142-421: The roseate tern ( Sterna dougallii ) is a species of tern in the family Laridae . The genus name Sterna is derived from Old English "stearn", "tern", and the specific dougallii refers to Scottish physician and collector Dr Peter McDougall (1777–1814). "Roseate" refers to the bird's pink breast in breeding plumage. English naturalist George Montagu described the roseate tern in 1813. Genetically, it
284-514: A 67–76 cm (26–30 in) wingspan, which can be confused with the common tern , Arctic tern, and the larger, but similarly plumaged, Sandwich tern . The thin sharp bill is black, with a red base which develops through the breeding season, and is more extensive (to fully red) in the tropical and southern hemisphere subspecies. It is shorter-winged and has faster wing beats than common or Arctic tern. The upper wings are pale grey and its under parts white, and this tern looks very pale in flight, like
426-446: A bare scrape in sand or gravel, but it is often lined or edged with whatever debris is available. Up to three eggs may be laid, their dull colours and blotchy patterns providing camouflage on the open beach. Incubation is by both sexes, and the eggs hatch in around 21–22 days, longer if the colony is disturbed by predators. The downy chicks fledge in 22–28 days. Like most terns, this species feeds by plunge-diving for fish, either in
568-582: A bare tree branch. Depending on the species, one to three eggs make up the clutch . Most species feed on fish caught by diving from flight, but the marsh terns are insect-eaters, and some large terns will supplement their diet with small land vertebrates . Many terns are long-distance migrants , and the Arctic tern may see more daylight in a year than any other animal. Terns are normally monogamous , although trios or female-female pairings have been observed in at least three species. Most terns breed annually and at
710-535: A black cap to the head. The legs and bill are various combinations of red, orange, yellow, or black depending on species. The pale plumage is conspicuous from a distance at sea, and may attract other birds to a good feeding area for these fish-eating species. When seen against the sky, the white underparts also help to hide the hunting bird from its intended prey. The Inca tern has mainly dark plumage, and three species that mainly eat insects, black tern , white-winged tern , and black-bellied tern , have black underparts in
852-573: A black cap, orange-red legs, and a narrow pointed bill. Depending on the subspecies, the bill may be mostly red with a black tip or all black. There are several similar species, including the partly sympatric Arctic tern , which can be separated on plumage details, leg and bill colour, or vocalisations . Breeding in a wider range of habitats than any of its relatives, the common tern nests on any flat, poorly vegetated surface close to water, including beaches and islands, and it readily adapts to artificial substrates such as floating rafts. The nest may be
994-424: A clutch is slightly smaller than the first laid. The average egg weight is 20.2 g (0.71 oz), of which five per cent is shell. The egg weight depends on how well-fed the female is, as well as on its position in the clutch. The eggs are cream, buff , or pale brown, marked with streaks, spots or blotches of black, brown or grey which help to camouflage them. Incubation is by both sexes, although more often by
1136-478: A concentrated solution from a specialised nasal gland. Fish bones and the hard exoskeletons of crustaceans or insects are regurgitated as pellets . Adults fly off the nest to defecate , and even small chicks walk a short distance from the scrape to deposit their faeces . Adults attacking animals (including humans) will often defecate as they dive, often successfully fouling the intruder. Rats will take tern eggs, and may even store large numbers in caches , and
1278-506: A decade, a pair fledged two chicks on the Skerries, off Anglesey after a RSPB project over previous years involving wardening, newly designed nest boxes being placed strategically around the islands along with lures playing roseate tern calls and hand-made decoys. In the UK the roseate tern has been designated for protection under the official government's national Biodiversity Action Plan . One of
1420-534: A few days before settling into a territory, and the actual start of nesting may be linked to a high availability of fish. Terns defend only a small area, with distances between nests sometimes being as little as 50 cm (20 in), although 150–350 cm (59–138 in) is more typical. As with many birds, the same site is re-used year after year, with a record of one pair returning for 17 successive breeding seasons. Around ninety per cent of experienced birds reuse their former territory, so young birds must nest on
1562-433: A fish, and is possibly used for individual recognition (chicks emerge from hiding when they hear their parents giving this call). Another common call is a kip uttered during social contact. Other vocalizations include a kakakakaka when attacking intruders, and a staccato kek-kek-kek from fighting males. Parents and chicks can locate one another by call, and siblings also recognise each other's vocalisations from about
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#17329013928411704-408: A fuller black cap than that species. As with other Sterna terns, roseate tern feeds by plunge-diving for fish , almost invariably from the sea; it is much more marine than allied terns, only rarely visiting freshwater lagoons on the coast to bathe and not fishing in fresh water. It usually dives directly, and not from the "stepped-hover" favoured by Arctic tern . The offering of fish by the male to
1846-762: A heavy head and thick bill, and long, strong legs; in all non-breeding plumages, its white head and dark eye patch make the American species unmistakable. In the wintering regions, there are also confusion species, including the Antarctic tern of the southern oceans, the South American tern , the Australasian white-fronted tern and the white-cheeked tern of the Indian Ocean . The plumage differences due to "opposite" breeding seasons may aid in identification. The Antarctic tern
1988-406: A large colony. Studies show that terns can find and excavate their eggs when they are buried, even if the nest material is removed and the sand smoothed over. They will find a nest placed 5 m (16 ft) from its original site, or even further if it is moved in several stages. Eggs are accepted if reshaped with plasticine or coloured yellow (but not red or blue). This ability to locate the eggs
2130-536: A lighter build, long pointed wings (which give them a fast, buoyant flight), a deeply forked tail, slender legs, and webbed feet. Most species are grey above and white below, and have a black cap which is reduced or flecked with white in the non-breeding season. The common tern's closest relatives appear to be the Antarctic tern , followed by the Eurasian Arctic and roseate terns . Genetic evidence suggests that
2272-567: A measure of protection, but adults and eggs of some species are still used for food in the tropics. Terns range in size from the least tern , at 23 cm (9.1 in) in length and weighing 30–45 g (1.1–1.6 oz), to the Caspian tern at 48–56 cm (19–22 in), 500–700 g (18–25 oz). They are longer-billed, lighter-bodied, and more streamlined than gulls, and their long tails and long narrow wings give them an elegance in flight. Male and female plumages are identical, although
2414-497: A non-breeding plumage, which usually involves a white forehead and much-reduced black cap. Terns are long-lived birds and are relatively free from natural predators and parasites ; most species are declining in numbers due directly or indirectly to human activities, including habitat loss, pollution, disturbance, and predation by introduced mammals . The Chinese crested tern is critically endangered and three other species are classed as endangered . International agreements provide
