90 U.S. NATIONAL MUSEUM BULLETIN 233 



vireo attending and feeding a recently fledged cowbird (subspecies 

 ater). 



Warbling Vireo 



Vireo gilvus (Vieillot) 



The warbling vireo is a frequent host of the brown-headed cowbird ; 

 64 records have come to my attention, involving three races of the 

 vireo, gilvus, swainsonii, and leucopolius, plus all three subspecies of 

 the parasite. The records range from British Columbia, Alberta, and 

 Washington eastward to Minnesota, Wisconsin, Illinois, Indiana, 

 Ohio, Ontario, Quebec, Connecticut, New York, New Jersey, and 

 Pennsylvania and southward to California, Oklahoma, Iowa, and 

 Tennessee. In my own field work at Ithaca, New York, I observed 

 only two cases, but in other localities this vireo seems to be imposed 

 upon to a greater extent. Eaton (1914, p. 227) lists the warbling 

 vireo as one of the most frequent victims in New York State. A 

 similar estimate was made in southwestern Pennsylvania. 



Since there are still relatively few records for the two western races 

 of both the vireo and the cowbird, these can be listed here. The 

 subspecies V.g. swainsonii has been recorded as a host of Al.a. obscurus 

 in California by Sherwood (1929, p. 3) and by H. W. Carriger near 

 Oaldand, June 2, 1929; a third record is a parasitized set of eggs from 

 San Diego County (G. Bancroft Collection) ; a fourth, from the San 

 Gabriel Mountains and now in the San Bernardino County Museum; 

 and a fifth, from the same area and now in the collections of the Wes- 

 tern Foundation of Vertebrate Zoology. Coues (1878, p. 513) stated 

 in an indefinite way that the host race V.g. swainsonii was victimized, 

 but he gave no actual instances. Nice (1931, p. 171) recorded this 

 race as a victim of M.a. ater in Oklahoma, with a record from Kenton, 

 Cimarron County. Mr. T. E. Randall informed me that he had 

 found swainsonii to be parasitized by M.a. artemisiae in Alberta, and 

 E. M. Tait found three victimized nests at Trout Creek Point, British 

 Columbia. 



For the subspecies V.g. leucopolius, there are the following two 

 records, both involving M.a. artemieiae. Jewett, Taylor, Shaw, and 

 Aldrich (1953, p. 551) mentioned that, at Spokane, Washington, 

 May 30, 1924, Sloanaker found a nest containing 3 eggs of the vireo 

 and 1 of the cowbird. Schultz (1958, p. 435) recorded an instance of 

 a pair of these vireos feeding a recently fledged cowbird near Seattle, 

 Washington. 



Slaty Vireo 



Neochloe brevipennis (Sclater) 



A single instance of the slaty vireo as a host of the smaU south- 

 western race of the brown-headed cowbird has been recorded by 



