Least Tern

The Least Tern is a very small tern which in breeding plumage 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.  Length: 9 in.  Wingspan: 20 in.

The sexes are similar.

Winter adults have gray primaries and a black bill.

Immature birds have faintly barred backs.

Least Terns inhabit large rivers, salt flats, and coastal beaches.

Least Terns eat fish, insects, and crustaceans.

Least Terns forage by plunging into the water after fish, or by plucking insects from the water’s surface.

Least Terns breed across parts of the Atlantic, Pacific, and Gulf Coasts, as well as along large river systems of the central U.S. They winter along coastal areas south of the U.S. The Pacific Coast and interior populations are endangered.

More information:

Bent Life History

Visit the Bent Life History for extensive additional information on the Least Tern.

Of the three subspecies, the Pacific and Interior birds are endangered.

Least Terns nest in colonies, and are sensitive to water level changes which can flood nests.

Common calls include a “pid-ik-adik”.

The Least Tern’s nest is a scrape lined with debris placed on open, sandy ground.

Number: Usually lay 1-3 eggs.
Color: Buffy or green with darker markings.

Incubation and fledging:
The young hatch at about 20-25 days, and leave the nest in several days, though they associate with the adults for some time.

Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.

Bent Life History for the Least Tern – the common name and sub-species reflect the nomenclature in use at the time the description was written.

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.

This and other Massachusetts colonies were practically annihilated during the next few years, but a few small colonies have always survived on the south coast of Martha’s Vineyard, though they became much reduced in numbers. On the much-frequented beaches, near the summer resorts, the birds were shot and their eggs were picked up by boys; cats undoubtedly did their part in the extermination; and occasionally a whole colony ‘eras washed out by an extra high tide. During recent years, since 1905, the least terns have been slowly increasing in Massachusetts; they are now breeding again in several places where they had been entirely extirpated, on the mainland as well as on the islands.

In Wilson’s time the least terns bred abundantly on the New Jersey coast. During his whole stay on the Cape May beaches they flew in clouds around him. Mr. G. S. Morris says, writing of the same spot in 1881, in some notes sent to Dr. Witmer Stone (1909):

The least terns bred in considerable numbers. and were equally vociferous in their protests against intruders. It Is difficult, at this late date (1909), to give an estimate of numbers, but I can remember standing in one spot and seeing five or six nests within n radius of 15 or 20 feet; but my recollections are that these conditions only pertained to an acre or so of the beach. In the summer of 1884, in July, I could find no least tern’s eggs, and natives told me they no longer found eggs on the beach. During, the period 1881ó1886 I saw a good deal of the slaughter of the birds in this region. I remember coming upon two professional millinery gunners, I think in the summer of 1885, who had two piles about knee-high of least and common terns, which they said they were sending to New York, my recollection being that they got 12 cents apiece for the birds.

Dr. Witmer Stone (1909), writing of the conditions in 1908, says:

Mr. H. G. Parker in 1888 estimated that there were only 30 pairs left on Seven Mile Beach, and Mr. Philip Laurent (1892) says that some still breed there. Since then we have no definite breeding record, but Mr. W. L. Baily saw two birds together at Stone Harbor, July 15, 1899, which he felt sure were nesting.

Since that time least terns have increased in numbers all along the coast where protected.

The most pitiful tale of destruction is the story of the Cobb’s Island and other colonies on the coast of Virginia. Mr. 11. B. Bailey (1876), in writing of the nesting habits of the least tern, or “little striker,” on Cobb’s Island in 1875, says: Colonies of about 50 pairs each of this species extend the whole length of the island at about a distance of 1 mile apart.

Least terns were astonishingly abundant all along the Virginia coast at that time, but during the next decade their destruction was appalling. Professional collectors for the millinery trade spent the greater part of the breeding season on the islands and killed the innocent birds in almost incredible numbers. The resident fishermen and oystermen also found it a lucrative occupation. As many as 1,200 birds were often killed in a day, and one of the residents, who had taken part in the slaughter himself, told me that as many as 100,000 terns were sometimes killed in a season. Mr. William H. Fisher (1897), writing of conditions in 1891, says:

When I first went to the island about 28 years ago the least, common, and Forster’s terns nested there in colonies of thousands, but now few of them breed and the least is seldom seen. During four days on the island in May, 1891, I only saw one of the latter, and it was as wild as an oyster catcher, which is a very wild bird. The royal tern also nested on the island at one time.

