Category Archives: Royal Tern (Sterna maxima)

Royal Tern (Sterna maxima).

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The Royal Tern (Thalasseus maximus, syn. Sterna maxima, see Bridge et al., 2005) is a seabird in the tern family Sternidae. This bird has two distinctive subspecies, T. m. maximus which lives on the Atlantic and Pacific coasts of the North and South America. 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 on the top of its head 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.

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Royal Terns are colonial nesters. Colonies are usually situated on islands where predators are scarce, and nests are nothing more than shallow scrapes densely packed. By laying their eggs at the same time (above), all the Royal Tern pairs reduce the chances of their eggs and young being eaten by predators, which have a greater choice of nests to prey upon.

Physical characteristics

Second in size after the Caspian Tern in the tern family, the Royal Tern has a slender body, pointed wings and notched tail like other terns of smaller size. However, its bill is much wider and more powerful. Wings and back are pale grey, and underparts are white. In breeding plumage, top of head shows a black crown, which disappears partially in winter. However, crest on rear head remains in all seasons. Orange-red bill is long, pointed and wide. Short legs are black and thick, and feet are webbed. Both sexes are similar.

Juvenile resembles non breeding adult, with smaller pale yellow bill, some dark spots on back and darker wingtips.

Range

North America, Latin Americatin America, Africa : coasts

Habitat

Royal Tern lives in coastal bays, lagoons, harbours and sandy shores, but it may sail up a river outside of breeding season. It nests on off shore islands.

Reproduction

Royal Tern nests in large and noisy colonies, up to several thousands pairs. These colonies often are mixed or close to those of Caspian and Sandwich Terns. Pairs perform courtship displays in a nearby area, male flying slowly and soaring to the ground, and offering a prey to female. Once pair formed, both mates choose a free place to establish the nest, and circle widely several times over the site. Then, they scratch a shallow depression, adding sometimes some shells.

Male and female take turns to brood the single egg, but they can abandon it sometimes and for several hours. Both parents raise the young covered with brown and buff down.

On the American continent, chicks leave the nest 24 hours after hatching and gather into large crches when they are two or three days old.

In Africa, they remain at nest during one week, and take part to a crche at about 15 days after hatching.

Young remain within these crches until their first flights, and parents feed only their own young, recognizing it by its call.

Although the young tern is able to fly at one month, it remains dependent from its parents during five to eight month, for protection and feeding.

Feeding habits

Royal Tern feeds mainly at mid-tide, in the early morning and in late afternoon, but it also fishes at night during breeding period.

It flies at about 5 to 10 metres above the water, along the beaches, searching for fish and other preys. Royal Tern fishes alone or in pairs, but sometimes in flocks too. These groups may contain up to 150 birds.

Usually, it remains at about 100 metres from the shore, but when it searches for food for the chick, it may flies away up to 65 km from the colony, along the coast.

When a prey is located, it hovers just above this one, with bill pointed downwards. Then it dives vertically and catches the prey with its bill. Royal Tern feeds mainly on small fish, but it also consumes crabs, shrimps and squids. It also follows fish boats, in order to eat the debris ejected out of the boat.

Conservation

This species has a large range, with an estimated global Extent of Occurrence of 100,000-1,000,000 km2. It has a large global population estimated to be 280,000-310,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.

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Royal Tern Distribution map world wide.