Greater Crested Tern

The Greater Crested Tern, Thalasseus bergii, also known as the Crested Tern or Swift Tern, is a robust seabird of the family Laridae. It is characterized by its grey upperparts, white underparts, and a distinctive shaggy black crest, which becomes less prominent in the non-breeding season. The species exhibits a yellow bill and black legs, adding to its striking appearance.

Identification Tips

Adult Greater Crested Terns can be identified by their long yellow bills and glossy black crests. During the breeding season, the crest is particularly shaggy at the rear. The forehead and underparts are white, while the back and inner wings are a dusky grey. In winter, the crown becomes white, blending into a peppered black crest and mask. Juveniles display a mottled grey, brown, and white plumage with dark bars on the inner flight feathers.

Habitat

This species is found along tropical and subtropical coastlines and islands, favoring low-lying sandy, rocky, or coral islands for nesting. Outside the breeding season, they may be seen resting on open shores, boats, or man-made structures near the sea.

Distribution

The Greater Crested Tern has a widespread distribution across the Old World, from South Africa, around the Indian Ocean, to the central Pacific and Australia. It breeds in dense colonies along coastlines and islands within this range.

Behaviour

The Greater Crested Tern is known for its adaptability, often following fishing boats for discarded bycatch and utilizing unconventional nesting sites such as building roofs and artificial islands. It is a migratory species, with populations dispersing widely after the breeding season.

Song & Calls

The species is highly vocal, especially at breeding grounds. The territorial call is a loud, raucous "kerrak," while other calls include an anxious "korrkorrkorr" at the nest and a hard "wep wep" in flight.

Breeding

Greater Crested Terns are monogamous and may maintain pair bonds year-round. They nest in colonies, often with other seabirds, and exhibit little site fidelity, changing nesting locations frequently. The nest is a simple scrape in the sand, and both parents incubate the eggs and care for the chicks.

Similar Species

The Royal Tern is similar in size but has a heavier build, broader wings, a paler back, and a more orange bill. The Lesser Crested Tern is smaller, with an orange-tinted bill and less variegated immature plumage.

Diet and Feeding

The diet is predominantly fish, which they catch by plunge diving or surface dipping. They are known to follow trawlers for discards and may forage up to 10 km from land during the breeding season.

Conservation Status

The Greater Crested Tern is classified as Least Concern by the IUCN, with a stable population exceeding 500,000 individuals. However, some local populations are affected by human activities such as fishing and egg harvesting.