Common tern

Lore & Background

The common tern was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae under its current scientific name, Sterna hirundo. The genus name Sterna derives from the Old English 'stearn,' used in the poem The Seafarer around 1000 A.D., while the species name hirundo is Latin for swallow, referencing the bird's superficial likeness to that unrelated bird. The informal name 'sea swallow' has been recorded since at least the seventeenth century. There was historical uncertainty whether Sterna hirundo applied to the common tern or the Arctic tern, as both species are very similar and occur in Sweden; in 1913, Swedish zoologist Einar Lönnberg concluded that the binomial name Sterna hirundo applies to the common tern.

Breeding adults have light grey upperparts, white to very light grey underparts, a black cap, orange-red legs, and a narrow pointed bill that may be mostly red with a black tip or all black depending on the subspecies. The common tern nests on any flat, poorly vegetated surface close to water, including beaches and islands, and readily adapts to artificial substrates such as floating rafts. Up to three eggs are laid, incubated by both sexes for about 21–22 days, with chicks fledging in 22–28 days. The species feeds by plunge-diving for fish, but also takes molluscs, crustaceans, and other invertebrates in some areas.

Reader's Guide

The common tern is significant as a widespread and adaptable seabird, breeding across a broader range of habitats than any of its relatives. Its large population and huge breeding range have led to its classification as least concern, though numbers in North America have declined sharply in recent decades. The species faces threats from habitat loss, pollution, and disturbance of breeding colonies, despite international legislation protecting it. The common tern's closest relatives appear to be the Antarctic tern, followed by the Eurasian Arctic and roseate terns, with genetic evidence suggesting it may have diverged from an ancestral stock earlier than its relatives. Its moult pattern is unusual among terns, with primaries replaced at least twice, occasionally three times in a year, and the freshness of wing feathers is used by females in mate selection. The species is also notable for its agile flight, capable of rapid turns, hovering, and vertical take-off, with an average flight speed of 30 km/h (19 mph) in the absence of a tail wind.

Did You Know?

• The common tern was first described by Carl Linnaeus in 1758 under the scientific name Sterna hirundo.
• The species name hirundo is Latin for swallow, referring to the tern's superficial likeness to that bird.
• Common terns may be infected by lice, parasitic worms, and mites, although blood parasites appear to be rare.