The Common tern (Sterna hirundo) is a seabird that has a circumpolar distribution. it has four subspecies breeding in temperate and subarctic regions of Europe, Asia, and North America. 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.
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DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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SeabirdSeabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, b...
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PrecocialPrecocial species are those in which the young are relatively mature and mobile from the moment of birth or hatching. Precocial species are normall...
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TerritorialA territory is a sociographical area that which an animal consistently defends against the conspecific competition (or, occasionally, against anima...
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CongregatoryCongregatory animals tend to gather in large numbers in specific areas as breeding colonies, for feeding, or for resting.
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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Soaring birdsSoaring birds can maintain flight without wing flapping, using rising air currents. Many gliding birds are able to "lock" their extended wings by m...
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SeabirdSeabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, b...
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MonogamyMonogamy is a form of relationship in which both the male and the female has only one partner. This pair may cohabitate in an area or territory for...
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ColonialColonial animals live in large aggregations composed of two or more conspecific individuals in close association with or connected to, one another....
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FlockingFlocking birds are those that tend to gather to forage or travel collectively. Avian flocks are typically associated with migration. Flocking also ...
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MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
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starts withKnown for its attractive plumage and graceful flight, Common terns have a slender body and a smoothly rounded head, and long pointed wings. Their breeding plumage is light silvery-gray upperparts and clear black outer primaries on its wingtips. Outside the breeding season, the birds keep some of their distinguishable black cap, but their forehead and face turn white. Their legs and bill turn black, losing their orange-red coloration. Male and female are similar in appearance throughout the year. Juvenile Common terns have pale grey upper wings with a dark carpal bar. The crown and nape are brown, and the forehead is ginger, wearing to white by autumn. The upper parts are ginger with brown and white scaling, and the tail lacks the adult's long outer feathers. Birds in their first post-juvenile plumage, which normally remain in their wintering areas, resemble the non-breeding adult but have a duskier crown, dark carpal bar, and often very worn plumage. By their second year, most young terns are either indistinguishable from adults, or show only minor differences such as a darker bill or white forehead.
Common terns occur from northern Canada to the Caribbean Sea in the south, throughout Europe, Northern Asia, the Middle East and North Africa. Outside of the mating season, these birds winter along the coasts of South America and Central America, along Africa’s coast and the Arabian Peninsula, as well as on islands in the Indian Ocean and throughout Australasia and much of Southeast Asia. They breed on sand spits, beaches and low-lying inshore islands. They also nest inland near slow-flowing rivers, and lakes in open country. This species favors areas that have close shallow waters where they can fish. During migration, they are mainly seen along coasts, at freshwater inland lakes and in estuaries. During winter, they are mostly coastal, in warm tropical and subtropical waters.
Common terns are diurnal birds and they live in colonies with no clear hierarchy among them, with all seeming to be equal. Although Common terns all migrate and live together, the family unit is responsible to feed and care for its own eggs and chicks, and individuals will often defend feeding territories. This species forages by flying above water and hovering, often plunge-diving to catch prey under the surface. It will also swim as it picks up food from the surface of the water or just below it. A highly migratory bird, it leaves the breeding grounds for the wintering sites typically from August to October, soon after all the chicks fledge. These birds communicate mostly by means of their unusual, hoarse voices, having three different and distinct calls. Communication during mating is mainly visual and/or tactile.
Common terns are carnivores (piscivores), they mainly eat fish, but also consume shrimps and other crustaceans, small squid, marine worms, and leeches.
Common terns are monogamous, which means they mate with only one partner during a breeding season. At the time of courtship, which starts in April, males establish their territories within the colony before commencing what is known as "courtship feeding," where a male brings a fish to a female to court her. Courtship displays include the male posturing followed by the pair circling each other. Eggs are laid from April to June. Common terns usually breed in huge colonies, though there may be some isolated pairs. Both parents construct their nest on bare ground, sometimes with low vegetation surrounding it or on dead floating vegetation. 2-3 eggs are laid and are incubated by both parents for 21-25 days. Chicks leave their nest after several days, but remain nearby and their parents still feed them. They fledge at around 22-28 days old, remaining in the family group for at least another two months. Common terns become reproductively mature at 3 years of age.
The Common tern enjoys a wide range, but its colonies are threatened by human disturbance through increase in recreational activities, naturally fluctuating water-levels flooding their nest sites, habitat loss from coastal development, erosion, pollution and invasive vegetation at nesting sites.
According to IUCN’s Red List, the total population size of the Common tern is 1,600,000-3,600,000 individuals. National population sizes were estimated at 10,000-100,000 breeding pairs; in China, 1,000-10,000 individuals migrating and 50-1,000 wintering, and in Russia, 10,000-100,000 breeding pairs and 1,000-10,000 migrating individuals. Overall, currently Common terns are classified as Least Concern (LC), however their numbers today are decreasing.
Common terns impact the populations of prey that they eat and act as an important source of food for their predators. Sometimes the uneaten fish they catch are eaten by scavenging animals that live in the same area.
Social animals are those animals that interact highly with other animals, usually of their own species (conspecifics), to the point of having a rec...