2556-609: A quarter to half a million pairs, the majority breeding in Asia. About 140 thousand pairs breed in Europe. Fewer than eighty thousand pairs breed in North America, with most breeding on the northeast Atlantic coast and a declining population of less than ten thousand pairs breeding in the Great Lakes region . In the nineteenth century, the use of tern feathers and wings in the millinery trade
2698-520: A return journey of more than 30,000 km (19,000 mi). A common tern that hatched in Sweden and was found dead five months later on Stewart Island , New Zealand , must have flown at least 25,000 km (16,000 mi). Actual flight distances are, of course, much greater than the shortest possible route. Arctic terns from Greenland were shown by radio geolocation to average 70,000 km (43,000 mi) on their annual migrations, while another from
2840-444: A scaly appearance. They have dark bands on the wings and short tails. In most species, the subsequent moult does not start until after migration, the plumage then becoming more like the adult, but with some retained juvenile feathers and a white forehead with only a partial dark cap. By the second summer, the appearance is very like the adult, and full mature plumage is usually attained by the third year. After breeding, terns moult into
2982-518: A second or so, but to no more than 50 cm (20 in) below the surface. When seeking fish, this tern flies head-down and with its bill held vertically. It may circle or hover before diving, and then plunges directly into the water, whereas the Arctic tern favours a "stepped-hover" technique, and the roseate tern dives at speed from a greater height, and submerges for longer. The common tern typically forages up to 5–10 km (3.1–6.2 mi) away from
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#17329013928413124-449: A significant part of the diet elsewhere. This may include worms , leeches , molluscs such as small squid , and crustaceans ( prawns , shrimp and mole crabs ). In freshwater areas, large insects may be caught, such as beetles , cockchafers and moths . Adult insects may be caught in the air, and larvae picked from the ground or from the water surface. Prey is caught in the bill and either swallowed head-first, or carried back to
3266-492: A similar word was used by the Frisians for the birds. "Stearn" appears in the poem The Seafarer , written around 1000 A.D. Linnaeus adopted this word for the genus name Sterna . The Latin for swallow is hirundo, and refers here to the tern's superficial likeness to that unrelated bird, which has a similar light build and long forked tail. This resemblance also leads to the informal name "sea swallow", recorded from at least
3408-402: A small Sandwich tern, although the outermost primary flight feathers darken during the summer. The adults have very long, flexible tail streamers and orange-red legs. In summer, the underparts of adults take on the pinkish tinge which gives this bird its name. In winter, the forehead becomes white and the bill black. Juvenile roseate terns have a scaly appearance like juvenile Sandwich Terns, but
3550-462: A smoother, more extensive black cap in non-breeding plumage. Like Antarctic, it lacks a strong carpal bar in non-breeding plumages, and it also shares the distinctive barring of the tertials in young birds. The white-fronted tern has a white forehead in breeding plumage, a heavier bill, and in non-breeding plumage is paler below than the common, with white underwings. The white-cheeked tern is smaller, has uniform grey upperparts, and in breeding plumage
3692-452: A sooty. Although several other species are known to live in captivity for up to 20 years, their greatest recorded ages are underestimates because the birds can outlive their rings . Interbreeding between tern species is rare, and involves closely related species when it occurs. Hybrids recorded include common tern with roseate, Sandwich with lesser-crested, and black with white-winged. Most terns hunt fish by diving, often hovering first, and
3834-454: A strong head wind, but 10–30 m (33–98 ft) above the water in a following wind. Unless migrating, normally it stays below 100 m (330 ft), and averages 30 km/h (19 mph) in the absence of a tail wind. Its average flight speed during the nocturnal migration flight is 43–54 km/h (27–34 mph) at a height of 1,000–3,000 m (3,300–9,800 ft). Juveniles moult into adult plumage in its first October; first
3976-414: A very early moult at the nesting colony is linked to breeding failure, both the onset of moult and reproductive behaviour being linked to falling levels of the hormone prolactin . There are several terns of a similar size and general appearance to the common tern. A traditionally difficult species to separate is the Arctic tern, and until the key characteristics were clarified, distant or flying birds of
4118-426: A winter plumage, typically showing a white forehead. Heavily worn or aberrant plumages such as melanism and albinism are much rarer in terns than in gulls. Terns have a wide repertoire of vocalisations. For example, the common tern has a distinctive alarm , kee-yah , also used as a warning to intruders, and a shorter kyar , given as an individual takes flight in response to a more serious threat; this quietens
4260-489: Is also a factor. The Peruvian tern was initially damaged by the collapse of anchoveta stocks in 1972, but breeding colonies have subsequently been lost due to building, disturbance and pollution in their coastal wetlands. The Australasian fairy tern is described as " vulnerable ". Disturbance by humans, dogs and vehicles, predation by introduced species and inappropriate water level management in South Australia are
4402-483: Is also some geographical variation; Californian birds are often in non-breeding plumage during migration. Juvenile common terns have pale grey upper wings with a dark carpal bar. The crown and nape are brown, and the forehead is ginger, wearing to white by autumn. The upper parts are ginger with brown and white scaling, and the tail lacks the adult's long outer feathers. Birds in their first post-juvenile plumage, which normally remain in their wintering areas, resemble
Roseate tern - Misplaced Pages Continue
4544-491: Is an adaptation to life in an unstable, wind-blown and tidal environment. The peak time for egg production is early May, with some birds, particularly first-time breeders, laying later in the month or in June. The clutch size is normally three eggs; larger clutches probably result from two females laying in the same nest. Egg size averages 41 mm × 31 mm (1.6 in × 1.2 in), although each successive egg in
4686-562: Is available it will eat small crabs, fish, crayfish , grasshoppers and other large insects, lizards and amphibians . Warm-blooded prey includes mice and the eggs and chicks of other beach-breeding birds; least terns, little terns and members of its own species may be victims. The greater crested tern will also occasionally catch unusual vertebrate species such as agamid lizards and green sea turtle hatchlings, and follows trawlers for discards. The eyes of terns cannot accommodate under water, so they rely on accurate sighting from
4828-445: Is classed as being of least concern , although numbers in North America have declined sharply in recent decades. Despite international legislation protecting the common tern, in some areas, populations are threatened by habitat loss , pollution, or the disturbance of breeding colonies . Terns are small to medium-sized seabirds closely related to the gulls , skimmers and skuas . They are gull-like in appearance, but typically have
4970-538: Is complete, the male makes a shallow depression in the sand, and the female scratches in the same place. Several trials may take place until the pair settle on a site for the actual nest. The eggs may be laid on bare sand, gravel or soil, but a lining of debris or vegetation is often added if available, or the nest may be rimmed with seaweed, stones or shells. The saucer-shaped scrape is typically 4 cm (1.6 in) deep and 10 cm (3.9 in) across, but may extend to as much as 24 cm (9.4 in) wide including
