Tern
Overview
 
Terns are seabird
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...

s in the family Sternidae, previously considered a subfamily (Sterninae) of the gull family Laridae (van Tuinen et al., 2004). They form a lineage with the gulls and skimmer
Skimmer
The Skimmers, Rynchopidae, are a small family of tern-like birds in the order Charadriiformes, which also includes the waders, gulls and auks. The family comprises three species found in South Asia, Africa, and the Americas....

s which in turn is related to skua
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....

s and auk
Auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...

s. Terns have a worldwide distribution.

Most terns were formerly treated as belonging to one large genus Sterna
Sterna
Sterna is a genus of terns in the bird family Sternidae. It used to encompass most "white" terns indiscriminately, but mtDNA sequence comparisons have recently determined that this arrangement is paraphyletic...

, with the other genera being small. However analysis of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

s supports the splitting of Sterna into several smaller genera (see list, below) (del Hoyo et al., 1996; Bridge et al., 2005; Collinson 2006).
Many terns breeding in temperate zones are long-distance migrants
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...

, and the 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...

 probably sees more daylight than any other creature, as it migrates from its northern breeding grounds to Antarctic waters.
Encyclopedia
Terns are seabird
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...

s in the family Sternidae, previously considered a subfamily (Sterninae) of the gull family Laridae (van Tuinen et al., 2004). They form a lineage with the gulls and skimmer
Skimmer
The Skimmers, Rynchopidae, are a small family of tern-like birds in the order Charadriiformes, which also includes the waders, gulls and auks. The family comprises three species found in South Asia, Africa, and the Americas....

s which in turn is related to skua
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....

s and auk
Auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...

s. Terns have a worldwide distribution.

Most terns were formerly treated as belonging to one large genus Sterna
Sterna
Sterna is a genus of terns in the bird family Sternidae. It used to encompass most "white" terns indiscriminately, but mtDNA sequence comparisons have recently determined that this arrangement is paraphyletic...

, with the other genera being small. However analysis of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

s supports the splitting of Sterna into several smaller genera (see list, below) (del Hoyo et al., 1996; Bridge et al., 2005; Collinson 2006).

Biology and habits

Many terns breeding in temperate zones are long-distance migrants
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...

, and the 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...

 probably sees more daylight than any other creature, as it migrates from its northern breeding grounds to Antarctic waters. One Arctic Tern, ringed
Bird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...

 as a chick (not yet able to fly) on the Farne Islands
Farne Islands
The Farne Islands are a group of islands off the coast of Northumberland, England. There are between 15 and 20 or more islands depending on the state of the tide. They are scattered about 2.5–7.5 km distant from the mainland, divided into two groups, the Inner Group and the Outer Group...

 off the Northumberland
Northumberland
Northumberland is the northernmost ceremonial county and a unitary district in North East England. For Eurostat purposes Northumberland is a NUTS 3 region and is one of three boroughs or unitary districts that comprise the "Northumberland and Tyne and Wear" NUTS 2 region...

 coast in eastern Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 in summer 1982, reached Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

, 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...

 in October 1982, a sea journey of over 22,000 km (14,000 statute miles) in just three months from fledging
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...

—an average of over 240 km per day, and one of the longest journeys ever recorded for a bird.

They are, in general, medium to large 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...

s, typically with grey or white plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...

, often with black markings on the head. They have longish bills
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

 and webbed feet. They are lighter bodied and more streamlined than gulls, and look elegant in flight with long tails and long narrow wings. Terns in the genus Sterna have deeply forked tails, those in Chlidonias and Larosterna shallowly forked tails, while the noddies (genera Anous, Procelsterna, Gygis) have unusual 'notched wedge' shaped tails, the longest tail feathers being the middle-outer, not the central nor the outermost. Terns ranges in size from the Least Tern, at 42 g (1.5 oz) and 23 cm (9 inches), to the Caspian Tern
Caspian Tern
The Caspian Tern is a species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no subspecies accepted either...

, at 630 g (1.4 lbs) and 53 cm (21 inches). They make harsh, single-note calls.

Most terns (Sterna and the noddies) hunt fish by diving, often hovering first, but the marsh terns (Chlidonias) pick insects of the surface of fresh water. Terns only glide infrequently; a few species, notably Sooty Tern
Sooty Tern
The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...

, will soar high above the sea. Apart from bathing, they only rarely swim, despite having webbed feet.