The least terns disappeared entirely during the next 10 years. Dr. Frank M. Chapman (1903) visited Cobb’s Island in 1902 to gather material for his habitat group, and found them entirely gone. He says of their destruction:

The former captain of the life-saving station told me of 1,400 least terns being killed in one day; willie the present captain of the station and Mr. E. B. Cobb, owner of the island, informed me that when terns were first killed for millinery purposes they, with another man, killed 2,800 birds in three days on and near Cobb’s Island. The birds were packed In cracked ice and shipped to New York for skinning, 10 cents being paid for each one.

The least terns were reported as increasing again in 1905, but when I visited the island during the height of the breeding season in 1907 I failed to see a single bird of this species.

The colonies on the coasts of North and South Carolina were not completely annihilated, but they were greatly reduced in numbers. Mr. Arthur T. Wayne (1910) says:

Hunters came from the north with regular outfits to wage war against these poor, defenseless creatures, and in one season alone all of these terns breeding on Bull’s Island were killed.

In Florida the same cruel work of destruction was systematically conducted. Mr. XV. E. D. Scott (1887) thus describes the methods employed:

About 4 o’clock this afternoon a “sharpie” schooner, some 45 feet In length, came from the direction of Big Gasparilia Pass and anchored within 200 feet of us. The crew to the number of four at once went on the beach, and from the time they landed until dark there was a perfect fusilade. Going over to see what they were doing I found that they were killing all kinds of shore birds and least terns. One of the men told me that this was Mr. Batty’s boat, and that they were collecting birds for the “plume market”; that Mr. Batty was down the beach shooting and would be back for supper. They had bunches of Wilson’s plover (breeding), least terns, and various kinds of sandplpers. These birds are skinned, partly filled out with cotton, and at once wrapped up in paper and packed away to be finished after reaching the north. They were killing and preparing by these methods, during the time I was near Mr. Batty’s party, from 100 to 150 birds a day. I called on Mr. Batty later in the evening and learned something of his work.

Spring: Mr. William Brewster (1879) has written the following attractive account of the arrival of the terns on their breeding grounds:

Spring comes over the sea later than upon the land, and fewer tokens are given of its presence. There is no freshening grass; no budding foliage, nor springing up of green things in sheltered places. Summer may be close at hand, but as yet the sea gives no sign. When the wind is from the north the waves in the bay have that steely glint that they have borne all winter. The sand drifts drearily over the wind-swept beach ridges, and the marshes are black and brown, while in the interior robins may be hopping nbout upon green lawns and violets blooming in every woodland nook. The ducks and geese, it is true, are marshaling their cohorts and stretching out in long lines northward, but the breath of ocean is still chill and cold. Indeed, the season is commonly far advanced and the apple orchards In bloom inland ere the winter gulls are gone to their distant breeding grounds. Scarcely has the rear-guard of their legions departed, when the terns begin to appear.

The least terns, although the smallest and seemingly the most delicate of their tribe, arrive first. By the middle of May they appear in certain favored spots – for they are not anywhere very numerous – and small colonies of from 10 to 50 pairs are soon formed at various points along the shores of Cape Cod and upon some of the more sandy islands in the Vineyard Sound.

Nesting: The localities usually selected by the least tern for nesting are broad, flat, open sand beaches, entirely devoid of vegetation, where there are more or less small stones and bits of shells scattered about, among which the eggs are quite difficult to detect. The eggs are usually laid well above the reach of the ordinary high tides, but occasionally the combination of a heavy gale with the spring tides will result in the washing out of a whole colony. This has occurred several times on the south shore of Martha’s Vineyard, where the beaches are low and much exposed. Whereas other terns almost always nest on islands, the least tern frequently breeds on suitable beaches on the mainland if they are not too near human habitations. The depredations of cats, rats, or small boys will drive them away from much frequented beaches.

In the northern portion of its range, at least, these terns usually select a section of beach somewhat apart from other species, though they often associate to some extent with piping plovers. In the Carolinas they are found breeding among or near the common terns and black skimmers. The nest is merely a small hollow scooped in the sand, in which usually two eggs are laid, occasionally three, and very rarely four; the larger numbers are more frequent northward and less so southward. On May 8, 1903, I found a small breeding colony of least terns on Lake Key, one of the Florida Keys, a low, flat island, with sandy or shelly beaches, frequented by migrating shore birds. Beyond a narrow strip of low mangroves, just above the beach, we came upon a small, shallow, muddy pond, where a small but very noisy colony of black-necked stilts were breeding. The least terns’ nests, about 40 of them, were on a narrow strip of beach on the shore of this pond, and consisted of little hollows in the sand, or finely broken shells, of which the beach was composed. Most of the nests contained two eggs, some only one, and those that we collected were all fresh. The nests were strung along in a row a few feet apart. A few pairs of Wilson’s plover were breeding on the beaches and among the small m~ngrove bushes. In the Florida Keys and West Indies the eggs of the least tern are gathered for food. The bird is locally known there by a variety of names, such as “killing peter,” “kill-em polly,” and “sand peter.”:

