HOST RELATIONS OF PARASITIC COWBIRDS 163 



occasions, to rear the alien young. Nuttall (1840, p. 105) recorded 

 watching a chipping sparrow remove its dead young from a nest 

 which contained a healthy young cowbird. I know of no case of a 

 chipping sparrow attempting to bury a cowbird egg under a new 

 nest-lining, and I am not aware of any instances of nest desertion 

 which could be ascribed to the presence of cowbird eggs. No one 

 yet has made a statistical survey of nesting success in the chipping 

 sparrow, a survey against which to appraise the effect of cowbird 

 parasitism, as Hofslund has done with the yellowthroat or Nice with 

 the song sparrow. 



Clay-colored Sparrow 



Spizella pallida (Swainson) 



The clay-colored sparrow is a frequent victim of the brown-headed 

 cowbird in Alberta. The late William Rowan told me that he had 

 collected a series of nearly 20 parasitized sets of eggs near Edmonton, 

 Rowan and T. E. Randall considered the clay-colored sparrow the 

 commonest victim in Alberta. 



Apart from this one area, the sparrow also has been found to be 

 imposed upon by the parasite in British Columbia (two records, now 

 in the collections of the Carnegie Museum), Saskatchewan, Montana, 

 North Dakota, Minnesota, and Wisconsin. The North Dakota 

 record, previously unpublished, consists of a set of 4 eggs of the 

 sparrow with 1 of the cowbird, taken at Stump Lake on June 1, 1901, 

 by A. C. Bent and now in the U.S. National Museum, 



Near Endersley, Saskatchewan, Fox (1961, p. 223) studied nine 

 nests of this sparrow in one season. Of these, eight were parasitized 

 by the brown-headed cowbu-d. In six of the eight, the parasitic eggs 

 were laid before the host had begun to incubate, but in one nest the 

 cowbird egg was deposited after the four young sparrows had hatched. 

 Three of the nests were deserted after they had been parasitized. In 

 none of the eight nests did any of the cowbird eggs hatch. No clay- 

 colored sparrows hatched in any of the nests which had been par- 

 asitized by the cowbird before the host eggs hatched. 



The claj^-colored sparrow has been known to rear the young parasite 

 (Raine, 1894, p. 120; Sparkes, 1952). 



All in all, some 50 records of parasitism have been noted. They 

 involve two races of the brown-headed cowbird; typical ater in 

 Wisconsin and Minnesota; artemisiae westward from North Dakota 

 and Saskatchewan. 



Brewer's Sparrow 



Spizella breweri Cassin 



Brewer's sparrow is a poorly knowm victim of the bro%vn-headed 

 cowbird. It has been recorded in this capacity only in Wyoming 