Terns generally nest in large, densely packed colonies
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in close proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony...

 (an exception to this is the White Tern
White Tern
The White Tern 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...

). Depending on the species and habitat, the nests may consist of unlined scrapes in the ground, or of flimsy collections of sticks on trees or floating vegetation. Terns are generally long-lived birds, with several species now known to live in excess of 25–30 years.

Classification and species list

A recent study (Thomas et al., 2004) of part of the cyt b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...

 gene sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...

 found a closer relationship between terns and the Thinocori, some species of aberrant wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...

s. These results are in disagreement with other molecular and morphological studies (see Paton & Baker, 2006) and are best interpreted to prove an extraordinary amount of molecular convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

 between the terns and these waders, or as retention of an ancient genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...

.

According the mtDNA studies and review by Bridge et al. (2005), the genera and species of terns are as follows:
  • Genera Anous
    Anous
    Anous is a genus of birds in the tern family. The genus as presently described consists of three species :* Brown Noddy or Common Noddy, Anous stolidus* Black Noddy, Anous minutus* Lesser Noddy, Anous tenuirostris...

    , Procelsterna
    Procelsterna
    Procelsterna is a genus of birds in the tern family. It consists of two species, which are sometimes considered to be conspecific.* Blue Noddy, Procelsterna cerulea* Grey Noddy, Procelsterna albivitta...

    , Gygis
    Gygis
    Gygis is a genus of birds in the tern family. It consists of one species,* White Tern, Gygis alba** Little White Tern, Gygis alba microrhyncha...

     - noddies
    Noddy (tern)
    Noddies are members of the tern family Sternidae in the genera Anous, Procelsterna, and Gygis. They are a tropical group, characterised by the notch-wedge shaped tail; coastal and pelagic oceanic...

    . A tropical group, characterised by the notch-wedge shaped (not forked) tail; coastal and pelagic oceanic.
    • Brown Noddy
      Brown Noddy
      The Brown Noddy or Common Noddy is a seabird from the tern family. The largest of the noddies, it can be told from the closely related Black Noddy by its larger size and plumage, which is dark brown rather than black...

       Anous stolidus
    • Black Noddy
      Black Noddy
      The Black Noddy or White-capped Noddy is a seabird from the tern family. It resembles the closely related Brown or Common Noddy , but is smaller with darker plumage, a whiter cap, a longer, straighter beak and shorter tail...

       Anous minutus
    • Lesser Noddy
      Lesser Noddy
      The Lesser Noddy , also known as the Sooty Noddy, is a species of tern in the Sternidae family.It is found in Comoros, Kenya, Liberia, Mauritius, Seychelles, South Africa, and United Arab Emirates.- References :...

       Anous tenuirostris
    • Blue Noddy
      Blue Noddy
      The Blue Noddy is a species of tern in the Sternidae family. It is also known as the Blue-grey Noddy.It is found in American Samoa, the Cook Islands, Fiji, French Polynesia, Kiribati, Marshall Islands, New Caledonia, Samoa, Tonga , Tuvalu and Hawaii. It has occurred as a vagrant in Australia and...

       Procelsterna cerulea
    • Grey Noddy
      Grey Noddy
      The Grey Noddy or Grey Ternlet is a seabird belonging to the tern family Sternidae. It was once regarded as a pale morph of the Blue Noddy but is now often considered to be a separate species....

       Procelsterna albivitta
    • White Tern
      White Tern
      The White Tern 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...

       Gygis alba

  • Genus Onychoprion
    Onychoprion
    Onychoprion, the "brown-backed terns", is a genus of seabirds in the tern family. Although the genus was first described in 1832 by Johann Georg Wagler the four species in the genus were until recently retained in the larger genus Sterna, the genus that most terns are in .Three of the four species...

     - "brown-backed" terns
    • Spectacled Tern Onychoprion lunatus
    • Bridled Tern
      Bridled Tern
      The Bridled Tern is a seabird of the tern family Sternidae. It is a bird of the tropical oceans.-Description:...

       Onychoprion anaethetus
    • Sooty Tern
      Sooty Tern
      The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...

       Onychoprion fuscatus
    • Aleutian Tern
      Aleutian Tern
      The Aleutian Tern is a seabird of the tern family Sternidae....

