HOST RELATIONS OF PARASITIC COWBIRDS 121 



for all three races of the cowbird. The nominate race of the chat is 

 parasitized by ater and artemisiae; the race auricollis is victimized by 

 artemisiae and ohscurus. 



The eggs of the chat are very similar in appearance to those of the 

 cowbird; nevertheless, in many parts of its range, the chat is said to 

 desert its nest if a parasitic egg is laid in it. This action is probably 

 due to the sh3mess and nervousness of the bird rather than to any 

 unusual acuit}^ in distinguishing strange eggs from its own. (Many 

 observers, particularly bird photographers, agree that the chat is one 

 of the most tmiid of birds, and hence one of the most difficult to 

 photograph at its nest.) Notwithstanding, on a fair number of 

 occasions, chats have hatched and reared cowbirds. Nehrling (1896, 

 p. 245) found such a case in southwestern Missouri. Smith (1921, 

 pp. 175-177) found a chat's nest in Birdcraft Sanctuary, New York, 

 containing 1 egg of its own and 1 of the cowbird. The next morning, 

 there was a 2i!d cowbird egg; the chat was flushed from the nest. 

 Smith visited this nest every morning, but no more eggs were laid. 

 After observing several day's incubation, he disturbed the nest and 

 eggs in order to photograph them ; even this did not seem to upset the 

 chat. All 3 eggs hatched and all three of the nestlings grew up 

 together and successfully fledged. 



In Oldahoma, Nice (1931, p. 163) quoted Kirn to the effect that 

 the chats there do not desert their nests when cowbird eggs are 

 deposited in them. At Copan, of 22 nests found between 1910 and 

 1917, 13 contained from 1 to 3 cowbird eggs apiece, and 1 nest 

 contained 4 chat eggs and 6 of the cowbird — a very crowded nest 

 indeed. 



In southern Michigan, Nickell (1955, pp. 89-90) found 11 nests, of 

 which all but 1 were parasitized by the brown-headed cowbird. 

 Five of these nests had a single cowbird egg apiece; two nests had 2 

 each; and the three remaining nests had 3, 4, and 5 of the parasitic 

 eggs, respectively. Cowbirds hatched in five of these nests. Four of 

 these five nests reared young to the fledging stage, as follows: first 

 nest, two cowbirds and no chats; second nest, one cowbird and two 

 chats; third nest, one cowbii'd and three chats; fourth nest, one cow- 

 bird and four chats. The fifth nest in which a cowbu-d hatched was 

 destroyed by accident when the young parasite was five days old. 

 Two of the other parasitized nests were not abandoned when first 

 molested but failed to come through successfully. Only 3 nests 

 out of the 10 that were parasitized were abandoned before incubation. 

 Another case in which the young parasite and the young chat grew up 

 together to the fledging stage was reported in North Carolina by 

 Chamberlain (1959). 



