Tern Bird

Terns are seabirds that belong to the Laridae family and can be found near the sea, rivers, or wetlands all over the world.  River tern birds are a subset of the Laridae family, which also contains gulls and skimmers and has eleven genera. They have long, forked tails, small wings, large beak, and short legs, and are slender, light-built birds. The marsh terns, Inca terns, and some noddies have dark plumage for at least part of the year, but the marsh terns, Inca terns, and some noddies have dark plumage for at least part of the year.

Although the sexes are visually identical, young birds can be distinguished from adults. Terns exhibit non-breeding plumage, which includes a white forehead and a much diminished black hat. Terns are long-lived birds with few natural predators or parasites; yet, most species are dropping in numbers as a result of human activities such as habitat loss, pollution, disturbance, and predation by introduced mammals.

The Chinese crested tern is critically endangered, and three additional species are on the verge of extinction. Although international agreements give some protection, certain species' adults and eggs are nevertheless consumed as food in the tropics. In the West Indies, two species of eggs are eaten because they are said to have aphrodisiac powers.

Description of Tern Bird

The least tern is 23 cm (9.1 in) long and weighs 30–45 g (1.1–1.6 oz), while the Caspian tern is 48–56 cm (19–22 in) long and weighs 500–700 g (18–25 oz). They have a longer bill, lighter body, and more streamlined appearance than gulls, and their long tails and long thin wings give them a graceful appearance when flying. Male and female plumages are nearly identical, except the male might be 2–5% larger and has a larger bill than the female.

All other species have at least a shallow "V" in their tails, with the exception of sea terns, which have deeply forked tails. The noddies (genera Anous, Procelsterna, and Gygis) have distinctive notched-wedge shaped tails, with the middle-outer tail feathers being longer than the centre or outermost. Despite their tiny legs, terns are capable runners. Despite possessing webbed feet, they rarely swim, preferring to bathe in water.

As adults, the majority of sea terns have light grey or white body plumage with a black crown. Depending on the species, the legs and bill are varied shades of red, orange, yellow, or black. At sea, the pale plumage stands out and may attract other birds to a favourable feeding place for these fish-eating species. The white underparts help to camouflage the hunting bird from its intended victim when seen against the sky. The Inca tern has mostly dark plumage, and the black tern, white-winged tern, and black-bellied tern, which primarily feed insects, have black underparts during the mating season.

The upperparts of juvenile terns are usually brown or yellow, and the feathers have dark edges that give the plumage a scaly look. Their wings feature dark bands and their tails are short. The subsequent moult does not begin until after migration in most species, with the plumage becoming more adult-like, but with some juvenile feathers preserved and a white forehead with just a partial dark cap. The appearance resembles that of an adult by the second summer, and full mature plumage is normally achieved by the third year. Terns moult into a winter plumage after breeding, which usually includes a white forehead.

Antarctic Tern

The Antarctic tern (Sterna vittata) belongs to the Laridae family of seabirds. It can be found on small islands around Antarctica as well as on the mainland's coastlines, and it can be found throughout the southern oceans. Small fish and crustaceans make up the majority of its food. It resembles the closely related Arctic tern in appearance, but it is stockier, and it is in breeding plumage during the southern summer, when the Arctic tern has shed old feathers to obtain its non-breeding plumage. Although the Antarctic tern does not migrate like the Arctic tern, it can nevertheless be found throughout a wide range of habitats. The South American tern is more closely linked to this tern species.

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Scientific Classification of Antarctic Tern

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Charadriiformes

Family: Laridae

Genus: Sterna

Species: S. vittata

Description of Antarctic Tern

The Antarctic Tern is a medium-sized tern with a wingspan of 74 to 79 cm and a length of 35 to 40 cm (14 to 16 in) (29 to 31 in). It weights between 150 and 180 g (5.3 and 6.3 oz), with the winter months being heavier.

The tern's body and wings are light grey in breeding plumage. It has white cheeks, a deeply forked tail, and a lower back just above it. It also has a characteristic black cap that runs from the nape to the bill, and a brownish-black eye. The bill, legs, and feet are all a vibrant crimson colour. The black crown is lowered to just below the eyes in non-breeding plumage, the underparts grow lighter, and the beak develops a dull reddish-black colour.

The backs of juveniles are yellowish-brown, grey, and white, with a yellowish-brown belly and breast. Their bill is a dark black colour, and their legs are a dark red colour. The females are yellowish-brown in colour, with black markings on their heads and backs. Their belly is greyish white, and their throat is darker. The bill, legs, and feet might be reddish black or flesh coloured.

Habitat and Distribution

The Antarctic tern favours rocky locations with or without vegetation, such as islets, where it is commonly found with other seabird species. It normally builds its nest on cliffs, although it can also be found on rocky beaches, areas where cats and rodents cannot get to. It also avoids beaches where sea lions are present, as they tend to take up all of the flat areas. Outside of the breeding season, this tern searches Antarctica for ice edges. It also travels to the beaches and rugged cliffs of South Africa.

Behavior 

Vocalizations

Around their roost areas, Antarctic terns make a lot of noise. When they are in flight or fishing, they make the sound “trr-trr-kriah.” They also utilise a "chrrrr" to protect their nests from predators or intruders. To get their partners' attention, they produce a higher-pitched call.

Diet

The Antarctic tern is an opportunistic feeder that feeds primarily on tiny fish and crustaceans such as Antarctic krill. When they find larger shoals, they frequently fish in large flocks of up to 100 birds. It catches fish by hovering a few metres above the water's surface. When a prey is found, the tern has two options: it can plunge dive and get entirely immersed most of the time, or it can just submerge its bill while in flight if the water is too choppy. It forages in the kelp zone along the shore.