       Onychoprion aleuticus

  • Genus Sternula
    Sternula
    Sternula is a genus of small white terns. It is often subsumed into the larger genus Sterna, although the most recent changes to the AOU checklist considers it a separate genus.* Fairy Tern Sternula nereis* Damara Tern Sternula balaenarum...

     - little white terns
    • Fairy Tern
      Fairy Tern
      The Fairy Tern is a small tern which occurs in the southwestern Pacific.There are three subspecies:* Australian Fairy Tern, Sterna nereis nereis - breeds in Australia...

       Sternula nereis
    • Damara Tern
      Damara Tern
      The Damara Tern is a species of tern in the Sternidae family.It breeds in western South Africa, Namibia and Angola...

       Sternula balaenarum
    • Little Tern
      Little Tern
      The Little Tern, Sternula albifrons or Sterna albifrons, is a seabird of the tern family Sternidae. It was formerly placed into the genus Sterna, which now is restricted to the large white terns . The former North American and Red Sea S. a...

       Sternula albifrons
    • Saunders's Tern
      Saunders's Tern
      The Saunders's Tern is a species of tern in the Sternidae family.It is found in Bahrain, Iran, Israel, Kenya, Madagascar, Pakistan, Oman, Saudi Arabia, Tanzania, United Arab Emirates, and Yemen.-References:...

       Sternula saundersi (formerly considered a subspecies of Little Tern)
    • Least Tern Sternula antillarum (formerly considered a subspecies of Little Tern)
    • Yellow-billed Tern
      Yellow-billed Tern
      The Yellow-billed Tern is a species of tern in the Sternidae family.It is found in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, and Venezuela.Its natural habitats are rivers, swamps, and freshwater...

       Sternula superciliaris
    • Peruvian Tern
      Peruvian Tern
      The Peruvian Tern is a species of tern in the Sternidae family.It is found in northern Chile, Ecuador, and Peru.Its natural habitats are hot deserts, sandy shores, and coastal saline lagoons.It is threatened by habitat loss....

       Sternula lorata

  • Genus Phaetusa - Large-billed Tern
    • Large-billed Tern
      Large-billed Tern
      The Large-billed Tern is a species of tern in the Sternidae family. It belongs to the monotypic genus Phaetusa....

        Phaetusa simplex

  • Genus Hydroprogne - Caspian Tern
    • Caspian Tern
      Caspian Tern
      The Caspian Tern is a species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no subspecies accepted either...

       Hydroprogne caspia


  • Genus Gelochelidon - Gull-billed Tern
    • Gull-billed Tern
      Gull-billed Tern
      The Gull-billed Tern formerly Sterna nilotica , is a seabird of the tern family Sternidae...

       Gelochelidon nilotica

  • Genus Larosterna - Inca Tern
    • Inca Tern
      Inca Tern
      The Inca Tern is a seabird in the family Sternidae. It is the only member of the genus Larosterna.This uniquely-plumaged bird breeds on the coasts of Peru and Chile, and is restricted to the Humboldt current...

       Larosterna inca


  • Genus Chlidonias
    Marsh tern
    The name marsh tern refers to terns of the genus Chlidonias, which are typically found in freshwater marshes, rather than coastal locations.There are four species:* Black Tern, Chlidonias niger...

     - marsh terns
    • Black Tern
      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.- Description :...

       Chlidonias niger
    • White-winged Tern
      White-winged Tern
      The White-winged Tern, or White-winged Black Tern, Chlidonias leucopterus, is a small tern generally found in or near bodies of fresh water across from Southeastern Europe east to Australia....

       or White-winged Black Tern Chlidonias leucopterus
    • Whiskered Tern
      Whiskered Tern
      The Whiskered Tern is a seabird of the tern family Sternidae. This bird has a number of geographical races, differing mainly in size and minor plumage details....

       Chlidonias hybridus
    • Black-fronted Tern
      Black-fronted Tern
      The Black-fronted Tern also known as Sea Martin, Ploughboy, Inland Tern, Riverbed Tern or Tarapiroe, is a small tern generally found in or near bodies of fresh water in New Zealand and forages for freshwater fish, arthropods and worms. It has a predominantly grey plumage...

       Chlidonias albostriatus (ex-Sterna albostriata)

  • Genus Thalasseus
    Thalasseus
    Thalasseus, the crested terns, is a genus of six species of seabirds in the tern family. Thalasseus signifies a "creature of the sea". It has a worldwide distribution, and many of its species are abundant and well-known birds in their ranges...

