Gull-billed Tern

The Gull-billed Tern was named for its bill, which is thicker than in most other terns and bears a faint resemblance to a gull’s bill in terms of size and shape, at least compared to bills of other terns. The bill is black in adults. Gull-billed Terns have pale gray upperparts, white underparts, and black legs and feet. Black cap and nape in the breeding season.  Length: 14 in.  Wingspan: 34 in.

Sexes similar.

Loses black cap in winter, and has a dark smudge behind the eye.

Similar to winter adults but has a paler bill.

Salt marshes and coastal areas.

Insects, shrimp, mollusks, small fish, and frogs.

Forages mainly from the air, plucking food off of the ground or water.

Breeds along much of the Atlantic Coast of the U.S. and winters in Mexico and Central America. Also more widely distributed in Europe, Asia, Africa, and Australia.

The Gull-billed Tern’s diet is somewhat unusual for that of a tern in that it does not rely heavily on fish.

Unlike many other terns, Gull-billed Terns usually nest in small, loose colonies rather than in large colonies.

The most common call consists of two syllables, sounding like a raspy “kay-wek”.

The nest is a shallow depression on open ground.

Eggs:
Number: 2-3.
Color: Buff with darker markings.

Incubation and fledging:
– Young hatch at 22-23 days.
– Young fledge (leave the nest) a day or two after hatching but remain 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 Gull-billed Tern – the common name and sub-species reflect the nomenclature in use at the time the description was written.

This species was referred to by the earlier writers as the marsh tern, on account of its preference for the salt marshes as a feeding ground, and in many places as a breeding ground also; but, based on my limited experience with it on the Atlantic coast, I should say that it hardly deserves that name, for, at the present time, on the coasts of Virginia and the Carolinas, it seems to prefer to nest on the sandy beaches. But, as it is a cosmopolitan species of wide distribution, its habits differ in different localities. It was formerly much more abundant and more widely distributed on our Atlantic coast than it is to-day, where it is now one of the rarest of the terns. The reduction in its numbers and the restriction of its breeding range may have resulted, by natural selection, in the survival of those individuals which chose to breed on the beaches, where their eggs were not so easily found, and the annihilation of those which nested in the marshes. In support of this theory Mr. H. H. Bailey (1913) says of its breeding habits on the Virginia coast:

The nest location of the few remaining pair has changed from the Inner side of the Island sand dunes and marsh edges to the open beach, but now well concealed amongst the oyster shells, rocks, and pebbles, not an unsimliar location from that of the oystercatcher.

Doctor Stone (1908) regards it as “a rare straggler” on the New Jersey coast to-day. He says:

Formerly it bred rather commonly on the marshes of Cape May County, where it was discovered by Wilson about 1813. In 1809 Turnbull regarded it as rare. In 2886 Mr. H. G. Parker reported it still nesting at the lower end of Seven Mile Beach, and Mr. C. S. Shick spoke of It as still present in 1890, associating with the laughing gulls. We have no subsequent record for the State.

On the Virginia coast Doctor Rives (1890) referred to it as “common at Cobb’s Island, and breeds, formerly in great abundance,” indicating that, even at that date, it had begun to decrease. He says further:

I have been informed that great numbers of the eggs have formerly been taken from the north end of Hog Island, adjoining Cobb’s.

Ten years later, in 1900, Captain Andrews reported to Mr. Dutcher (1901) that the gull-billed terns on Cobb’s Island had been reduced to about a thousand. The following year, according to the same authority, their number had been reduced to 300. In 1903, Doctor Chapman (1903) found only eight pairs there; and when Doctor Bishop and I visited Virginia in 1907 we saw only two pairs on Cobb’s Island, and perhaps 8 or 10 pairs on Wreck Island, a few miles distant. Mr. A. B. Howell (1911) visited Cobb’s Island in 1909 and recorded eight pairs. This record shows clearly the results of the same causes which annihilated the least terns in this region – the demands of the millinery trade for the decoration of women’s hats and the zeal with which a lucrative trade was pushed by local gunners. Apparently the few survivors are holding their ground and perhaps increasing under adequate protection.

Spring: From its winter quarters in Central and South America the gull-billed tern makes it spring migration along the coast in March and April. Audubon (1840) gives the following account of it:

The marsh tern is pretty abundant about the salt marshes of the mouths of the Mississippi in the beginning of April; and by following the shores of the Gulf of Mexico you will find that it comes to us from beyond Texas, as many make their appearance along that coast In a straggling mariner during spring, there being seldom more than half a dozen together, and generally only two. Their journeys are performed over the waters of the sea, a few hundred yards from the shore; and when in want of food they diverge from their ordinary course, and ranging over the land satisfy their hunger, when they resume their route.