5112-411: Is darker above with whiter cheeks. Juvenile common terns are easily separated from similar-aged birds of related species. They show extensive ginger colouration to the back, and have a pale base to the bill. Young Arctic terns have a grey back and black bill, and juvenile roseate terns have a distinctive scalloped "saddle". Hybrids between common and roseate terns have been recorded, particularly from
5254-565: Is declining due to egg collection, human disturbance and the loss of coastal wetlands in China. Three other species are categorised as " endangered ", with declining populations of less than 10,000 birds. The South Asian black-bellied tern is threatened by habitat loss, egg collecting for food, pollution and predation. In New Zealand, the black-fronted tern is facing a rapid fall in numbers due to predation by introduced mammals and Australian magpies . Disturbance by cattle and sheep and by human activities
5396-410: Is more sturdy than the common, with a heavier bill. In breeding condition, its dusky underparts and full black cap outline a white cheek stripe. In non-breeding plumages, it lacks, or has only an indistinct, carpal bar, and young birds show dark bars on the tertials , obvious on the closed wing and in flight. The South American tern is larger than the common, with a larger, more curved red bill, and has
5538-513: Is most closely related to the white-fronted tern ( S. striata ), with their common ancestor a sister lineage to the black-naped tern ( S. sumatrana ). This species has a number of geographical subspecies, differing mainly in bill colour and minor plumage details. S. d. dougallii breeds on the Atlantic coasts of Europe and North America, and winters south to the Caribbean and west Africa. Both
5680-452: Is pale above and white, sometimes pink-tinged, below. It retains the long tail streamers, and has a black bill. In flight, the roseate's heavier head and neck, long bill and faster, stiffer wingbeats are also characteristic. It feeds further out to sea than the common tern. In North America, the Forster's tern in breeding plumage is obviously larger than the common, with relatively short wings,
5822-465: Is significantly affected by this hunting, with adult survival 10% lower than would otherwise be expected. In the West Indies, the eggs of roseate and sooty terns are believed to be aphrodisiacs , and are disproportionately targeted by egg collectors. Tern skins and feathers have long been used for making items of clothing such as capes and hats, and this became a large-scale activity in the second half of
Roseate tern - Misplaced Pages Continue
5964-487: Is similar, although there is a greater emphasis on protection. Common tern The common tern ( Sterna hirundo ) is a seabird in the family Laridae . This bird has a circumpolar distribution , its four subspecies breeding in temperate and subarctic regions of Europe, Asia and North America. It is strongly migratory , wintering in coastal tropical and subtropical regions. Breeding adults have light grey upperparts, white to very light grey underparts,
6106-561: Is sufficiently stable. A few species nest in small or dispersed groups, but most breed in colonies of up to a few hundred pairs, often alongside other seabirds such as gulls or skimmers. Large tern species tend to form larger colonies, which in the case of the sooty tern can contain up to two million pairs. Large species nest very close together and sit tightly, making it difficult for aerial predators to land among them. Smaller species are less closely packed and mob intruders. Peruvian and Damara terns have small dispersed colonies and rely on
6248-565: Is susceptible. In 1961 the common tern was the first wild bird species identified as infected with avian influenza, the H5N3 variant being found in an outbreak of South African birds. The common tern is classed as least concern on the IUCN Red List . It has a large population of 1.6 to 3.3 million mature individuals and a huge breeding range estimated at 84,300,000 km (32,500,000 sq mi). Breeding numbers have been estimated at
6390-406: Is the alarm KEE-yah , stressed on the first syllable, in contrast to the second-syllable stress of the Arctic tern. The alarm call doubles up as a warning to intruders, although serious threats evoke a kyar , given as a tern takes flight, and quietens the usually noisy colony while its residents assess the danger. A down-slurred keeur is given when an adult is approaching the nest while carrying
6532-401: Is to confuse fast-flying predators. The common tern hosts feather lice , which are quite different from those found in Arctic terns, despite the close relationship of the two birds. It may also be infected by parasitic worms, such as the widespread Diphyllobothrium species, the duck parasite Ligula intestinalis , and Schistocephalus species carried initially by fish. Tapeworms of
6674-614: Is uncertain whether they are sighting the phytoplankton on which the fish feed, or observing other terns diving for food. Tern's eyes are not particularly ultraviolet sensitive, an adaptation more suited to terrestrial feeders like the gulls. The common tern preferentially hunts fish 5–15 cm (2.0–5.9 in) long. The species caught depend on what is available, but if there is a choice, terns feeding several chicks will take larger prey than those with smaller broods. The proportion of fish fed to chicks may be as high as ninety-five per cent in some areas, but invertebrate prey may form
6816-594: Is uncertain whether they are sighting the phytoplankton on which the fish feed, or other feeding birds. The red colouring reduces ultraviolet sensitivity, which in any case is an adaptation more suited to terrestrial feeders like the gulls, and this protects the eye from UV damage. The inaccessibility of many tern colonies gave them a measure of protection from mammalian predators, especially on islands, but introduced species brought by humans can seriously affect breeding birds. These can be predators such as foxes , raccoons , cats and rats , or animals that destroy
6958-528: Is unclear. A bird ringed at the nest in Sweden was found dead on Stewart Island , New Zealand, five months later, having flown an estimated 25,000 km (15,000 mi). As long-distance migrants, common terns sometimes occur well outside their normal range. Stray birds have been found inland in Africa (Zambia and Malawi), and on the Maldives and Comoros islands; the nominate subspecies has reached Australia,
7100-414: Is unique in that it lays its single egg on a bare tree branch. Tropical species usually lay just one egg, but two or three is typical in cooler regions if there is an adequate food supply. The time taken to complete the clutch varies, but for temperate species incubation takes 21–28 days. The eggs of most gulls and terns are brown with dark splotches, so they are difficult for predators to spot on
7242-757: The American mink is an important predator of hatched chicks, both in North America, and in Scotland where it has been introduced . The red fox can also be a local problem. Because common terns nest on islands, the most common predators are normally other birds rather than mammals. The ruddy turnstone will take eggs from unattended nests, and gulls may take chicks. Great horned owls and short-eared owls will kill both adults and chicks, and black-crowned night herons will also eat small chicks. Merlins and peregrine falcons may attack flying terns; as with other birds, it seems likely that one advantage of flocking behaviour
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#17329013928417384-588: The Caribbean for commercial sale as food. Breeding success may be enhanced by the use of floating nest rafts, manmade islands or other artificial nest sites, and by preventing human disturbance. Overgrown vegetation may be burned to clear the ground, and gulls can be killed or discouraged by deliberate disturbance. Contamination with polychlorinated biphenyls (PCBs) resulted in enhanced levels of feminisation in male embryos, which seemed to disappear prior to fledging, with no effect on colony productivity, but dichlorodiphenyldichloroethylene (DDE), which results from
