Gull-billed Terns are very rare in New York and are known currently from only five saltmarsh islands off the south shore of Long Island in Nassau County.
Gull-billed Terns are at the northern extent of their range in New York and their statewide distribution is highly restricted. They are known to breed on only five marsh islands off the south coast of Long Island in Nassau County. They are threatened by habitat loss and human disturbance. Their coastal salt marsh habitat is threatened by changes to hydrological processes due to coastal development and by sea-level rise and increasing storms due to global climate change. This species is especially sensitive to human activity near nesting locations (Molina et al. 2009).
This species is so rare in New York that it is difficult to compare distribution over a limited time period. Gull-billed Terns were found in three blocks in the first Breeding Bird Atlas from 1980 to 1985 and in five in the second atlas from 2000 to 2005 (McGowan and Corwin 2008). During both atlases the species was restricted to the south shore of Long Island in Nassau County, with one record from the first atlas from nearby southwestern Suffolk County (McGowan and Corwin 2008).
Gull-billed Terns have likely always been a rare and local breeder in the state. The long-term trends are unclear. A few specimens were taken in the 1880s during the breeding season from sites where breeding is presently known or suspected (Griscom 1923, Bull 1964, McGowan and Corwin 2008). The species was likely extirpated from the state for an unknown extent of time soon after those specimens were taken (Griscom 1923, McGowan and Corwin 2008). There are only sporadic records; some associated with hurricanes during migration in the fall from 1934 to 1975 (Cruickshank 1942, McGowan and Corwin 2008). Breeding was confirmed in the state in 1975 by the discovery of a pair with a nest with eggs on South Line Island in Nassau County (Levine 1998).
Although Gull-billed Terns don't occur in large numbers in New York, populations may be threatened by habitat loss and human disturbance. A combination of factors may contribute to the dramatic declines of coastal salt marsh, that Gull-billed terns use for both nesting and foraging, on Long Island over the last 50 years (Hartig 2002). Changes to hydrologic processes resulting from coastal developement coupled with increases in sedimentary sulfide associated with human development are also believed to play primary roles in the decline of coastal salt marsh (Montalto and Steenhuis 2004, Kolker 2005). Sea-level rise and increased storms and flooding due to global climate change ia also a threat. Gull-billed Terns are particularly sensitive to disturbance and may abandon nests more readily than other tern species (Molina et al. 2009). Recreational boaters driving at high speeds or anchoring near salt marsh islands may disrupt terns from parental care of eggs and chicks leaving them vulnerable to predation. If colonies were to reestablish on beaches in New York they may be restricted by available habitat that is undeveloped and free of disturbance from recreational beachgoers and beach driving.
Management for Gull-billed Terns requires both the protection of existing colonies to enable populations to perpetuate and grow, and the restoration and protection of habitat for terns to move into as populations expand or disturbed colonies need to relocate. Discouraging gull colonies at some locations may be necessary to reestablish previous nesting locations and can be done through a variety of methods including establishing a monofilament grid over the area, culling, or disturbance by dogs (Kress et al. 1983, Kress 1997, Nisbet 2002, Blokpoel et al. 1997). Managing predators may be effective in certain circumstances where nest predation is high (Molina et al. 2010). Maintaining and protecting habitat at a number of suitable nesting locations is ideal even if some sites are temporarily unoccupied to allow colonies to relocate when disturbance occurs. Posting educational signs just prior to the nesting season has been an effective method at limiting human disturbance to colonies of other tern species on beaches (Burger 1989).
At a minimum, continued monitoring of known nesting locations in New York and inventory of past and potential nesting locations is needed. Information on reproductive success in addition to the population index counts that are conducted annually by NY DEC would be useful to determine trends in productivity. If breeding success is deemed to be low, then threats to individual colonies may be identified and management actions can be taken if needed. Migration routes, stopover locations, and overwintering sites need to be determined especially along the Pacific and Mexican coasts (Molina et al. 2009). More research and monitoring of environmental toxin loads, genetic research on subspecies distributions, and dermining productivity of roof nests in the southeastern U.S. are also priorities (Molina et al. 2009).
Historical habitat in New York is unclear due to lack of historical nesting descriptions in the state. Bent (1921) called this species the "marsh tern" because it nested along marshes and fed over them (Molina et al. 2009). However, most colonies along both the Atlantic and Gulf coasts nest on sandy beaches, barrier islands, or dredge spoils and often occur near ocean inlets (Portnoy 1977, Chaney et al. 1978, Schreiber and Schreiber 1978, Parnell and Soots 1979, Molina et al. 2009). In New York, Gull-billed Tern nests have been found on dredge spoil islands within bays and marshes and on barrier beaches (McGowan and Corwin 2008). The one barrier beach location previously known from New York has been abandoned and all currently known breeding locations are on bay islands consisting of marsh.
New York is at the northern extent of the Gull-billed Tern's range and its statewide distribution is highly restricted. They are currently only known during the breeding season in small numbers from five locations off the south shore of Long Island in Nassau county and previously in southwestern Suffolk County (Levine 1998, McGowan and Corwin 2008, NYSDEC 2011). The known recent breeding locations include East Channel Islands, Cinder Islands group, Garrett marsh, Long Meadow Island, and an island off of Big Hassock (McGowan and Corwin 2008, NYSDEC 2011). The species doesn't spend the winter in New York (see Global Distribution).
