Tern

Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consist of eleven genera. They are slender, lightly built birds with long, forked tails, narrow wings, long bills, and relatively short legs. Most species are pale grey above and white below, with a contrasting black cap to the head, but the marsh terns, the Inca tern, and some noddies have dark plumage for at least part of the year. The sexes are identical in appearance, but young birds are readily distinguishable from adults. Terns have a non-breeding plumage, which usually involves a white forehead and much-reduced black cap.

The terns are birds of open habitats that typically breed in noisy colonies and lay their eggs on bare ground with little or no nest material. Marsh terns construct floating nests from the vegetation in their wetland habitats, and a few species build simple nests in trees, on cliffs or in crevices. The white tern, uniquely, lays its single egg on a bare tree branch. Depending on the species, one to three eggs make up the clutch. Most species feed on fish caught by diving from flight, but the marsh terns are insect-eaters, and some large terns will supplement their diet with small land vertebrates. Many terns are long-distance migrants, and the Arctic tern may see more daylight in a year than any other animal.

Terns are long-lived birds and are relatively free from natural predators and parasites; most species are declining in numbers due directly or indirectly to human activities, including habitat loss, pollution, disturbance, and predation by introduced mammals. The Chinese crested tern is in a critical situation and three other species are classed as endangered. International agreements provide a measure of protection, but adults and eggs of some species are still used for food in the tropics. The eggs of two species are eaten in the West Indies because they are believed to have aphrodisiac properties.

Terns
Temporal range: Early Miocene to present
Crested tern444 edit
Greater crested tern in first-year plumage
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Laridae
Subfamily: Sterninae
Genera
Birds of Sweden 2016 07
Common tern in flight
Birds of Sweden 2016 08
Common tern in flight

Taxonomy

The Charadriiformes order of birds contains 18 coastal seabird and wader families. Within the order, the terns form a lineage with the gulls, and, less closely, with the skimmers, skuas, and auks.[1][2] Early authors such as Conrad Gessner, Francis Willughby, and William Turner did not clearly separate terns from gulls,[3] but Linnaeus recognised the distinction in his 1758 Systema Naturae, placing the gulls in the genus Larus and the terns in Sterna. He gave Sterna the description rostrum subulatum, "awl-shaped bill", referring to the long, pointed bills typical of this group of birds, a feature that distinguishes them from the thicker-billed gulls.[4][5][6] Behaviour and morphology suggest that the terns are more closely related to the gulls than to the skimmers or skuas, and although Charles Lucien Bonaparte created the family Sternidae for the terns in 1838, for many years they were considered to be a subfamily, Sterninae, of the gull family, Laridae. Relationships between various tern species, and between the terns and the other Charadriiformes, were formerly difficult to resolve because of a poor fossil record and the misidentification of some finds.[7][8]

Following genetic research in the early twenty-first century, the terns were historically treated as a separate family: Sternidae.[9][10] Most terns were formerly treated as belonging to one large genus, Sterna, with just a few dark species placed in other genera; in 1959, only the noddies and the Inca tern were excluded from Sterna.[11][12] A recent analysis of DNA sequences supported the splitting of Sterna into several smaller genera.[12][13] One study of part of the cytochrome b gene sequence found a close relationship between terns and a group of waders in the suborder Thinocori.[14] These results are in disagreement with other molecular and morphological studies, and have been interpreted as showing either a large degree of molecular convergent evolution between the terns and these waders, or the retention of an ancient genotype.[9]

The word "stearn" was used for these birds in Old English as early as the eighth century, and appears in the poem The Seafarer, written in the ninth century or earlier. Variants such as "tearn" occurred by the eleventh century, although the older form lingered on in Norfolk dialect for several centuries.[3] As now, the term was used for the inland black tern as well as the marine species.[15][16] Some authorities consider "tearn" and similar forms to be variants of "stearn",[3] while others derive the English words from Scandinavian equivalents such as Danish and Norwegian terne or Swedish tärna, and ultimately from Old Norse þerna.[17][18] Linnaeus adopted "stearn" or "sterna" (which the naturalist William Turner had used in 1544 as a Latinisation of an English word, presumably "stern", for the black tern)[19][20] or a North Germanic equivalent for his genus name Sterna.[21]

Species

The cladogram shows the relationships between the tern genera, and the currently recognised species, based on mitochondrial DNA studies, are listed below:[13]

Sternidae
 

Anous

 
 

Gygis

 
 

Onychoprion

 
 

Sternula

 
 

Phaetusa

 
 

Phaetusa

 
 

Gelochelidon

 
 

Hydroprogne

 
 

Chlidonias

 
 

Thalasseus

 
 

