Bird-Lore's Twenty-first Christmas Bird Census 347 



These records will be published in the February issue of Bird-Lore, and 



it is particularly requested that they be sent to the Editor (at the American 

 Museum of Natural History, New York City) by the first possible mail. It will 

 save the Editor much clerical labor if the model here given and the order of the 

 A.V. U. 'Check-List' be closely followed.— ]. T. N. 



Notes on the Plumage of North American Birds 



FIFTY-EIGHTH PAPER 



By FRANK M. CHAPMAN 



(See Frontispiece) 



Cowbird (Molothrus ater. Figs. 1-3). A Cowbird in nestling plumage may 

 be cared for by any one of the ninety-odd species on which female Cowbirds 

 have imposed their maternal duties, but one may be sure that it will never be 

 under the charge of a Cowbird. Its identity, therefore, will not be revealed by 

 its apparent parent and a drawing (Fig. 3) of it is therefore presented in our 

 plate of its species. This young bird, it should be added, is making its character- 

 istic appeal to the bird world at large rather than to the adult Cowbirds with 

 which the exigencies of illustration associate it. 



The post-juvenal, or first fall molt, begins, in the vicinity of New York City, 

 in late August or early September, and by a complete change of plumage the 

 young bird now acquires its first winter dress which is essentially like that of the 

 adult. During the molt the young male presents a strikingly mottled appear- 

 ance as the new incoming black feathers patch its grayish nestling dress. There 

 is no spring molt and the very slight difference between summer and winter 

 plumage is due to wear and fading. 



Bronzed Cowbird {Tangavius ceneus. Figs, 4, 5). The nestling plumage 

 of the Bronzed or Red-eyed Cowbird is much darker than that of our northern 

 species; in fact, resembles in color our figure (No. 2) of the adult female of that 

 species. 



Unlike Molothrus ater, the young male does not acquire the plumage of the 

 adult at the first fall, or post-juvenal, molt, but at this time passes into a plumage 

 like that of the adult female. The species further differs from M. ater in evidently 

 undergoing a partial spring molt by which the anterior parts of the body ac- 

 quire the bronzy plumage (including the neck 'ruff') of the adult. The fully 

 adult plumage is therefore not gained until the first post-nuptial (second fall) 

 molt. 



