Old World sparrow  Old World sparrows are a family of small passerine birds. They are also known as true sparrows, names also used for a particular genus of the family, "Passer". They are distinct from both the American sparrows, in the family Passerellidae, and from a few other birds sharing their name, such as the Java sparrow of the family Estrildidae. Many species nest on buildings and the house and Eurasian tree sparrows, in particular, inhabit cities in large numbers, so sparrows are among the most familiar of all wild birds. They are primarily seed-eaters, though they also consume small insects. Some species scavenge for food around cities and, similarly to gulls or rock doves, will happily eat small quantities of virtually anything. Generally, Old World sparrows are small, plump, brown and 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 and , to the parrot-billed sparrow ("Passer gongonensis"), at and . 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. 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. The family Passeridae was introduced (as Passernia) by the French polymath Constantine Samuel Rafinesque in 1815. 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 morphologically similar to "Passer". 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".