Common Tern

The Common Tern, Sterna hirundo, is a slender seabird with a circumpolar distribution, breeding in temperate and subarctic regions of Europe, Asia, and North America. It is a migratory species, wintering in coastal tropical and subtropical regions. Adults display light grey upperparts, white to very light grey underparts, and a black cap. Their legs are orange-red, and they possess a narrow pointed bill, which varies in color between subspecies.

Identification Tips

To identify the Common Tern, look for its pale grey upper wings, which develop a dark feather shaft as the season progresses, creating a grey wedge. The rump and tail are white, and the tail extends no further than the folded wingtips when the bird is standing. The bill is mostly red with a black tip or entirely black, depending on the subspecies. In non-breeding adults, the forehead and underparts become white, and the bill turns black.

Habitat

Common Terns are found nesting on flat, poorly vegetated surfaces close to water, such as beaches, islands, and artificial substrates like floating rafts. They adapt to a variety of habitats, from the taiga to tropical shores, and avoid excessively rainy, windy, or icy areas.

Distribution

This species has a wide breeding range, encompassing Europe, North Africa, Asia, and North America. It migrates to winter along the coasts of Central and South America, Africa, and southern Asia, with some populations remaining partially migratory in the Caribbean.

Behaviour

Common Terns are agile flyers, capable of rapid turns, hovering, and vertical take-off. They are known for their powerful, direct flight and can fly at speeds averaging 30 km/h, increasing during migration. They breed in colonies, often alongside other seabird species, and exhibit strong territorial behavior.

Song & Calls

The Common Tern has a distinctive alarm call, a KEE-yah, and a repertoire of other vocalizations used for communication within the colony and with their chicks. Parents and chicks recognize each other's calls, aiding in maintaining family bonds.

Breeding

Breeding involves aerial courtship displays and ground rituals. Nests are shallow scrapes, sometimes lined with debris. Clutch size is typically three eggs, camouflaged with blotchy patterns. Both sexes incubate, and chicks fledge in 22–28 days. Adults are defensive of their nest and young, often harassing intruders.

Similar Species

The Common Tern can be confused with the Arctic Tern, Roseate Tern, and Forster's Tern, but differences in plumage details, leg and bill color, and vocalizations aid in distinguishing them.

Diet and Feeding

The diet consists mainly of fish, which they catch by plunge-diving, but may also include molluscs, crustaceans, and large insects. They forage up to 15 km from the breeding colony and may follow schools of fish or predatory fish to locate prey.

Conservation Status

The Common Tern is classified as Least Concern, with a large population and extensive breeding range. However, threats such as habitat loss, pollution, and disturbance have led to declines in some areas, particularly in North America. Conservation efforts include habitat management and protection from human disturbance.