There are a few small breeding colonies of least terns in the reservations on the coast of Louisiana. In the lower Mississippi Valley there are a few colonies breeding on low, sandy islands in the Mississippi and Missouri Rivers, where their nesting is much delayed by high water in the spring. Mr. Gideon Mabbett, who has studied the breeding habits of this species on the sand bars of the Mississippi River, near Rodney, Mississippi, sent to Major Benclire the following notes: On their first appearance they are generally resting on an old log or piece of drift-wood floating in the back water of the Mississippi River, and remain very quiet for sometimes for a day or two, as though they were tired from a long flight. In a few days they are here in great numbers, flying around and chasing each other as though making love to each other. As the waters recede they take themselves more to the river proper; when the high places are out of water they then prepare the nest, which is nothing more than a small depression scooped in the sand about the size of a half-closed hand.

Mr. F. W. Kelsey (1902) says of their nesting habits near San Diego, California:

In this section we seldom find a set of this species containing more than two eggs. The nesting places vary considerably, sometimes being merely a little wallow, 3 or 4 inches across, in the fine gray or black sand; at other times the eggs are deposited among coarse gravel and broken shells, while at others the nest is in the plain sand, hut is more or less elaborately decorated with bits of rock, shell, or wood. In all cases, however, that have come to my notice, the nests have been on almost level ground, and entirely devoid of shelter.

Mr. A. I. McCormick (1899) describes their breeding grounds in Los Angeles County as follows:

The beaches of this county, from Santa Monica southward, afford excellent breeding grounds for numberless birds of this species. The coast consists mainly of low sandy beaches, extending back 100 to 200 feet from the water’s edge. Back of the beach proper come low sand hills, interspersed with small valleys, and farthest from the ocean are the higher lands, covered with a thick growth of low sage and other shrubs, about 200 feet from the water’s edge. Water on the one side and sage brush on the other mark the boundaries of the nesting grounds of least terns, most of which last year (1897) arrived from the south about May 10. For 10 days they remained, flying high over the sea, seldom if ever coming within gunshot range.

My second and last trip to the beach was made on June 5, when I was fortunate enough to take 15 sets of least tern’s eggs. Six of them consisted of three eggs each. This is exceptional in the county. I have consulted several collectors who have had considerable experience with least terns in this locality, and with one or two exceptions two eggs has been the invariable complement found.

Judging from my own experience I should say that the least tern normally raises only one brood in a season, at least in the northern portions of its range. But Mr. W. Lee Chambers (1908), in speaking of a protected colony in southern California, says:

I should say that fully 75 per cent of the birds in this Colony raised two or three broods.

Probably in warm climates, where the breeding season is more prolonged, second broods are more often raised.

Eggs: The eggs of the least tern are good examples of protective coloration, for they match their surroundings remarkably well and can hardly be distinguished from mottled pebbles. The usual ground color varies from deep rich “cartridge buff” to very “pale olive buff,” or to a color between “pale olive buff” and white. This is more or less unevenly sprinkled with small spots, and sometimes with a few large spots or blotches of dark shades of brown, such as “Mars brown,~~ “sepia,” or “mummy brown.” Most eggs show some spots and many, particularly of the lighter types, show large underlying blotches of “Rood’s lavender” or other shades of “lavender gray.” Some eggs show very handsome patterns of bold dark markings over lighter shades. The shape varies from ovate to short ovate and the shell is thin and lusterless. The measurements of 63 eggs, in the ‘United States National Museum, average 31 by 23.5 millimeters; the eggs showing the four extremes measure 37 by 24, 28.5 by 23 and 29.5 by 22 millimeters.

Young: The period of incubation is said to be from 14 to 16 days. The young remain in the nest for a few days, but soon begin to develop powers of locomotion. They realize the value of the hiding pose and are well aware of their protective coloration; they lie prostrate on the sand, where they are nearly invisible, until almost touched, when they start up and run away with astonishing rapidity. When once started they seldom attempt to hide again and are very difficult to catch.

