Waders, called shorebirds (where "wader" is used to refer to long-legged wading birds such as storks and herons), are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas (Stercorariidae), gulls (Laridae), terns (Sternidae), skimmers (Rynchopidae), and auks (Alcidae). Also, the pratincoles (Glareolidae) and the crab plover (Dromadidae), which bear greater resemblance to waders, are closely related to the seabirds.
This leaves about 210 species, most of which are associated with wetland or coastal environments. Many species of Arctic and temperate regions are strongly migratory, but tropical birds are often resident, or move only in response to rainfall patterns. Some of the Arctic species, such as little stint, are amongst the longest distance migrants, spending the non-breeding season in the southern hemisphere.
The majority of species eat small invertebrates picked out of mud or exposed soil. Different lengths of bills enable different species to feed in the same habitat, particularly on the coast, without direct competition for food. Many waders have sensitive nerve endings at the end of their bills which enable them to detect prey items hidden in mud or soft soil. Some larger species, particularly those adapted to drier habitats will take larger prey including insects and small reptiles.
Many of the smaller species found in coastal habitats, particularly but not exclusively the calidrids, are often named as "sandpipers", but this term does not have a strict meaning, since the upland sandpiper is a grassland species.
The smallest member of this group is the least sandpiper, small adults of which can weigh as little as 15.5 grams and measure just over 13 cm (5 inches). The largest species is believed to be the Far Eastern curlew, at about 63 cm (25 inches) and 860 grams (1.9 lb), although the beach thick-knee, is the heaviest at about 1 kg (2.2 lb).
|Wikipedia, the free encyclopedia