Lesser crested tern

Subspecies

Three geographical subspecies exist, differing mainly in size and minor plumage. T. b. emigratus breeds off Libya and winters in West Africa; it is pale grey and slightly larger. T. b. bengalensis occurs from the Red Sea to the Persian Gulf, wintering to South Africa; it is medium-dark grey and slightly smaller. T. b. torresii ranges from Indonesia to Australia, wintering locally; it is dark grey and slightly larger.

Description

This tern measures 35–43 cm in length with a wingspan of 88–105 cm and a weight of 185–242 g. In summer, it has a black cap, black legs, and a long sharp orange bill; the upperwings, rump, and central tail feathers are grey, while underparts are white.

Primary flight feathers darken during summer, and in winter the forehead becomes white. Its call is a loud grating noise similar to that of the Sandwich tern. The grey rump aids flight identification, distinguishing it from related species such as the Elegant tern (which has a longer, slenderer bill) and the Chinese crested tern (which has a black-tipped bill).

Juveniles resemble young Sandwich terns but have a yellow-orange bill and paler overall plumage with faint dark crescents on the mantle. Two other orange-billed terns occur within its range: the West African crested tern (larger, stouter-billed, with a white rump) and the Greater crested tern (darker above with a yellower bill). Like all Thalasseus terns, it feeds by plunge-diving for fish, usually from saline environments, diving directly rather than from a hover.

Males offer fish to females during courtship. It breeds in dense colonies on coasts and islands, nesting in a ground scrape and laying one to two (rarely three) eggs. Nesting behaviour resembles that of Sandwich terns; T. b. emigratus nests in late summer when predatory yellow-legged gulls have finished breeding and departed.

Did You Know?

• The genus name Thalasseus comes from Ancient Greek for 'fisherman', derived from thalassa meaning 'sea'.
• The specific name bengalensis means 'of Bengal', the type locality historically referring to Bangladesh and part of Northeast India.
• This species is protected in the PM Sayeed Marine Birds Conservation Reserve in India.