The Zoologist/3rd series, vol 1 (1877)/Issue 5/On the Occurrence of the Smaller Sooty Tern at the Mouth of the Thames

by Howard Saunders

 

ON THE OCCURRENCE OF THE SMALLER SOOTY TERN
AT THE MOUTH OF THE THAMES.

By Howard Saunders, F.L.S., F.Z.S.

 

Some months ago Mr. E. Bidwell, whose name will be familiar to readers of 'The Zoologist,' and who is unremitting in his researches for rarities in the markets and neighbourhood of London, asked me to examine a specimen of a Tern in the possession of a local birdstuffer, named Barton, residing near the West India Docks. It proved to be an adult example of the Smaller Sooty Tern, Sterna anæstheta, Scop., a species not hitherto recorded even as a straggler to the British or indeed to the European coasts, and it bore every appearance of having been recently mounted "from the flesh." Mr. Bidwell subsequently purchased it, and at his request I exhibited it at the meeting of the Zoological Society at Hanover Square on the 6th February, 1877.^[1] The following letter, addressed to him by the son of the man from whom he purchased it, contains all the information that has yet been obtained as regards the locality where the specimen was procured:—

"The Tern you purchased of my father was brought to him in the flesh by one of the Trinity-House men who had just returned from duly on board a lightship at the mouth of the Thames in September, 1875. My father skinned the bird and brought it to me to stuff. The skin was perfectly fresh then, and portions of the flesh were adhering to it. I cleaned the skin and set it up."

Mr. Bidwell and I interviewed both father and son on the matter, and there does not seem to be the slightest ground for doubting that the specimen in question really was obtained somewhere at the mouth of the Thames as stated. The man who brought it in returned to his duty, and unless he reads this or revisits either of the Bartons with some other bird "out of the common," we shall probably remain in ignorance as to the precise lightship where the bird was taken, doubtless during the equinoctial gales, as it was obtained in September.

There are at present three known species of the Sooty Tern group, the largest and best known of which is—

Sterna fuliginosa, Gm. Syst. Nat., i., p. 605 (1788). Its habitat may be described as intertropical, or at most between 40° N. and 40° S. lat., with the exception of the two or three stragglers which have wandered out of their usual limits as far as our coasts (vide Harting's Brit. Birds, p. 169). I can detect no difference amongst the large series I have examined from various localities in the warmer portions of the globe, such as the American coasts and islands, the island of Ascension, the coast of Africa, including the Red Sea, the Polynesian Islands, Australia, and the South of Japan, and the accounts of its habits and nidification seem to agree. Its most noted breeding-place is at Ascension, where the great nesting colony known as "Wide-awake Fair" is one of the few attractions of that huge cinder-heap, and excellent accounts of it have been given by various visitors, the most recent being that by Dr. C. Collingwood (Zool. 2nd ser. p. 979–984), and the late Commander Sperling (Ibis, 1868, pp. 286–288). In all cases the bird seems to sit upon a single egg laid upon the bare ground or amongst the cavities of the lava or coral, according to the locality, making no nest whatever, wherein it differs from the Noddies (Anous), and as soon as the duties of incubation are ended and the young can fly, away they all go to sea. Being single-brooded birds, it was natural to suppose that they bred but once in a year, and at tolerably corresponding periods in either hemisphere; still one was continually meeting with immature specimens, whose plumage at the date of their acquisition was not at all what it ought to have been if they had been hatched at the normal periods or at those at which the birds had been found breeding by various explorers. The explanation of this apparent discrepancy was given me by Drs. Drew and Purchas, R.N., who had recently returned from Ascension, and on enquiring of Lieut. Mountjoy Squire, R.N., at present stationed there, the statements of my friends were confirmed, viz., "that the 'Wide-awakes' come up from the sea to breed about every eight months, or three times in two years."

Probably this is the case in other breeding-places, but I only know it as a fact of this one, and a very remarkable and interesting fact it is. As regards the plumage of this well-known species, it is hardly necessary to say more than that it is sooty black on the mantle, wings and tail, except outer webs of streamers; white on under parts and neck; black on crown and occiput, with a black streak from base of bill to eye, and a broad white frontal band from extending to a little above the eye, but not beyond it; the feet are webbed to the extremities, and the young are for some time dusky on the under parts. The reason for laying stress on these particulars will be shown in treating of the next species.

