HOST RELATIONS OF PARASITIC COWBIRDS 147 



it. The two adult sisldns were observed feeding both of the young 

 birds. 



At Haj^s, Kansas, on April 28, 1961, Dr. Charles Ely found a cow- 

 bird egg and an egg of the host in a pine siskin's nest. On May 5 

 only the cowbhd egg remained; on May 8 a 2nd cowbird egg had 

 been laid in the nest. Krause (1954, p. 42) found six nests of the 

 pine siskin at Sioux Falls, South Dakota, one nest of which contained a 

 cowbird 's egg. Dr. Ian McTaggert Cowan informed me that a 

 parasitized nest was found at Enderby, British Columbia. This and 

 Krause's South Dakota record are the only instances I have noted in 

 which the northwestern race of the parasite, M.a. artemisiae, was 

 involved; all the other cases refer to M.a. ater. The race of the host 

 in all these instances is the typical one S.v. pinus. 



American Goldfinch 



Spinus tristis (Linnaeus) 



In some parts of its range the goldfinch breeds so late in the summer 

 (from July to mid-September in many northern portions) that it 

 obviously becomes unavailable as a host for the brown-headed cow- 

 bird; but the overlap elsewhere is sufficient to enable the latter to 

 parasitize this bird rather frequently. This fact is due to variations 

 not only in the date of inception of breeding by the goldfinch but also 

 in the date of termination of egg-laying by the cowbird. Jensen 

 (1918, p. 347), writing of the birds of Wahpeton, North Dakota, 

 reported a nest of the goldfinch with 4 newly-laid eggs of its own 

 and 1 of the cowbird on August 6 — over a month later than my 

 latest date for a cowbird's egg in central New York. 



Some 53 records have been noted: from British Columbia, Alberta, 

 Saskatchewan, Ontario, and Quebec in Canada; from California, 

 Connecticut, Illinois, Indiana, Iowa, Massachusetts, Michigan, 

 Minnesota, Missouri, New York, North Dakota, Ohio, Oklahoma, 

 Pennsylvania, and Wisconsin in the United States. In most areas 

 the goldfinch is a rare victim; in southern Quebec, Terrill (1961, 

 p. 9) found 313 nests during nearly 60 yeare of observing, and of these 

 only 7 contained eggs of the cowbird. Similarly, at Ithaca, 

 New York, an area where both the goldfinch and the cowbird are 

 common and where many nests of the former had been found prior 

 to the end of my work there in 1923, no instances of cowbird para- 

 sitism on this bird were on record. In his extensive study of the 

 goldfinch in southern Michigan, Nickell (1951) noted 264 nests but 

 he mentioned cowbirds in connection with only a single instance — 

 a nest which had b? abandoned with three young cowbirds in it. 

 The presence of the pa asites was not linked directly or inferentially 

 with the abandonment of the nest. In the same region, Walkinshaw 



