HOST RELATIONS OF PARASITIC COWBIRDS 69 



of the cowbird on June 17, 1914. Herr Schonwetter informed me that 

 he has m his collection a parasitized set taken in Kansas, May 12, 1913, 

 and Mr. Guy Love wrote to me that he had collected no less than 

 twelve parasitized sets in Decatur County, where Col. Wolfe had 

 obtained his set. It appears from this that the rock wren (nominate 

 race) must be a fairly frequent victim in Kansas. 



Mockingbird 



Mimus polyglotlos (Linnaeus) 



The mockingbu'd is molested by the brown-headed cowbird infre- 

 quently, in sharp contrast to the situation in Ai-gentina where the 

 several species of the genus are among the regular hosts of the shiny 

 cowbird. Both the eastern and the western subspecies of the mocking- 

 bird have been reported as victims, and two races of the cowbird, ater 

 and obscurus, are involved in the several records, which come from 

 Maryland, Arkansas, Kansas, Oklahoma, and Texas. The actual 

 records are as follows. E. J. Court informed me that he once found a 

 parasitized nest in St. Mary County, Maryland. This and one other 

 Maryland record are noted by Stewart and Robbins (1958, p. 329). 

 Plank (1919, p. 18) found a similar case near Decatur, Arkansas. 

 According to R. F. Johnston (in litt.), of 49 nests found in Kansas, 

 1 was reported as having a cowbird egg in it. Nice (1931, p. 138) lists 

 another instance, discovered by T. R. Beard at Sapulpa, Creek 

 County, Oklahoma. This record is the same as one which earlier 

 and tentatively I had allocated (1929, p. 252) to the western race of 

 the host, M.p. leucopterus, but it turns out that the nominate eastern 

 race is the form involved. The western race is, however, the one 

 recorded as a cowbird victim in McLennan County, Texas, by Old- 

 right (1890a, p. 58) and at Austm, Texas, by Simmons (1925, p. 172). 

 Oldright (1890b, pp. 33, 34) wi'ites that dwarf cowbirds' eggs seldom 

 are found in mockingbirds' nests but that in 1890 several were found. 

 E. J. Court informed me that he once found a parasitized nest near 

 San Antonio, Texas. 



Catbird 



Dumetella carolinensis Linnaeus 



This bird is an infrequently used host and one with which the cow- 

 bird is generally unsuccessful because, in the majority of cases, the 

 catbird throws out the cowbird's eggs. Many years ago at Ithaca, 

 New York, I conducted some crude experiments to see whether or 

 not this reaction of the catbu'd was correlated with ability to distin- 

 guish its own eggs from those of other birds, specifically those eggs 

 differing in coloration and in size from its own. House sparrow and 

 chipping sparrow eggs were placed in two catbird nests, and in each 