Mr. Edward H. Forbush has sent me the following interesting observations on the behavior of the young:

Near me were two little young, just hatched and their down hardly dry, yee they were able to run about a little. Near by were several other youngsters. As I lay there propped up on my elbows, awaiting the return of the mother birds, several of them flitted back and forth, and soon their cheeping cries changed to a musical metallic ‘ pid ink,” which has something of the tinkling quality of the bobolink’s note. Soon the mother of the two nearest little ones alighted, and, running to her charges, settled easily upon them, shading them from the hot sun’s rays. Then she turned her gaze upward and called softly in reply to the tender notes of the male, which circled overhead. Soon he alighted and took the mother’s place in shading the young, while she flew away, perhaps to fish and bathe. Soon she returned with a little sand eel, which she gave to one of the tiny ones, who ran to her for it. Then she flew again, descended Into the sea and returned to her charges which the male relinquished to her care. She stood over them with ruffled feathers, and seemed to shake off some drops of water on their little panting forms, and then raised her wings a trifle to shade them from the hot sun. All this I saw at a distance of about 7 or 8 feet, and photographed some of It, the male meantime standing near by. He then took flight, and she nestled over the chick nearest me, coaxing him gently farther away by using her bill and calling the other, which finally followed to her new position and settled by her side.

Again the gentle twittering, and the father came down on the sand with a tiny, bright, silvery fish. A little one stuck Its head out between the mother’s wing and her body, the father courteously passed the fish to the mother, and she fed the chick, which begged for It with open mouth. Again the breadwinner winged his way over the sunny sea and returned with another fish. Now the little ones were asleep under the mother’s breast. He offered her the fish. She refused It. He flew away, but soon alighted and proffered it again, only to be refused again. At last, having full assurance that his family did not need food, he swallowed it himself. Where shall we look to find a lovelier picture of happy, harmonious family relations than that shown here on this desolate beach, beside the roaring surf?:

Plumages: The colors of the downy young are very pale, to match their sandy surroundings. They are practically white, tinged locally above with “ivory yellow” or “pale olive buff.” mainly on the crown and wings; they are spotted or mottled on the head and back with various shades of ” mouse gray”; the under parts are pure white. When about half grown the juvenal plumage appears on the back and then on the head, “pinkish buff” on the back with U -shaped markings of “sepia” or “brownish olive,” one on each feather. The pure white breast feathers appear at about this time, and the dusky wing quills are growing rapidly.

As the young bird attains its growth, in August, the colors become grayer, “pallid mouse gray,” or “pallid neutral gray” on the back and wing-coverts; the forehead and crown “pale olive buff,” with a dusky orbital and cervical crescent, and with numerous subapical, U-shaped spots of “brownish olive.” The wing quills are gray, darker externally, and margined inwardly with white. The lesser wing-coverts, particularly on the bend of the wing, are mottled with dusky and the greater wing-coverts are white clouded with pearl gray.”:

In the first winter plumage according to Coues (1877) the young bird begins to resemble the adult, but differs from it as follows:

It Is somewhat smaller, with considerably weaker bill, the basal portions of which are still more or less dirty flesh color. The forehead and vertex are rather grayish-white than pure white, and the brownish-black of the nape Is Interrupted with light grayish. The uniformity of the colors of the upper parts is interfered with by the still remaining lighter tips of most of the feathers, while some may yet retain the brownish subapical spots of the ama hornotina. The tail has still some traces of dark subapical spots. It is only in early winter that this particular plumage can be seen, for toward spring the birds are hardly to be distinguished from the adults.

The distinguishing features of this plumage usually disappear at a complete prenuptial molt in the spring. At the first postnuptial molt, which occurs in July and August, the young birds become wholly indistinguishable from adults. The winter plumage of the adult is mainly characterized by the brownish black occiput and nape, by the grayish black on the bend of the wing, and by the black bill. The adult nuptial plumage is produced by a complete prenuptial molt in the spring. It is characterized by the glossy black pileum, the pure white forehead, the yellow, black-tipped bill, and other minor points in which its differs from the winter plumage.

Food: The least tern does not differ materially in its feeding habits from other species of the genus. It obtains its food, which is mainly small fish, by skimming over the surface or by hovering in the air and plunging down into the water after its prey. This plunging habit has given it the name of “little striker.” It is very active while feeding and light and graceful in its movements, darting down upon its quarry with speed and accuracy. Its food is generally swallowed on the wing, but if not properly adjusted in the bill it is sometimes dropped and caught again before it reaches the water. Occasionally a bird will alight on the ground to devour its food, and often it flies away with it to feed its mate or its young. Mr. Ora W. Knight (1908) saw them in southern California “lightly skimming over the surface of the water and feeding on the various small surface-swimming crustaceans and small fish or engaged in feeding on various species of beach insects.” The examination of 75 stomachs of birds by Warren (1890) killed on the New Jersey coast in summer “showed that they had fed almost exclusively on little fish; not more than four or five had any traces of insects in their stomachs.” Audubon (1840) refers to their feeding on “shrimps and prawns.” Sand eels are also eaten.

