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the web of life in southern Africa

Sterna caspia (Caspian tern) 

[= Hydroprogne caspia] 

Reusesterretjie [Afrikaans]; Reuzenstern [Dutch]; Sterne caspienne [French]; Raubseeschwalbe [German]; Gaivina-de-bico-vermelho [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 caspia (Caspian tern)  Sterna caspia (Caspian tern) 
Caspian tern. [photo Jeff Poklen ©] Caspian tern carrying fish [photo Jeff Poklen ©]

Distribution and habitat

Occurs across much of the world, excluding South America and Antarctica. Within southern Africa it is locally common along the coast of the region as well as inland in Botswana and east-central South Africa. It generally prefers sheltered bays, estuaries and large inland water bodies, especially dams and saline pans.

Distribution of Caspian 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

  • Predators of eggs and chicks

Movements and migrations

Likely to be resident, however its movements are not well understood.

Food 

It mainly eats fish, doing most of its foraging 3-20 metres above clear, shallow water, facing downwards so that it can spot fish. Once prey is spotted it momentarily hovers before diving head-first into the water. The following food items have been recorded in its diet:

  • Fish
    • Acanthopagrus berda (Riverbream)
    • Johnius belengerii (Small kob)
    • Clarias gariepinus (Sharptooth catfish)
    • Pomadasys commersonnii (Spotted grunter)
    • Oreochromis mossambicus (Mozambique tilapia)
    • Thryssa vitrirostris (Orangemouth glassnose)
    • Liza richardsonii (Southern mullet)
    • soles (Soleidae)
    • breams (Cichlidae)

Breeding

  • Hardly studied in southern Africa, so most of the following information comes from Europe. It is a monogamous, solitary or colonial nester, maintaining a pair bond year-round.
  • The nest (see image below) is excavated by both adults, consisting of a shallow scrape in sand, gravel, soil or pebbles, often lined with some dry vegetation.
Sterna caspia (Caspian tern)   

Caspian tern nest with eggs, Grootdraai Dam, Mpumalanga, South Africa. [photo Johan van Rensburg ©]

 
  • Egg-laying season is from December-April in Namibia and Botswana, June-August in north-eastern South Africa, February-July in KwaZulu-Natal and the Eastern Cape and from October-January in the Western Cape.
  • It lays 1-3 eggs, which are incubated by both sexes for about 22-24 days.
  • The chicks are brooded and fed by both parents, leaving the nest after about a week, taking their first flight at approximately 30-35 days old but only becoming independent about eight months later.

Threats

Near-threatened in South Africa.

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.