     - crested terns
    • Lesser Crested Tern
      Lesser Crested Tern
      The Lesser Crested Tern is a seabird of the tern family Sternidae...

       Thalasseus bengalensis
    • 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...

       Thalasseus maximus
    • 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...

       or Swift Tern, Thalasseus bergii
    • 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...

       Thalasseus bernsteini
    • 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....

       Thalasseus elegans
    • Sandwich Tern Thalasseus sandvicensis


  • Genus Sterna
    Sterna
    Sterna is a genus of terns in the bird family Sternidae. It used to encompass most "white" terns indiscriminately, but mtDNA sequence comparisons have recently determined that this arrangement is paraphyletic...

     - large white terns
    • Forster's Tern
      Forster's Tern
      The Forster's Tern, Sterna forsteri, is a member of the tern family Sternidae. It breeds inland in North America and winters south to the Caribbean and northern South America....

       Sterna forsteri
    • Snowy-crowned Tern
      Snowy-crowned Tern
      The Snowy-crowned Tern or Trudeau's Tern is a species of tern in the Sternidae family.It is found in Argentina, south-east Brazil, Chile, Paraguay and Uruguay. It has occurred as a vagrant in the Falkland Islands....

       Sterna trudeaui
    • Common Tern
      Common Tern
      The Common Tern is a seabird of the tern family Sternidae. This bird has a circumpolar distribution, breeding in temperate and sub-Arctic regions of Europe, Asia and east and central North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. It is sometimes...

       Sterna hirundo
    • Roseate Tern
      Roseate Tern
      The Roseate Tern is a seabird of the tern family Sternidae. This bird has a number of geographical races, differing mainly in bill colour and minor plumage details....

       Sterna dougallii
    • White-fronted Tern
      White-fronted Tern
      The White-fronted Tern is the most common tern of New Zealand. It rarely swims, apart from bathing, despite having webbed feet. The species is protected....

       Sterna striata
    • Black-naped Tern
      Black-naped Tern
      The Black-naped Tern is an oceanic tern mostly found in tropical and subtropical areas of the Pacific and Indian Oceans. It is rarely found inland....

       Sterna sumatrana
    • South American Tern
      South American Tern
      The South American Tern is a species of tern found in coastal regions of southern South America, including the Falkland Islands, ranging north to Peru and Brazil . It is generally the commonest tern in its range. It closely resembles the smaller, highly migratory Common Tern.-References:*...

       Sterna hirundinacea
    • Antarctic Tern
      Antarctic Tern
      The Antarctic Tern is a typical tern. It ranges throughout the southern oceans. It is very similar in appearance to the closely related Arctic Tern, but is stockier, and the wing tips are grey instead of blackish in flight...

       Sterna vittata
    • Kerguelen Tern
      Kerguelen Tern
      The Kerguelen Tern is a tern of the southern hemisphere.This seabird mainly breeds colonially in the Kerguelen Islands, as its common name implies. However, smaller colonies are also found in the Prince Edward Islands and Crozet Islands...

       Sterna virgata
    • 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...

       Sterna paradisaea
    • River Tern
      River Tern (bird)
      The Indian River Tern or just River Tern is a bird in the tern family . It is a resident breeder along inland rivers from Iran east through Pakistan into India and Myanmar to Thailand, where it is uncommon. It does not occur in Sri Lanka...

       Sterna aurantia
    • Black-bellied Tern
      Black-bellied Tern
      The Black-bellied Tern is a tern found near large rivers in South Asia. They have a black belly in the summer and a deep forked tail. They can sometimes resemble Whiskered Terns but the deeper fork and the black on the lower belly distinguish it from the shallow fork and black closer to the breast...

       Sterna acuticauda (possibly Chlidonias)
    • White-cheeked Tern
      White-cheeked Tern
      The White-cheeked Tern is a species of tern in the Sternidae family.It is found in Bahrain, Djibouti, Egypt, Eritrea, India, Iran, Iraq, Israel, Jordan, Kenya, Kuwait, Maldives, Oman, Pakistan, Qatar, Saudi Arabia, Seychelles, Somalia, South Africa, Sudan, Tanzania, United Arab Emirates, and...

      Sterna repressa (possibly Chlidonias)

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