Lesser Crested Tern
Encyclopedia
The Lesser Crested Tern (Thalasseus bengalensis, syn. Sterna bengalensis - see Bridge et al., 2005) is a seabird
of the tern
family Sternidae. 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 Libya
n 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
.
This bird
has a number of geographical subspecies
, differing mainly in size and minor plumage details:
The Mediterranean race is a rare vagrant to Europe
, and has bred in pure or mixed pairs (with Sandwich Tern) in Italy
, Spain
and England
.
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 race emigrata at least) by nesting in the late summer when predatory Yellow-legged Gull
s have finished breeding and departed from the nesting area.
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 is a medium-large tern, 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.
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.
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, Royal Tern
and Greater Crested Tern
. Both are much larger and stouter-billed; Royal also has a white rump and tail, while Crested (which shares the grey rump) is darker overall above and has a yellower bill. See also Orange-billed tern
.
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 http://www.rac-spa.org/index.php?option=com_content&task=view&id=97&Itemid=154.
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
of the tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
family Sternidae. It breeds in subtropical coastal parts of the world mainly from the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
across the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
to the western Pacific, and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, with a significant population on the southern coast of the Mediterranean on two islands off the Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
n coast. Accidental breeding has also been reported in Italy and France. The Australian birds are probably sedentary, but other populations are migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, wintering south to South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
.
This bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
has a number of geographical subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, differing mainly in size and minor plumage details:
- T. b. emigrata: breeding in the Mediterranean on islands off the coast of LibyaLibyaLibya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
, wintering West AfricaWest AfricaWest Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
. Pale grey above (only marginally darker than Sandwich Tern); slightly larger. - T. b. bengalensis: northern Indian OceanIndian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, wintering to South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Medium-dark grey above; slightly smaller. - T. b. torresii: IndonesiaIndonesiaIndonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
south to QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, wintering in the same area (birds breeding in the Persian GulfPersian GulfThe Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
are also often given as this race). Dark grey above; slightly larger.
The Mediterranean race is a rare vagrant to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and has bred in pure or mixed pairs (with Sandwich Tern) in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
and England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
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 race emigrata at least) by nesting in the late summer when predatory Yellow-legged Gull
Yellow-legged Gull
The Yellow-legged Gull , sometimes referred to as Western Yellow-legged Gull , is a large gull of Europe, the Middle East and North Africa, which has only recently achieved wide recognition as a distinct species...
s have finished breeding and departed from the nesting area.
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
Arctic Tern
The Arctic Tern is a seabird of the tern family Sternidae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America...
. The offering of fish by the male to the female is part of the courtship display.
This is a medium-large tern, very similar in size and general appearance to its three very close relatives Sandwich Tern, Elegant Tern
Elegant Tern
The Elegant Tern is a seabird of the tern family Sternidae. It breeds on the Pacific coasts of the southern USA and Mexico and winters south to Peru, Ecuador and Chile....
and Chinese Crested Tern
Chinese Crested Tern
The Chinese Crested Tern is a seabird of the tern family Sternidae, closely related to Sandwich Tern T. sandvicensis and Lesser Crested Tern T. bengalensis...
. 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.
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.
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, Royal Tern
Royal Tern
The Royal Tern is a seabird in the tern family Sternidae. This bird has two distinctive subspecies. T. m. maximus breeds on the Atlantic and Pacific coasts of the southern USA and Mexico into the Caribbean. The slightly smaller T. m. albididorsalis breeds in coastal west Africa...
and Greater Crested Tern
Greater Crested Tern
The Greater Crested Tern , also called Crested Tern or Swift Tern, is a seabird in the tern family which nests in dense colonies on coastlines and islands in the tropical and subtropical Old World...
. Both are much larger and stouter-billed; Royal also has a white rump and tail, while Crested (which shares the grey rump) is darker overall above and has a yellower bill. See also Orange-billed tern
Orange-billed tern
Orange-billed tern is a name applied to a group of three large terns in the genus Thalasseus with orange bills, which are quite similar in appearance and often considered difficult to identify, namely:* Royal Tern, Thalasseus maximus...
.
T. bengalensis is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA
AEWA
The Agreement on the Conservation of African-Eurasian Migratory Waterbirds is the largest of its kind developed so far under the Bonn Convention. It was concluded on 16 June 1995 at The Hague, the Netherlands and entered into force on 1 November 1999 after the required number of at least fourteen...
) applies, and one of 10 marine bird species listed in Mediterranean marine birds Action Plan http://www.rac-spa.org/index.php?option=com_content&task=view&id=97&Itemid=154.
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.
- 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. Molecular Phylogenetics and Evolution 35: 459–469. PDF fulltext
- del Hoyo, J.; Elliott, A. & Sargatal, J. (editors) (1996): Handbook of birds of the world, Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona. ISBN 84-87334-22-9
- 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.
- Meininger, Peter L., Pim A. Wolf, Dan A. Hadoud and Mohamed F. A. Essghaier (1994) Rediscovery of Lesser Crested Tern breeding in Libya British BirdsBritish Birds (magazine)British Birds is a monthly ornithology magazine that was established in 1907. It is now published by BB 2000 Ltd, which is wholly owned by The British Birds Charitable Trust , established for the benefit of British ornithology...
87(4):160-170. - Moltoni E. (1938). Escursione ornitologica all’Isola degli Uccelli (Golfo della Gran Sirte, Cirenaica). Riv. Ital. Orn 8 : 1-16.