Habitat and Ecology
Behaviour Although some populations of this species are sedentary or only disperse short distances1, most inland and northern coastal populations3 are fully migratory and have distinct separate breeding and wintering ranges1. The species occupies its breeding grounds chiefly from March to October3, dispersing from late-June immediately after the young fledge, with the southward migration peaking in September1. The species nests solitarily or in loose semicolonial groups1, 2, 4, usually in densities of 0.5 to 20 pairs per hectare (exceptionally up to 100 pairs per hectare)2, and sometimes in association with other species (e.g. Least Tern Sterna antillarum)12. Outside of the breeding season5 the species feeds singly7 or in small flocks of 20-30 individuals1, 5, and occasionally in larger flocks of up to 260 individuals4, often roosting in large mixed-species flocks4. Habitat During all seasons the species is predominantly coastal1, 2, 3 and is usually found on sand, silt or dry mud surfaces1, generally avoiding very exposed oceanic coastlines5 and rocky or broken ground1. It also shows a preference for sparsely vegetated and sandy areas when breeding2. Typical habitats include sandy, pebbly or muddy shores2, 3, 6, dunes2, coastal lagoons1, coastal marshes (China)7, tropical shores of coral limestone2, estuaries and tidal mudflats (Africa)4. It is uncommon on freshwater, even when migrating3, but frequently occurs on inland habitats not far from the coast such as seasonal watercourses1, open flats near brackish or saline lakes1, 3, salt-pans1, 6, salty steppes with scattered grasses2, sandy deserts2, pebbly or muddy plains2, gravel pits1, and less frequently sandy riverbanks (Africa)2, 4, 6, sandy pond margins6 and barren reservoir shores1, 2. Diet Its diet consists mainly of insects and their larvae1, 2 (e.g. beetles and flies)1, gammarids2, crabs4, other crustaceans1 and brine shrimps2, bivalve and univalve molluscs1, 2, polychaete worms1, 2, spiders1 and small pieces of seaweed4. Breeding site The nest is a shallow scrape1 positioned near water on bare earth or in sparse vegetation1, often on slightly raised ground5 and partly sheltered by plants5 or near conspicuous objects such as grass clumps or shrubs2. The species nests in semicolonial groups, with nests spaced between 2 and 5 m (western Paleartic)5 or more than 20 m apart (up to 80 m)1. Management information Shallowly flooding a previously dry habitat at Owens Lake, California, was found to attract more breeding pairs to the area and had the effect of extending the nesting season by c.1 month11. At Batiquitos Lagoon, California, creating new nesting areas from dredging spoils (e.g. coarse-grained sand and shell fragments) attracted more breeding pairs and non-breeding individuals, possibly because the new areas were covered with less debris and a smaller amount of tall vegetation than older sites12. In the Salt Plains National Wildlife Refuge, Oklahoma, there is evidence that nests adjacent to herbaceous and shrub vegetation suffer significantly lower losses to flooding but significantly higher losses to mammalian predation than those 500 or 1,000 m away1, 4. In the same area artificial nest ridges (made by ploughing) and nest mounds constructed from existing materials (gravel, sand and clay) were found not to reduce nest flooding13. Predator exclusion experiments from nesting areas using electric fences in the Salt Plains National Wildlife Refuge, Oklahoma13 and in Monterey Bay, California were unsuccessful in increasing the number of chicks fledged per male16 or significantly reducing annual egg predation (this was probably still limited by avian predation)13, although in Monterey Bay the hatching success of nests within the exclosure did increase16 and the overall nesting success was higher for breeding pairs within the Salt Plains National Wildlife Refuge exclosures13. At Monterey Bay the predator exclosures were also not successful in increasing adult breeding numbers, and the mortality of incubating adults was actually higher within the enclosures than outside them16. On beaches in Santa Barbara, California, erecting protective barriers to direct tourist foot-traffic away from sections of upper beach was found to decrease disturbance of the species by more than half and attracted increased numbers of breeding pairs, although the distribution of the species on the beach contracted to within the protected area15.
Systems
- Terrestrial
- Freshwater
- Marine