HOST RELATIONS OF PARASITIC COWBIRDS 125 



sitism. He implied that this form of behavior might explain the 

 fact that, out of 18 nests found, only 1 was parasitized. Terrill 

 noted that the redstart seldom tolerates the cowbird's parasitism in 

 cases wherein the latter lays first. Nine such nests which were known 

 to him were deserted. 



House Sparrow 



Passer domesticus (Linnaeus) 



This widespread, introduced species is molested very seldom by the 

 brown-headed cowbird. The fact that the sparrow is so much a town 

 and city bird has something to do with the phenomenon, but this, 

 itself, in is not enough to account for the relative immunity of P. 

 domesticus to parasitism. The following are the only records which 

 have been noted. In the Hudson highlands of New York, Mearns 

 (1878, p. 23) found that a cowbird egg had been hatched by house 

 sparrows in Highland Falls; moreover, the young cowbird flourished 

 and remained with the sparrows for some time. Davie (1889) listed 

 the house sparrow as a cowbird host — possibly on the basis of the 

 above statement. R. B. Rockwell (1909, p. 92) found a partially 

 incubated cowbird egg in a house sparrow's nest at Barr, Colorado. 

 Linsdale (1937, p. 177) noted, also at Barr, that a pair of house spar- 

 rows took over a magpie's nest after the original owners had left and 

 started to build their own nest in it; afterwards, he found a cowbird's 

 egg in the nest. Burleigh (1923, pp. 90-91) found a cowbird's egg in a 

 house sparrow's nest inside a bird nestingbox in Alleghany County, 

 Pennsylvania. Williams (1950, p. 153) listed the house sparrow as a 

 cowbird victim in the Cleveland, Ohio, area. Ellis (1924, p. 208) 

 noted it as fosterer in southern California. Imhoff (in litt.) saw a 

 house sparrov/ feeding a fledged cowbird at Bethesda, Maryland, on 

 July 19, 1960. Leathers (1956, p. 68) reported that near his home at 

 New Castle, Pennsylvania, there were in use every year a half dozen 

 house sparrow nests which the cowbirds parasitized regularly. Stamm 

 (1961) made a similar observation in eastern Kentucky. 



The Colorado data involve the race M.a. arfemisae of the cowbird ; 

 the Ohio, New York, Pennsylvania, Maryland, and Kentucky records 

 refer to typical M.a. afer; the southern California record refers to 

 M.a. ohscurus. 



Bobolink 



Dolichonyx oryzivorus (Linnaeus) 



The bobolink is an infrequently used host, but, in Iowa, Gabrielson 

 (1914, p. 79) considered it to be one of the commonest victims of the 

 parasite (although he actually recorded only a single instance of cow- 

 bird parasitism on this species). Some 22 records have been noted 

 in all, distributed among the following states : Connecticut, New York, 

 Ohio, Michigan, Wisconsin, Iowa, Minnesota, and Montana. When 



