Tag Archives: Swift Tern

Swift Tern

Thalasseus (Sterna) bergii

The Swift Tern, or Greater Crested Tern, usually inhabits the shallow tropical and sub-tropical waters of lagoons, estuaries, bays, harbours and open beaches where it feeds mainly on fish (up to 90% of its diet) as well as squid, crustaceans and insects. Adults have a wingspan of up to 1.2m and weigh up to 430g.

These terns are gregarious birds, nesting and roosting in fairly large and dense colonies, often mixed with gulls and cormorants, usually on offshore islands, reefs or sandbanks and occasionally on top of buildings. Nests are shallow scrapes in the bare sand or on rocks and often quite exposed. The breeding season in Swift Terns stretches from late summer through winter to early spring. Pairs are monogamous. Clutches consist of 1 or 2 eggs and are incubated for around 4 weeks by both parents. Chicks fledge at a little over a month old, but don’t become fully independent until they’re about 5  months old.

The IUCN considers the Swift Tern to be of least concern, estimating the total population at around a million birds, with an enormous distribution stretching from Namibia and South Africa along the Indian Ocean coasts of Africa, the Middle East and Asia, and into the Pacific Ocean far to the north-east of Australia. They occur along the entire South African coastline, though about 80% of the local population, estimated in the region of 25,000 birds and increasing, is found in the Western Cape during the breeding season.