7526-542: The Chlidonias species are the marsh terns, and all other species comprise the sea terns. Terns have a worldwide distribution, breeding on all continents including Antarctica. The northernmost and southernmost breeders are the Arctic tern and Antarctic tern respectively. Many terns breeding in temperate zones are long-distance migrants , and the Arctic tern sees more annual daylight than any other animal as it migrates from its northern breeding grounds to Antarctic waters,
7668-1041: The Farne Islands in Northumberland tagged 'G82' covered a staggering 96,000 km in just 10 months from the end of one breeding season to the start of the next, travelling not just the length of the Atlantic Ocean and the width of the Indian Ocean, but also half way across the South Pacific to the boundary between the Ross and Amundsen Seas before returning back west. Most terns breed on open sandy or rocky areas on coasts and islands. The yellow-billed , large-billed , and black-fronted terns breed only on rivers, and common, least and little terns also sometimes use inland locations. The marsh terns , Trudeau's tern and some Forster's terns nest in inland marshes. The black noddy and
7810-555: The H5N3 variant being found in an outbreak involving South African birds. Several species of terns have been implicated as carriers of West Nile virus . Terns and their eggs have long been eaten by humans and island colonies were raided by sailors on long voyages since the eggs or large chicks were an easily obtained source of protein . Eggs are still illegally harvested in southern Europe, and adults of wintering birds are taken as food in West Africa and South America. The roseate tern
7952-489: The black-naped tern ( S. sumatrana ), lesser crested tern ( Thalasseus bengalensis ), greater crested tern ( T. bergii ), fairy tern ( Sternula nereis ), bridled tern ( Onychoprion anaethetus ) and silver gull ( Chroicocephalus novaehollandiae ). It nests in a ground scrape, often in a hollow or under dense vegetation, and lays one or two (rarely three) eggs. It is less defensive of its nest and young than other white terns, often relying on Arctic and common terns in
8094-453: The crustacean Reighardia sternae , and tapeworms such as Ligula intestinalis and members of the genera Diphyllobothrium and Schistocephalus . Terns are normally free of blood parasites, unlike gulls that often carry Haemoproteus species. An exception is the brown noddy, which sometimes harbours protozoa of that genus. In 1961 the common tern was the first wild bird species identified as being infected with avian influenza,
8236-440: The cryptic plumage of the eggs and young for protection. The male selects a territory , which he defends against conspecifics , and re-establishes a pair bond with his mate or attracts a new female if necessary. Courtship involves ritualised flight and ground displays, and the male often presents a fish to his partner. Most species have little or no nest, laying the eggs onto bare ground, but Trudeau's tern, Forster's tern and
8378-420: The cytochrome b gene sequence found a close relationship between terns and a group of waders in the suborder Thinocori . These results are in disagreement with other molecular and morphological studies, and have been interpreted as showing either a large degree of molecular convergent evolution between the terns and these waders, or the retention of an ancient genotype . Research in 2007 had suggested that
8520-529: The skimmers ( Rynchops ). They are slender, lightly built birds with long, forked tails, narrow wings, long bills, and relatively short legs. Most species are pale grey above and white below with a contrasting black cap to the head, but the marsh terns , the black-bellied tern , the Inca tern , and some noddies have dark body plumage for at least part of the year. The sexes are identical in appearance, but young birds are readily distinguishable from adults. Terns have
8662-461: The spotted redshank , quite distinct from other terns. In the late 19th century, these birds were hunted for their plumes which were used to decorate hats. More recently, their numbers have decreased in some regions due to increased competition and predation by large gulls , whose numbers have increased in recent times. This species, as of 2019, is one of the UK's rarest breeding seabird. The largest European colony, accounting for more than 75% of
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#17329013928418804-449: The wader . Outside the breeding season, all that is needed in terms of habitat is access to fishing areas, and somewhere to land. In addition to natural beaches and rocks, boats, buoys and piers are often used both as perches and as night-time roosts. The common tern breeds in colonies which do not normally exceed two thousand pairs , but may occasionally number more than twenty thousand pairs. Colonies inland tend to be smaller than on
8946-498: The white tern nest above ground level on cliffs or in trees. Migratory terns move to the coast after breeding, and most species winter near land, although some marine species, like the Aleutian tern , may wander far from land. The sooty tern is entirely oceanic when not breeding, and healthy young birds are not seen on land for up to five years after fledging until they return to breed. They lack waterproof plumage, so they cannot rest on
9088-555: The 1980s, organochlorides caused severe declines in the Great Lakes area of the US. Because of their sensitivity to pollutants, terns are sometimes used as indicators of contamination levels. Habitat enhancements used to increase the breeding success of terns include floating nest platforms for black, common and Caspian terns, and artificial islands created for a number of different species. More specialised interventions include providing nest boxes for roseate terns, which normally nest in
9230-601: The Andes, and the interior of South America. Asian S. h. longipennis has recent records from western Europe. The common tern breeds over a wider range of habitats than any of its relatives, nesting from the taiga of Asia to tropical shores, and at altitudes up to 2,000 m (6,600 ft) in Armenia, and 4,800 m (15,700 ft) in Asia. It avoids areas which are frequently exposed to excessive rain or wind, and also icy waters, so it does not breed as far north as
9372-403: The Arctic tern. The common tern breeds close to freshwater or the sea on almost any open flat habitat, including sand or shingle beaches , firm dune areas, salt marsh , or, most commonly, islands. Flat grassland or heath , or even large flat rocks may be suitable in an island environment. In mixed colonies, common terns will tolerate somewhat longer ground vegetation than Arctic terns, but avoid
9514-462: The Arctic, and gull-billed terns in little tern colonies. Adults may be robbed of their catch by avian kleptoparasites such as frigatebirds , skuas, other terns or large gulls. External parasites include chewing lice of the genus Saemundssonia , feather lice and fleas such as Ceratophyllus borealis . Lice are often host specific, and the closely related common and Arctic terns carry quite different species. Internal parasites include
9656-796: The Atlantic coast from Labrador to North Carolina , and inland throughout much of Canada east of the Rocky Mountains . In the United States, some breeding populations can also be found in the states bordering the Great Lakes , and locally on the Gulf coast. There are small, only partially migratory, colonies in the Caribbean ; these are in The Bahamas and Cuba, and off Venezuela in the Los Roques and Las Aves archipelagos . New World birds winter along both coasts of Central and South America, to Argentina on
9798-844: The Cayenne tern, in the Caribbean . Terns are protected by international legislation such as the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the US-Canada Migratory Bird Treaty Act of 1918 . Parties to the AWEA agreement are required to engage in a wide range of conservation strategies described in a detailed action plan. The plan is intended to address key issues such as species and habitat conservation , management of human activities, research, education, and implementation. The North American legislation
