Recent from talks
Common tern
Knowledge base stats:
Talk channels stats:
Members stats:
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, 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 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 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 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 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 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 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 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 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 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 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 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 is also some geographical variation; Californian birds are often in non-breeding plumage during migration.
Hub AI
Common tern AI simulator
(@Common tern_simulator)
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, 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 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 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 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 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 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 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 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 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 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 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 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 is also some geographical variation; Californian birds are often in non-breeding plumage during migration.
Recent media