 

Sterna anæstheta (originally printed S. anæthetus), Scopoli, Deliciæ Flora et Faunæ Insubricæ, i. p. 92, No. 72 (1786), ex Sonnerat's Voyages, p. 125, pl. 84, where the species is described as the Hirondelle de Mer de Panay (Phillipine Islands), whence it is sometimes called the Panay Tern, S. panayensis, Gm. (1788), &c. The range of this species is almost the same as that of its congener, whose example, as we have seen, it has followed in straggling as far as our coast, but the information we possess tends to show that it is rather less oceanic in its habits, and more inclined to hug the shore. In distribution of colour it resembles S.fuliginosa, but it is somewhat smaller in size; the mantle and wings are decidedly less sooty, the white from the frontal band extends both above and beyond the eye, and the web between the middle and inner toes only extends to the last joint of the latter, and does not come down to the claw; the young also are light on the under parts on emerging from the downy stage. A woodcut of the above differences in the formation of the feet of the two species will be found in my paper on the Sterninæ (Proc. Zool. Soc, 1876, p. 605).

 

The third species of the group is Sterna lunata, Peale, U.S. Expl. Exped.—Birds, p. 277 (1848). It is intermediate in size between the other two, has a more distinctly slate-gray mantle, and is altogether washed with a grayish tint; the webs of the feet are similarly incised with those of S. anæstheta, to which it is more closely related than to S. fuliginosa. Its range, so far as we know it at present, only extends from the Moluccas to the Phenix and Paumatu groups of the Polynesian Islands. I do not know of any specimens in collections in this country, but the Leyden Museum, which is far in advance of our national collection in Laridæ, possesses several examples.

 

The Sooty Terns have been separated generically from the true Terns by Wagler, and as one or other of his generic names have been pretty freely adopted, it may be edifying to consider them for a moment, for they supply an excellent sample of the way in which our scientific nomenclature is encumbered by useless and confusing subdivisions. First, Wagler took the MS. description, or perhaps even the type specimen, of J.R. Forster's Sterna serrata, which he identified, and correctly, with S. fuliginosa, but as that individual specimen had a claw somewhat notched and jagged from contact with rocks, he formed for its reception the genus Onychoprion (Isis, 1832, p. 277^[2]), from ὅνυξ, nail, πρίων, a saw. He then took another of Forster's types, named in his MS. Sterna guttata, which this time happened to be an example of S. fuliginosa, in which the accidental serration above referred to was not observable: here it seemed to him was another structural (!) difference, on which he accordingly based the genus Planetis (Isis, 1832, p. 1222^[3]), from πλάνητός, wandering. Not yet satisfied, he took a third specimen of S. fuliginosa, and, almost on the same page, gave it generic distinction under the name of Haliplana (Isis, 1832, p. 1224^[4]), from άλίπλανος, sea-wandering. That was pretty well for one systematist's work with a single species: others have placed the same bird in two other genera besides Sterna, but let that pass.

With regard to the propriety of separating the Sooty Terns generically from the other Sea Terns, I would remark that I can find no structural difference in the former, their only peculiarity consisting in their coloration,—a distinction insufficient in my opinion for the formation of a genus,—and even in that respect there is a species found at Alaska, Sterna aleutica, which, with head markings and mantle similar to those of S. fuliginosa, has a while rump and tail, thus forming a connecting link. But although there is no well-defined structural difference between S. fuliginosa and the typical Sea Terns, there actually exists a real noticeable structural variation in the formation of the feet of such closely allied-species as S. fuliginosa and S. anæstheta—forms which the most persistent genus-maker would hardly venture to place in different genera—yet it is clearly shown that they differ more markedly inter se than they do from typical Sterna.

Under these circumstances, I would submit it to the judgment of ornithologists whether it is not advisable to disregard Wagler's genera, and to retain the Sooty Terns in the genus Sterna.

 

 

1. See: "Proceedings" in The Zoologist, 3rd series, vol. 1, issue 3, p. 113 (Wikisource-ed.)
2. See: digital copy in BHL (Wikisource-ed.).
3. See: digital copy in BHL (Wikisource-ed.).
4. See: digital copy in BHL (Wikisource-ed.).