Swedenborg watched a 

 blackburnian warbler feeding a recently fledged cowbird near Minne- 

 apolis on July 15, 1928. 



A similar record from an area near Ottawa, observed by Taverner, 

 was mentioned by Lloyd (1944, p. 169); Snyder (1942, p. 144) noted a 

 parasitized nest found by Shortt in the Sault Ste. Marie Region of 

 Ontario. 



Preston (1889) recorded a nest with 2 newly laid eggs of the owner 

 and 1 of the cowbird, and "at the foot of the tree were fragments of two 

 more eggs which had been crowded from the nest by this parasite." 

 He also recorded another nest with 3 eggs and "with one of the 

 inevitable cowbird." 



Wood (1957, p. 394) reported a nest with 4 eggs of the warbler and 1 

 of the cowbird, near Kalamazoo, Michigan. 



The records all refer to the eastern race of the cowbird. 