Sterna

Based on Bridge et al (2005). Procelsterna DNA was not available for the study, but that genus usually place between Anous and Gygis [13]
White tern with fish
White tern with fish
Sterna fuscata
The sooty tern is a dark-backed oceanic species
Sternula albifrons 2 - Little Swanport
Little tern in flight showing the forked tail
Tern in Chilka, Orissa I IMG 9309
The gull-billed tern will sometimes prey on the chicks and young of other terns
  • Genus Gelochelidon — gull-billed terns
  • Genus Larosterna — Inca terns
Chlidonias hybrida 2 (Marek Szczepanek)
The whiskered tern is an insect-eating marsh tern
River Tern (Sterna aurantia)- Adult & Immature W IMG 9721
River tern adult and immatures

In addition to extant species, the fossil record includes a Miocene palaeospecies, Sterna milne-edwardsii.[26]

The genera Anous, Procelsterna and Gygis are collectively known as noddies, the Chlidonias species are the marsh terns,[7] and all other species comprise the sea terns.[27][28]

Description

Larosterna inca (Inca Tern - Inkaseeschwalbe) Weltvogelpark Walsrode 2012-015
The Inca tern's plumage is atypical of the family.

Terns range in size from the least tern, at 23 cm (9.1 in) in length and weighing 30–45 g (1.1–1.6 oz),[29][30] to the Caspian tern at 48–56 cm (19–22 in), 500–700 g (18–25 oz).[31][32] They are longer-billed, lighter-bodied, and more streamlined than gulls, and their long tails and long narrow wings give them an elegance in flight. Male and female plumages are identical, although the male can be 2–5% larger than the female and often has a relatively larger bill. Sea terns have deeply forked tails, and at least a shallow "V" is shown by all other species.[7] The noddies (genera Anous, Procelsterna and Gygis) have unusual notched-wedge shaped tails, the longest tail feathers being the middle-outer, rather than the central or outermost.[22][33] Although their legs are short, terns can run well. They rarely swim, despite having webbed feet, usually landing on water only to bathe.[7]

The majority of sea terns have light grey or white body plumage as adults, with a black cap to the head. The legs and bill are various combinations of red, orange, yellow, or black depending on species. The pale plumage is conspicuous from a distance at sea, and may attract other birds to a good feeding area for these fish-eating species. When seen against the sky, the white underparts also help to hide the hunting bird from its intended prey. The Inca tern has mainly dark plumage, and three species that mainly eat insects, the black tern, white-winged tern, and black-bellied tern, have black underparts in the breeding season. The Anous noddies have dark plumage with a pale head cap. The reason for their dark plumage is unknown, but it has been suggested that in tropical areas, where food resources are scarce, the less conspicuous colouration makes it harder for other noddies to detect a feeding bird.[34] Plumage type, especially the head pattern, is linked to the phylogeny of the terns, and the pale-capped, dark-bodied noddies are believed to have diverged earlier than the other genera from an ancestral white-headed gull, followed by the partially black-headed Onychoprion and Sternula groupings.[13]

Juvenile terns typically have brown- or yellow-tinged upperparts, and the feathers have dark edges that give the plumage a scaly appearance. They have dark bands on the wings and short tails. In most species, the subsequent moult does not start until after migration, the plumage then becoming more like the adult, but with some retained juvenile feathers and a white forehead with only a partial dark cap. By the second summer, the appearance is very like the adult, and full mature plumage is usually attained by the third year. After breeding, terns moult into a winter plumage, typically showing a white forehead. Heavily worn or aberrant plumages such as melanism and albinism are much rarer in terns than in gulls.[35]

Voice

Terns have a wide repertoire of vocalisations. For example, the common tern has a distinctive alarm, kee-yah, also used as a warning to intruders, and a shorter kyar, given as an individual takes flight in response to a more serious threat; this quietens the usually noisy colony while its residents assess the danger. Other calls include a down-slurred keeur given when an adult is approaching the nest with a fish, and a kip uttered during social contact.[36] Parents and chicks can locate one another by call,[37] and siblings also recognise each other's vocalisations from about the twelfth day after hatching, which helps to keep the brood together.[38][39]

Vocal differences reinforce species separation between closely related birds such as the least and little terns,[40] and can help humans distinguish similar species, such as common and Arctic terns, since flight calls are unique to each species.[41][42]

Distribution and habitat

Chlidonias niger
The black tern breeds on inland marshes.

Terns have a worldwide distribution, breeding on all continents including Antarctica. The northernmost and southernmost breeders are the Arctic tern and Antarctic tern respectively.[7][43] Many terns breeding in temperate zones are long-distance migrants, and the Arctic tern probably sees more annual daylight than any other animal as it migrates from its northern breeding grounds to Antarctic waters, a return journey of more than 30,000 km (19,000 mi). A common tern that hatched in Sweden and was found dead five months later on Stewart Island, New Zealand, must have flown at least 25,000 km (16,000 mi).[44] Actual flight distances are, of course, much greater than the shortest possible route. Arctic terns from Greenland were shown by radio geolocation to average 70,000 km (43,000 mi) on their annual migrations.[45]

