SWIFT (GREATER CRESTED) TERN

SWIFT (GREATER CRESTED) TERN

Thalasseus bergii

afrikaans: Geelbeksterretjie

46–49 cm; 320–430 g; wingspan 95–115 cm

Description:-

A large tern with a long, slightly drooped yellow or greenish-yellow bill (not orange, as in Royal, Lesser Crested and Elegant Terns). Appreciably larger than Lesser Crested and Elegant Terns. Br. ads have black cap and shaggy crest, but black does not extend to bill. Non-br. ads have white forecrown. Back colour pale grey in nominate race; some darker grey T. b. velox may occur in Mozambique. Juv. has dusky, yellow-olive bill; upperparts mottled blackish brown with blackish margins to flight feathers, appearing dark grey in flight. Imm. retains dark flight feathers. Legs usually black, but some juvs have yellow-orange legs.

Voice:-

Harsh ‘kree-eck’; juv. has a thin, vibrating, whistled begging call.

Status and biology:-

Common resident and local migrant in coastal waters, rarely out to shelf break; also estuaries and coastal wetlands. Nominate race is endemic to s Africa; population increasing; 8 000–12 000 pairs breed colonially at islands and coastal wetlands from central Namibia to Port Elizabeth, E Cape. Large numbers follow sardine run along the east coast in winter.