The graceful “sea swallow” faces threats from storms and humans.

Adult Least Tern

With a length of only 9 inches the diminutive Least Tern is the smallest Northern American Tern.

Two of the three subspecies of Least Tern are endangered, including the California and Interior Least Terns. The East Coast subspecies is much more numerous and is not classified as endangered.

Despite its small size, the Least Tern migrates to Central and South America in the winter.

Least Terns nest in colonies, so their territories are limited to an area of about three feet from their nest. Least Tern nests are vulnerable to loss through flooding, predation, and disturbance by human activity. Colony sites of the endangered subspecies usually have special protection to keep people away during the breeding season.

The Least Tern is easy to identify. In breeding plumage it has pale gray upperparts, white underparts, mostly gray wings with two black outer primaries, a black cap with a white forehead, a rather shallowly forked tail, yellowish legs, and a yellow bill with a black tip.

First summer and winter-plumaged birds have a black bill.

Least Tern Chick

 

Juvenile Least Tern

Storms can be a threat to nesting terns, as described in this beautiful video from Steven Siegel of Raven on the Mountain.

 

The Bent Life History series, published by the Smithsonian, has this to say about the Least Tern and its early interaction with humans.

Clearly impressed upon my mind is a vivid picture of a peaceful summer scene in a remote corner of Cape Cod; a broad, flat sandy point stretched for a mile or more out into the sea; the deep blue ocean with its cooling breezes made a pleasing contrast to the glaring white sands which reflected the heat of the midday sun; scattered about on the sandy plain around me were the little hollows containing the eggs of the least tern, almost invisible among the pebbles, hits of shells, and small stones, which they resembled so closely; and overhead the air was full of the graceful, flitting forms of this little “sea swallow,” darting down at me, with sharp cries of anxiety, or soaring far aloft until they were lost to sight in the ethereal blue of a cloudless sky. Such a picture as this was a common sight, in those days, anywhere along the Atlantic coast from Massachusetts to Florida, where the least tern was widely distributed and very abundant in all suitable localities. But its graceful form and delicate plumage was so much in demand for the millinery trade that it was practically extirpated in nearly all places where it was easily accessible, leaving only a delightful memory of a joy that had passed. It was never particularly shy and was easily killed on its breeding grounds, its social and sympathetic habits making it a simple matter to practically annihilate a whole colony in a single season.

Numerous colonies formerly existed on the southern coasts of New England. Mr. William Brewster (1879) wrote that “formerly a small colony of least terns nested annually upon the Ipswich sand hills, but they have been entirely driven away by persecution,” but since that time they have not been found breeding north of Cape Cod. Mr. John C. Cahoon (1890) wrote:

Not a day passes in the summer that the fishermen about this island do not patrol the beach In search of the tern’s and piping plover’s eggs. The birds have no chance to breed. When I first visited the island about six years ago there were several hundred pairs of least tern breeding, but they have now become reduced to less than 25 pair.

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