Common Tern

The common tern (Sterna hirundo) is a graceful seabird recognized by its slender body, long wings, and forked tail. Its range encompasses several continents, breeding in temperate and subarctic regions of Europe, Asia, and North America, and wintering in coastal tropical and subtropical regions. Adults have a black cap on their heads, light grey upperparts, white underparts, and a red bill with a black tip. They measure approximately 31-35 cm (12.2-13.8 in) in length, with a wingspan of 77-98 cm (30-38 in). The common tern is very similar to the Arctic tern (Sterna paradisaea), but it can be distinguished from this by its slightly shorter tail and red bill with a dark tip, as opposed to the Arctic tern’s wholly red bill. The Arctic tern typically also has darker grey underparts, compared to the whiter underparts of the common tern.

Common terns inhabit lakes, rivers, marshes, and coastal areas, displaying a preference for islands and beaches for breeding to avoid predators. During breeding season they are found both by the sea and inland, even at high altitudes. In winter they are almost strictly marine, and mostly found at sea near coastlines. Their diet mainly consists of fish, which they catch by performing spectacular dives into the water from heights of up to 30 meters. They also consume crustaceans and insects. 

These birds are long-distance migrants, showcasing remarkable journeys twice a year. The common tern migrates southward from its breeding grounds in late summer to early autumn, heading towards the southern hemisphere’s coasts and oceans. They return north in the spring to their breeding sites. This migration ensures they enjoy endless summer, exploiting the rich feeding grounds in both hemispheres.

The breeding season begins in late spring. Common terns are monogamous, and during courtship the male performs a fish flight, where he offers a fish to the female. A pair exhibits strong site fidelity, often returning to the same breeding sites yearly. Nests are typically shallow scrapes in the ground on sandy or gravelly areas, where they lay 1-3 eggs. Both parents partake in incubation, which lasts about 21-22 days. Chicks are semi-precocial, meaning they are downy and open-eyed at hatching but rely on their parents for food. Fledging occurs around 22-28 days post-hatching, after which juveniles learn to fish and gradually gain independence.

Because of its large population and widespread distribution, the common tern is listed as least concern on the IUCN Red List. However, they face threats from habitat loss, pollution, and human disturbance, particularly at breeding sites. Conservation efforts focus on protecting nesting areas and monitoring population trends to prevent declines.