544 PROCEEDINGS OF THE ACADEMY OF 



being almost unmixed with white on the extreme nape. The front alone is 

 white. The character, therefore, of a black ocular fascia, and white crown, 

 cannot be considered as diagnostic of the adult full-plumaged bird. 



The chief, and, indeed, the only point to be examined, is the relationship 

 of this species with the . Forsteri, winter specimens of which agree very 

 closely with it. In discussing this question, it must be borne in mind that 

 Audubon was entirely unacquainted with S. Forsteri, or at least did not recog- 

 nize its claims to specific validity, as distinct from S. Mr undo. Indeed, if we 

 compare Audubon's description of his " Havelli" with a winter specimen of <S. 

 Forsteri it will be found that they correspond minutely in every particular of 

 size, form and colors ; and the characters given apply as well to the one 

 as to the other. For, though summer specimens of Forsteri are quite different 

 in the elongation of the tail, color of bill, black pileum, &c, yet in winter these 

 features are quite changed, the tail becoming shortened, the bill blackened, 

 and the pileum restricted to a circumocular fascia. Basing an argument, 

 therefore, upon these data, " S. Havelli, Aud.," might, without the slightest 

 impropriety, be reckoned as a synonym of S. Forsteri. 



Three Terus, obligingly furnished for examination by Mr. Lawrence, and la- 

 belled by him " Havelli," differ in some respect from any winter skins of Fors- 

 teri which have as yet fallen under my observation. Their size and proportions, 

 length of tarsi, elongation of tail, &c, are quite identical. The most perfect of 

 these, evidently an adult bird in full winter plumage, has a stout bill, almost 

 black, its tip for more than a fourth of an inch bright yellow. The bill in fact 

 looks something like that of Thalasseus cantiacus or acxiflavidus. There is a well- 

 defined lateral stripe on the head ; the whole crown is pure white, and even on 

 the nape there are no traces of black, that part being light pearl color, much as 

 the back. But the most distinctive feature of this specimen is that the tail is 

 entirely very light pearl, the inner web of the lateral feather being scarcely, if at 

 all, darker than the outer. A second specimen, a younger bird apparently, and 

 evidently, from the ragged dull brown condition of its primaries, in moult, has 

 the same decided character of tail as has the first one. The bill is even stouter 

 at the base, and the extreme point only is slightly yellowish. The whole crown 

 is variegated with black and white, the former being left nearly pure on the 

 nape. The third specimen is quite like the last, but the inner web of the lateral 

 feather is quite decidedly dusky, showing an approach to S. Forsteri. It will 

 be noticed that where these three specimens are quite identical with each other, 

 in size and proportions, they differ among themselves in colors, both of bill and 

 feathers, and show quite a gradation towards S. Forsteri. 



From the above remarks it will be seen that the question really hinges upon 

 the following point, as yet not positively determined : Does the S. Forsteri in 

 winter, when fully adult, ever acquire a very broad bright yellow tip to its 

 otherwise wholly black bill, and lose entirely the dark character of the inner 

 web of its exterior tail feather? 



Now it is well known, that the younger a Forster's Tern is, the darker is the 

 inner web of the lateral feather ; and the natural inference from this fact is, that 

 with increasing age the inner web may become nearly or even quite as light as 

 the outer. With regard to the broad yellow tip of the bill, it will be noticed, 

 that of the three specimens purporting to be " S. Havelli," each one varies in 

 this particular; so that it would be quite impossible to consider it as diagnos- 

 tic. Therefore, though unable to prove the point incontrovertably, I am de- 

 cidedly of opinion that Sterna " Havelli," is merely the adult winter plumage of 

 S. Forsteri, and not a distinct species. 



Sterna Forsteri Nuttall. 



Sterna hirando, Sw. et Rich., F. B. A., 1831, ii. 412, nee Linn. 

 Sterna Forsteri, Nuttall, Man. Orn., 1834, ii. p. 274 (in note to S. hirundo), and 

 of authors. 



[Dec 



