62 U.S. NATIONAL MUSEUM BULLETIN 233 



by circumstances to use an unlikely but available nest, such a record 

 means no more than a record of the accidental occurrence of a bird 

 outside its usual range. The fact that the crow was listed as a "cow- 

 bii'd-raiser" cannot be taken as evidence that it reared a young 

 cowbird; the most that can be assumed is that an egg of the latter 

 was found in a crow's nest. The geographical location of the "record" 

 implies that the cowbird involved was typical ater and the crow, 

 typical brachyrhynchos. 



Black -capped Chickadee 



Parus atricapillus Linnaeus 



The black-capped chickadee is a rarely imposed upon victim. Out 

 of many hundreds of nests reported on, only four instances of para- 

 sitism by the brown-headed cowbird have come to my notice — from 

 Iowa, Massachusetts, and Michigan. Goelitz (1915, p. 152) found a 

 nest with 4 eggs of the chickadee and 1 of the brown-headed cowbu'd 

 at Ravina, Illinois, May 8, 1915. The record as published specified 

 the Carolina chickadee but, on geographic grounds, the bird is much 

 more likely to have been the black-capped species. Blocher (1936, 

 pp. 131-133) found it to be parasitized at Amboy, Illinois. Packard 

 (1936) found a nest on May 25 at North Eastham, Cape Cod, Massa- 

 chusetts, containing 4 eggs of the chickadee and 2 of the cowbird. On 

 June 6 the 2 cowbird eggs hatched and 1 chickadee egg was missing. 

 Two days later 2 chickadee eggs hatched but 1 young chickadee was 

 dead. On June 10 the second young chickadee was missing; the other 

 egg of the host never hatched. That same date the young cowbirds 

 were removed for parasitological study. Recently, one other record 

 of this unusual fosterer has been reported. Nickell (1956, p. 136), in 

 a willow stump in southeastern Michigan, found a nest in which a 

 cowbird egg had been laid about 13 inches from the entrance on a 

 narrow ledge of rotten wood, which was just broad enough to prevent 

 it from rolling off. This egg was laid on June 12, 1952, at a time when 

 the nesthng chickadees were already 10 days old; thus it almost 

 certainly would have been abandoned and not hatched by the chick- 

 adees. In Nickell's discussion of the few instances of cowbird para- 

 sitism of this bird, he states that this was the only parasitized nest he 

 had discovered, out of 38 nests observed during 14 years of study in 

 the area. However, in the 1952 survey of the area, the Detroit 

 Audubon Society (1953, p. 70) lists a nest containing 5 eggs of the 

 black-capped chickadee and 1 of the cowbird which had been found 

 by Nickell at Cranbrook. In spite of the discrepancy, I am convinced 

 that these refer to the same instance. 



AH of the above records involve the nominate races of both host and 

 parasite. 



