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Least Tern


Least Tern


The definitive website on wildbirds & nature



Birds of America

By John James Audubon, F. R. SS. L. & E.

VOLUME VII.

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Family
Genus

LEAST TERN.
[Least Tern.]

STERNA MINUTA, Linn.
[Sterna antillarum.]

PLATE CCCCXXXIX.--ADULT AND YOUNG.

As no account of this species exists in the Fauna Boreali-Americana, it is to be supposed that it is not met with beyond the western shores of Labrador, where however I found it in abundance, and breeding, in the beginning of June 1833. On the 14th of August following I observed them at Newfoundland, moving southward in detached parties of old and young, against a strong breeze, and uttering their clamorous cries. Again, in the end of April 1837, hundreds of pairs were breeding on the islands of Galveston Bay in Texas, the numerous specimens which I then examined exhibiting no difference from those obtained in Labrador and in our Middle Districts. Nay, once, in the middle of June, while wading through the quick-sands of Bayou Sara in Louisiana, I came to a high and dry sand-bar where I picked up several eggs belonging to three pairs of birds of this species, although the distance was about two hundred miles from the sea in a direct line. I have at various times observed this Tern on the waters of the Ohio in autumn, and now and then in spring, at the latter period in company with the Short-tailed Tern, Sterna nigra, and have again met with it on the shores of Lake Erie. I have also found it in winter on the eastern coast of the Floridas, but in small numbers. Few birds indeed seem to me to be so irregular in their migratory movements, for they appear to stop at any convenient breeding place from Texas to Labrador.

Few birds are more gentle than this delicate species is at times; for, apparently unaware of danger from the vicinity of man, it allows him to approach within a few yards, whether it be on wing or on the ground. Indeed, in the latter case, I have seen it when gorged so reluctant to fly off that I have more than once thought it was asleep, although on coming up I was always disappointed in my attempts to catch it. Nothing can exceed the lightness of the flight of this bird, which seems to me to be among water-fowls, the analogue of the Humming-bird. They move with great swiftness at times, at others balance themselves like Hawks over their prey, then dart with the velocity of thought to procure the tiny fry beneath the surface of the waters. When you invade their breeding place, they will sometimes sweep far away, and suddenly return, coming so near as almost to strike you. While travelling, their light but firm flight is wonderfully sustained; and on hearing and seeing them on such occasions, one is tempted to believe them to be the happiest of the happy. They seem as if marshalled and proceeding to a merry-making, so gaily do they dance along, as if to the music of their own lively cries. Now you see the whole group suddenly check their onward speed, hover over a deep eddy supplied with numberless shrimps, and dash headlong on their prey. Up rises the little thing with the shrimp in its bill, and again down it plunges; and its movements are so light and graceful that you look on with pleasure, and are in no haste to depart. Should this scene be enacted while they have young in their company, the latter await in the air the rise of their parent, meet them, and receive the food from them. When all are satiated, they proceed on their journey, stopping at another similar but distant place.

Although along our Southern and Middle Districts, the Least Tern merely scoops a very slight hollow in which to deposit its eggs, doing this from the first of April to the first of June, according to the latitude of the place, those which I found breeding on the coast of Labrador had formed very snug nests, composed of short fragments of dry moss, well matted together, and nearly of the size of that of the American Robin, Turdus migratorius; while those met with on the islands near the Bay of Galveston, were observed to have laid their eggs upon the dry drifted weeds which appeared to have been gathered by them for the purpose. The nests are generally placed out of reach of the tides, but on some occasions I have known the hopes of a whole colony destroyed by the sudden overflow of their selected places caused by a severe gale, and have observed that, on such occasions, their clamour was as great as if they had been robbed of their eggs by man.

The number of eggs deposited by this species is more frequently three than four. Like those of most other Terns, they differ somewhat in size and markings, although I never found any so large as those described by WILSON, who states that they measure nearly an inch and three quarters in length, which would better agree with the eggs of the Common Tern. The average of a basketful was found to be one inch and two and a half eighths in length, by seven and a half eighths in breadth. They are rather pointed at the smaller end, and their ground colour is pale yellowish-white, blotched with irregular dark brown spots, intermixed with others of a dull purplish tint.

I have found this Tern breeding among Shearwaters along the Florida coast; and my friend the Reverend JOHN BACHMAN has observed the same circumstance on the "Bird's Banks," on the coasts of South Carolina, where it is abundant, as well as on Sullivan Island.

The common note of our Least Tern resembles that of the Barn Swallow when disturbed about its nest, being as smartly and rapidly repeated at times. When it proves convenient for it to alight on the ground or on a sand-beach, after it has secured a prawn or small fish, it does so, and there devours its prey piecemeal, but it more usually swallows it on wing. On the ground it walks prettily, with short steps, keeping its tail somewhat raised.

