Columbidae (pigeons, doves; class Aves, order Columbiformes) A family of small to large birds that have soft, dense plumage, plump bodies, and small heads. The bill is short to medium with a bare cere, and the legs are generally short. Most are arboreal, though some are terrestrial, and feed mainly on seeds and fruit, regurgitating a milky fluid for their young. Green pigeons (23 species of Treron, mainly bright green birds, some with yellow, orange, and mauve markings, found in Africa, southern Asia, and Indonesia) feed on figs; their gizzards can grind up the seeds they ingest. Pigeons usually nest in a tree or on a ledge. They are gregarious, and many are migratory. Fruit doves (49 species of Ptilinopus, found in southern Asia, Australia, and the Pacific islands) are mainly green or sometimes orange with areas of contrasting colours. Quail doves (13 species of Geotrygon, found in Central and S. America) live in forests. Imperial pigeons (36 species of Ducula, found in southern Asia, Australasia, and the Pacific region) are arboreal and feed on fruit and leaves. There are 40 genera in the family, with 296 species, found worldwide. The 51 species of Columba comprise the typical pigeons (C. livia (rock dove) is the wild ancestor of the domestic pigeon) and there are seven species of Columbina (ground doves) in America. Ectopistes migratorius (passenger pigeon) is one of many extinct species. During the second half of the 20th century Streptopelia decaocto (collared dove), one of 16 Streptopelia species (turtle doves), has spread westward from Asia to colonize Europe.