True sparrows, the Old World sparrows in the family Passeridae, are small passerine birds. As eight or more species nest in or near buildings, and the House Sparrow and Eurasian Tree Sparrow in particular inhabit cities in large numbers, sparrows may be the most familiar of all wild birds.
Characteristics and classification
Generally, sparrows tend to be small, plump brown-grey birds with short tails and stubby, powerful beaks. The differences between sparrow species can be subtle. They are primarily seed-eaters, though they also consume small insects. A few species scavenge for food around cities and, like gulls or pigeons, will happily eat virtually anything in small quantities. Members of this family range in size from the Chestnut Sparrow (Passer eminibey), at 11.4 cm (4.5 inches) and 13.4 g, to the Parrot-billed Sparrow (Passer gongonensis), at 18 cm (7 inches) and 42 g (1.5 oz). Sparrows are physically similar to other seed-eating birds, such as finches, but have a vestigial dorsal outer primary feather and an extra bone in the tongue.
The Old World true sparrows are indigenous to Europe, Africa and Asia. In Australia and the Americas, early settlers imported some species which quickly naturalised, particularly in urban and degraded areas. House Sparrows, for example, are now found throughout North America, in every state of Australia except Western Australia, and over much of the heavily populated parts of South America.
Some authorities previously classified the related estrildid finches of the Old World tropics and Australasia as members of the Passeridae. Like the true sparrows, the estrildid finches are small, gregarious and often colonial seed-eaters with short, thick, but pointed bills. They are broadly similar in structure and habits, but tend to be very colourful and vary greatly in their plumage. There are about 140 species. The 2008 Christidis and Boles taxonomic scheme lists the estrildid finches as the separate family Estrildidae, leaving just the true sparrows in Passeridae.
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