Common Terns exhibit a variety of breeding displays including a "greeting ceremony" between pairs where the female stands erect and the male bowed and a "parade" where the male walks in a circle around the female (Nisbet et al. 2002).
Common Terns were historically impacted by hunting and the millinery trade in New York. They are currently threatened by restricted habitat availability, human-commensal predators, habitat loss from coastal development and rising sea-levels from climate change. The Common Tern is state-listed as threatened by the NY Department of Environmental Conservation. There are roughly 50 colonies in a year on Long Island with additional inland populations that are generally smaller and scattered.
The statewide distribution of the Common Tern in NY has remained relatively stable from the first Breeding Bird Atlas (1980-1985) where it was reported in 122 blocks, to the second breeding bird atlas (2000-2005) where the species was reported in 121 atlas blocks (McGowan and Corwin 2008). Inland populations expanded from 25 blocks in the first atlas to 42 in the second (McGowan and Corwin 2008). Year to year variation in numbers on Long Island is generally high. Numbers peaked with 27,270 pairs in 1987 and were at a low in 1995 of 17,442 pairs (Hays 1998, Sommers and Alfieri 1998).
Common Terns were historically abundant on Long Island in the mid-1800s (Giraud 1844, DeKay 1844). It is unclear whether or not there were significant inland breeding populations during this time. Inland populations were first documented along islands in the St. Lawrence river in 1917 (Merwin 1918). After the passage of the Migratory Bird Treaty Act in 1918, nesting colonies began to rebound statewide (McGowan and Corwin 2008, Courtney and Blokpoel 1983, Peterson et al. 1985). More inland populations were established and first documented in along Oneida Lake in 1929 (Stoner 1932) and in Buffalo in 1944 (Beardslee and Mitchell 1965). Upstate numbers declined in the 1970s, while Long Island populations grew with four new colonies (Bull 1964, Hays 1998, McGowan and Corwin 2008).
Common Tern colonies may be threatened by human disturbance, high predation rates from predators associated with human development, flooding and habitat loss due to storms and rising sea-levels due to global climate change. Boating near saltmarsh islands and beach driving and recreation near barrier beach colonies can disturb nesting birds leaving nests and young vulnerable to predation. Elevated levels of environmental toxins such as DDE, DDT, PCBs, mercury, lead, selenium, chromium, and cadmium have been found Common Tern tissues, feathers and eggs in parts of their range (Hays and Risebrough 1972, Custer et al. 1986, Burger and Gochfeld 1988b, Burger et al. 1992, Bishop et al. 1992, Nisbet 2002). Common Terns are particularly susceptible to the effects of DDE and DDT which can cause eggshell fragility and issues with embryo and chick growth and reproductive fitness in adults. Although concentrations of organochlorides like DDT, DDE, and PCBs affected Common Tern populations historically, concentrations were already declining when first reported in the 1960s and 70s (Bishop et al. 1992, Nisbet and Reynolds 1984, Nisbet 2002). Significant levels of DDE, high enough to reduce hatching success, persisted in Common Terns in some Great Lakes sites into the 1980s (Weseloh et al. 1989, Hoffman et al. 1993). Displacement by Herring and Great Black-backed Gulls has been an issue on coastal sites (Kress et al. 1983) and displacement by Herring and Ring-billed Gulls has been an issue on the Great Lakes (Courtney and Blokpoel 1983).
Management for Common Terns requires protection of nesting habitat from development and human disturbance. Posting tern colonies with conspicuous educational signs and symbolic string fencing prior to the birds arrival in the spring has been beneficial to limiting human disturbance. Discouraging gull colonies at some locations may be necessary to reestablish previous nesting locations and can be done through a variety of methods including culling or disturbance by dogs (Kress et al. 1983, Kress 1997, Nisbet 2002). Researchers at some Great Lakes and Lake Champlain islands have had success deterring gulls by constructing a string grid system over nesting areas (Blokpoel et al. 1997, Nisbet 2002). The terns are able to maneuver around the string while the gulls avoid the site. Management of vegetation may be required at some sites where natural overwash and sand scouring is not occurring and predator control may be warranted in some areas.
