118 BULLETIN 19 6, UNITED STATES NATIONAL MUSEUM 



the fact that it is longer-tailed and is streaked below rather than 

 spotted. The large dark eye of the thrush is to be compared with 

 the yellow eye of the thrasher (Forbush, 1929). The fox sparrow is 

 reddish-tailed, underparts streaked, not spotted, and the bill is thick, 

 conical, and sparrowlike rather than slender like that of the thrush. 



Enemies. — Cats are responsible for the destruction of some wood 

 thrushes. "Causes of death" listed on banding returns in the files of 

 the United States Fish and Wildlife Service show that on 74 returns 

 8 percent of the deaths were due to cats. 



In 1938 three nests were deserted because of the destruction of the 

 entire clutch of eggs. In each case a few very tiny bits of the shells 

 were found in the nests. Those acquainted with the predators of the 

 region offered the suggestion that the red squirrel may have been guilty. 



Approximately one-fifth of the nests studied were parasitized by the 

 cowbird. This social parasitism decreases the numerical strength of 

 the species by causing desertion in some cases. A few instances will 

 be cited. In a nest containing one cowbird egg and three wood-thrush 

 eggs, the thrush eggs disappeared, one each day, until only the cow- 

 bird egg was left. The nest was deserted after the last egg disappeared. 

 In another case the writer removed three cowbird eggs from one nest. 

 In one nest containing a day-old cowbird and one thrush egg, the 

 thrush egg did not hatch. In contrast, however, a nest contained 

 four wood-thrush eggs and one cowbird egg, all of which hatched and 

 all the young survived to leave the nest. 



Friedmann (1929) in his book on the cowbird gives interesting in- 

 formation on its relation to the wood thrush. The wood thrush is 

 larger than the cowbird yet is frequently parasitized and is also seen 

 caring for young cowbirds. Often the cowbird is the only survivor 

 in a thrush nest. Records of such parasitism come from New Eng- 

 land, Connecticut, New York, Pennsylvania, and Maryland, Ohio, 

 and Indiana. 



Perry (1908) describes a wood-thrush nest in Illinois in which five 

 cowbird eggs were laid. These were laid by at least two cowbirds, 

 since two were deposited on the same day. Despite this, one young 

 wood thrush lived to leave the nest successfully. 



In one instance I recorded the feeding times of a young cowbird 

 which was in a nest with one wood thrush. There are many uncon- 

 trolled factors that would discount any conclusions drawn, but in this 

 case the feedings were of the same number, averaging about one every 

 15 minutes. 



Wood thrushes react to cowbird eggs in several ways. There was 

 some evidence that the wood thrush tried to imbed the intruder's eggs. 

 Friedmann (1929) said in the majority of cases the eggs and young 



