iqoi 1 DwiGHT, Moults and Plumages of Gulls and Terns. 6 1 



is nearly identical with that of Larus argeniatus, as I have deter- 

 mined by series of birds of several species taken at important 

 transition points of the moults. 



Of the first class, in juvenal plumage the primaries are wholly dull 

 black with a similar tail, the body feathers being more or less gray 

 or brown, the darkest species of those examined being Z. heer- 

 man?ii, with Z. mariniis., L. occidc?iia/is., L. caHfornicus and Z. argen- 

 iatus somewhat lighter. Z. delawarensis^ L. caniis and Z. brachy- 

 rhy?ichtis are similar in plumage except for their banded tails, the 

 first species differing from all the others in its dusky spotted body 

 plumage. At the postjuvenal and first prenuptial moults the faded 

 dress is partly exchanged for one less brown, the smaller species 

 apparently sometimes assuming a few bluish gray feathers on the 

 back. At the first postnuptial moult, the black primaries and tail 

 are reassumed, and in those species which, when adult, have spotted 

 primaries, there is often the suggestion of a white spot on the first 

 primary. The new tail is speckled with gray, being white basally 

 and laterally ; in banded species the band becomes narrower 

 but does not disappear as is usual in gulls of the type of Z. 

 Philadelphia. The body plvunage acquired is largely white, veiled 

 with brown, except that the gray mantle, mixed with speckled 

 feathers, is now apparent. S. heermanni remains wholly dark. 

 Birds pass their second winter in this plumage, which varies in 

 the proportion of adult characters according to the individual. 

 The second prenuptial moult adds to the grayness of the mantle 

 and to the whiteness of the head and lower parts, and birds would 

 pass for adults were it not for the wings and tails. When these 

 are again renewed at the second postnuptial moult the first pri- 

 mary shows a spot and the rectrices become wholly white or with 

 but a touch of darker color. Later than this we can scarcely 

 follow differences of plumage. The nuptial and the winter man- 

 tles hardly differ, and -the brown streaking of the head in winter 

 appears to diminish with age, while the areas of white on the 

 wings apparently increase, as well as the proportions of the 

 whole bird. 



The gulls which have white primaries when adult, 77.3;., Z. 

 g/aucus, L. barroi'iaiins and Z. leiicoptenis., do not in juvenal plum- 

 age differ very much from Z. argetifatus, being of a uniform 