BREEDING: The breeding range of the Gull-billed Tern includes southern California (San Diego Bay, Salton Sea), the western coast of Mexico (Sonora, Sinaloa, Baja California, Gulf of California), the Atlantic and Gulf coasts of North America from New York (Long Island; scarce north of Maryland) south to Florida and west to southern Texas (also inland); and probably also in Tamaulipas and Veracruz in eastern Mexico, the Bahamas, and Virgin Islands (Anegada, probably Sombrero, formerly Cockroach Bay); in South America (southwestern Ecuador, and from central Brazil south to northern Argentina); and in the Old World from northern Europe, central Russia, southern Mongolia, and eastern China south to northwestern Africa, Asia Minor, Iran, India, Sri Lanka, and southern China; and in Australia (Sprunt 1954, AOU 1998, Molina et al. 2009). NONBREEDING: The nonbreeding range in the Americas includes coastal areas from Nayarit, the Gulf Coast, and southern Florida south through Middle America and the West Indies to Peru and northern Argentina (AOU 1998). In the Old World, the nonbreeding range extends from tropical Africa, Persian Gulf, India, Southeast Asia, eastern China, and the Philippines south to southern Africa, Java, and Borneo; also Australia and Tasmania (AOU 1998).
The Gull-billed Tern is a medium-sized tern. Adults in breeding plumage display a stout black bill, black legs, black cap, and light grey back.
Gull-billed Terns are stout, white, blunt-billed birds that feed in marshes and adjacent coastal uplands (Forbush 1939, Harrison 1983, Cramp 1985). They are similar in size to other medium-sized terns. Their flight is usually more buoyant and gull-like than that of other terns (Vinicombe and Harris 1989). While in breeding plumage, a black cap extends from the feathers between the eye and bill, around the eyes, to the nape. The rest of the upper parts, wings, and tail are pale gray. The side of the head, underparts, and wing linings are white. The long flight feathers that extend along the outer edge of the wings and that form the lower border of the folded wing (primaries) are grayish-black underneath and frosty-gray above. The legs and feet are black. The heavy black bill lacks the sharp tip of other terns and is stouter and proportionately shorter. The sexes are similar in appearance. Winter plumage is similar to the breeding plumage except that the black cap is nearly absent, with only some remnant spotting near the rear of the crown. A blackish patch extends from the eye to the feathers covering the ears (auriculars), although the extent of this is quite variable (Harrison 1983, Cramp 1985). Recently fledged juveniles are similar to adults in winter plumage except that the head is darker with more blackish spots and the gray back and upper wing are edged in tan, giving the back and wings a buff-colored appearance when the bird is in flight. The downy young are variable in appearance but generally cream, buff, or peach-colored, with darker down on the dorsal surfaces. Young usually have two dorsal stripes on the crown, nape, and back, and a distinctive dark smudge behind the eye. The bill is typically light pink at hatching and darkens with age. The feet are light pink and darken to an orange-brown with age (Harrison 1983, Cramp 1985). The typical call is a nasal "tee-hee-hee" or "kat-y-did" (Bent 1921). Terns attacking terrestrial predators will frequently utter a harsh "grack" call during defensive dives (Sears 1981). Nests can be scraped in sandy barrier beaches and dunes above the high tide line, shell bars or banks, or saltmarsh islands (Bent 1921). The eggs are cryptically colored. The background color may vary from buff to olive, and the mottling is somewhat finer grained than the pattern of the Common Tern (Sterna hirundo) egg. The eggs also have a characteristic "frosty" appearance which also distinguishes Gull-billed Tern eggs from those of the Common Tern (Bent 1921, Harrison 1975).
The Gull-billed Tern is a medium-sized tern with a stout black bill, black cap, black legs, and a light grey back. The thick black bill distinguishes this species from other terns.
Adults in breeding plumage are easiest to identify but juveniles and birds in their winter plumage can also be distinguised from other tern species.
Gull-billed Terns nest in colonies usually among other terns or Black Skimmers. They are essentially monogamous and form long-term pair bonds (Moller 1981). See Sears (1981) for a description of the aerial and ground displays Gull-billed Terns enact during pair bonding, courtship, and before and after copulation. They also have an array of threat displays which may include opening their bill in a gape at the intruder, extending neck outward and abducting wings, or tossing their head back and forth. See Sears (1981), Cramp (1985) and Molina et al. (2009) for further description. They aggressively defend colonies from nest predators and may dive and threaten much larger predatory birds that approach their colonies such as egrets and herons (Molina et al. 2009). Once eggs are laid, both the male and female incubate them. One study in California documented roughly equal incubation times by the male and female (Molina 1999). Young are precocial, meaning they are fully developed and mobile at hatching. Gull-billed Tern chicks, do however, rely on their parents for food. Both parents feed and brood the young; the female feeds them more often (Molina et al. 2009, Lind 1963).
The Gull-billed Tern's diet mostly consists of a variety of marine and terrestrial insects. In addition, they eat other invertebrates, small vertebrates, and the eggs and young of other birds. Major dietary items include arthropods, locusts, grasshoppers, dragonflies, insects, spiders, and marine life such as fiddler crabs, crustaceans, crabs, and sand bugs (Wilson 1840, Bent 1921, Sprunt 1954, Rohwer and Woolfenden 1968, Cramp 1985, Quinn and Wiggins 1990). Vertebrate fauna consumed include fish, frogs, toads, lizards, and small mammals (Bent 1921, Dement'ev and Gladkov 1951, Bannerman 1962). They are occasionally opportunistic predators on the downy chicks of other beach-nesting birds (Densmore 1990, Molina et al. 2009).
Gull-billed Terns generally occur on Long Island from mid-May through August or into early September. Extreme dates are May 2 and September 17 (Levine 1998).
The time of year you would expect to find Gull-billed Tern active and reproducing in New York.
Gelochelidon nilotica (Gmelin, 1789)
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This guide was authored by: Kelly A. Perkins
Information for this guide was last updated on: June 17, 2011
Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Gelochelidon nilotica. Available from: https://guides.nynhp.org/gull-billed-tern/. Accessed September 22, 2019.