454 Beebe, Spring Moult of Larus atricilla. [oc^ 



THE SPRING MOULT OF LARUS ATRICILLA LINN. 



BY C. WILLIAM BEEBE. 



Plate IX. 



The subject of the alleged color change in full-grown feathers 

 in certain specific cases, would seem hardly worthy of renewed 

 comment after the thorough papers of Allen and Chapman in the 

 'Bulletin' of the American Museum, Vol. VIII, 1896, pp. 1-44, 

 and of others since then. But judging by analogous biological 

 problems, it is only by reiterated and absolutely overwhelming 

 proof, that any theory, which has once gained wide credence, can 

 be refuted. 



With this intent I offer a few brief notes made in a series of weekly 

 observations on the spring moult of the head and neck of an indi- 

 vidual Laughing Gull (Larus atricilla Linn.), which, brought as a 

 nearly hatched embryo three years ago from Cobb Island, Virginia, 

 was hatched and reared in the New York Zoological Park, and 

 has assumed the full adult plumage. 



Although the individual gull under consideration was kept in 

 an indoor flying cage in a house heated to about 60° throughout 

 the whole of last winter, yet on February 24, the time of the first 

 examination, the early condition of the moult showed that it was 

 normal as compared with the first appearance of black feathers 

 in birds shot in Virginia. From this date on, the bird was con- 

 fined in an outdoor flying cage, with plenty of room for flight. 



February 24. — At this time the forehead is almost white, the 

 feathers of this part showing but a small ashy portion near the base 

 of the shaft. Proceeding backward over the crown and occiput, 

 the winter feathers show an increasing amount of ashy color and 

 consequent diminution of white tips to the barbs, until on the nape, 

 the predominance of the former hue produces the effect of the dull 

 nuchal ring of winter. The only feathers which appear loose in 

 their sockets and about to be moulted are the small ones about the 

 eyes. At this examination there are on the head twenty half- 

 grown new feathers, all in a narrow area on the crown, partly 