9940-458: The English words from Scandinavian equivalents such as Danish and Norwegian terne or Swedish tärna , and ultimately from Old Norse þerna . Linnaeus adopted "stearn" or "sterna" (which the naturalist William Turner had used in 1544 as a Latinisation of an English word, presumably "stern", for the black tern) or a North Germanic equivalent for his genus name Sterna . The cladogram shows
10082-466: The European and North American populations have been in long-term decline, though active conservation measures have reversed the decline in the last few years at some colonies, most notably at Rockabill Island off the coast of Dublin, Ireland, which now holds most of the European population (about 1200 pairs). The tropical forms S. d. korustes and S. d. bangsi are resident breeders from east Africa across
10224-518: The European population, is in Ireland, at Rockabill Island , County Dublin . In 2013, 1213 pairs nested at Rockabill. The colony at Lady's Island Lake , County Wexford , is also of crucial importance, with 155 pairs nesting there in 2013. With their favouring partly hidden nest sites, the provision of nestboxes has proven a dramatic conservation success, with the birds taking to them very readily. This results in greatly increased breeding productivity with
10366-563: The Inca, Damara, and river terns , are expected to decline in the future due to habitat loss and disturbance. Some tern subspecies are endangered, including the California least tern and the Easter Island race of the grey noddy. Most tern species are declining in numbers due to the loss or disturbance of breeding habitat, pollution and increased predation. Gull populations have increased over
10508-465: The Indian Ocean to Japan . They have more red on the bill. The long-billed and short-winged S. d. gracilis breeds in Australia and New Caledonia . The north-western Indian Ocean holds populations of S. d. arideensis . Some authors suggest that only three subspecies arideensis , gracilis and nominate dougallii should be retained. This is a small-medium tern, 33–36 cm (13–14 in) long with
10650-724: The Northern Hemisphere winter. Birds from further north and east in Asia, such as S. h. longipennis , move through Japan, Thailand and the western Pacific as far as southern Australia. There are small and erratic colonies in West Africa , in Nigeria and Guinea-Bissau, unusual in that they are within what is mainly a wintering area. Only a few common terns have been recorded in New Zealand, and this species' status in Polynesia
10792-402: The US, and the intermediate plumage and calls shown by these birds is a potential identification pitfall. Such birds may have more extensive black on the bill, but confirmation of mixed breeding may depend on the exact details of individual flight feathers. Common terns have a wide repertoire of calls, which have a lower pitch than the equivalent calls of Arctic terns. The most distinctive sound
10934-436: The aggression shown to adults, wandering chicks are usually tolerated, whereas in a gull colony they would be attacked and killed. The nest is defended until the chicks have fledged, and all the adults in the colony will collectively repel potential predators. Pairs are established or confirmed through aerial courtship displays in which a male and a female fly in wide circles up to 200 m (660 ft) or more, calling all
11076-461: The air before they plunge-dive. Like other seabirds that feed at the surface or dive for food, terns have red oil droplets in the cones of their retinas ; birds that have to look through an air/water interface have more deeply coloured carotenoid pigments in the oil drops than other species. The pigment also improves visual contrast and sharpens distance vision, especially in hazy conditions, and helps terns to locate shoals of fish, although it
11218-472: The beach. The precocial chicks fledge in about four weeks after hatching. Tropical species take longer because of the poorer food supply. Both parents incubate the eggs and feed the chicks, although the female does more incubating and less fishing than her partner. Young birds migrate with the adults. Terns are generally long-lived birds, with individuals typically returning for 7–10 breeding seasons. Maximum known ages include 34 for an Arctic tern and 32 for
11360-420: The biggest increase is in the first five years. The maximum documented lifespan in the wild is 23 years in North America and 33 years in Europe, but twelve years is a more typical lifespan. Like all Sterna terns, the common tern feeds by plunge-diving for fish, from a height of 1–6 m (3.3–19.7 ft), either in the sea or in freshwater lakes and large rivers. The bird may submerge for
11502-410: The birds could lead them to fish shoals. Overfishing of small fish such as sand eels can lead to steep declines in the colonies relying on these prey items. More generally, the loss or disruption to tern colonies caused by human activities has caused declines in many species. Pollution has been a problem in some areas, and in the 1960s and 1970s DDT caused egg loss through thinning of the shells. In
11644-555: The breakdown of DDT , led to very low levels of successful breeding in some US locations. The common tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the US–Canada Migratory Bird Treaty Act of 1918 apply. Parties to the AEWA agreement are required to engage in a wide range of conservation strategies described in a detailed action plan. The plan
11786-404: The breeding colony, sometimes as far as 15 km (9.3 mi). It will follow schools of fish, and its west African migration route is affected by the location of huge shoals of sardines off the coast of Ghana; it will also track groups of predatory fish or dolphins , waiting for their prey to be driven to the sea's surface. Terns often feed in flocks, especially if food is plentiful, and
11928-458: The breeding season. Three of the Anous noddies have dark plumage with a pale head cap, the other two (formerly separated in the genus Procelsterna paler grey. The reason for their dark plumage is unknown, but it has been suggested that in tropical areas, where food resources are scarce, the less conspicuous colouration makes it harder for other noddies to detect a feeding bird. Plumage type, especially
12070-725: The chicks. Occasionally, two or more small fish may be carried simultaneously. When adults take food back to the nest, they recognise their young by call, rather than visual identification. The common tern may attempt to steal fish from Arctic terns, but might itself be harassed by kleptoparasitic skuas, laughing gulls , roseate terns, or by other common terns while bringing fish back to its nest. In one study, two males whose mates had died spent much time stealing food from neighbouring broods. Terns normally drink in flight, usually taking seawater in preference to freshwater, if both are available. Chicks do not drink before fledging, reabsorbing water, and, like adults, excreting excess salt in
12212-409: The coast. Common terns often nest alongside other coastal species, such as Arctic, roseate and Sandwich terns , black-headed gulls , and black skimmers . Especially in the early part of the breeding season, for no known reason, most or all of the terns will fly in silence low and fast out to sea. This phenomenon is called a "dread". On their return to the breeding sites, the terns may loiter for
12354-400: The common tern is 31–35 cm (12–14 in) long, including a 6–9 cm (2.4–3.5 in) fork in the tail, with a 77–98 cm (30–39 in) wingspan. It weighs 110–141 g (3.9–5.0 oz). Breeding adults have pale grey upperparts, very pale grey underparts, a black cap, orange-red legs, and a narrow pointed bill that can be mostly red with a black tip, or all black, depending on
