Habitat and Ecology
Habitat and Ecology
Behaviour The species is a very strong migrant and makes exceptional long-distance movements offshore or along western continental coastlines1, 6 between its high Arctic breeding grounds and Antarctic wintering grounds1. It breeds between May and July (although the exact timing varies with temperature and food availability) in solitary pairs or colonies of a few to several hundred pairs (usually 2-25)1, and remains gregarious throughout the year especially when roosting, foraging4 and on passage5. The species generally feeds within 3 km of breeding colonies but may occasionally forage up to 50 km away1. On its wintering grounds in Antarctica it may also forage in association with Antarctic Minke Whale Balaenoptera bonaerensis in the open ocean north of the pack-ice zone5. Habitat Breeding The species breeds along northern coastlines1 and on inshore islands3, 4 as well as inland on tundra and forest-tundra3. It shows a preference for habitats with a vegetation cover of less than 40 %, nesting on sand or shingle beaches, ridges1 and spits3, rocky ground1, 2, 3 and small islands1, 3, 4 in lakes and coastal lagoons1. It may also nest on islets or banks along rivers4, on swampy tundra1, 3 and peatlands with bog hummocks1 and reed-covered flats3, or on inland heaths, rough pastures1, 4, meadows1 and sedge grassland4 not far from water3. The species also forages offshore, in ice-filled coastal bays or over wet tundra1. Non-breeding On passage it largely flies over open ocean4 resting at sea on kelp, logs or flotsam, but may occur inland or along coastlines on beaches, reefs and spits5. During the winter the species is pelagic, foraging at the edges of pack-ice, icebergs and ice-floes near shore (especially in channels between ice-floes)5 and up to 24 km offshore1, 5 often in association with Antarctic Minke Whale Balaenoptera bonaerensis5. It also roosts on ice-floes and icebergs during this season5. Diet Its diet consists predominantly of fishas well as crustaceans (especially planktonic species), molluscs, insects (e.g. caterpillars, Chironomidae) and earthworms1. It will also take berries in the early spring on arrival on its breeding grounds but does not readily switch to other prey items when preferred prey supplies fail1. Breeding site The nest is a shallow scrape1 in sand, shingle or turf2 on beaches, ridges1 and spits3, rocky ground1, 2, 3, small islands1, 3, 4 in lakes, coastal lagoons1 and rivers4, swampy tundra1, 3 and peatlands with bog hummocks1 and reed-covered flats3, or on inland heaths, rough pastures1, 4, meadows1 and sedge grassland4 not far from water3. It will also nest on artificial structures1. Management information Removing feral American mink Neovison vison from a large archipelago with many small islands in the Baltic Sea resulted in an increase in the breeding density of this species in the area8. Gull control measures may also be practised successfully at some sites to reduce predation and displacement, especially when carried out in conjunction with the use of recordings and models to induce recolonistion of nesting terns7.
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