162 U.S. NATIONAL MUSEUM BULLETIN 233 



Alberta, British Columbia, New Brunswick, Ontario, Quebec, and 

 Saskatchewan in Canada to the following of the United States: Ark- 

 ansas, California, Colorado, Connecticut, Delaware, the District of 

 Columbia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, 

 Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, 

 New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, 

 Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, 

 Texas, Virginia, Washington, West Virginia, and Wisconsin. 



Three races of the sparrow are involved — passerina, arizonae, 

 boreophila — plus all three races of the cowbird. Typical ater is known 

 to parasitize passerina and arizonae; artemisiae is a parasite on 

 boreophila; obscurus molests arizonae. Strangely, this last combina- 

 tion has been recorded but once, to my knowledge; a parasitized nest 

 was found by Talmadge (1948, p. 273) at Hooper, Humboldt County, 

 California, in June, 1948. To the recently described and officially 

 recognized race boreophila should be referred the records formerly 

 assigned to arizonae from Alberta, British Columbia, Saskatchewan, 

 and the recent records published by King (1954, pp. 150-154) from 

 Washington, 



Not only is the chipping sparrow a very frequent victim — in the 

 total number of loiown instances of cowbird parasitism — but it seems 

 to be one of the main fosterers in almost every locality. In Ohio, 

 Hicks (1934) found 115 nests of this bird, of which 60, or more than 

 half, were parasitized. In Maryland, Stewart and Robbins (1958, 

 p. 329) listed 18 records. In southern Quebec, Terrill (1961, p. 10) 

 reported cowbird eggs in 16 out of 138 nests. 



In my own field studies in central New York, over a dozen cases 

 were observed. The percentage of parasitized nests of this species 

 in that region was not as high as it was for some other bu'ds, such as 

 the phoebe, the red-eyed vireo, and the redstart; judging solely from 

 my own local records, the percentage was about 15. This agrees 

 roughly with Terrill's experience in Quebec but falls far short of Hicks's 

 Ohio data. A surprisingly low incidence of parasitism was reported 

 in Michigan by Walkinshaw (1949, pp. 193-205), who found that 

 only 3 nests had been molested out of a total of 66 observed nests — 

 less than five percent. An even lower degree of parasitism was 

 reported in an adjacent area by Sutton (1960, p. 50). In the Edwin 

 S. George Reserve of southeastern Michigan, he found only a single 

 parasitized nest out of 38 observed. Sutton suggested that, since 

 most chipping sparrow nests in that area were well hidden in the 

 dense foliage of red cedars, such a phenomenon might be a factor in 

 reducing the incidence of parasitism. 



Not only is this sparrow a frequent victim, but it seems to be 

 uniformly tolerant of the parasitic eggs; it has been known, on many 



