HOST RELATIONS OF PARASITIC COWBIRDS 95 



also in Alberta by Donald Wilby. Street (m Houston and Street, 

 1959, p. 176) discovered that this warbler was parasitized at Nipawin, 

 Saskatchewan. Although these are all the records I have located, 

 it appears that some earlier cases (or at least one) must have been 

 reported but not published, since Oberholser included the Tennessee 

 warbler within his list of cowbird hosts in his unpublished manuscript 

 on the birds of Texas — a work written long before any of the above 

 instances were observed. 



Orange-crowned Warbler 



Vermivora celata (Say) 



The orange-crowned warbler has been recorded but once, to my 

 knowledge, as a host of the brown-headed cowbird. A. R. Davidson 

 (in Utt.) informed me that on August 18, 1959, he saw one of these 

 warblers (race V.c. lutescens) feeding a fledgling of the parasite (race 

 M.a. artemisiae) in Vancouver Island, British Columbia. (For an- 

 other, possible record see Wilson's warbler, p. 123.) 



Nashville Warbler 

 Vermivora ruficapilla (Wilson) 



The Nashville warbler and the brown-headed cowbird are rela- 

 tively unimportant to each other as host and parasite. I have been 

 able to learn of only 16 instances of cowbird parasitism on this species. 

 The records come from Quebec, Massachusetts, New York, Michigan, 

 Ontario, Minnesota, and Manitoba. In southern Quebec, over a 

 period of nearly 60 years, TerriU (1961, p. 6) found 83 nests of the 

 Nashville warbler, 6 of which, or a Uttle over seven percent, were 

 parasitized. While the total number, 6 nests in 60 years, is small as 

 far as the cowbird is concerned, the percentage of victimized nests is 

 high enough to be a factor, at least locally, in the economy of the 

 warbler. In no other part of its range, however, has anyone found a 

 comparable frequency of parasitism. In Masspxhusetts, a state where 

 a great many observers have been working continuously for over a 

 century, only three instances have been noted: J. A. Allen (1864, 

 p. 60) found the first set of eggs near Springfield on June 5, 1863; on 

 June 8, 1888, another set was collected near Farmington for the 

 J. P. Norris collection; and on June 15, 1907, F. H. Carpenter col- 

 lected the third set, now in the U.S. National Museum (Bent collec- 

 tion). From New York, another weU worked state, I know of but a 

 single record, a set collected at Holland Patent, on June 2, 1888, and 

 now in the U.S. National Museum. 



In Ontario, Lawrence (1948) watched a parasitized nest and found 

 that eventually it produced a young cowbird together mth two young 

 warblers. This is the only observed case which resulted in the rearing 