12496-453: The common tern may have diverged from an ancestral stock earlier than its relatives. No fossils are known from North America, and those claimed in Europe are of uncertain age and species. The common tern was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae under its current scientific name, Sterna hirundo . "Stearn" was used in Old English , and
12638-455: The distinction in his 1758 Systema Naturae , placing the gulls in the genus Larus and the terns in Sterna . He gave Sterna the description rostrum subulatum , " awl-shaped bill", referring to the long, pointed bills typical of this group of birds, a feature that distinguishes them from the thicker-billed gulls. Behaviour and morphology suggest that the terns are more closely related to
12780-447: The early twenty-first century, the terns were historically treated as a separate family, Sternidae. Most terns were formerly treated as belonging to one large genus, Sterna , with just a few dark species placed in other genera; in one 1959 paper, only the noddies and the Inca tern were excluded from Sterna . A recent analysis of DNA sequences supported the splitting of Sterna into several smaller genera. One study of part of
12922-558: The east coast and to northern Chile on the west coast. Records from South America and the Azores show that some birds may cross the Atlantic in both directions on their migration. The common tern breeds across most of Europe, with the highest numbers in the north and east of the continent. There are small populations on the north African coast, and in the Azores , Canary Islands and Madeira . Most winter off western or southern Africa, birds from
13064-401: The eggs hatch. The precocial downy chick is yellowish with black or brown markings, and like the eggs, is similar to the equivalent stage of the Arctic tern. The chicks fledge in 22–28 days, usually 25–26. Fledged juveniles are fed at the nest for about five days, and then accompany the adults on fishing expeditions. The young birds may receive supplementary feeds from the parents until
13206-479: The eighth century, and appears in the poem The Seafarer , written in the ninth century or earlier. Variants such as "tearn" occurred by the eleventh century, although the older form lingered on in Norfolk dialect for several centuries. As now, the term was used for the inland black tern as well as the marine species. Some authorities consider "tearn" and similar forms to be variants of "stearn", while others derive
13348-407: The end of the breeding season, and beyond. Common terns have been recorded feeding their offspring on migration and in the wintering grounds, at least until the adults move further south in about December. Like many terns, this species is very defensive of its nest and young, and will harass humans, dogs, muskrats and most diurnal birds, but unlike the more aggressive Arctic tern, it rarely hits
13490-454: The even taller growth acceptable to roseate terns; the relevant factor here is the different leg lengths of the three species. Common terns adapt readily to artificial floating rafts, and may even nest on flat factory roofs. Unusual nest sites include hay bales, a stump 0.6 m (2 ft) above the water, and floating logs or vegetation. There is a record of a common tern taking over a spotted sandpiper nest and laying its eggs with those of
13632-422: The family Cyclophyllidea may also infect this species. The mite Reighardia sternae has been found in common terns from Italy, North America and China. A study of 75 breeding common terns found that none carried blood parasites. Colonies have been affected by avian cholera and ornithosis , and it is possible that the common tern may be threatened in the future by outbreaks of avian influenza to which it
13774-546: The female is part of the courtship display. Unusual for a tern, the roseate tern shows some kleptoparasitic behaviour, stealing fish from other seabirds, at British colonies most often from puffins . This habit greatly increases their food-collecting ability during bad weather when fish swim deeper, out of reach of plunge-diving terns, but still within reach of the deeper-diving Puffins. This species breeds in colonies on coasts and islands, at times with other seabirds. In Australian colonies, it has been recorded nesting alongside
13916-444: The female, and lasts 21–22 days, extending to 25 days if there are frequent disturbances at the colony which cause the adults to leave the eggs unattended; nocturnal predation may lead to incubation taking up to 34 days. On hot days the incubating parent may fly to water to wet its belly feathers before returning to the eggs, thus affording the eggs some cooling. Except when the colony suffers disaster, ninety per cent of
14058-586: The first is lost. Rarely, a second clutch may be laid and incubated while some chicks from the first clutch are still being fed. The first breeding attempt is usually at four years of age, sometimes at three years. The average number of young per pair surviving to fledging can vary from zero in the event of the colony being flooded to over 2.5 in a good year. In North America, productivity was between 1.0 and 2.0 on islands, but less than 1.0 at coastal and inland sites. Birds become more successful at raising chicks with age. This continues throughout their breeding lives, but
14200-516: The fishing success rate in a flock is typically about one-third higher than for individuals. Terns have red oil droplets in the cone cells of the retinas of their eyes. This improves contrast and sharpens distance vision , especially in hazy conditions. Birds that have to see through an air/water interface, such as terns and gulls, have more strongly coloured carotenoid pigments in the cone oil drops than other avian species. The improved eyesight helps terns to locate shoals of fish, although it
14342-429: The frequency in which they moult their primaries, which are replaced at least twice, occasionally three times in a year. The visible difference in feather age is accentuated in the greater ultraviolet reflectance of new primaries, and the freshness of the wing feathers is used by females in mate selection. Experienced females favour mates which best show their fitness through the quality of their wing feathers. Rarely,
14484-470: The gulls than to the skimmers or skuas, and although Charles Lucien Bonaparte created the family Sternidae for the terns in 1838, for many years they were considered to be a subfamily, Sterninae, of the gull family, Laridae. Relationships between various tern species, and between the terns and the other Charadriiformes, were formerly difficult to resolve because of a poor fossil record and the misidentification of some finds. Following genetic research in
14626-425: The habitat, including rabbits , goats and pigs . Problems arise not only on formerly mammal-free islands, as in New Zealand, but also where an alien carnivore , such as the American mink in Scotland , presents an unfamiliar threat. Adult terns may be hunted by owls and raptors , and their chicks and eggs may be taken by herons , crows or gulls. Less obvious nest predators include ruddy turnstones in
14768-406: The head pattern, is linked to the phylogeny of the terns, and the pale-capped, dark-bodied noddies are believed to have diverged earlier than the other genera from an ancestral white-headed gull, followed by the partially black-headed Onychoprion and Sternula groupings. Juvenile terns typically have brown- or yellow-tinged upperparts, and the feathers have dark edges that give the plumage
14910-468: The head, tail, and body plumage is replaced, mostly by February, then the wing feathers. The primaries are replaced in stages; the innermost feathers moult first, then replacement is suspended during the southern winter (birds of this age staying in their wintering areas) and recommences in the autumn. In May to June of the second year, a similar moult sequence starts, with a pause during primary moult for birds that return north, but not for those that stay in
15052-414: The intruder, usually swerving off at the last moment. Adults can discriminate between individual humans, attacking familiar people more intensely than strangers. Nocturnal predators do not elicit similar attacks; colonies can be wiped out by rats, and adults desert the colony for up to eight hours when great horned owls are present. Common terns usually breed once a year. Second clutches are possible if
