106 U.S. NATIONAL MUSEUM BULLETIN 233 



Yellow-throated Warbler 



Dendroica dominica (Linnaeus) 



The yellow-tliroated warbler is known as a host of the cowbird 

 (typical race) only in Oldahoma and on the basis of single record: 

 a parasitized nest found by T. R. Beard {in Nice, 1931) at Sapulpa, 

 Creek County. The warbler involved is the race alhilora. The 

 absence of additional instances is difficult to explain as this warbler 

 seems to be a suitable host and the cowbird is common in the same 

 areas. 



Grace's Warbler 



Dendroica graciae Baird 



This is another rarely reported cowbird victim about which it is 

 premature to form an estimate. Three instances of cowbird para- 

 sitism have been reported. The late J. P. Norris informed me that 

 in his collection he had a set of 3 eggs of the warbler and 1 of the 

 cowbu'd, taken by O. W. Howard in the Chiricahua Mountains, 

 Cochise County, Arizona, on June 23, 1900. Marshall (1957, p. 112) 

 saw Grace's warbler feeding a fledgling cowbird in the pine-oak wood- 

 lands of southern Aiizona. Sheppard (1959) found a cowbird's egg in 

 a nest of this warbler in McKinley County, northwestern New Mexico. 

 This record, on geographic grounds, must be referred to M.a. artemisiae 

 the two Arizona instances are M.a. obscurus. 



Chestnut-sided Warbler 



Dendroica pensylvanica (Linnaeus) 



The chestnut-sided warbler is a frequent victim of the brown- 

 headed cowbird (races ater and artemisiae). Over 75 definite records 

 have been reported, distributed among three provinces of Canada — 

 Saskatchewan, Ontario, Quebec — and the following of the United 

 States : Maine, Massachusetts, Connecticut, New York, New Jersey, 

 Pennsylvania, and Maryland to Ohio, Michigan, Minnesota, Iowa, 

 and Nebraska. The one record from Saskatchewan, a nest containing 

 1 egg of the warbler and 1 of the cowbird, which was found at 

 Nipawin, on June 24, 1941 by Street {in Houston and Street, 1959, 

 p. 161, 176), is the only record for the cowbird race artemisiae; all 

 the others involve typical ater. In southern Quebec, Terrill (1961, 

 p. 7) found 55 nests of this warbler during about 60 years of field 

 observation, and of these, 16, or 29 percent, contained eggs of the cow- 

 bird. This is a higher incidence of parasitism than has been reported 

 in most other parts of the common range of the warbler and the cowbird. 

 In a much smaller series of nests in Ohio, Hicks (1934) found four 

 cases of parasitism in 12 nests, or 33.3 percent. 



At Ithaca, New York, I observed three parasitized nests and found 

 the chestnut-sided warbler to be a tolerant host, accepting, incubating, 



