The species breeds on fresh or brackish wetlands (Richards 1990) such as small pools, lakes, marshes (Richards 1990, Gochfeld and Burger 1996), ditches, overgrown canals, quiet reaches of rivers, swampy meadows (Richards 1990), peat bogs and rice-fields, showing a preference for well-vegetated areas with sparse, open emergent vegetation (Gochfeld and Burger 1996) (e.g. Typha spp., sedge or reeds) (Flint et al. 1984) and floating water-lilies. It generally avoids small marshland areas less than 4 ha in area.

It breeds between May and June in colonies, usually of less than 20 pairs (rarely more than 100 pairs) (Gochfeld and Burger 1996) and often close to other species (Flint et al. 1984, Snow and Perrins 1998). The nest may be a low compressed mound of plant matter (Flint et al. 1984, Snow and Perrins 1998) placed in very shallow water (Snow and Perrins 1998) or on a floating mat of aquatic vegetation (Flint et al. 1984) over water more than 50 cm deep (Gochfeld and Burger 1996). The nest may also be a shallow scrape (Snow and Perrins 1998) on the ground amongst marsh vegetation (Snow and Perrins 1998). The species breeds in small colonies and may forage up to two to five kilometres from breeding sites. Clutches are two or three eggs.

During the breeding season, the diet consists predominantly of insects (e.g. chironomids, Odonata, Ephemeroptera and Coleoptera) as well as small fish (Gochfeld and Burger 1996) and amphibians (Snow and Perrins 1998) (e.g. tadpoles and frogs).

This species is strongly migratory (Gochfeld and Burger 1996) and travels both over land and over sea (Snow and Perrins 1998). After breeding, it departs for its wintering grounds from July onwards (Richards 1990), returning north again from late-March (Snow and Perrins 1998). The species is gregarious throughout the year (Snow and Perrins 1998), foraging in small groups during the breeding season and congregating in large flocks offshore on passage and in the winter over shoals of predatory fish (Richards 1990, Gochfeld and Burger 1996, Snow and Perrins 1998).

Although the generation length for both EU and Europe regional assessments were calculated using the same methodology, new information arriving after the EU assessments were undertaken gave rise to an update in the generation lengths. This new information was then used for the Europe level assessments giving rise to a difference between the generation lengths used for the EU and Europe regions.

In Europe, the species stronghold is Russia, with smaller numbers in Belarus, Ukraine and Lithuania.

Conservation Actions Underway
Bern Convention Appendix II. CMS Appendix II. The species has been included as a target species in two EU LIFE Projects. In the Netherlands the provision of anchored artificial nesting rafts has been partly successful as a conservation measure (van der Winden et al. 2004, 2005), especially in habitats where unstable nest substrates (such as floating water-lilies) result in poor breeding successes (van der Winden et al. 2004). In the Netherlands there have also been successful programmes to reduce disturbance and improve habitat quality in agricultural areas, which has benefited the species (van der Winden 2005).

Conservation Actions Proposed
The application of glyphosphate-based herbicides to combat and prevent the overgrowth of Typha spp. in wetlands may also benefit the species (Linz and Blixt 1997).