Description[edit] A close-up of a male house sparrow Yellow-throated sparrow at Keoladeo National Park, IndiaGenerally, sparrows are small, plump, brown-grey birds with short tails and stubby, powerful beaks. The differences between sparrow species can be subtle. Members of this family range in size from the chestnut sparrow (Passer eminibey), at 11.4 centimetres (4.5 in) and 13.4 grams (0.47 oz), to the parrot-billed sparrow (Passer gongonensis), at 18 centimetres (7.1 in) and 42 grams (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.[2][3] This bone, the preglossale, helps stiffen the tongue when holding seeds. Other adaptations towards eating seeds are specialised bills and elongated and specialised alimentary canals.[4]Taxonomy and systematics[edit] A sparrow chick in Italy Painting of black-winged snowfinchesUnder 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.[4] Some classifications also include the sparrow-weavers (Plocepasser) and several other African genera (otherwise classified among the weavers, Ploceidae)[4] which are morphologically similar to Passer.[5] According to a study of molecular and skeletal evidence by Jon Fjelds 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. They therefore classify it as its own subfamily within Passeridae.[5]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).[4]