Most terns breed on open sandy or rocky areas on coasts and islands. The yellow-billed, large-billed, and black-fronted terns breed only on rivers, and common, least and little terns also sometimes use inland locations. The marsh terns, Trudeau's tern and some Forster's terns nest in inland marshes. The black noddy and the white tern nest above ground level on cliffs or in trees. Migratory terns move to the coast after breeding, and most species winter near land, although some marine species, like the Aleutian tern, may wander far from land. The sooty tern is entirely oceanic when not breeding, and healthy young birds are not seen on land for up to five years after fledging until they return to breed. They lack waterproof plumage, so they cannot rest on the sea. Where they spend the years prior to breeding is unknown.[7]

Behaviour

Breeding

Terns are normally monogamous, although trios or female-female pairings have been observed in at least three species.[7][46] Most terns breed annually and at the same time of year, but some tropical species may nest at intervals shorter than 12 months or asynchronously. Most terns become sexually mature when aged three, although some small species may breed in their second year. Some large sea terns, including the sooty and bridled terns, are four or older when they first breed. Terns normally breed in colonies, and are site-faithful if their habitat is sufficiently stable. A few species nest in small or dispersed groups, but most breed in colonies of up to a few hundred pairs, often alongside other seabirds such as gulls or skimmers.[7] Large tern species tend to form larger colonies,[42] which in the case of the sooty tern can contain up to two million pairs. Large species nest very close together and sit tightly, making it difficult for aerial predators to land among them. Smaller species are less closely packed and mob intruders. Peruvian and Damara terns have small dispersed colonies and rely on the cryptic plumage of the eggs and young for protection.[7]

The male selects a territory, which he defends against conspecifics, and re-establishes a pair bond with his mate or attracts a new female if necessary. Courtship involves ritualised flight and ground displays, and the male often presents a fish to his partner. Most species have little or no nest, laying the eggs onto bare ground, but Trudeau's tern, Forster's tern and the marsh terns construct floating nests from the vegetation in their wetland habitats. Black and lesser noddies build nests of twigs, feathers and excreta on tree branches, and brown, blue, and grey noddies make rough platforms of grass and seaweed on cliff ledges, in cavities or on other rocky surfaces.[7][47] The Inca tern nests in crevices, caves and disused burrows, such as that of a Humboldt penguin.[48] The white tern is unique in that it lays its single egg on a bare tree branch.[49]

Tropical species usually lay just one egg, but two or three is typical in cooler regions if there is an adequate food supply. The time taken to complete the clutch varies, but for temperate species incubation takes 21–28 days.[7] The eggs of most gulls and terns are brown with dark splotches, so they are difficult for predators to spot on the beach.[42] The precocial chicks fledge in about four weeks after hatching. Tropical species take longer because of the poorer food supply. Both parents incubate the eggs and feed the chicks, although the female does more incubating and less fishing than her partner.[7] Young birds migrate with the adults.[42] Terns are generally long-lived birds, with individuals typically returning for 7–10 breeding seasons. Maximum known ages include 34 for an Arctic tern and 32 for a sooty. Although several other species are known to live in captivity for up to 20 years, their greatest recorded ages are underestimates because the birds can outlive their rings.[7] Interbreeding between tern species is rare, and involves closely related species when it occurs. Hybrids recorded include common tern with roseate, Sandwich with lesser-crested, and black with white-winged.[50]

Feeding

Sterna hirundo -Nantucket National Wildlife Refuge, Massachusetts, USA -adult and juvenile-8
An adult common tern bringing a sand eel to a juvenile

Most terns hunt fish by diving, often hovering first, and the particular approach technique used can help to distinguish similar species at a distance.[51] Sea terns often hunt in association with porpoises or predatory fish, such as bluefish, tuna or bonitos, since these large marine animals drive the prey to the surface. Sooty terns feed at night as the fish rise to the surface, and are believed to sleep on the wing since they become waterlogged easily. Terns of several species will feed on invertebrates, following the plough or hunting on foot on mudflats.[7] The marsh terns normally catch insects in the air or pick them off the surface of fresh water. Other species will sometimes use these techniques if the opportunity arises.[52] An individual tern's foraging efficiency increases with its age.[42]

The gull-billed tern is an opportunist predator, taking a wide variety of prey from marine, freshwater and terrestrial habitats. Depending on what is available it will eat small crabs, fish, crayfish, grasshoppers and other large insects, lizards and amphibians. Warm-blooded prey includes mice and the eggs and chicks of other beach-breeding birds; least terns, little terns and members of its own species may be victims.[53][54][55] The greater crested tern will also occasionally catch unusual vertebrate species such as agamid lizards and green sea turtle hatchlings, and follows trawlers for discards.[56]

The eyes of terns cannot accommodate under water, so they rely on accurate sighting from the air before they plunge-dive.[57] Like other seabirds that feed at the surface or dive for food, terns have red oil droplets in the cones of their retinas;[58] birds that have to look through an air/water interface have more deeply coloured carotenoid pigments in the oil drops than other species.[59] The pigment also improves visual contrast and sharpens distance vision, especially in hazy conditions,[58] and helps terns to locate shoals of fish, although it is uncertain whether they are sighting the phytoplankton on which the fish feed, or other feeding birds.[60] The red colouring reduces ultraviolet sensitivity, which in any case is an adaptation more suited to terrestrial feeders like the gulls,[61] and this protects the eye from UV damage.[57]

