|Great egret (Ardea alba)|
Birders in Canada and the United States refer to several families of long-legged wading birds in semi-aquatic ecosystems as waders. These include the families Phoenicopteridae (flamingos), Ciconiidae (storks), Threskiornithidae (ibises and spoonbills), Ardeidae (herons, egrets, and bitterns), and the extralimital families Scopidae (hamerkop) and Balaenicipitidae (shoebill) of Africa. Elsewhere in the world, the word refers to what North Americans call a "shorebird", various families of the order Charadriiformes. In the past all of these families were classified in the order Ciconiiformes based on overall similarity in anatomy and ecology, as well as some molecular data. However recent genomic studies have found that this group to be polyphyletic, with flamingos being more closely related to grebes while ibises, herons, the hamerkop and shoebill to be more closely related to pelicans. As a result of these changes flamingos are placed in their own order Phoenicopteriformes and Ciconiiformes solely just restricted to the storks. The rest of the waders have been reclassified into the order Pelecaniformes.
In some field guides, the families Gruidae (cranes) and Aramidae (limpkin) are also considered to be waders too. However unlike the previously mentioned families, cranes and the limpkin were never thought to be closely to the heron-like birds and have always been classified as members of the order Gruiformes.
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- Wetmore, A. (1960). "A classification for the birds of the world" (PDF). Smithsonian Miscellaneous Collections. 139 (11): 1–37.
- Sibley, Charles G., and Ahlquist, Jon E.. 1991. Phylogeny and Classification of Birds: A Study in Molecular Evolution. Yale University Press. ISBN 0-300-04085-7. Accessed January 4, 2021.
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- International Ornithological Committee (July 25, 2020). "Ibis, spoonbills, herons, hamerkop, shoebill, pelicans". IOC World Bird Names: Version 2.11. WorldBirdNames.org. Retrieved January 24, 2021.
- Mackenzie, J. (1997). WADING BIRDS (Birds of the World Series). Toronto: Key Porter Books. p. 1-144 pages. ISBN 1550137999.