HOST RELATIONS OF PARASITIC COWBIRDS 67 



Evidence of still another instance of a young cowbird being reared 

 by a house wren is afforded from a photograph of such an incident, 

 probably in New York State, taken by A. A. Allen and reproduced in 

 Armstrong (1955, opp. p. 217, fig. b). 



Of comparative interest is the fact that the European wren {Troglo- 

 dytes troglodytes) — a species more like the North American winter 

 wren {T. hiemalis) than it is like the house wren, but yet not too dis- 

 similar in habits — is parasitized frequently by the European cuckoo, a 

 bird larger than the cowbird. Armstrong (1955, pp. 240-242) con- 

 cluded that, in Britain, wrens' nests are parasitized occasionally, 

 apparently only when the nests of other fosterers are not available, but 

 he noted that there were numerous records from continental Europe. 

 As he stated, "it would be difficult to believe that the popularity of 

 the wren with the cuckoo as a fosterer had not been exaggerated did 

 not the evidence of so many authorities concur." In Germany, on 

 more than one occasion, as many as three cuckoo eggs have been 

 reported from a single wren's nest. 



Bewack's Wren 



Thryomanes bewickii (Audubon) 



Bewick's wren is an infrequent victim. Only six actual instances, 

 involving three races of the wren and two of the parasite, have come 

 to my notice. Of the nominate T.b. bewickii, there is a single record, 

 from Missouri, where Nehrhng (1893, p. 244) found a brown-headed 

 cowbird's egg in this wren's nest, which was in a nest box he had 

 provided. He noted that "the entrance hole was very small so that 

 no Bluebird and not even the Tufted Titmouse could enter. Never- 

 theless the cowbird deposited its egg in the nest." Henninger (1902, 

 pp. 400-401) found a parasitized nest of the subspecies T.b. alius 

 in southern Ohio, containing 5 eggs of the Wren and 1 of the parasite. 

 The other four records refer to the Texas race T.b. cryptus and the 

 dwarf form of the brown-headed cowbird, M.a. obscurus. R. W. 

 Quilhn wrote to me many years ago that in the summer of 1925 he 

 collected two sets of eggs, each containing 5 eggs of the wren and 

 1 of the cowbird. In both cases the wrens were flushed from the nest. 

 Quilhn previously had found cowbird eggs in a number of this wren's 

 nests but they were deserted and in most cases did not contain any 

 eggs of the wren. AU the nests used by the parasite were in holes 

 that had been broken or otherwise enlarged so that the rim of the 

 nest was visible. Recently, Air. E. J. Court sent me a card written 

 at San Angelo, Texas, in April 1954, by Fred Nye, describing an 

 incomplete set, which comprised 2 eggs of the host and 1 of the cow- 

 bird. The nest was in a cavity in a rotten stmnp eight feet above 

 the ground; the cowbird egg was on the rim of the nest about four 



