HOST RELATIONS OF PARASITIC COWBIRDS 151 



cowbird seemed to disturb the towhees greatly but he observed no 

 parasitism. Davis (1960, p. 455) also commented on the scarcity of 

 instances in California but he predicted that the spread and increase 

 of the brown-headed cowbird in coastal California would result in 

 more frequent usage of towhees' nests by the parasite. A parasitized 

 set of eggs, taken near Riverside, is now in the San Bernardino 

 County Museum. 



The towhee is one of the larger of the regular victims of the cow- 

 bird. With none of its fosterers is the parasite more successful. I 

 have learned of no case of a towhee covering over, or in any way 

 trying to get rid of, the strange eggs. Moreover, no host has been 

 saddled so often with large numbers of parasitic eggs; the highest total 

 found in a single nest was 8 cowbird eggs together with 5 of the tow- 

 hee, a set taken in northern Iowa. Sanborn and Goelitz (1915, 

 p. 444) found a nest in Lake County, Ilhnois, also with 8 cowbnd 

 eggs, but with only a single egg of the towhee. There are other 

 records of nests with 8, 6, 5, and 4 cowbird eggs, but, unfortunately, 

 none of these were watched to see what the outcome would be. Most 

 of them were collected as specimens for egg collections — after the 

 manner of the time in which they were found. 



In other nests, with smaller numbers of eggs, the rufous-sided 

 towhee has been found to rear the young cowbirds to the fledging 

 stage. There is, however, a dearth of information as to the fre- 

 quency with which any of the rightful brood survive with the para- 

 site. This is a case wherein observers have failed to place data on 

 record, probably because of their feehng that the occurrence was too 

 common to be worth reporting. 



Brown Towhee 



Pipilo fuscus Swainson 



The brown towhee has been reported as a victim of the brown- 

 headed cowbird a few times in north-central New Mexico, Ai'izona, 

 and California. GrifRng Bancroft informed me many years ago 

 (Friedmann, 1934, pp. 109-110) that he had in his collection two 

 parasitized sets of eggs of this bird; of the race mesoleucus, they had 

 been collected in Santa Fe County, New Mexico, on June 4 and 12 of 

 that year. A third and similar set was mthout precise data ; taken at 

 Santa Fe, New Mexico, on June 12, 1925, it is now in the collection of 

 the Western Foundation for Vertebrate Zoology. Another parasitized 

 set of eggs, taken near Tucson, Arizona, on May 18, 1936, is now in 

 the collections of the Carnegie Museum. J. T. Marshall, Jr. (in 

 litt.) wrote to me that, in the few nests of the brown towhee which he 

 found in the mesquite covered areas near Tucson, Arizona, there were 

 no cowbird eggs but that, in nearby desert locaHties, R. S. Crossin 



630590—63 11 