Predators and parasites

The inaccessibility of many tern colonies gave them a measure of protection from mammalian predators, especially on islands, but introduced species brought by humans can seriously affect breeding birds. These can be predators such as foxes, raccoons, cats and rats, or animals that destroy the habitat, including rabbits, goats and pigs.[7] Problems arise not only on formerly mammal-free islands, as in New Zealand, but also where an alien carnivore, such as the American mink in Scotland, presents an unfamiliar threat.[62]

Adult terns may be hunted by owls and raptors, and their chicks and eggs may be taken by herons, crows or gulls.[7][53] Less obvious nest predators include ruddy turnstones in the Arctic, and gull-billed terns in little tern colonies.[53][63] Adults may be robbed of their catch by avian kleptoparasites such as frigatebirds, skuas, other terns or large gulls.[7][64]

External parasites include chewing lice of the genus Saemundssonia,[65] feather lice and fleas such as Ceratophyllus borealis.[66] Lice are often host specific, and the closely related common and Arctic terns carry quite different species.[67] Internal parasites include the crustacean Reighardia sternae, and tapeworms such as Ligula intestinalis and members of the genera Diphyllobothrium and Schistocephalus.[68] Terns are normally free of blood parasites, unlike gulls that often carry Haemoproteus species. An exception is the brown noddy, which sometimes harbours protozoa of that genus.[69] In 1961 the common tern was the first wild bird species identified as being infected with avian influenza, the H5N3 variant being found in an outbreak involving South African birds.[70] Several species of terns have been implicated as carriers of West Nile virus.[71]

Relationships with humans

Roseate Tern portrait
The roseate tern is trapped for food on its wintering grounds.

Terns and their eggs have long been eaten by humans and island colonies were raided by sailors on long voyages since the eggs or large chicks were an easily obtained source of protein. Eggs are still illegally harvested in southern Europe, and adults of wintering birds are taken as food in West Africa and South America. The roseate tern is significantly affected by this hunting, with adult survival 10% lower than would otherwise be expected. In the West Indies, the eggs of roseate and sooty terns are believed to be aphrodisiacs, and are disproportionately targeted by egg collectors. Tern skins and feathers have long been used for making items of clothing such as capes and hats, and this became a large-scale activity in the second half of the nineteenth century when it became fashionable to use feathers in hatmaking. This trend started in Europe but soon spread to the Americas and Australia. White was the preferred colour, and sometimes wings or entire birds were used.[7][72]

Terns have sometimes benefited from human activities, following the plough or fishing boats for easy food supplies, although some birds get trapped in nets or swallow plastic. Fishermen looked for feeding tern flocks, since the birds could lead them to fish shoals. Overfishing of small fish such as sand eels can lead to steep declines in the colonies relying on these prey items. More generally, the loss or disruption to tern colonies caused by human activities has caused declines in many species.[7] Pollution has been a problem in some areas, and in the 1960s and 1970s DDT caused egg loss through thinning of the shells. In the 1980s, organochlorides caused severe declines in the Great Lakes area of the US.[42] Because of their sensitivity to pollutants, terns are sometimes used as indicators of contamination levels.[7]

Habitat enhancements used to increase the breeding success of terns include floating nest platforms for black, common and Caspian terns,[73][74][75] and artificial islands created for a number of different species.[76][77] More specialised interventions include providing nest boxes for roseate terns, which normally nest in the shelter of tallish vegetation,[78] and using artificial eelgrass mats to encourage common terns to nest in areas not vulnerable to flooding.[79]

Conservation status

Ranganathittu 3
The black-bellied tern is endangered by human activities.

A number of terns face serious threats, and the Chinese crested tern is classed as "critically endangered" by BirdLife International. It has a population of fewer than 50 birds and a breeding range of just 9 km2 (3.5 mi2). It is declining due to egg collection, human disturbance and the loss of coastal wetlands in China.[80] Three other species are categorised as "endangered", with declining populations of less than 10,000 birds. The South Asian black-bellied tern is threatened by habitat loss, egg collecting for food, pollution and predation.[81] In New Zealand, the black-fronted tern is facing a rapid fall in numbers due to predation by introduced mammals and Australian magpies. Disturbance by cattle and sheep and by human activities is also a factor.[24] The Peruvian tern was initially damaged by the collapse of anchoveta stocks in 1972, but breeding colonies have subsequently been lost due to building, disturbance and pollution in their coastal wetlands.[82]

