Taxonomy
Under the classification used in the Handbook of the Birds of the World (HBW) main groupings of the sparrows are the true sparrows (genus Passer), the snowfinches (typically one genus, Montifringilla), and the rock sparrows (Petronia and the Pale Rockfinch). These groups are similar to each other, and are each fairly homogeneous, especially Passer. Some classifications also include the sparrow-weavers (Plocepasser) and several other African genera otherwise classified among the weavers (Ploceidae) which are similar morphologically. According to a study of molecular and skeletal evidence by Jon Fjeldså and colleagues, the Cinnamon Ibon of the Philippines, previously considered to be a white-eye, is a sister taxon to the sparrows as defined by the HBW, best classified as a subfamily of the Passeridae.
Many early classifications of the sparrows placed them as close relatives of the weavers among the various families of small seed-eating birds, based on the similarity of their breeding behaviour, bill structure, and moult, among other characters. Some, starting with P. P. Suskin in the 1920s, placed the sparrows in the weaver family as the subfamily Passerinae, and tied them to Plocepasser. Another family sparrows were classed with was the finches (Fringillidae).
Some authorities previously classified the related estrildid finches of the Old World tropics and Australasia as members of the Passeridae. Like 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. The 2008 Christidis and Boles taxonomic scheme lists the estrildid finches as the separate family Estrildidae, leaving just the true sparrows in Passeridae.
Despite some resemblance such as the seed-eater's bill and frequently well-marked heads, American sparrows, or New World sparrows, are members of a different family, Emberizidae, which also includes the buntings. The Hedge Sparrow or Dunnock (Prunella modularis) is similarly unrelated. It is a sparrow in name only, a relict of the old practice of calling more types of small birds "sparrows". A few further bird species are also called sparrows, such as the Java Sparrow, an estrildid finch.
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