Waders are birds commonly found along shorelines and mudflats that wade in order to forage for food (such as insects or crustaceans) in the mud or sand. They are called shorebirds in North America, where the term "wader" is used to refer to long-legged wading birds such as storks and herons. Waders are members of the order Charadriiformes, which includes gulls, auks and their allies.
There are about 210 species of wader, most of which live in 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 the little stint, are amongst the longest distance migrants, spending the non-breeding season in the southern hemisphere.
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 (5.1 in). The largest species is believed to be the Far Eastern curlew, at about 63 cm (25 in) and 860 grams (1.90 pounds), although the beach thick- knee is the heaviest at about 1 kg (2.2 lb).
In the Sibley-Ahlquist taxonomy, waders and many other groups are subsumed into a greatly enlarged Ciconiiformes order.
