Roseate Tern (Sterna dougallii)

Roseate Tern

[order] CHARADRIIFORMES | [family] Laridae | [latin] Sterna dougallii | [UK] Roseate Tern | [FR] Sterne de Dougall | [DE] Rosen-Seeschwalbe | [ES] Charran rosado | [NL] Dougalls Stern

Subspecies

Genus Species subspecies Breeding Range Breeding Range 2 Non Breeding Range
Sterna dougallii Worldwide widespread coasts
Sterna dougallii arideensis Seychelles to Madagascar and Rodrigues I.
Sterna dougallii bangsi Ryukyu Is. and e China to New Guinea, ne Australia and islands of the sw Pacific
Sterna dougallii dougallii e North America, West Indies, Azores, Europe, Africa
Sterna dougallii gracilis Moluccas, w and n Australia
Sterna dougallii korustes Sri Lanka, Andaman Is. and Mergui Arch. (sw Burma)

Physical charateristics

The adult Roseate Tern is 33 to 34 cm in length and has a wingspan of 72 to 80 cm. At a weight of approximately 100 to 120 g, an adult is slightly smaller than a Mourning Dove. It has a black forehead and nape, and its upper wing is a pale grey. Its tail is white with deeply forked outer feathers that give the impression of long streamers when the bird is in flight. The underside of the tern is white, tinged with pink early in the breeding season; however, this pale rosy tint is not a good field mark, or identification characteristic, because it varies from bird to bird, and the colour tends to be bleached out by the sun. The legs and feet are reddish, and the bill is mostly black, although bills of breeding birds may be red at the base. Male and female birds look alike. The head of the nonbreeding adult is mottled black and white.

The juvenile Roseate Tern has a mottled greyish back and rump and dark bill and legs. Chicks are unevenly covered with down, giving them a spiky appearance; their legs are dark purplish to black.

Listen to the sound of Roseate Tern

[audio:http://www.aviflevoland.nl/sounddb/R/Roseate Tern.mp3]

Copyright remark: Most sounds derived from xeno-canto

wingspan min.: 67 cm wingspan max.: 76 cm
size min.: 33 cm size max.: 36 cm
incubation min.: 23 days incubation max.: 24 days
fledging min.: 25 days fledging max.: 24 days
broods: 1   eggs min.: 2  
      eggs max.: 4  

Range

Worldwide oriental region: widespread coasts

Habitat

Roseate, Common, and Arctic terns nest together to take advantage of the benefits of living within a colony. All species of terns join together to threaten and mob invading predators. The Roseate Tern breeds on coasts and islands in the tropics along the Indian, Pacific, and Atlantic oceans and in temperate zones of North America and Europe, South Africa, and western Australia

Reproduction

Evidence suggests that immature birds remain in the south during their first potential breeding season. Many two-year-olds return to the nesting colony. A few of these may breed, but most young Roseates wait until they are three or four.

After Roseate Terns arrive in their breeding colonies in early to mid-May, the pairs begin courtship displays. These displays include an elaborate, ritualized flight in which the male, often carrying a fish, ascends in circles high into the air, closely followed by one or more females; the male and the lead female descend together in a zig-zag glide. Courtship feeding-the presentation of fish to the female by the male-helps compensate the female for the energy used in egg production.

Roseate Terns often choose nesting sites that provide cover and usually hide their nests under dense grasses and other plants, boulders, or washed-up debris. The nests are not much more than a bare scrape in sand or rubble.

The birds begin laying eggs by late May. The usual clutch, or set of eggs, contains one or two eggs laid two to three days apart. Incubation, or warming the eggs until they hatch, begins when the clutch is complete. The parents take turns incubating the eggs for 23 to 24 days. After the chicks hatch, they stay near the nest area where they are guarded and fed by both parents. Several days later, the chicks leave the nest to find new hiding places. Although some parents are able to raise two chicks to fledging, or first flight, the second chick usually starves because the adults, who must sometimes fly long distances to find food, cannot provide enough for both. Chicks fledge 25 to 28 days after hatching and leave the colony with their parents within a few days. Their parents tend them for at least six weeks after fledging, while they learn to fish on their own.

Feeding habits

Roseate Terns feed in salt water on small fish, most frequently sand lance but also white hake, juvenile herring, mackerel, gadids, cod, pollock, and haddock. They plunge into the water in a high dive to catch their prey and can immerse themselves completely and “fly” under water short distances in pursuit of fish. They prefer to fish in rips, or places where currents meet, and other turbulent waters and will hunt for food as far as 20 km from their colony. The birds usually carry one fish at a time in their bills but occasionally will carry more. They will steal fish from other terns and are often the victims of similar piracy by gulls and even crows and ravens.

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Roseate Tern status Least Concern

Migration

Migratory. At all seasons the most thoroughly marine of European terns; only a vagrant inland anywhere. European population winters exclusively in West Africa. Brief post-fledging dispersal of juveniles and adults in August, including northward movement in Britain, is followed by rapid movement along Atlantic seaboard towards winter quarters. By November, all recoveries of ringed birds are from coast of West Africa at 0-10 degrees N. 1st-summer birds remain in tropics. At 2 years old, at least some return to Europe, and may visit breeding grounds, but rarely breed; most breed first at 3 years old. Arrival on breeding grounds mostly in mid-May.

Distribution map

Roseate Tern distribution range map

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