LEAST TERN, Sterna minuta, Wils. Amer. Orn., vol. vii. p. 80.
STERNA MINUTA, Bonap. Syn., p. 355.
SILVERY TERN, Sterna argentea, Nutt. Man., vol. ii. p. 280.

LEAST TERN, Sterna minuta, Aud. Orn. Biog., vol. iv. p. 175.

Adult, 8 3/4, 18 3/4.

Breeds from Galveston along the shores to Labrador. Not mentioned as found in the Fur Countries. Returns southward, and passes beyond Texas in autumn. Extremely abundant at times on the Great Lakes, as well as the Ohio and Mississippi.

Adult Male.

Bill about the length of the head, slender, tapering, much compressed, nearly straight, extremely attenuated towards the end. Upper mandible with the dorsal line slightly arched, the ridge rather broad and convex at the base, narrow towards the end, the sides nearly erect, the edges sharp and direct. Nasal groove short, extending to a fourth of the length of the bill; nostrils basal, linear, direct, pervious. Lower mandible with the angle extremely narrow, very acute, extending to the middle, the dorsal line straightish, the sides erect, the edges sharp and inflected, the tip extremely acute.

Head of moderate size, ovate; neck short; body very slender; feet small. Tibia bare below; tarsus very short, slender, compressed, covered anteriorly with small scutella, laterally and behind with reticular scales; toes small, slender, the first extremely small, the third longest, the fourth considerably shorter, all scutellate above, the anterior united by reticulated webs having a deeply concave margin. Claws arched, compressed, acute, that of hind toe smallest, of middle toe by much the largest, and having its inner edge thin and dilated.

Plumage soft, close, blended, very short on the fore part of the head; the feathers in general broad and rounded. Wings very long, narrow, and pointed; primary quills tapering, straight, the first longest, the next five-twelfths of an inch shorter, the rest rapidly graduated; secondary quills short, broad, incurved, narrowed towards the end, the inner straight. Tail rather long, very deeply forked, the lateral feathers extending an inch and seven-twelfths beyond the fork.

Bill light yellowish-orange, its tips black, but the extreme points horn-colour. Iris hazel; feet light orange-red, the bare part of the tibia dusky; claws black. On the forehead, a triangular white patch extending to the middle of the eye; upper part of the head and the nape, with a line from the eye to the bill, deep black; sides of the head, fore-neck and lower parts, pure white; back and wings very pale bluish-grey; first two quills with the outer web greyish-black, and rather less than half of their inner web of the same colour, the rest white, extending to about half an inch from their extremities. Tail white in summer, of a paler tint than the back at other times.

Length to end of tail 8 3/4 inches, to end of wings 9 1/2, to end of claws 7 1/2, to end of shortest tail-feathers 7; extent of wings 18 3/4; wing from flexure 6 11/12; tail 3 1/2; bill along the ridge 7 1/2 twelfths, along the edge of lower mandible 1 5/12; tarsus 7/12; middle toe 7/12, its claw 3/12.

The Female is a little smaller than the male, but otherwise similar.

Young fledged.

Bill greenish-black. Iris dusky. Feet pale yellowish-orange. All the under parts dull greyish-white, as are the upper parts, including the tail; the hind part of the head streaked with dusky, on the back and rump the feathers with a curved marginal band of greyish-brown; primary quills greyish-brown, the outer two darker. At this period the tail is even, each feather narrowly margined with greyish-white.

In a male bird the tongue is 10 twelfths long, slender, triangular, tapering to a point, horny beneath, emarginate and papillate at the base. On the palate are five longitudinal ridges. The posterior aperture of the nares is linear, 7 twelfths long. The oesophagus is 4 inches 2 twelfths long, very wide, its average diameter on the neck 4 1/2 twelfths, within the thorax 9 twelfths; it is exceedingly thin and delicate, its muscular fibres scarcely apparent, unless closely examined. The proventriculus is only a quarter of an inch long. The stomach is 9 twelfths long, 8 twelfths broad, its lateral muscles of considerable size, the cuticular lining dense, tough, longitudinally rugous, and of a reddish-brown colour, as in Gulls. Contents of stomach and oesophagus, small fishes, one of them 2 inches long. The intestine is 14 inches long, its diameter 1 1/2 twelfths. The coeca are 2 twelfths long, nearly 1 twelfth in diameter.

The trachea is 2 inches and 4 twelfths long, its diameter 2 twelfths at the top, diminishing to 1 twelfth; its rings about 105, unossified; its lateral muscles moderate, as are the sterno-tracheal, and single pair of inferior laryngeal. The bronchial half-rings about 25.

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