Sterna bergii (Swift tern) 

Geelbeksterretjie [Afrikaans]; Grote kuifstern [Dutch]; Sterne huppée [French]; Eilseeschwalbe [German]; Gaivina-de-bico-amarelo [Portuguese]

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia > Chordata > Craniata > Vertebrata (vertebrates)  > Gnathostomata (jawed vertebrates) > Teleostomi (teleost fish) > Osteichthyes (bony fish) > Class: Sarcopterygii (lobe-finned fish) > Stegocephalia (terrestrial vertebrates) > Tetrapoda (four-legged vertebrates) > Reptiliomorpha > Amniota > Reptilia (reptiles) > Romeriida > Diapsida > Archosauromorpha > Archosauria > Dinosauria (dinosaurs) > Saurischia > Theropoda (bipedal predatory dinosaurs) > Coelurosauria > Maniraptora > Aves (birds) > Order: Charadriiformes > Family: Laridae > Genus: Sterna

Sterna bergii (Swift tern)  Sterna bergii (Swift tern) 
Swift tern. (photo H. Robertson, Iziko ©] Swift tern, Kleinmond, Western Cape, South Africa. (photo H. Robertson, Iziko ©]

Distribution and habitat

Occurs the coasts of the west-central Pacific, south-east Atlantic, and Indian Oceans. In southern Africa it is common along the entire coastline of the region, generally preferring lagoons, estuaries, coastal islands and exposed ocean beaches.

Distribution of Swift tern in southern Africa, based on statistical smoothing of the records from first SA Bird Atlas Project (© Animal Demography unit, University of Cape Town; smoothing by Birgit Erni and Francesca Little). Colours range from dark blue (most common) through to yellow (least common). See here for the latest distribution from the SABAP2.  

Predators and parasites

Movements and migrations

After breeding, it departs from the colonies and heads south and east to the coastline of the Indian Ocean, travelling back again at the onset of the following breeding season.

Food 

Mainly eats pelagic schooling fish, doing most of its foraging within sight of land, plunge-diving or dipping into the sea to catch prey. The following food items have been recorded in its diet:

  • Fish
    • Engraulis encrasicolus (Anchovy)
    • Sardinops sagax (Sardines)
    • Sufflogobius bibarbatus (Pelagic goby)
    • Merluccius (hakes, usually scavenged)

Breeding

  • Monogamous, usually nesting in colonies of roughly 500-3000 pairs, maintaining a pair bond year round.
  • The nest (see image below) is a shallow scrape in flat, open sand, either unlined or with a thin lining of stones and cuttlefish (Sepia) bones, or alternatively it may use the roof of a building.
Sterna bergii (Swift tern)
Swift tern on nest. [photo Peter Steyn ©]
  • Egg-laying season is from January-September, peaking from February-June.
  • It lays a single egg, rarely two, which is incubated by both sexes for about 21-30 days.
  • The chicks are brooded and fed by both parents, leaving the nest after about three days, after which it forms crèches along with other chicks, fledging at about 38-40 days old and becoming fully independent roughly four months later.

Threats

Not threatened, as although some colonies (such as one at Strandfontein Sewage Works, Western Cape) have been abandoned due to predators or bush encroachment, it is still common and widespread.

References

  • Hockey PAR, Dean WRJ and Ryan PG 2005. Roberts - Birds of southern Africa, VIIth ed. The Trustees of the John Voelcker Bird Book Fund, Cape Town. 

 

 

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