Habitat and Ecology
Behaviour All populations of this species undergo post-breeding dispersive movements1. Populations breeding in the tropics are sedentary1 or partially migratory (in relation to rainfall)4, whereas Palearctic and Nearctic populations are migratory1, 6. The timing of the breeding season varies geographically1 although temperate breeders tend to nest in the spring and summer (e.g. April to July) and tropical breeders nest in the part of the rain cycle when food becomes maximally available (this may be during the rains or in the dry season)2. The species typically breeds in colonies of tens, hundreds or even a thousand pairs1, 2, sometimes with other species (e.g. 450 pairs in a mixed colony of over 3,000 nests in Australia)1. Some populations also show a tendency to breed solitarily or in small groups1. Outside of the breeding season the species may feed solitarily1 or in small loose groups9 (e.g. of 12-50 individuals)4, although flocks of hundreds or more individuals may form where food is abundant1. The species is a diurnal feeder1 but is most active at dawn and dusk (although in coastal environments it feeding habits are determined by tidal stages)2, and roosts at night in trees4 alongside lakes or rivers or in mangroves, often with other species7. Habitat The species inhabits all kinds of inland and coastal wetlands1 although it is mainly found along the coast in the winter (e.g. in the Palearctic Region)8 or during droughts (e.g. in Australia)9. It frequents river margins, lakes shores, marshes, flood-plains1, oxbows, streams8, damp meadows2, rice-fields, drainage ditches1, aquaculture ponds, reservoirs2, 9 and sewage works5, 9 inland, and the shallows of salt-lakes9, saltpans, mudflats, coastal swamps, mangroves1, saltmarshes, seagrass flats, offshore coral reefs, lagoons2 and estuaries when in coastal locations1. Diet In aquatic habitats its diet consists of fish, amphibians, snakes, aquatic insects and crustaceans although in drier habitats terrestrial insects, lizards, small birds and mammals are more commonly taken1. Breeding site The nest is constructed from sticks2 and vegetation4 and is normally positioned over water at a height of 1-15 m2 in reedbeds, bamboos2, bushes, trees1 (e.g. willow Salix spp.), mangroves3 and other plants near water or on islands in sites that are protected from ground predators2. The species usually nests colonially in single- or mixed-species groups where nests may be less than 1 m apart or touching, although they are usually placed more spread out in reedbeds2. Breeding pairs may also reuse nests from previous years2. Management information Breeding site conservation should include colony protection, control of disturbance and vegetation management, and the conservation of feeding areas should include the management of hydrology, salt intrusion, contaminants and disturbance2. An artificial island nesting site created in the Camargue, France succeeded in attracting nesting pairs to the area10.
Systems
- Terrestrial
- Freshwater
- Marine
