EASTERN BROWN-HEADED COWBIRD 429 



commence his gallantries once more, when the female darts into the air again and 

 the males dash vehemently after her as before. 



In this connection, it may be well to consider the sex ratio and 

 the sex relations. The prevailing impression that the males far out- 

 number the females is probably more apparent than real, for the 

 males are more conspicuous and less retiring; Friedmann (1929) says: 

 "From my observations I would put it as about three males to two 

 females." The sexual relations of the cowbirds may not be above 

 criticism, but they are probably not as bad as they are often painted. 

 Cowbirds have been called monogamous, polygamous, polyandrous, 

 and even plain promiscuous; probably any one of these terms could 

 be applied to certain individuals under certain circumstances; but 

 there is much evidence to indicate that the cowbird was originally 

 monogamous and is so by preference today in most cases. 



Friedmann (1929) writes: 



At Ithaca I have found that each male and each female has a definite terri- 

 tory * * * and that there is a more or less definite pairing between the birds. 

 My experience has been that if the birds are not strictly monogamous, at least 

 the tendency towards monogamy is very strong. My observations have been 

 supported by those of Dr. Alexander Wetmore, of the Smithsonian Institution. 

 He informs me that in Utah he had exceptionally favorable conditions for observ- 

 ing the sexual relations of the Cowbirds, and that in a relatively small area, 

 (which was quite open and made observation of the birds an easy matter), he 

 watched six pairs of Cowbirds, each pair having their own territory, and the 

 birds remaining true to their mates. The male of pair A stayed with female A, 

 and did not consort with any of the other five females. 



At Lake Burford, N. Mex., Wetmore (1920) noted that a pair of 

 cowbirds, mated on June 2, "remained constantly nearby for ten 

 days or more. On June 5 and 6 a second female appeared and fed 

 with the others. The male was seen running at them with his bill 

 pointing straight in the air and then pausing to sing and display. 

 The second female disappeared at once while the pah* remained 

 together until June 13." 



Cowbirds are often seen in small flocks even during the breeding 

 season, which might give the impression of loose sexual relations, and 

 it is well known that, if one of a pair of mated birds is killed, the 

 survivor secures a new mate in a surprisingly short time, showing 

 that there is always an available supply of unmated birds ready to 

 fill in the gap. These flocks are probably made up of such unmated, 

 surplus individuals and are usually seen in places where there are 

 few or no nests; they are not, therefore, breeding birds. Moreover, 

 these flocks may consist of immature, 1 -year-old birds, which cannot 

 be distinguished in the field from adults, which have arrived later 

 in the season than the adults and have not mated. 



