Habitat and Ecology
Habitat and Ecology
Behaviour Northern breeding populations of this species are strongly migratory although populations at lower latitudes tend to be sedentary or locally dispersive1. The species breeds between April and May1 in dense colonies of up to several thousand pairs1, 4 often with other gull or tern species3. It generally remains gregarious throughout the year4 and may roost in large flocks during the winter2. Habitat Breeding The species chiefly breeds inland and shows a preference for shallow, calm4, temporarily flooded wetland habitats1 with lush vegetation1, 3. It forms nesting colonies on the margins of lakes1, 2, 3, lagoons3, 4, slow-flowing rivers, deltas, estuaries4 and on tussocky marshes1, 2, 3, but may also nest on the upper zones of saltmarshes1, 4, coastal dunes and offshore islands in more coastal areas1. The species will also utilise artificial sites such as sewage ponds, gravel- and clay-pits, ponds, canals and floodlands4 and may nest on the dry ground of heather moors, sand-dunes, beaches1, 4 and stony islets4. Non-breeding During the winter the species is most common in coastal habitats1 and tidal inshore waters, showing a preference for inlets or estuaries with sandy or muddy beaches, and generally avoiding rocky or exposed coastlines4. It may also occur inland during this season, frequenting ploughed fields, moist grasslands, urban parks, sewage farms, refuse tips, reservoirs, ponds and ornamental waters4, and roosts on sandy and gravel sites or on inland reservoirs2. Diet Its diet consists predominantly of aquatic and terrestrial insects, earthworms and marine invertebrates (e.g. molluscs, crustaceans and marine worms)1 although it may also take fish1 (usually dead or sick)3, rodents (e.g. voles)3 and agricultural grain1. During the non-breeding season the species may rely heavily on artificial food sources provided by man, especially in Western Europe1, and often scavenges from refuse tips during this period2. Breeding site The nest is a rough construction of vegetation2 based on a shallow scrape4 and placed on a floating mat, in broken reeds, on a hummock, or sometimes on dry, grassy or sandy ground1, 3. The species shows a strong preference for nesting near vegetation (although vegetation overgrowth can lead to the desertion of colony sites)1. It usually nests in dense colonies with neighbouring nests placed an average of 1 m apart1.
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