[order] Charadriiformes | [family] Sternidae | [latin] Sterna dougallii | [UK] Roseate Tern | [FR] Sterne de Dougall | [DE] Rosenseeschwalbe | [ES] Charrán rosado | [IT] Sterna di McDougal | [NL] Dougalls Stern

Dougalls Stern determination

copyright: youtube

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.

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

This tern has a nearly cosmopolitan but very fragmented distribution. In Europe it is breeding on the Atlantic coasts of France and the British Isles, in the Irish Sea, along the Mediterranean coats of France, on the Azores and Madeira. This European population is wintering along the Atlantic coast of West Africa. Currently about 1650 breeding pairs inhabit the European Union, but this population has considerably declined during the last decades. This decline, currently perhaps halted, is related to a loss of breeding sites and taking in the winter quarters

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.

Sterna dougallii breeds in widely but sparsely distributed colonies along the east coast and offshore islands of Canada, USA, from Honduras to Venezuela, possibly to Brazil, the Caribbean, UK, France, Ireland, Portugal, Spain (Canary Islands), South Africa, Kenya, Somalia, Madagascar, Oman, Seychelles, Sri Lanka, Indonesia, Fiji, Solomon Islands, New Guinea (Papua New Guinea), New Caledonia (to France) and Australia. This species has a large range, with an estimated global Extent of Occurrence of 1,000,000-10,000,000 km2. It has a large global population estimated to be 78,000-82,000 individuals. The population in North America underwent a significant decline in 40 years, decreasing from 8,500 pairs in the early 1930s to 2,500 in 1978. Numbers, however, appear to have stabilised at 3,000 pairs. Between 1969 and 1992, the UK population declined from 1,018 pairs to 57, and pairs in Ireland dropped from 1,435 to 454. In 1995, however, over 1,700 pairs bred in Europe. The French population is 100-110 pairs which may be a decline from c.500 in 1973. The large Azores population has fluctuated between 550 and 1,028 pairs from 1989/90 to 1995. The tropical Indian Ocean may be the most secure region for this species. The species is threatened by a number of agents of which hunting in the wintering quarters may be the most significant. Trapping of tern species is still prevalent in Ghana, which has the highest number of wintering S. dougalli of the western African countries. At the northern European breeding grounds it is not clear which threats are having the most impact. Disturbance and egg-collecting have been stopped in most areas by the use of wardens, but the former still threatens some major colonies in the Azores. Predation by rats, ferrets, red foxes and Peregrine Falcon Falco peregrinus occurs locally, and can have significant effects, including complete breeding failure at some Azores colonies. Natural predators can often take a great toll on localised colonies, particularly when terns are disturbed from the nest by other birds and humans. Habitat loss in northern Europe is not a major problem but has caused the local extinction of some colonies, as have extreme weather events. 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. [conservation status from birdlife.org]

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.

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°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.