The leg of passerine birds contains an additional special adaptation for perching. The toes have no webbing or joining, but in some cotingas, the second and third toes are united at their basal third. This arrangement enables passerine birds to easily perch upright on branches. The foot of a passerine has three toes directed forward and one toe directed backward, called anisodactyl arrangement, and the hind toe ( hallux) joins the leg at approximately the same level as the front toes. The smallest passerine is the short-tailed pygmy tyrant, at 6.5 cm (2.6 in) and 4.2 g (0.15 oz). The superb lyrebird and some birds-of-paradise, due to very long tails or tail coverts, are longer overall. The heaviest and altogether largest passerines are the thick-billed raven and the larger races of common raven, each exceeding 1.5 kg (3.3 lb) and 70 cm (28 in). Most passerines are smaller than typical members of other avian orders. Pterylosis or the feather tracts in a typical passerine The terms "passerine" and "Passeriformes" are derived from the scientific name of the house sparrow, Passer domesticus, and ultimately from the Latin term passer, which refers to sparrows and similar small birds. Most passerines are omnivorous, while the shrikes are carnivorous. The passerines contain several groups of brood parasites such as the viduas, cuckoo-finches, and the cowbirds. Passerines are divided into three suborders: Acanthisitti (New Zealand wrens), Tyranni (suboscines), and Passeri (oscines). With more than 140 families and some 6,500 identified species, Passeriformes is the largest order of birds and among the most diverse orders of terrestrial vertebrates, representing 60% of birds. Sometimes known as perching birds or songbirds, passerines are distinguished from other orders of birds by the arrangement of their toes (three pointing forward and one back), which facilitates perching. Song of a purple-crowned fairywren ( Malurus coronatus)Ī passerine ( / ˈ p æ s ə r aɪ n/) is any bird of the order Passeriformes ( / ˈ p æ s ə r ɪ f ɔːr m iː z/ from Latin passer 'sparrow' and formis '-shaped'), which includes more than half of all bird species.