HOST RELATIONS OF PARASITIC COWBIRDS 117 



MacGillivray's Warbler 



Oporornis tolmiei (Townsend) 



This warbler still is observed rather seldom; as a result, it is difficult 

 to interpret the nine records of cowbird parasitism. Nine records 

 would be very few for a well-known bird, but in the present species 

 such a number is more significant. It appears, therefore, that Mac- 

 Gillivray's warbler should be looked upon as a regular, if not a very 

 frequent, victim of the brown-headed cowbird. 



Both of the currently recognized races of this warbler are known 

 to be parasitized b}^ the western race of the brown-headed cowbhxl, 

 M.a. artemisiae. The nominate race of the warbler has been recorded 

 as a host by S. J. Darcus from Penticton, British Columbia (Fried- 

 mann, 1934a, p. 104), and by Schultz (1958, p. 435) on the basis of an 

 observation by Da\ddson at Victoria, British Columbia. Stephens 

 (1932, p. 2) found the race O.t. monticola to be parasitized in Yosemite 

 Valley, Cahfornia, and French (1907, p. 156) found it thus in Colorado. 

 A few additional cases for this race follow. LaFave (1955, p. 25) 

 saw a fledgling cowbird attended and fed by a male MacGillivray's 

 warbler near Wandermere, Washington, on Jidy 29, 1954. King 

 (1954) found a parasitized nest in Whitman County, Washington; 

 still another Washington record is the basis for a statement by Jewett, 

 Taylor, Shaw, and Aldrich (1953, p. 767). Kogers (1958, p. 430) 

 made an observation similar to LaFave's at Baker, Oregon, on August 

 6. In the files of the U.S. Fish and Wildhfe Service there is an ob- 

 servation by Edwin WiUis of an adult MacGilhvray's warbler attend- 

 ing a fledgling cowbird near Camp ConneU, Calaveras County, 

 Cahfornia. 



Yellowthroat 



Geothlypis trichas (Linnaeus) 



This wide-ranging species is one of the common victims of the 

 brown-headed cowbird. Over 270 records have been noted from 

 provinces of Canada — British Columbia, Alberta, Saskatchewan, On- 

 tario, Quebec, New Brunswick — and the following of the United 

 States: Arizona, Arkansas, California, Colorado, Connecticut, Dela- 

 ware, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, 

 Massachusetts, Minnesota, Missouri, Montana, Nebraska, New Jer- 

 sey, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode 

 Island, Tennessee, Texas, Utah, Virginia, Washington, West Virginia, 

 Wisconsin, and Wyoming. AH 3 races of the cowbird are involved 

 as are 10 races of the yellowthroat: brachydadylus, trichas, ignota, 

 campicola, occidentalis, inseperata, chryseola, arizela, sinuosa, and 

 scirpicola. 



For some of the western races of the yellowthroat, the records are 

 few in number, but this fact seems to be due more to a lack of observers 



