|Dunlin Calidris alpina |
A calidrid wader
|Scientific classification |
Waders, called Shorebirds in North America (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 (Stercoraracidae), gulls (Laridae), terns (Sternidae), skimmers (Rhynchopidae), sheathbill (Chionididae) and auks (Alcidae).
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 Little Stint are amongst the longest distance migrants, wintering in the southern hemisphere
The majority of species eat small invertebrates picked out of the mud or 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. The pratincoles are aerial insect eaters, hunting like swallows.
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 following shows the groups of Charadriiform birds normally classed as waders.
The large family Scolopacidae is often further subdivided into groups of similar birds. These groups do not necessarily consist of a single genus. The approximate number of species is in brackets. The groups are:
In the Sibley-Ahlquist taxonomy, waders and many other groups are subsumed into a greatly enlarged order Ciconiiformes.