544 
PROCEEDINGS OE 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 S. 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. hirundo. 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, u S. Havelli, Aud.,” might, without the slightest 
impropriety, be reckoned as a synonym of S. Forsteri. 
Three Terns, 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 acuflavidus. 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 w T ell 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 u Bavelli is merely the adult winter plumage of 
S. Forsteri , and not a distinct species. 
Sterna Forsteri Nuttall. 
Sterna hirundo , Sw. et Rich., F. B. A., 1831, ii. 412, nec Linn. 
Sterna Forsteri , Nuttall, Man. Orn., 1834, ii. p. 274 (in note to S. hirundo ), and 
of authors. 
[Dec. 