15194-569: The last century because of reduced persecution and the availability of food from human activities, and terns have been forced out of many traditional nesting areas by the larger birds. A few species are defying the trend and showing local increases, including the Arctic tern in Scandinavia , Forster's tern around the Great Lakes, the Sandwich tern in eastern North America and its yellow-billed subspecies,
15336-445: The last forty years, and there is an overall negative trend in the global estimates for this species. Threats come from habitat loss through building, pollution or vegetation growth, or disturbance of breeding birds by humans, vehicles, boats or dogs. Local natural flooding may lead to nest losses, and some colonies are vulnerable to predation by rats and large gulls. Gulls also compete with terns for nest sites. Some birds are hunted in
15478-530: The least and little terns , and can help humans distinguish similar species, such as common and arctic terns , since flight calls are unique to each species. The bird order Charadriiformes contains 18 coastal seabird and wader families . Within the order, the terns form a lineage with the gulls , and, less closely, with the skimmers , skuas , and auks . Early authors such as Conrad Gessner , Francis Willughby , and William Turner did not clearly separate terns from gulls, but Linnaeus recognised
15620-478: The main reasons for its decline. Five species are " near threatened ", indicating less severe concerns or only potential vulnerability. The elegant tern is so categorised because 95% of the population breeds on one island, Isla Rasa in the Gulf of California , and the Kerguelen tern has a population of less than 5,000 adults breeding on small and often stormy islands in the southern Indian Ocean . Three species,
15762-420: The main reasons given in the UK plan for threat to the species is global warming , creating an alteration of vertical profile distribution for its food source fishes. The roseate tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds ( AEWA ) applies. The Canadian Wildlife Service lists the roseate tern as Threatened. The U.S. Department of Interior lists
15904-588: The male can be 2–5% larger than the female and often has a relatively larger bill. Sea terns have deeply forked tails, and at least a shallow "V" is shown by all other species. The noddies (genera Anous , Procelsterna and Gygis ) have unusual notched-wedge shaped tails, the longest tail feathers being the middle-outer, rather than the central or outermost. Although their legs are short, terns can run well. They rarely swim, despite having webbed feet, usually landing on water only to bathe. The majority of sea terns have light grey or white body plumage as adults, with
16046-430: The marsh terns construct floating nests from the vegetation in their wetland habitats. Black and lesser noddies build nests of twigs, feathers and excreta on tree branches, and brown , blue , and grey noddies make rough platforms of grass and seaweed on cliff ledges, in cavities or on other rocky surfaces. The Inca tern nests in crevices, caves and disused burrows, such as that of a Humboldt penguin . The white tern
16188-515: The nineteenth century when it became fashionable to use feathers in hatmaking . This trend started in Europe but soon spread to the Americas and Australia. White was the preferred colour, and sometimes wings or entire birds were used. Terns have sometimes benefited from human activities, following the plough or fishing boats for easy food supplies, although some birds get trapped in nets or swallow plastic. Fishermen looked for feeding tern flocks, since
16330-555: The noddies were not terns at all, but were basal to all the other genera in Laridae, a taxonomy that was followed by the IOC World Bird List for several years up to 2023, but more comprehensive analysis has now shown that the noddies are basal to only the other terns, not the whole family; this has now been followed by the IOC World Bird List version 14.1 in 2024. The word "stearn" was used for these birds in Old English as early as
16472-413: The non-breeding adult, but have a duskier crown, dark carpal bar, and often very worn plumage. By their second year, most young terns are either indistinguishable from adults, or show only minor differences such as a darker bill or white forehead. The common tern is an agile flyer, capable of rapid turns and swoops, hovering, and vertical take-off. When commuting with fish, it flies close to the surface in
16614-452: The northeastern population as Endangered and the Caribbean population as Threatened. Tern Terns are seabirds in the family Laridae , subfamily Sterninae , that have a worldwide distribution and are normally found near the sea , rivers , or wetlands . Terns are treated in eleven genera in a subgroup of the family Laridae, which also includes several genera of gulls and
16756-539: The outer flight feathers is a thin black line in the Arctic tern, but thicker and less defined in the common. The bill of an adult common tern is orange-red with a black tip, except in black-billed S. h. longipennis , and its legs are bright red, while both features are a darker red colour in the Arctic tern, which also lacks the black bill tip. In the breeding areas, the roseate tern can be distinguished by its pale plumage, long, mainly black bill and very long tail feathers. The non-breeding plumage of roseate
16898-471: The particular approach technique used can help to distinguish similar species at a distance. Sea terns often hunt in association with porpoises or predatory fish, such as bluefish , tuna or bonitos , since these large marine animals drive the prey to the surface. Sooty terns feed at night as the fish rise to the surface, and are believed to sleep on the wing since they become waterlogged easily. Terns of several species will feed on invertebrates , following
17040-441: The periphery, find a bereaved mate, or move to another colony. A male selects a nesting territory a few days after his arrival in the spring, and is joined by his previous partner unless she is more than five days late, in which case the pair may separate. Inbreeding among close S. hirundo relatives appears to be avoided passively by immigration and dispersal rather than by kin discrimination and mate choice . The defence of
17182-435: The plough or hunting on foot on mudflats . The marsh terns normally catch insects in the air or pick them off the surface of fresh water. Other species will sometimes use these techniques if the opportunity arises. An individual tern's foraging efficiency increases with its age. The gull-billed tern is an opportunist predator, taking a wide variety of prey from marine, freshwater and terrestrial habitats. Depending on what
17324-467: The protection given to the young from predatory birds like herring gulls . At the UK's most important colony, on Coquet Island , Northumberland , the population rose from 25 pairs 1997 to 154 pairs in 2022 after nestboxes were provided. Similar measures have been undertaken at the Anglesey tern colonies along with clearance of vegetation, in particular Tree Mallow . In 2018, for the first time in more than
17466-512: The relationships between the tern genera, and the currently recognised species, based on mitochondrial DNA studies, are listed below: Anous Gygis Onychoprion Sternula Phaetusa Gelochelidon Hydroprogne Larosterna Chlidonias Thalasseus Sterna In addition to extant species, the fossil record includes a Miocene palaeospecies , Sterna milne-edwardsii . The genera Anous , Procelsterna and Gygis are collectively known as noddies,
17608-447: The rump of the common tern can be greyish in non-breeding plumage, compared to the white of its relative. The common tern develops a dark wedge on the wings as the breeding season progresses, but the wings of the Arctic stay white throughout the northern summer. All the flight feathers of the Arctic tern are translucent against a bright sky, only the four innermost wing feathers of the common tern share this property. The trailing edge of