The Australasian fairy tern is described as "vulnerable". Disturbance by humans, dogs and vehicles, predation by introduced species and inappropriate water level management in South Australia are the main reasons for its decline.[83] Five species are "near threatened", indicating less severe concerns or only potential vulnerability. The elegant tern is so categorised because 95% of the population breeds on one island, Isla Rasa in the Gulf of California, and the Kerguelen tern has a population of less than 5,000 adults breeding on small and often stormy Pacific islands.[84][85] Three species, the Inca, Damara, and river terns, are expected to decline in the future due to habitat loss and disturbance.[48][86][87] Some tern subspecies are endangered, including the California least tern and the Easter Island race of the grey noddy.[7]

Most tern species are declining in numbers due to the loss or disturbance of breeding habitat, pollution and increased predation. Gull populations have increased over the last century because of reduced persecution and the availability of food from human activities, and terns have been forced out of many traditional nesting areas by the larger birds. A few species are defying the trend and showing local increases, including the Arctic tern in Scandinavia, Forster's tern around the Great Lakes, the Sandwich tern in eastern North America and its yellow-billed subspecies, the Cayenne tern, in the Caribbean.[7]

Terns are protected by international legislation such as the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the US-Canada Migratory Bird Treaty Act of 1918.[88][89] Parties to the AWEA agreement are required to engage in a wide range of conservation strategies described in a detailed action plan. The plan is intended to address key issues such as species and habitat conservation, management of human activities, research, education, and implementation.[90] The North American legislation is similar, although there is a greater emphasis on protection.[91]

See also

References

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Cited texts

  • Barlow, Clive; Wacher, Tim; Disley, Tony (1997). A Field Guide to Birds of The Gambia and Senegal. Robertsbridge: Pica Press. ISBN 1-873403-32-1.
  • Brookes, Ian (editor-in-chief) (2006). The Chambers Dictionary, ninth edition. Edinburgh: Chambers. ISBN 0-550-10105-5.
  • Burton, Robert (1985). Bird Behaviour. London: Granada Publishing. ISBN 0-246-12440-7.
  • Constantine, Mark; The Sound Approach (2006). The Sound Approach to birding: a guide to understanding bird sound. Poole: The Sound Approach. ISBN 90-810933-1-2.
  • Coles, Brian (2007). Essentials of Avian Medicine and Surgery. Oxford: Wiley. ISBN 1-4051-5755-0.
  • Gochfeld, M; Burger, J. "Family Sternidae (Terns)" pp. 624–667 in del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi (editors) (1996). Handbook of Birds of the World. 3: Hoatzin to Auks. Barcelona: Lynx Edicions. ISBN 978-84-87334-20-7.CS1 maint: Extra text: authors list (link)
  • Harrison, Peter (1988). Seabirds: An Identification Guide. London: Christopher Helm. ISBN 0-7470-1410-8.
  • Hume, Rob (1993). The Common Tern. London: Hamlyn. ISBN 0-540-01266-1.
  • Hume, Rob; Pearson, Bruce (1993). Seabirds. London: Hamlyn. ISBN 0-600-57951-4.
  • Hutton, Frederick Wollaston; Drummond, James (2011) [1904]. The animals of New Zealand: an account of the dominion's air-breathing vertebrates (reprint ed.). Cambridge: Cambridge University Press. ISBN 1-108-04002-0.
  • Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names (PDF). London: Christopher Helm. ISBN 978-1-4081-2501-4.
  • Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata (in Latin). Holmiae [Stockholm]: Laurentii Salvii.
  • Lockwood, W B (1984). Oxford Book of British Bird Names. Oxford: Oxford University Press. ISBN 0-19-214155-4.
  • Lythgoe, J N (1979). The Ecology of Vision. Oxford: Clarendon Press. ISBN 0-19-854529-0.
  • Maehr, David S; Kale, Herbert W (2005). Florida's Birds. Sarasota: Pineapple Press. ISBN 1-56164-335-1.
  • Merriam-Webster (2014). "Tern - Definition and More from the Free Merriam-Webster Dictionary". Encyclopædia Britannica. Retrieved January 11, 2014.
  • Newton, Ian (2010). Bird Migration (Collins New Naturalist Library 113). London: Collins. ISBN 0-00-730732-2.
  • Olsen, Klaus Malling; Larsson, Hans (1995). Terns of Europe and North America. London: Christopher Helm. ISBN 0-7136-4056-1.
  • Perrins, Christopher M; Arlott, Norman (1987). New generation guide to the birds of Britain and Europe. Austin: University of Texas Press. ISBN 0-292-75532-5.
  • Rothschild, Miriam; Clay, Theresa (1953). Fleas, Flukes and Cuckoos. A study of bird parasites. London: Collins.CS1 maint: Multiple names: authors list (link)
  • Sinclair, Sandra (1985). How Animals See: Other Visions of Our World. Beckenham, London: Croom Helm. ISBN 0-7099-3336-3.
  • Steele, John H; Thorpe Steve A; Turekian, Karl K (editors) (2001). Encyclopedia of Ocean Sciences. London: Academic Press. ISBN 978-0-12-227430-5.CS1 maint: Extra text: authors list (link)
  • Svensson, Lars; Mullarney, Killian; Zetterstrom, Dan; Grant, Peter (1999). Collins Bird Guide. London: Collins. ISBN 0-00-219728-6.
  • Takken, Willem; Knols, Bart G J (editors) (2007). Emerging pests and vector-borne diseases in Europe. Wageningen: Wageningen Academic Publishers. ISBN 90-8686-053-2.CS1 maint: Extra text: authors list (link)
  • Turner, William. Evans, A H, ed. Turner on Birds (Auium præcipuarum, quarum apud Plinium et Aristotelem mentio est, breuis et succincta historia) (1903 ed.). Cambridge: Cambridge University Press. Retrieved January 11, 2014. huius generis est & alia parua auis, nostrati lingua sterna apellata 'There is another small bird of this type, called Stern in local dialect'
  • Watling, Dick (2003). A Guide to the Birds of Fiji and Western Polynesia. Suva, Fiji: Environmental Con-sultants. ISBN 982-9030-04-0.
  • Ziegler, Harris Philip; Bischof, Hans-Joachim (eds) (1993). Vision, Brain, and Behavior in Birds: A comparative review. Cambridge: MIT Press. ISBN 0-262-24036-X.CS1 maint: Extra text: authors list (link)

