HOST RELATIONS OF PARASITIC COWBIRDS 107 



and rearing the parasites. Occasionally, however, it has been known 

 to bury cowbird eggs if the latter are laid first. Sage and Bishop 

 (1913, pp. 110-111) in Connecticut recorded such a case: a nest con- 

 taining 4 eggs of the warbler and 1 of the cowbhd, which was buried 

 under a new nest lining. The nest had been observed previously for 

 over a week, and the cowbird's egg was known to have been laid 

 before any of the warbler's. Mercer (1911) reported a double- 

 storied nest of this M^arbler with a buried cowbird egg in the lower 

 portion. Terrill found that, while this warbler was a frequent host, 

 it was not always submissive. Six nests, in which the cowbird had 

 laid before the owner, were destroyed, and in a seventh, the parasitic 

 egg was buried partly in the nest lining. 



Bay-breasted Warbler 



Dendroica castanea (Wilson) 



This northern breeding warbler is geographically and ecologically 

 sympatric with the brown-headed cowbird only to a limited degree, a 

 factor which undoubtedly helps to protect it from parasitism. There 

 are, however, two records — both observed by F. Napier Smith, who 

 reported the first (1951, p. 44) from Kamouraska, Quebec, about 150 

 miles north of the latitude of Montreal, on July 2, 1951; the nest 

 contained 2 eggs of the warbler and 1 of the cowbird. The second nest, 

 from the same area, was found on June 18, 1952, about 60 feet from the 

 site of the first one, according to Terrill (1961, p. 8). 



Pine Warbler 



Dendroica pinus (Wilson) 



The brown-headed cowbird seldom inflicts its eggs upon the pine 

 warbler. Only 10 records — from Ontario, New York, New Jersey, 

 Michigan, Wisconsin, and Minnesota — have been noted. At Ithaca, 

 New York, on June 29, 1921, I watched a pine warbler feeding a 

 young cowbu'd at the foot of a tree in which there was a nest some 60 

 feet from the ground. Since only one pair of pine warblers was in 

 the immediate vicinity and previously I had heard cowbird-like 

 food cries from the upper part of this tree, it seemed fairly certain 

 that the young cowbird came from that nest. No young pine war- 

 blers were seen. Eaton (1914, p. 429) reported a nest, also in New 

 York, with 3 eggs of the host, 1 egg of which was punctured, and 1 

 of the cowbird. Ord (1836, p. 59) found a parasitized nest in New 

 Jersey in May, 1813. Wood, Smith, and Gates (1916, p. 14) saw a 

 pine warbler feeding a fledged cowbird in Cheboygan County, Mich- 

 igan. Recently, other Michigan records have become available. 

 Wickerstrom (1953, p. 147) noted one instance in the Port Huron 

 game area on July 5, 1953, and Walkinshaw (1952, p. 96) found two 