Continued monitoring of nesting success in addition to the annual population index counts would be beneficial. This would help identify the most successful colonies for conservation and also highlight threats in colonies with low productivity so that management actions may be taken when necessary. The highest priorities for future research are on the wintering grounds. Common Terns have been found wintering along the coasts of Brazil and Argentina (Hays et al. 1997, 1999), however, their distribution along the Pacific coast of South America is poorly known. Basic information on foraging ecology, energetics, and causes of death are poorly known throughout their winter range on either South American coast (Nisbet 2002).
Common Terns use a variety of habitats and may be found on coastal beaches or barrier islands, marshes or inland lakes. They nest on sand, gravel, shell, or cobble in open areas with some scattered vegetation or other cover in which chicks can find shelter (Nisbet 2002). Selection of nesting locations may vary by habitat in different parts of the state. On two islands in Oneida Lake, Severinghaus (1982) found Common Terns selected dried grass as the nesting substrate over stony areas when available and these nests hatched significantly more young than nests located on stony substrate. The relatively recent discovery and apparent expansion into saltmarshes since the 1970s (Buckley and Buckley 1980, Burger and Lesser 1978) has lead to some conjecture as to whether beaches are the preferred habitat on Long Island and human disturbance has forced Common Terns to nest in lower quality marsh habitat which is subject to increased flooding (Buckley and Buckley 2000). Selection in the absence of human presence is difficult to determine, however, both habitat types are currently used successfully in New York (Buckley and Buckley 2000). Safina et al. (1989) reported that despite generally lower hatching success and generally greater nest destruction in saltmarshes on Long Island, colonies in both habitats produced similar numbers of fledglings. Most variability in nesting sucess was between colonies and years rather than between habitat types (Safina et al. 1989). Similarly, Buckley and Buckley (2000) concluded that marsh-nesting Common Tern colonies were not at any serious disadvantage when comparing factors such as colony size, establishment, and stability to beach-nesting colonies.
The Common Tern's statewide distribution includes Long island, along Lake Erie and Lake Ontario, islands within the Saint Lawrence river, the Finger Lakes, Lake Champlain, and a few sites along the Hudson River. The largest colonies in New York are found on Long Island and include locations on both the north and south shores and off the eastern tip (McGowan and Corwin 2008). Great Gull Island is the largest colony in the state, and in the western hemisphere, and Buffalo harbor is the largest colony upstate.
BREEDING: Common Terns breed from northern Alberta across central Ontario and southern Quebec to southern Labrador, south to eastern Washington, southeastern Alberta, northeastern Montana, North Dakota, northeastern South Dakota, central Minnesota, northeastern Illinois, northwestern Indiana, southern Michigan, northern Ohio, northwestern Pennsylvania, southeastern, central and northern New York, and northwestern Vermont, locally along coast to North Carolina, and locally on Gulf Coast and Bermuda, Greater Antilles, and Netherlands Antilles (AOU 1983, van Halewyn and Norton 1984). Nonbreeders occur in summer at James Bay, throughout Great Lakes region, along Atlantic-Gulf coast, south in Middle America to Costa Rica, and throughout West Indies. Common Terns also breed outside of the Americas throughout temperate Europe and Asia (see Nisbet 2002 for description). NON-BREEDING: The winter range of Common Terns includes the west coast of Central America and both coasts of South America, south to Peru on the Pacific and northern Argentina on the Atlantic (Hays, et al. 1997, Hays, et al. 1999, AOU 1983, Nisbet 2002); rare in Hawaii.
Common Terns are a medium-sized tern with a medium grey back, black cap, orange-red legs, and an orange-red bill that is black tipped.