External links

Arctic tern

The Arctic tern (Sterna paradisaea) is a tern in the family Laridae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America (as far south as Brittany and Massachusetts). The species is strongly migratory, seeing two summers each year as it migrates along a convoluted route from its northern breeding grounds to the Antarctic coast for the southern summer and back again about six months later. Recent studies have shown average annual roundtrip lengths of about 70,900 km (44,100 mi) for birds nesting in Iceland and Greenland and about 90,000 km (56,000 mi) for birds nesting in the Netherlands. These are by far the longest migrations known in the animal kingdom. The Arctic tern flies as well as glides through the air. It nests once every one to three years (depending on its mating cycle); once it has finished nesting it takes to the sky for another long southern migration.

Arctic terns are medium-sized birds. They have a length of 28–39 cm (11–15 in) and a wingspan of 65–75 cm (26–30 in). They are mainly grey and white plumaged, with a red/orangish beak and feet, white forehead, a black nape and crown (streaked white), and white cheeks. The grey mantle is 305 mm, and the scapulae are fringed brown, some tipped white. The upper wing is grey with a white leading edge, and the collar is completely white, as is the rump. The deeply forked tail is whitish, with grey outer webs.

Arctic terns are long-lived birds, with many reaching fifteen to thirty years of age. They eat mainly fish and small marine invertebrates. The species is abundant, with an estimated one million individuals. While the trend in the number of individuals in the species as a whole is not known, exploitation in the past has reduced this bird's numbers in the southern reaches of its range.

The Arctic tern was known as sea swallow describing their slender shape as they swoop over the water.

Black tern

The black tern (Chlidonias niger) is a small tern generally found in or near inland water in Europe and North America. As its name suggests, it has predominantly dark plumage. In some lights it can appear blue in the breeding season, hence the old English name "blue darr". The genus name is from Ancient Greek khelidonios, "swallow-like", from khelidon, "swallow": another old English name for the black tern is "carr (i.e. lake) swallow". The species name is from Latin niger "shining black".

Bridled tern

The bridled tern (Onychoprion anaethetus) is a seabird of the family Laridae. It is a bird of the tropical oceans. The scientific name is from Ancient Greek. The genus is onux, "claw", and "prion", nail. The specific anaethetus means "senseless, stupid".

Caspian tern

The Caspian tern (Hydroprogne caspia) is a species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no accepted subspecies. The genus name is from Ancient Greek hudros, "water", and Latin progne, "swallow". The specific caspia is from Latin and, like the English name, refers to the Caspian Sea.

Common tern

The common tern (Sterna hirundo) is a seabird in the family Laridae. This bird has a circumpolar distribution, its four subspecies breeding in temperate and subarctic regions of Europe, Asia and North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. Breeding adults have light grey upperparts, white to very light grey underparts, a black cap, orange-red legs, and a narrow pointed bill. Depending on the subspecies, the bill may be mostly red with a black tip or all black. There are a number of similar species, including the partly sympatric Arctic tern, which can be separated on plumage details, leg and bill colour, or vocalisations.

Breeding in a wider range of habitats than any of its relatives, the common tern nests on any flat, poorly vegetated surface close to water, including beaches and islands, and it readily adapts to artificial substrates such as floating rafts. The nest may be a bare scrape in sand or gravel, but it is often lined or edged with whatever debris is available. Up to three eggs may be laid, their dull colours and blotchy patterns providing camouflage on the open beach. Incubation is by both sexes, and the eggs hatch in around 21–22 days, longer if the colony is disturbed by predators. The downy chicks fledge in 22–28 days. Like most terns, this species feeds by plunge-diving for fish, either in the sea or in freshwater, but molluscs, crustaceans and other invertebrate prey may form a significant part of the diet in some areas.

