Co DwiGHT, Moults a7id Plumages of Gulls atid Terns. \^t^ 



The moulting of the Gulls and Terns has received little attention 

 save at the hands of C. L. Brehm in 1854, although their plumage 

 has been elaborately discussed by many writers, especially Saun- 

 ders and Coues. It is my present purpose to point out as clearly 

 as circumstances permit the relation that exists between the differ- 

 ent stages of plumage and moult of these interesting birds. It 

 would be far easier to do this if th*fe age of the specimens in hand 

 could be accurately known, but unfortunately there are limits to 

 the physiological and osteological evidences of immaturity even in 

 fresh birds, while dried skins tell us nothing of age unless they 

 chance to show transition stages at a period of active moult. Such 

 specimens in my own collection as I have studied while fresh have 

 enabled me to follow details of moult obscured or completely lost 

 in museum specimens, and I have had opportunity afforded me, 

 through the courtesy of Dr. J. A. Allen, of examining the large 

 series in the American Museum of Natural History. Mr. Wm. 

 Brewster has also given me opportunity of examining his extensive 

 collection, so that I have been able not only to trace successive 

 stages of plumage in a large number of species of Gulls and 

 Terns, chiefly North American, but in many cases I have found 

 specimens in the midst of moult which fill the gaps between the 

 stages. As a result of my studies I can confidently affirm that 

 these birds conform to the same laws of plumage development 

 that operate in other species. These I have so fully explained in 

 a recent article (Annals N. Y. Acad. Sci., XIII, 1900, pp. 74-345, 

 pll. vii), intended to be the first of a series but delayed in publica- 

 tion, that I need only refer to it. Among the Laridae will be found 

 the same definite sequence of plumages and moults as in other 

 species. Adults wear a winter or autumnal and a nuptial, summer 

 or breeding plumage separated by postnuptial and prenuptial 

 moults, while young birds pass from the downy or natal plumage 

 to the Juvenal and first winter dresses by a postnatal and a post- 

 ju venal moult respectively. The moults occur at definite periods, 

 and the feather growth spreads from definite points in the feather 

 tracts, so that nothing is a matter of chance unless it be the arrested 

 development that befalls all organisms and occasions in birds the 

 retention of old feathers among those that are replaced by new at 

 the time of a partial moult. So it often happens that some plum- 