Reproduction

The Antarctic tern breeds in November and December, however this might vary depending on the environment and food availability. The birds normally nest in loose colonies of 5 to 20 pairs, but they can occasionally be seen in single pairs. Some islands, on the other hand, have significantly bigger populations, with colonies of over 1000 pairs. For breeding, this tern species prefers depressions or scrapes on the cliff ledge. It nests in the soil, sand, glacial moraines, or a plant mat, usually within a tiny pit of pebbles or shells.

During the breeding season, the female will lay one or two eggs, which will be incubated by both parents for 23 to 25 days. During the summer months, from December through February, chicks hatch. The chicks must then be fed by their parents for 27 to 32 days until their flying feathers develop properly. Even after this stage, both members of the couple visit their young for several weeks. Antarctic terns who survive their first year have a life expectancy of around 17 years and a reproductive time span of about 10 years because they can begin reproducing at the age of three.

Arctic Tern Bird

The Arctic tern (Sterna paradisaea) belongs to the Laridae family of terns. This bird has a circumpolar breeding range that includes Europe, Asia, and North America's Arctic and sub-Arctic areas (as far south as Brittany and Massachusetts). The species is very migratory, spending two summers a year migrating from its northern breeding grounds to the Antarctic coast for the southern summer, then returning roughly six months later. Birds nesting in Iceland and Greenland have average yearly round trip lengths of around 70,900 km (44,100 mi) whereas birds nesting in the Netherlands have average annual roundtrip lengths of about 90,000 km (56,000 mi) according to recent studies.

These are by far the longest animal migrations ever recorded. The Arctic tern glides in the air as well as flying. It only nests once every one to three years (depending on its mating cycle), after which it departs for another long southern trip.

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Scientific Classification of Arctic Tern Bird

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Charadriiformes

Family: Laridae

Genus: Sterna

Species: S.paradisaea

Description of Arctic Tern Bird

Arctic terns are medium-sized birds that live in the Arctic. They measure 28–39 cm (11–15 in) in length and 65–75 cm (26–30 in) in wingspan. With a red/orangish beak and feet, white forehead, black nape and crown (streaked white), and white cheeks, they are mostly grey and white. The grey mantle measures 305 mm in length, and the scapulae are brown with white tips. The upper wing is grey with a white leading edge, and the collar, like the rump, is totally white. The pale tail has grey outer webs and is deeply forked. 

Reproduction

Around the third or fourth year, breeding occurs. Arctic terns are monogamous and, in the majority of cases, return to the same colony year after year. Courtship is extensive, especially in first-time nesting birds. Courtship begins with a "high flight," in which a female chases a male to a high height and then descends slowly. This is followed by "fish flights," in which the male offers the female fish. On the ground, courtship entails strutting with a lifted tail and depressed wings. Both birds will normally fly and circle each other after that.

Both sexes agree on a nesting place, and they will both protect it. The male continues to feed the female during this period. Soon after, mating takes place. Breeding occurs in colonies around the beaches, on islands, and on rare occasions inland on tundra near water. It frequently joins flocks of common terns. It lays one to three eggs every clutch, with two being the most common.

Relationships with Humans 

• Humans have traditionally eaten terns and their eggs, and island colonies were invaded by sailors on lengthy trips because the eggs or huge chicks provided an easy source of nourishment. Adults of wintering birds are taken as food in West Africa and South America, and eggs are still illegally gathered in southern Europe. This hunting has a major impact on the roseate tern, with adult survival rates 10 percent lower than projected. Roseate and sooty tern eggs are thought to be aphrodisiacs in the West Indies, and egg collectors target them disproportionately.

• Tern skins and feathers have long been used to make clothes like capes and hats, and when it became trendy to employ feathers in hat making in the second half of the nineteenth century, this became a large-scale enterprise. The movement began in Europe and quickly expanded to the Americas and Australia. White was the preferred colour, and wings or complete birds were occasionally used.

• Terns have profited from human activity in the past, following the plough or fishing boats for cheap food, while some birds become entangled in nets or consume trash. Fishermen were on the lookout for feeding tern flocks, which may lead them to fish shoals. Small fish, such as sand eels, are vulnerable to overfishing, which can result in dramatic losses in colonies that rely on these prey items. Many species have declined as a result of the loss or disturbance of tern colonies due to human activities.

• Pollution has been a concern in some locations, and DDT affected egg loss by thinning the shells in the 1960s and 1970s. Organochlorines caused substantial decreases in the Great Lakes region of the United States in the 1980s. Terns are occasionally employed as markers of pollution levels due to their sensitivity to contaminants.

• Floating nest platforms for black, common, and Caspian terns, as well as artificial islands for a variety of species, have been utilised to improve the breeding success of terns.

Conclusion

Terns are a subset of the Laridae family, which includes gulls and skimmers and is divided into eleven genera. They are thin, light-built birds with long, forked tails, small wings, a big beak, and short legs. For at least part of the year, marsh terns, Inca terns, and some noddies have dark plumage, but for at least part of the year, marsh terns, Inca terns, and some noddies have dark plumage. The Antarctic tern (Sterna vittata) is a seabird in the Laridae family. It can be found on small islands around Antarctica as well as on the coasts of the continent, and it can be found all across the southern oceans. The majority of its diet consists of small fish and crustaceans. Its look is similar to that of the closely related Arctic tern, but it is stockier, and it is in breeding plumage during the southern summer, when the Arctic tern has lost its old feathers to gain its non-breeding plumage. The Arctic tern (Sterna paradisaea) is a member of the Laridae tern family. This bird's circumpolar breeding range encompasses Europe, Asia, and the Arctic and sub-Arctic regions of North America (as far south as Brittany and Massachusetts).