Eggs and young are vulnerable to predation by mammals such as rats and American mink, and large birds including gulls, owls and herons. Common terns may be infected by lice, parasitic worms, and mites, although blood parasites appear to be rare. Its large population and huge breeding range mean that this species is classed as being of least concern, although numbers in North America have declined sharply in recent decades. Despite international legislation protecting the common tern, in some areas populations are threatened by habitat loss, pollution or the disturbance of breeding colonies.

Greater crested tern

The greater crested tern (Thalasseus bergii), also called crested tern or swift tern, is a tern in the family Laridae that nests in dense colonies on coastlines and islands in the tropical and subtropical Old World. Its five subspecies breed in the area from South Africa around the Indian Ocean to the central Pacific and Australia, all populations dispersing widely from the breeding range after nesting. This large tern is closely related to the royal and lesser crested terns, but can be distinguished by its size and bill colour.

The greater crested tern has grey upperparts, white underparts, a yellow bill, and a shaggy black crest that recedes in winter. Its young have a distinctive appearance, with strongly patterned grey, brown and white plumage, and rely on their parents for food for several months after they have fledged. Like all members of the genus Thalasseus, the greater crested tern feeds by plunge diving for fish, usually in marine environments; the male offers fish to the female as part of the courtship ritual.

This is an adaptable species that has learned to follow fishing boats for jettisoned bycatch, and to use unusual nest sites such as the roofs of buildings and artificial islands in salt pans and sewage works. Its eggs and young are taken by gulls and ibises, and human activities such as fishing, shooting and egg harvesting have caused local population declines. There are no global conservation concerns for this bird, which has a stable total population of more than 500,000 individuals.

Gull-billed tern

The gull-billed tern (Gelochelidon nilotica), formerly Sterna nilotica, is a tern in the family Laridae. It is now considered to be in its own genus. The genus name is from Ancient Greek gelao, "to laugh", and khelidon, "swallow". The specific niloticus is from Latin and means of the Nile.

Least tern

The least tern (Sternula antillarum) is a species of tern that breeds in North America and locally in northern South America. It is closely related to, and was formerly often considered conspecific with, the little tern of the Old World. Other close relatives include the yellow-billed tern and Peruvian tern, both from South America.

It is a small tern, 22–24 cm (8.7–9.4 in) long, with a wingspan of 50 cm (20 in), and weighing 39–52 g (1.4–1.8 oz). The upper parts are a fairly uniform pale gray, and the underparts white. The head is white, with a black cap and line through the eye to the base of the bill, and a small white forehead patch above the bill; in winter, the white forehead is more extensive, with a smaller and less sharply defined black cap. The bill is yellow with a small black tip in summer, all blackish in winter. The legs are yellowish. The wings are mostly pale gray, but with conspicuous black markings on their outermost primaries. It flies over water with fast, jerky wingbeats and a distinctive hunchback appearance, with the bill pointing slightly downward.

It is migratory, wintering in Central America, the Caribbean and northern South America. Many spend their whole first year in their wintering area. It has occurred as a vagrant to Europe, with one record in Great Britain.

It differs from the little tern mainly in that its rump and tail are gray, not white, and it has a different, more squeaking call; from the yellow-billed tern in being paler gray above and having a black tip to the bill; and from the Peruvian tern in being paler gray above and white (not pale gray) below and having a shorter black tip to the bill.

Lesser crested tern

The lesser crested tern (Thalasseus bengalensis) is a tern in the family, Laridae.

Little tern

The little tern (Sternula albifrons) is a seabird of the family Sternidae. It was formerly placed into the genus Sterna, which now is restricted to the large white terns. The genus name is a diminutive of Sterna, "tern". The specific albifrons is from Latin albus, "white", and "frons", forehead. The former North American (S. a. antillarum) and Red Sea S. a. saundersi subspecies are now considered to be separate species, the least tern (Sternula antillarum) and Saunders's tern (Sternula saundersi).

This bird breeds on the coasts and inland waterways of temperate and tropical Europe and Asia. It is strongly migratory, wintering in the subtropical and tropical oceans as far south as South Africa and Australia.

There are three subspecies, the nominate albifrons occurring in Europe to North Africa and western Asia; guineae of western and central Africa; and sinensis of East Asia and the north and east coasts of Australia.The little tern breeds in colonies on gravel or shingle coasts and islands. It lays two to four eggs on the ground. Like all white terns, it is defensive of its nest and young and will attack intruders.

Like most other white terns, the little tern feeds by plunge-diving for fish, usually from saline environments. The offering of fish by the male to the female is part of the courtship display.

This is a small tern, 21–25 cm long with a 41–47 cm wingspan. It is not likely to be confused with other species, apart from fairy tern and Saunders's tern, because of its size and white forehead in breeding plumage. Its thin sharp bill is yellow with a black tip and its legs are also yellow. In winter, the forehead is more extensively white, the bill is black and the legs duller. The call is a loud and distinctive creaking noise.

The little tern was described by the German naturalist Peter Simon Pallas in 1764 and given the binomial name Sterna albifrons.

