Habitat and Ecology
Behaviour This species is fully migratory5, although the extent of migration varies between populations1, and some populations remain predominantly sedentary (e.g. in Spain)1, 5. Autumn movements are often protracted, with dispersal beginning in mid-August and lasting until late-November (peaking in October)5, with the return migration beginning in March5. The species migratory movements are mainly nocturnal, although diurnal migration is known in the Palearctic1. It breeds between May and June in the Northern Hemisphere2 (although laying dates often vary extensively between years and lakes)2, and nests in reed swamps1 in small or large colonies of up to 2000 nests (although the species may also nest in isolated pairs)2. It forages diurnally2, 6 and is highly gregarious1, 2, both on migration and during the winter, forming concentrations of hundreds of thousands at certain sites in North America and Asia1. After arrival in autumn staging grounds (e.g. Mono Lake in California) the species becomes flightless for 3 to 4 months due to loss of weight from the pectoral muscles4. Habitat Breeding During the breeding season this species frequents permanent and temporary5 small, shallow, highly eutrophic pools with lush vegetation, such as freshwater marshes and lakes1 with dispersed submergent vegetation and patches of reeds2, 3, as well as ponds and fish ponds, sewage farms, quiet river backwaters and newly flooded areas1. In southern Russia and Kazakhstan it shows a preference for variably developed reed swamps and gypsotrophic lakes (alkaline waters with rich submergent vegetation such as Chara and Potamogeton pectinatus)2. Non-breeding Outside of the breeding season the species moves to salt lakes1, hyper-saline industrial evaporation ponds2 and reservoirs5, or to coastal estuaries, arms of the sea, and inshore shallows in bays and channels1, 5. Diet The species is carnivorous, its diet consisting of adult and larval insects (such as aquatic bugs, terrestrial and aquatic beetles, damselflies, dragonflies1, midges and brine-flies2), molluscs, crustaceans (e.g. brine shrimps), amphibians (e.g. small frogs and tadpoles)1, nereid worms2, snails3 and small fish1, 2. Breeding site It usually nests colonially in thinly spaced, emergent marsh vegetation (such as Scirpus, Typha or sedge Carex), or on dense mats of floating waterweed, sometimes far from the shore2. The nest is a floating platform of aquatic vegetation anchored to emergent vegetation1, 5 such as reeds2.
Systems
- Terrestrial
- Freshwater
- Marine
