442 U. S. NATIONAL MUSEUM BULLETIN 211 



bore Biological Survey band No. 64782, continued to feed the banded 

 fledgling and no other, although there were other young Cowbirds 

 near. 



None of these observations prove that the female cowbird recognizes 

 its own young; but they do indicate a lingering vestige of the lost 

 maternal instinct. 



Since the above was written, Russell T. Norris (1947) has published 

 the results of his extensive study of the cowbirds of Preston Frith, to 

 which the reader is referred. The conclusions he arrived at are not 

 far different from what is indicated above, but the following paragraphs 

 are of special interest: 



Of 19 Cowbird eggs, one hatched four days before the host; 4 hatched one day 

 before; 10 hatched the same day as the host; 3 hatched one day later than the 

 host; and one hatched five days later than the host. * * * 



In the 237 observed nests, the hosts laid 668 eggs, of which 383 (57.3 per cent) 

 hatched; the Cowbirds laid 108 eggs, of which 46 (42.6 per cent) hatched; 37.7 per 

 cent of the host eggs, 26.8 per cent of the Cowbird eggs produced fledglings. Of 

 the host eggs that hatched, 64 per cent produced fledglings; of the Cowbird eggs 

 that hatched, 63 per cent produced fledglings. 



With four exceptions all parasitized nests that produced young produced at 

 least one host young. 



The 35 non-parasitized (successful) nests produced 2.94 fledglings per nest; 

 19 parasitized (successful) nests fledged 2.05 host young per nest, indicating that 

 each parasite was raised at the expense of about one host young. 



Plumages. — The plumage changes of the cowbird are simple. 

 The natal down is described by Dwight (1900) as olive-gray. He de- 

 scribes the juvenal plumage in which the sexes are alike, as "above, 

 including sides of head and neck, wings and tail, dark olive-brown, the 

 feathers edged with pale buff, whitish on the primaries. Below, dull 

 white, buffy on throat, breast and flanks much streaked with olive 

 brown. Chin white or yellowish." 



A complete postnuptial molt occurs in August or early September, 

 producing a first winter plumage which is indistinguishable from that 

 of the adult. In the male, the head, throat, and nape are purplish 

 "clove-brown," but all the rest of the plumage, including the wings 

 and the tail, is clear lustrous black with green and purple reflections. 

 The female assumes at this molt the "mouse-gray" plumage of 

 maturity. The nuptial plumage in both sexes is acquired by wear, 

 which is not conspicuous. Adults have a complete molt in September 

 and no prenuptial molt. The seasonal changes are inconspicuous. 



Food. — Beal (1900) reports on the contents of 544 stomachs of 

 the cowbird, taken in 20 States during every month in the year, ex- 

 amined by the Biological Survey: 



The total food in these stomachs was divided as follows: Animal matter, 22.3 

 percent; vegetable, 77.7 percent. * * * The animal food consists almost entirely 