River Tern

The River Tern (also historically known as the Tearne) is a river in Shropshire, England. It rises north-east of Market Drayton in the north of the county. The source of the Tern is considered to be the lake in the grounds of Maer Hall, Staffordshire. From here it flows for about 30 miles (48 km), being fed by the River Meese and the River Roden, until it joins the River Severn near Attingham Park, Atcham.

Extensive peat bog formerly existed, extending from Crudgington on the Tern as far as Newport.

At Longdon-on-Tern, the Tern is spanned by the Longdon-on-Tern Aqueduct, the world's first large-scale cast iron navigable aqueduct, designed by Thomas Telford to carry the Shrewsbury Canal. The 62-yard (57 m) long structure still stands today, but is marooned in the middle of a field.

Roseate tern

The roseate tern (Sterna dougallii) is a tern in the family Laridae. The genus name Sterna is derived from Old English "stearn", "tern", and the specific dougallii refers to Scottish physician and collector Dr Peter McDougall (1777–1814). "Roseate" refers to the bird's pink breast in breeding plumage.

Royal tern

The royal tern (Thalasseus maximus) is a tern in the family Laridae. The genus name is from Ancient Greek Thalasseus, "fisherman", from thalassa, "sea". The specific maximus is Latin for '"greatest".This bird has two distinctive subspecies: T. m. maximus which lives on the Atlantic and Pacific coasts of the North and South America, and the slightly smaller T. m. albididorsalis lives on the coast of West Africa. The royal tern has a red-orange bill and a black cap during the breeding season, but in the winter the cap becomes patchy. The royal tern is found in Europe, Africa, the Americas, and the Caribbean islands. The royal tern lives on the coast and is only found near salt water. They tend to feed near the shore, close to the beach or in backwater bays. The royal tern's conservation status is listed as least concern.

Sandwich tern

The Sandwich tern (Thalasseus sandvicensis) is a tern in the family Laridae. It is very closely related to the lesser crested tern (T. bengalensis), Chinese crested tern (T. bernsteini), Cabot's tern (T. acuflavidus), and elegant tern (T. elegans) and has been known to interbreed with the lesser crested.

The Sandwich tern is a medium-large tern with grey upperparts, white underparts, a yellow-tipped black bill and a shaggy black crest which becomes less extensive in winter with a white crown. Young birds bear grey and brown scalloped plumage on their backs and wings. It is a vocal bird. It nests in a ground scrape and lays one to three eggs.

Like all Thalasseus terns, the Sandwich tern feeds by plunge diving for fish, usually in marine environments, and the offering of fish by the male to the female is part of the courtship display.

Sooty tern

The sooty tern (Onychoprion fuscatus) is a seabird in the family Laridae. It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone.

Tern Island (Nunavut)

Tern Island is an island located in Nunavut's Qikiqtaaluk Region in the northern Canadian Arctic. It is situated in the Foxe Basin. The mainland's Melville Peninsula is to the west, Baffin Island is to the northwest, and Jens Munk Island is to the northeast. The closest Inuit community, Igloolik, is approximately 43.3 km (26.9 mi) to the west.

Whiskered tern

The whiskered tern (Chlidonias hybrida) is a tern in the family Laridae. The genus name is from Ancient Greek khelidonios, "swallow-like", from khelidon, "swallow". The specific hybridus is Latin for hybrid; Pallas thought it might be a hybrid of white-winged black tern and common tern, writing "Sterna fissipes [Chlidonias leucopterus] et Hirundine [Sterna hirundo] natam”.This bird has a number of geographical races, differing mainly in size and minor plumage details.

C. h. hybrida breeds in warmer parts of Europe and Asia. The smaller-billed and darker C. h. delalandii is found in east and south Africa, and the paler C. h. javanicus from Java to Australia.

The tropical forms are resident, but European and Asian birds winter south to Africa and the Indian Subcontinent.

This species breeds in colonies on inland marshes, sometimes amongst black-headed gulls, which provide some protection. The scientific name arises from the fact that this, the largest marsh tern, show similarities in appearance to both the white Sterna terns and to black tern.

White-winged tern

The white-winged tern, or white-winged black tern (Chlidonias leucopterus or Chlidonias leucoptera), is a species of tern in the family Laridae. It is a small species generally found in or near bodies of fresh water across much of the world, including Europe, Africa, Asia, and Australia. The genus name is from Ancient Greek khelidonios, "swallow-like", from khelidon, "swallow". The specific leptopterus is also Greek from leptos, "slender", and pteros,

"feathered", itself from pteron, "wing".The name 'white-winged tern' is the standard in most English-speaking countries; in the United Kingdom, this name is also the one used by the formal ornithological recording authorities, but the older alternative 'white-winged black tern' is still frequent in popular use.

White tern

The white tern (Gygis alba) is a small seabird found across the tropical oceans of the world. It is sometimes known as the fairy tern although this name is potentially confusing as it is the common name of the fairy tern (Sternula nereis). Other names for the species include angel tern and white noddy.

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