HOST RELATIONS OF PARASITIC COWBIRDS 155 



parasitized by two subspecies of the cowbird, artemisiae and ater; 

 pratensis is molested by ater; and ammolegus, by ohscurus (one record, 

 a parasitized nest from Ai'izona, now in the collections of the Carnegie 

 Museum). 



Considering the difficulty of finding the nests of this bird, Price's 

 experience (1934, pp. 107-108) is exceptional. He examined about 100 

 nests in Paulding County, Ohio, and found cowbird eggs in 2 of 

 them. This is the only even slightly quantitative data available as 

 to the frequency of parasitism on this host. 



A review of the actual records, all previously listed in my earlier 

 summaries (1929, p. 219; 1931, p. 62; 1934, p. 110; 1938, p. 49), 

 reveals that no one has ever attempted to study a parasitized grass- 

 hopper sparrow: all that the cases show is that eggs of the parasite 

 were seen in nests of this bird. No one has jQi recorded this host as 

 rearing a young cowbu'd, but there is no reason to assume that it can 

 not and does not do so. It seems probable, however, that the grass- 

 hopper sparrow and the cowbird are of little importance to each other 

 as host and parasite. 



Baird's Sparrow 



Ammodramus hairdii (Audubon) 



So little is known of the life history of this sparrow that it is not 

 possible to estimate the extent to which the bird is affected by the 

 parasitism of the cowbird. There are only six records — from Mani- 

 toba and North Dakota — and one without definite locality. Raine 

 (1894, p. 71) reported a nest of Bau-d's sparrow with 2 eggs of its own 

 and 3 of the cowbird. No locality was given, but it was either in 

 Montana or in some adjacent area of Canada. Alfred Eastgate wTOte 

 me many years ago that he had found a parasitized nest in North 

 Dakota. L. B. Bishop collected two parasitized sets of eggs near 

 Devil's Lake, North Dakota. B. W. Cartwright wi-ote me that T. S. 

 Roberts found a nest with 4 eggs of the sparrow and 2 of the parasite 

 in northern Sargent County, North Dakota, on June 18, 1883. Cart- 

 wright's co-worker, R. D. Harris, found eight nests of Bau'd's sparrow 

 in Manitoba in 1931, one nest of which contained a cowbird egg in 

 addition to 3 of the sparrows. On July 14, Harris, watching another 

 nest from a blind, saw a female cowbird approach the nest at 4 : 50 

 p.m. It inspected the blind but came within only two feet of the nest, 

 which held young of the sparrow. The female Bau'd's sparrow re- 

 turned and fed its young; then it saw and drove away the cowbird, 

 after which it returned and began to brood the chicks. 



LeConte's Sparrow 



Passerherbulus caudacutus (Latham) 



LeConte's sparrow is known to be parasitized by the brown-headed 

 cowbird in Alberta, Saskatchewan, and Minnesota. Although the 



