HOST RELATIONS OF PARASITIC COWBIRDS 179 



unspotted egg in it, as well as 3 of the ordinary mockingbird eggs. 

 When my informant was shown several assorted eggs, he picked out 

 a bronzed cowbird's egg and said it was like the one he saw in the 

 mocldngbird's nest. Since then, no additional records have come to 

 my attention. The mockingbird at Brownsville is of the race M.p. 

 leucopterus; the cowbird is nominate aeneus. 



Southern Mockingbird 



Mimus gilvus (Vieillot) 



On the basis of Owen's observations (1861, pp. 60-62) at San 

 Geronimo, Guatemala, this bird is known as a host of the bronzed 

 cowbird. Owens considered it to be a frequent victim and, in one 

 nest, he noted as many as 5 eggs of the parasite together with 2 of 

 the host. Salvin and Godman (1886, p. 452), on the basis of Owen's 

 notes, merely listed this mockingbird as a cowbird host; they gave 

 no additional data, and, indeed, since then no one else has done so. 



The race of the mockingbird at San Geronimo is M.g. gracilis; 

 that of the cowbird is T.a. aeneus. 



Long-billed Thrasher 



Toxostoma longirostre (Lafresnaye) 



There are only a very few records of this thrasher as a host of the 

 bronzed cowbird. In my fu-st account (1929, p. 334), I listed two 

 parasitized nests in Cameron County, Texas, both found by the late 

 R. D. Camp. Since then, one additional case has been reported: 

 Webster (1956, p. 396) saw a pair of long-billed thrashers feeding 

 two newly fledged bronzed cowbirds at Ohnito, Texas, on July 28. 

 This is the first observation showing that this host may rear the para- 

 sitic young; the earlier records were only of observed eggs. The local 

 race of the thrasher is T.l. sennetti; of the cowbird, T.a. aeneus. 



LeConte's Thrasher 



Toxostoma lecontei Lawrence 



In the collections of the Hancock Foundation at the University 

 of Southern California there is an egg of the bronzed cowbird which 

 is reported to have been found in a nest of Le Conte's tkrasher. Un- 

 fortunately, no locaUty nor date is given on the label. Since the 

 ranges of this thrasher and of the bronzed cowbird overlap chiefly in 

 Arizona, it seems likely that the record came from somewhere in that 

 area; if so, the report would involve the nominate race of the host 

 and the northwestern race, T.a. milleri, of the parasite. 



This is the only record that has come to my attention. Since Le 

 Conte's thrasher is a denizen of exceedingly barren and hot desert 

 plains and valleys, the bird probably is largely ecologically allopatric 



