114 U.S. NATIONAL MUSEUM BULLETIN 233 



examined contained cowbird eggs. This is more than half of all the 

 cases noted. The reasons for this local difference (if there is a real 

 difference in the facts and not in the intensiveness of the observa- 

 tional field work) are not readily apparent. 



Mr. John B. Hurley informed me that Dr. F. A. Starr collected a 

 parasitized set of eggs of this warbler at Stm'geon Lake, Ontario. 

 Bendire was the first to list the northern waterthrush as a cowbird 

 victim but he gave no specific records. However, since this was 

 earlier than any of the published instances, it seems to follow that 

 he must have known of one or more parasitized nests. Anderson 

 (1907, p. 229) mentions this waterthrush as a victim in Iowa, where 

 the breeding race is notabilis. Short (1896, p. 14) found that the race 

 noveboracensis was parasitized in New York. In southern Quebec, 

 three instances of cowbird parasitism out of 18 occupied nests which 

 were examuied were found by Terrill (1961, p. 8). Near Woodville, 

 Ontario, Starr (1931, p. 154) discovered a nest with 3 eggs of the 

 waterthrush and 1 of the cowbird; in Wayne County, Michigan, a 

 nest with similar contents was foimd by Barrows (1897, p. 47). 



Louisiana Waterthrush 



Seiurus motacilla (Vieillot) 



This species is parasitized rather frequently by the brown-headed 

 cowbird, much more so than the northern waterthrush, but it cannot 

 be ranked as one of the most used victims of the parasite. About 

 76 records, ranging from Ontario, New York, Connecticut, and 

 Pennsylvania to West Virginia, Tennessee, Indiana, and Michigan, 

 have come to my attention. The degree to which this bird is affected 

 by the parasite appears to depend upon local conditions. In regions 

 traversed by narrow wooded ravines and gorges, with open and 

 imforested country between, this waterthrush often is victimized, 

 whereas, in more consistently and extensively sylvan areas, it is less 

 likely to be imposed upon. Cowbirds do not penetrate far into forests, 

 and, as a result, seldom have occasion to make contact with this species 

 in such areas. 



At Ithaca, New York, I twice found fledgling cowbirds attended 

 by these warblers; I was told by A. A. Allen that the great majority 

 of all their nests which he had found in the past contained eggs or 

 young of the cowbird. Similarly, Eaton (1914, p. 444), quoting 

 Clarence Stone, wrote that "this warbler is much imposed upon by 

 the cowbird whose visits annually cause disaster by its clumsiness in 

 filHng the nest with loose shale or dirt while kicking two to three 

 of the . . . eggs out of the nest. In two instances I have noticed 

 five eggs of the Louisiana water-thrush with two of the cowbird. 



