Lesser crested tern

The lesser crested tern (Thalasseus bengalensis)<ref name=Bridge>Bridge, E. S.; Jones, A. W. & Baker, A. J. (2005). A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution Template:Webarchive. Molecular Phylogenetics and Evolution 35: 459–469.</ref> is a tern in the family Laridae.

Etymology

The genus name is from Ancient Greek Thalasseus, "fisherman" from thalassa, "sea". The specific bengalensis means "of Bengal", the type locality, historically referring to much of northern India and Bangladesh.<ref name=job>Template:Cite book</ref>

Distribution

It breeds in subtropical coastal parts of the world mainly from the Red Sea across the Indian Ocean to the western Pacific, and Australia, with a significant population on the southern coast of the Mediterranean on two islands off the Libyan coast. Accidental breeding has also been reported in Italy and France. The Australian birds are probably sedentary, but other populations are migratory, wintering south to South Africa.

Subspecies

This bird has three geographical subspecies, differing mainly in size and minor plumage details:<ref name="IOC">Template:Cite web</ref><ref name="HBW">Template:Cite book</ref>

• T. b. emigratus (Neumann, 1934): breeding in the Mediterranean on islands off the coast of Libya, wintering West Africa. Pale grey above (only marginally darker than Sandwich tern); slightly larger.
• T. b. bengalensis (Lesson, 1831): northern Indian Ocean including the Red Sea and the Persian Gulf, wintering to South Africa. Medium-dark grey above; slightly smaller.
• T. b. torresii (Gould, 1843): Indonesia south to Queensland, Australia, wintering in the same area (birds breeding in the Persian Gulf were formerly also sometimes cited as this subspecies<ref name="HBW"/>). Dark grey above; slightly larger.

• 
  T. b. emigratus, Senegal
• 
  T. b. bengalensis, Kutch, India
• 
  T. b. torresii, Michaelmas Cay, Queensland

The Mediterranean subspecies is a rare vagrant to Europe, and has bred in pure or mixed pairs (with Sandwich tern) in Italy, Spain and England.

Thalasseus bengalensis egg, Muséum de Toulouse.

Description

Lesser crested terns T. b. bengalensis in winter plumage, Akshi Beach, Maharashtra, India

This is a medium-large tern, 35–43 cm long and with a 88–105 cm wingspan; its weight ranges from 185–242 g.<ref name="HBW"/> It is very similar in size and general appearance to its three very close relatives Sandwich tern, Elegant tern and Chinese crested tern. The summer adult has a black cap, black legs and a long sharp orange bill. The upperwings, rump and central tail feathers are grey and the underparts white. The primary flight feathers darken during the summer. In winter, the forehead becomes white. The call is a loud grating noise like Sandwich tern.<ref name="Svensson">Template:Cite book</ref>

The grey rump is a useful flight identification feature distinguishing it from the related species. The Elegant tern also differs in a slightly longer, slenderer bill, while Chinese crested tern differs in a black tip to the bill and Sandwich tern a black bill with a yellow tip.<ref name="Svensson"/>

Juvenile lesser crested terns resemble same-age Sandwich terns, but with a yellow-orange bill, and paler overall, with only faint dark crescents on the mantle feathers.

There are two other orange-billed terns within the range of this species, West African crested tern, and Greater crested tern. Both are larger and stouter-billed; West African crested tern also has a white rump and tail, while crested tern (which shares the grey rump) is darker overall above and has a yellower to greenish-yellow bill.<ref name="HBW"/>

Like all Thalasseus terns, lesser crested tern feeds by plunge-diving for fish, usually from saline environments. It usually dives directly, and not from the "stepped-hover" favoured by Arctic tern. The offering of fish by the male to the female is part of the courtship display.

This species breeds in dense colonies on coasts and islands. It nests in a ground scrape and lays one to two (rarely three) eggs. Nesting behaviour is very similar to that of Sandwich terns, with predator avoidance by nesting in very dense colonies, and also (in T. b. emigratus at least) by nesting in the late summer when predatory yellow-legged gulls have finished breeding and departed from the nesting area.<ref name="BB87">Template:Cite journal</ref>

Conservation

T. bengalensis is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies, and one of 10 marine bird species listed in Mediterranean marine birds Action Plan.<ref>Template:Cite web</ref>

In India the Lesser crested tern is protected in the PM Sayeed Marine Birds Conservation Reserve.<ref>Template:Cite news</ref>

• 
  T. b. emigratus, Algeria
• 
  T. b. torresii at Manly Marina, SE Queensland, with crested and Caspian terns, silver gulls and pied oystercatcher
• 
  Lesser crested terns at Muzhappilangad beach

Further reading

• Azafzaf, H., Etayeb, K. & Hamza, A. 2006: Report on the census of Lesser Crested Tern Sterna bengalensis in the Eastern coast of Libya. (1–7 August 2006). Unpublished report to Regional Activities Centre/Special Protected Areas (MAP/UNEP), Environment General Agency (Libya) and African-Eurasian Waterbird Agreement (UNEP/AEWA). 18 pp with map and four Appendices.
• Baker N.E (1984). Lesser Crested Tern in Bengazi, Libya. Bull. Orn. Soc. Middle East.
• Hamza, A., H. Azafzaf, N. Baccetti, E.M. Bourass, J. J.Borg, P. Defos du Rau, A. Saied, J. Sultana, M. Zenatello (2008) Report on census and ringing of Lesser Crested Tern in Libya (2-10 Aug. 2007), with a preliminary inventory of Libyan islands. UNEP-MAP-RAC/SPA and EGA. Tech. Report.
• Moltoni E. (1938). Escursione ornitologica all'Isola degli Uccelli (Golfo della Gran Sirte, Cirenaica). Riv. Ital. Orn 8 : 1-16.

External links

• Lesser crested tern - Species text in The Atlas of Southern African Birds