Common Terns are a medium-sized tern, measuring 31-35 cm (12.2-13.8 in.) in total length and weighing 110-145 g (3.9-5.1 oz.). Breeding adults have a black cap and nape. They are medium gray above, lighter gray below, and have orange-red legs and an orange-red bill with black tip. The long outer tail feathers form a 6-9 cm (2.4-3.5 in) fork. The main flight feathers that extend along the outer edge of the wings and that form the lower border of the folded wing (primaries) have extensive black that stands out when the wings are closed. When birds are in flight, the leading and trailing edges of the outer primaries appear dark, and, in all plumages, a dark wedge is visible near the tip of the upperwing. Also when in flight, the outer edge of the tail feathers is dark gray, and the rump and small feathers covering the base of the tail feathers are white, contrasting with the gray back. In the winter plumage, the forehead and feathers between the eye and bill are white, the underparts are white, the bill is all black or black with a dark red base, and the legs are reddish black. Juveniles appear variable. The forehead is buff colored or whitish, which contrasts with the dark brown top of the head and ears. Many of the upperparts are gray with distinct or faint brown bars, and the feather tips are dark. There is a dark-colored bar on the upperwing. The collar and underparts are white. The legs are pinkish or orange-brown. The bill is dark with an orange or pink base. Primaries are grayish brown, secondaries are darker, and both have whitish edges. The tail is gray with dark edges. The fork is shallow, 3-5 cm (1.2-2.0 in). Birds usually attain breeding plumage by age four. Calls have a unique, sharp, and harsh-sounding irritable tone. The descending "kee-ur" or "kee-uri" advertising call and "kee-arrrr" alarm call of adults can be used to distinguish Common Terns from all other similar terns. In the late summer, juveniles have a grating flight call ("krrrri") and a relentless begging call ("kri-kri-kri-kri-..."). Nests consist of scrapes in loose substrate like sand, gravel, shell, or cobble. Clutches almost always contain between one and four eggs (usually two to three eggs). Eggs are smooth and nonglossy, with a fine grainy surface. They have a background color that is cream, buff, or medium brown, which is sometimes tinted with green or olive. The eggs are marked with fine streaks, spots, blotches, or thin lines of black, brown, or gray.
Common Terns have a medium grey back, orange-red legs, and an orange-red bill that is black tipped.The tail is comparatively shorter than a lot of other terns. They display a dark wedge on the upper wing during flight (National Geographic Society 1999).
Adults in breeding plumage are easiest to identify but juveniles and birds in their winter plumage can also be distinguised from other tern species.
Common Terns breed in large colonies sometimes with other tern species. They are generally monagoumous and establish long-term pair bonds (Nisbet et al. 2002). They exhibit a varitety of breeding displays such as aerial displays, a "greeting ceremony" where the female stand erect and the male bowed, and a "parade" where the male walks in a circle around the female. During the "honeymoon" period the female will join the male in his feeding territory and the male will catch fish and give them to the female (Nisbet et al. 2002, Nisbet 1977). Common Terns may agressively attack predators or humans percieved as predators, dive-bombing and deficating on them. An alternate strategy is desertion. Entire colonies may flee nesting areas for a time in response to noctural predators or may desert breeding sites and move to another location in response to high predation, especially early in the breeding season (Gochfeld 1979, Kress 1997, Nisbet and Welton 1984). Adults may circle around other terns displaying abnormal behavior (such as when injured) and sometimes peck at them. This behavior was exploited during the nineteenth century by the millinery trade enabling a large number of birds to be killed at one time (Brewster 1879, Bent 1921). Common Terns feed in scattered small flocks along marshes or coasal areas. Coastal breeders may sometimes form large feeding flocks, especially over predatory fish which may drive smaller schooling fish to the surface (Nisbet et al. 2002).
Adults feed on a wide variety of small fish, crustaeceans, insects and occasionally squid. Chicks are fed mostly fish (Nisbet 2002).
On coast rare before May and after mid-Oct. Inland - rare before mid-April and after mid-Nov. Average spring arrival date in 1987 was 3 May for NYS (A87SPA01NY).
The time of year you would expect to find Common Tern active and reproducing in New York.
Sterna hirundo Linnaeus, 1758
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This guide was authored by: Kelly A. Perkins
Information for this guide was last updated on: April 5, 2019
Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Sterna hirundo. Available from: https://guides.nynhp.org/common-tern/. Accessed May 22, 2019.