Wayne (1910) says that it arrives in South Carolina “about the middle of April and is sometimes common up to May 10, but does not breed. It does not frequent the salt marshes while on this coast, but prefers the sandy beaches.”:

Courtship: Audubon (1840) has given us the only account of what might be considered a nuptial flight. He says:

Excepting the Cayenne tern, I know no American species that has so powerful a flight as the present. To this power is added an elegant lightness that renders It most conspicuous and pleasing during the love season. Then “the happy pair” are seen to rise in elegant circling sweeps, almost in the manner of hawks, and only a few feet apart. until they attain a height of about 200 yards, when they come close together, and then glide with extended pinions through the air, the male over the female, both emitting tender and plaintive notes, while they vary their evolutions at the same height for five or six minutes. After this the winged lovers separate, plunge toward the earth with wonderful rapidity, resume their ordinary notes, and seek for food in concert.

Nesting: On Cobb’s Island and Wreck Island, Virginia, we found four nests on June 26 and 28, 1907. These were all placed on the high, dry sand flats, back of the beaches, beyond the reach of the ordinary tides, but where the spring tides had deposited large quantities of oyster, clam, and scallop shells, with numerous small stones scattered over the sand. These were excellent places for the concealment of the eggs, which so closely resembled small spotted stones that it was very difficult to find them. The nests were quite characteristic and entirely different from other terns’ nests; three of them were merely slight hollows in the sand, among the clam and oyster shells, lined with a few small pieces of shells and bits of straw. The other was a very elaborate structure – a large pile of dead sedge stems, gathered from a neighboring marsh, and the shells of oysters, clams, and scallops. It was lined with small clam and oyster shells, making quite a pretty picture. I measured this nest and found it to be about 18 inches in diameter externally and 4 inches internally. All of these nests were in or near breeding colonies of black skimmers, among which a few pairs of common terns were also nesting. Dr. Paul Bartsch writes to me as follows regarding a breeding colony of this species that he found in the Bahama Islands:

On May 23, 1912, we visited Little Golden Key, which is listed as Middle High Key on the Andros Island chart. The northwest corner of this island consists of a sand spit, the edge of which has been worn off by strong tidal currents. Here we found a large flock of gull-billed and least terns. I crawled up to the edge of the sand bar from the rear and found myself face to face with them, almost too close to them to take a picture, but succeeded In capturing several snapshots, one of which I send to you herewith. On the northeast side of this same Island we found the gull-billed terns breeding. I should say that the colony probably embraced 25 pairs. It seemed rather remarkable to find gull-billed terns assembled in a colony, for my experience heretofore had been to find them nesting scattered among colonies of the common tern; at least this has been the case wherever I have observed them breeding on our Atlantic coast.

I have no recent information about its nesting habits in Texas, but Davie (1889) says:

Dr. James C. Merrill and George B. Sennett found a colony of this species, In company with Sterna forsteri, breeding on a grassy island among lagoons and marshes near Fort Brown, Tex., May 16, 1877. The nests were slight depressions among the short grass, and the eggs were frequently ~vet.

It also breeds on the sandy islands on the coast of Texas, depositing its eggs in slight hollows in the sand.

Eggs: The gull-billed tern raises but one brood in a season and lays ordinarily two or three eggs; sets of four eggs are occasionally laid, but they are uncommon. The eggs are characteristic and are easily recognized by their size and shape. In general appearance they are rounder and lighter colored than the eggs of any of the medium-sized terns. In shape they are usually ovate or short ovate, well rounded at the small end. The ground color varies from “warm buff’s or “pinkish buff” in the darkest eggs to “cartridge buff’~ or “ivory yellow” in the lightest eggs; the prevailing colors are the lighter shades of buff. The markings consist of spots and blotches of various sizes and shapes scattered irregularly over the egg in varying amounts, but a majority of the eggs are not very heavily marked. The underlying spots show all five shades of “brownish drab,” and the heavier markings are in various shades of the darker browns, such as “Vandyke brown,” “bister,” and “sepia.” The measurements of 47 eggs in the United States National Museum average 47 by 34 millimeters; the eggs showing the four extremes measure 51 by 35.5, 49 by 36, 44 by 33.5, and 46 by 32.5 millimeters.

Plumages: The downy young is “pinkish buff” or “cream buff” on the upper parts, shading off to white on the breast and belly; sometimes it is almost unspotted, but usually it is more or less mottled, streaked or spotted with black on the back and on the head. The juvenal plumage is acquired first on the wings, then on the scapulars, back and breast. This plumage is largely “pale gull gray” on the back, with a decided brownish suffusion, which is due to broad edgings of “snuff brown” and “clay color,” deepest on the back and most extensive on the scapulars. These browns gradually fade out, before the bird is fully grown, to produce a soft mottled effect on the upper parts, pale huffy tints on a pale gray ground color. The partial post juvenal molt begins early in September, and the change into the first winter plumage is rapid. The mottled or dusky marked feathers of the upper parts are replaced by the “pale gull gray” feathers of the adult and the heads become whiter. The young bird in its first winter plumage is much like the winter adult, but can be recognized by its slightly smaller bill and by having more dusky streaks on the crown and cervix, as well as traces of dusky in the tail. I have not been able to trace the first prenuptial molt, but infer that it is complete, and that it probably produces a plumage indistinguishable from the adult. I have not been able to find any spring birds showing any signs of immaturity.