17750-406: The same time of year, but some tropical species may nest at intervals shorter than 12 months or asynchronously . Most terns become sexually mature when aged three, although some small species may breed in their second year. Some large sea terns, including the sooty and bridled terns , are four or older when they first breed. Terns normally breed in colonies , and are site-faithful if their habitat
17892-474: The sea or in freshwater, but molluscs , crustaceans and other invertebrate prey may form a significant part of the diet in some areas. Eggs and young are vulnerable to predation by mammals such as rats and American mink , and large birds including gulls , owls and herons . Common terns may be infected by lice , parasitic worms , and mites , although blood parasites appear to be rare. Its large population and huge breeding range mean that this species
18034-421: The sea. Where they spend the years prior to breeding is unknown. The terns are birds of open habitats that typically breed in noisy colonies and lay their eggs on bare ground with little or no nest material. Marsh terns construct floating nests from the vegetation in their wetland habitats, and a few species build simple nests in trees, on cliffs or in crevices. The white tern , uniquely, lays its single egg on
18176-402: The seventeenth century. The Scots names picktarnie , tarrock and their many variants are also believed to be onomatopoeic , derived from the distinctive call. Because of the difficulty in distinguishing the two species, all the informal common names are shared with the Arctic tern . There was some uncertainty whether Sterna hirundo should apply to the common tern or the arctic tern as
18318-435: The sexes. In non-breeding adults, the forehead and underparts become white, the bill is all black or black with a red base, and the legs are dark red or black. The upper wings have an obvious dark area at the front edge of the wing, the carpal bar. Terns that have not bred successfully may moult into non-breeding adult plumage beginning in June, though late July is more typical, with the moult suspended during migration. There
18460-449: The shelter of tallish vegetation, and using artificial eelgrass mats to encourage common terns to nest in areas not vulnerable to flooding. A number of terns face serious threats, and the Chinese crested tern is classed as " critically endangered " by BirdLife International . It has a population of fewer than 50 birds and a breeding range of just 9 km (3.5 sq mi). It
18602-660: The south and west of Europe tending to stay north of the equator and other European birds moving further south. The breeding range continues across the temperate and taiga zones of Asia, with scattered outposts on the Persian Gulf and the coast of Iran. Small populations breed on islands off Sri Lanka, and in the Ladakh region of the Tibetan plateau. Western Asian birds winter in the northern Indian Ocean , and S. h. tibetana appears to be common off East Africa during
18744-487: The species are very similar and both occur in Sweden. In 1913, the Swedish zoologist Einar Lönnberg concluded that the binomial name Sterna hirundo applied to the common tern. Four subspecies of the common tern are generally recognized, although S. h. minussensis is sometimes considered an intergrade between S. h. hirundo and S. h. longipennis . The nominate subspecies of
18886-437: The subspecies. The common tern's upper wings are pale grey, but as the summer wears on, the dark feather shafts of the outer flight feathers become exposed, and a grey wedge appears on the wings. The rump and tail are white, and on a standing bird the long tail extends no further than the folded wingtips, unlike the Arctic and roseate terns in which the tail protrudes beyond the wings. There are no significant differences between
19028-448: The surrounding colony to defend them. In smaller colonies, they may rarely mate with these other tern species. The white-bellied sea-eagle ( Haliaeetus leucogaster ) and silver gull are known to prey on eggs and chicks, while the turnstone ( Arenaria interpres ), black rat ( Rattus rattus ) and King's skink ( Egernia kingii ) are suspected predators. The call of the roseate tern is a very characteristic chuwit , similar to that of
19170-461: The surrounding decorative material. Breeding success in areas prone to flooding has been enhanced by the provision of artificial mats made from eelgrass , which encourage the terns to nest in higher, less vulnerable areas, since many prefer the mats to bare sand. The common tern tends to use more nest material than roseate or Arctic terns, although roseate often nests in areas with more growing vegetation. Terns are expert at locating their nests in
19312-420: The territory is mainly by the male, who repels intruders of either sex. He gives an alarm call, opens his wings, raises his tail and bows his head to show the black cap. If the intruder persists, the male stops calling and fights by bill grappling until the intruder submits by raising its head to expose the throat. Aerial trespassers are simply attacked, sometimes following a joint upward spiralling flight. Despite
19454-417: The twelfth day from hatching, which helps to keep the brood together. Most populations of the common tern are strongly migratory, wintering south of their temperate and subarctic Northern Hemisphere breeding ranges. First summer birds usually remain in their wintering quarters, although a few return to breeding colonies some time after the arrival of the adults. In North America, the common tern breeds along
19596-406: The two species were often jointly recorded as "commic terns". Although similar in size, the two terns differ in structure and flight. The common tern has a larger head, thicker neck, longer legs, and more triangular and stiffer wings than its relative, and has a more powerful, direct flight. Arctic terns have greyer underparts than the common variety, which makes its white cheeks more obvious, whereas
19738-488: The usually noisy colony while its residents assess the danger. Other calls include a down-slurred keeur given when an adult is approaching the nest with a fish, and a kip uttered during social contact. Parents and chicks can locate one another by call, and siblings also recognise each other's vocalisations from about the twelfth day after hatching, which helps to keep the brood together. Vocal differences reinforce species separation between closely related birds such as
19880-495: The while, before the two birds descend together in zigzag glides. If the male is carrying a fish, he may attract the attention of other males too. On the ground, the male courts the female by circling her with his tail and neck raised, head pointing down, and wings partially open. If she responds, they may both adopt a posture with the head pointed skywards. The male may tease a female with the fish, not parting with his offering until she has displayed to him sufficiently. Once courtship
20022-455: The winter quarters. A major moult to adult breeding plumage occurs in the next February to June, between forty and ninety per cent of feathers being replaced. Old primary feathers wear away to reveal the blackish barbs beneath. The moult pattern means that the oldest feathers are those nearest the middle of the wing, so as the northern summer progresses, a dark wedge appears on the wing because of this feather ageing process. Terns are unusual in
20164-448: Was the main cause of large reductions in common tern populations in both Europe and North America, especially on the Atlantic coasts and inland. Sometimes entire stuffed birds were used to make hats. Numbers largely recovered early in the twentieth century mainly due to legislation and the work of conservation organizations. Although some Eurasian populations are stable, numbers in North America have fallen by more than seventy per cent in
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