HOST RELATIONS OF PARASITIC COWBIRDS 217 



that, many years earlier, Hudson (Sclater and Hudson, 1888, vol. 1, 

 p. 97) once saw two young "bay-winged cowbirds" following and being 

 fed by a yellow-breasted marsh bu'd. This originally caused Hudson 

 to assume that the bay-wing was occasionally parasitic, but later, as 

 he learned of the parasitic breeding of the screaming cowbird, he 

 felt that this observation must have been of two fledglings of that 

 species. This is the most nearly "evidential" observation on record 

 for M. rufo-axiUaris parasitizing any bu'ds other than AI. badius. 

 By itself it is not too good, as young cowbirds are apt to beg for food 

 from adults that did not rear them and very frequently succeed in 

 getting fed by them. 



On the basis of eggs collected by Pablo Girard in western Argentina, 

 Pereyra (1938, p. 260) listed half a dozen other species of birds as 

 hosts of M. rufo-axillaris — an ovenbird, Furnarius rufus; an ant shrike, 

 Taraba major; a flycatcher, Pitangus sulphuratus; a mocking bird. 

 Animus saturninus; a thi'ush, Turdus rufiventris; and a finch, Sicalis 

 pelzelni; but these seem almost certainly to be misidentified records 

 of M. bonariensis, a species which is known to parasitize all of these bu'ds. 



