Passerine
General info
A passerine (/ˈpæsəraɪn/) is any bird of the order Passeriformes (/ˈpæsərɪfɔːrmiːz/; from Latin passer ‘sparrow’ and formis ‘-shaped’), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by the arrangement of their toes (three pointing forward and one back), which facilitates perching.
With more than 140 families and some 6,500 identified species, Passeriformes is the largest clade of birds and among the most diverse clades of terrestrial vertebrates, representing 60% of birds. Passerines are divided into three clades: Acanthisitti (New Zealand wrens), Tyranni (suboscines), and Passeri (oscines or songbirds). The passerines contain several groups of brood parasites such as the viduas, cuckoo-finches, and the cowbirds. Most passerines are omnivorous, while the shrikes are carnivorous.
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.
Description
The order is divided into three suborders, Tyranni (suboscines), Passeri (oscines or songbirds), and the basal Acanthisitti.
Oscines have the best control of their syrinx muscles among birds, producing a wide range of songs and other vocalizations, though some of them, such as the crows, do not sound musical to human beings.Some, such as the lyrebird, are accomplished mimics.
The New Zealand wrens are tiny birds restricted to New Zealand, at least in modern times; they were long placed in Passeri.
Most passerines are smaller than typical members of other avian orders.
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).
The superb lyrebird and some birds-of-paradise, due to very long tails or tail coverts, are longer overall.
The smallest passerine is the short-tailed pygmy tyrant, at 6.5 cm (2.6 in) and 4.2 g (0.15 oz).
Anatomy
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. This arrangement enables passerine birds to easily perch upright on branches. The toes have no webbing or joining, but in some cotingas, the second and third toes are united at their basal third.
The leg of passerine birds contains an additional special adaptation for perching. A tendon in the rear of the leg running from the underside of the toes to the muscle behind the tibiotarsus will automatically be pulled and tighten when the leg bends, causing the foot to curl and become stiff when the bird lands on a branch. This enables passerines to sleep while perching without falling off.
Most passerine birds have 12 tail feathers but the superb lyrebird has 16, and several spinetails in the family Furnariidae have 10, 8, or even 6, as is the case of Des Murs’s wiretail. Species adapted to tree trunk climbing such as woodcreeper and treecreepers have stiff tail feathers that are used as props during climbing. Extremely long tails used as sexual ornaments are shown by species in different families. A well-known example is the long-tailed widowbird.
Eggs and nests
The chicks of passerines are altricial: blind, featherless, and helpless when hatched from their eggs. Hence, the chicks require extensive parental care. Most passerines lay colored eggs, in contrast with nonpasserines, most of whose eggs are white except in some ground-nesting groups such as Charadriiformes and nightjars, where camouflage is necessary, and in some parasitic cuckoos, which match the passerine host’s egg. The vinous-throated parrotbill has two egg colors, white and blue, to deter the brood parasitic common cuckoo.
Clutches vary considerably in size: some larger passerines of Australia such as lyrebirds and scrub-robins lay only a single egg, most smaller passerines in warmer climates lay between two and five, while in the higher latitudes of the Northern Hemisphere, hole-nesting species like tits can lay up to a dozen and other species around five or six. The family Viduidae do not build their own nests, instead, they lay eggs in other birds’ nests.