Behavior: The flight of this delicate little “sea swallow” is exceedingly light, graceful, and buoyant; it is at times swift and well sustained. Audubon (1840) has well described its movements as follows:

When you invade their breeding place they ~viil sometimes sweep far away and suddenly return, coming so near as almost to strike you. While traveling 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 marshaled and proceeding to a merrymaking, 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 parents, meet them~ and receive the food from them. When all are satiated they proceed on their journey, stopping at another similar but distant place.

When their breeding grounds are invaded these terns show their anxiety by hovering over the intruder or darting down at him with shrill, strident cries of protest. Wilson (1832) described their cries as sounding like the “squealing of young pigs.” Their ordinary call note, the one most often heard on their breeding grounds, is a shrill, rasping cry, sounding like the syllables “zree ee eep.” They also have a variety of cackling and whistling notes. When attacking an intruder, at which they are very bold, they, utter a sharp “yip” or a series of vehement notes like “keck, keck, keck,” rapidly repeated. While hovering over a school of small fish they become very much excited and noisy, indulging in a constant chorus of shrill cries.

Least terns are particularly gentle and harmless birds. They are not as sociable as some other species, but they live in perfect harmony with their neighbors on their breeding grounds. They seem to prefer the same localities, and become intimately associated with piping plovers, Wilson’s plovers, and snowy plovers in their respective breeding ranges. Their chief enemies are, human beings, who shoot them and destroy their eggs, and dogs, cats, and rats, which eat their eggs and young. Fortunately protection has come in time to save this beautiful species from complete extermination, with which it certainly was threatened.

Winter: There is not much to be said about their winter habits, for most of them spend the winter south of our borders in warmer climes, though a few winter on our southern coasts. They are more given to wandering during the fall and winter, and are more often seen inland then than at other seasons.

DISTRIBUTION
Breeding range: All along the Atlantic coast, from Massachusetts (Chatham) to the Florida Keys, and along the Gulf coast to southern Texas (Cameron County). Islands in the Mississippi and Missouri Rivers; north, formerly at least, ,to southern South Dakota (Vermilion) and central northern Iowa (Clear Lake); and west to northern Nebraska (Niobrara River) and southwestern Kansas (Cimarron River). From the Bahamas (Andros, Abaco, Eleuthera, Watlings Island, etc.) and the Greater .Mitilles (Cuba, Porto Rico, Cayman Islands, etc.), southward throughout the Lesser Antilles to Venezuela (Aruba and Bonaire Islands), and westward to British Honduras. On the Pacific coast, from central California (Monterey Bay) southward to southern Mexico (Tehuantepec). Pacific coast birds are now considered subspecifically distinct.

Breeding grounds protected in the following national reservations: In Florida, Mosquito Inlet, Tortugas Islands.

Winter range: From the Gulf of Mexico (Louisiana coast) south, along the east coasts of Central and South America, to Argentina (Corrientes); and from the Gulf of California, south, along the west coast to Peru (Sarayacu).

Spring migration: Early dates of arrival: New Jersey, Long Beach, May 12; Rhode Island, Newport, May 15; Massachusetts, Chatham, May 2; Nebraska, April 2.

Fall migration: Late dates of departure: New York, September 11; New Jersey, Long Beach, August 25; Maryland, Baltimore, September 4; Kansas, Emporia, August 12; Missouri, St. Louis, August 31; Texas, Bonham, August 20; Lower California, San Jose del Cabo, September 6.

Casual records: S aid to wander in summer north to Minnesota, Ontario, and Nova Scotia, but many of the records are doubtful. Labrador and Newfoundland records are very doubtful. Occurs occasionally in winter on Atlantic coasts of Africa.

Egg dates: California: Eighty-nine records, May 20 to August 12; forty-five records, June 5 to 25. South Carolina and Georgia: Thirty-seven records, May 8 to July 20; nineteen records, May 21 to June 21. Florida: Fourteen records, May 3 to June 29; seven records, May 8 to 21. Massachusetts: Eleven records, May 29 to July 4; six records, June 2 to 29.