Adults probably have two complete molts each year, as in the other terns. They are in full nuptial plumage when they arrive in March; the postnuptial molt occurs in August and September. The adult winter plumage is like the nuptial, except that the head is wholly white, with more or less slaty-gray in the orbital and auricular regions.

Food: All observers seem to agree that the gull-billed tern is mainly, if not wholly, insectivorous in its feeding habits. Wilson (1832) says:

This new species I first met on the shores of Cape May, particularly over the salt marshes, and darting down after a kind of large black spider, plenty in such places. This spider can travel under water, as well as above, and during summer at least, seems to constitute the principal food of the present tern. In several which I opened the stomach was crammed with a mass of these spiders alone. These they frequently pick up from the pools as well as from the grass, dashing down on them In the manner of their tribe.

Audubon’s (1840) spirited drawing illustrates this species in pursuit of an insect. He says:

I believe that these birds never Immerse themselves In the water, as other terns are wont to do; nor do I think that they procure fish, as, on examining a number of individuals, I never found any other food in their stomachs than insects of various kinds.

Gatke (1895) notes similar habits for the species in Heligoland, in the following words:

Anyone who, day after day, has watched the terns darting down Into the sea from great heights, so that the foam spurts high into the air must feel particularly surprised to see a bird so similar In appearance roving about over the fields, suddenly dropping among the long stalks of the potatoes and disappearing from sight. Such, howevcr, is the only way in which the bird seeks its food on this island; for it has never been seen fishing on the sea like the other members of the genus.

Yarrell (1871) credits it with eating other food to some extent, as follows:

The food of this species is somewhat varied. In Ceylon Gol. W. V. Legge found it to consist of frogs, crabs, end fish; in Egypt, Von Heuglin observed the bird darting into the dense smoke of a prairie fire in pursuit of locusts; and in Algeria Mr. Salvin noticed it hovering over glass fields and pouncing upon grasshoppers and beetles. It also captures many species of insects on the wing.

Behavior: The flight of the gull-billed tern is slightly heavier and steadier than that of the other small terns, but it is strong and at times very swift; it seems to have better command of itself on the wing. When traveling it usually flies at a considerable height with rapid wing beats and with steady and direct purpose. When in pursuit of its insect prey its plunges are exceedingly swift and daring. It shows also much of the skill of a swallow in making quick turns or in darting about with great velocity. It shows its command of its movements in its sudden plunges to the ground or to the surface of the water, where it secures its food, as it checks its descent, and darts away again, all of which is done with the grace and ease of an expert. I believe that it never dives and seldom swims, though, of course, it can do both.

I know of no very distinctive field mark by which the gull-billed tern may be easily recognized, although its flight is characteristic, its tail is shorter and less deeply forked than that of the common tern, and, if near enough, its heavy black bill will identify it. The hoarse voice of this species and its characteristic notes will serve to identify it with certainty. On its breeding grounds its notes sounded to me like “Katydid, Katydid,” or “Kadid,” accented on the last syllable, or sometimes like ” Killy ” dr ” Killy-Kadid,” all quickly uttered, loud, and rasping. Mr. Montague Chamberlain (1891) describes the notes “by the syllables Kay-wek, Kay-wek.” Yarrell (1871) says:

During the breeding season its note resembles the syllables che-ah, and, at other times it utters a laughing af, af, af, like a gull.

Its behavior with relation to other species seems to be above reproach. It associates freely on its breeding grounds with common terns, Forster’s terns, laughing gulls, and black skimmers. Reports that it destroys the eggs of other birds seem to have no foundation in fact. Audubon (1840) says that he has seen “this species mastered and driven from its feeding grounds by the kingbirds and the martins,” which would seem to indicate that it is a gentle bird and far from quarrelsome.

Winter: The winter home of the gull-billed tern is far beyond our borders in southern Mexico and South America. Very little seems to be known, or to have been published, regarding its winter habits.

DISTRIBUTION
Breeding range: The American form breeds on the Atlantic and Gulf coasts, formerly from New Jersey, now from Virginia (Northampton County) southward to southern Texas (Nueces and Cameron Counties) and Mexico (Tamaulipas). On the Bahama Islands (Andros, Eleuthera, Inagua, Long Island, etc.) and Cuba. Closely allied forms breed in other parts of the world, making the species cosmopolitan.

Winter range: Mainly in South America, southern Brazil, Argentina, Patagonia, and Chile. A few winter as far north as Guatemala (Chiapam), Mexico (Tehuantepec) and even Texas and Louisiana.

Spring migration: Early dates of arrival: Bahama Islands, May 5; Bermuda, April 29; Virginia, Cobb’s Island, May 10.

Fall migration: Southward along both coasts of South America, arriving in Argentina, September 18, and Ecuador in September. Recorded at Barbados, October 7.

Casual records: Stragglers have been taken at various points along the coast as far east as New Brunswick (Grand Manan, August, 1879).

Egg dates: Virginia: Forty records, June 2 to July 8; twenty records, June 12 to 26. Texas: Nineteen records, May 3 to June 10; ten records, May 6 to 28.