Gruiform

Habitat

Gruiform birds live in a variety of habitats, from water and marshes to arid plains. The most aquatic are the finfoots and coots (Fulica). The former live along slow-flowing streams where heavy overhanging vegetation affords them cover, the latter on more open water. Most rails live in saltwater or freshwater marshes. The limpkin (Aramus guarauna) is essentially a marsh bird; in Florida it inhabits the sawgrass marshes and cypress swamps of the Everglades. Cranes bridge the gap between marsh and dryland birds, nesting in marshes but occurring in open plains and cultivated fields on migration and in winter. The sun bittern prefers wooded muddy riverbanks but also occurs in woods well away from water. Trumpeters, mesites, the kagu, and some rails live in forest and dense brush. The remaining gruiform families inhabit more-open country: the seriemas (or cariamas) of South America favour grassland or hot dusty plains with scattered bushes; the Old World bustards, button quails, and the plains wanderer prefer open, grassy plains, although they will accept old pastures and cultivated fields.

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Food habits

Corresponding to the wide variety of habitats utilized by the gruiforms is the great diversity of food taken by them. In general, more animal than vegetable food is taken, but the gruiforms as a group are omnivorous. Coots and gallinules consume much aquatic vegetation. Finfoots live largely on mollusks, frogs, and small fish. The limpkin has a more specialized diet, consisting chiefly of certain large snails, which are broken open at certain favourite feeding stations that contain telltale piles of broken shells. The limpkins’ near relatives, the cranes, eat almost any animal food, including rats, mice, moles, lemmings, lizards, snakes, frogs, tadpoles, snails, and a variety of insects. On its wintering grounds in Texas, the whooping crane (Grus americana), an endangered species, lives largely on crustaceans. The sandhill crane includes berries and grass in its otherwise animal diet on the northern tundra and gleans some plant material from old potato and grain fields on its southern wintering grounds. The Asiatic cranes that winter in Japan (such as the hooded crane, Grus monacha, and the white-naped crane, G. vipio) glean grain in rice paddies, and Japanese cranes in Hokkaido are fed corn (maize) by the local farmers. Cranes use their powerful bills for digging in the ground to get at bulbs and roots below the surface, and a similar foraging action has been noted for the gray-necked wood rail (Aramides cajanea) of tropical America, which probes in ground debris, flicking it aside with the bill. Rails as a group, like cranes, are omnivorous, though the bulk of their diet consists of small marsh animals, such as snails, crustaceans, frogs, and water insects. The purple swamphen (Porphyrio porphyrio), a vegetarian, often has a feeding platform on which it stands and pulls up the surrounding water plants; it also climbs up reeds and eats the flower heads.

The other members of the order have a similar mixed animal-and-vegetable diet, though with the emphasis always on the animal side. Captive kagus can eat meat, whereas captive seriemas readily consume it. Bustards are fond of grasshoppers, and their varied diet also includes dung beetles, termites, centipedes, grass, clover, vegetable crops, and even, in Africa, the gum from the trunks of Acacia trees. The sun bittern stalks insects as a heron stalks fish, stealthily approaching its prey with neck drawn in, then grabbing it with a sudden stabbing thrust of the bill.

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