Passerine

A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. They are perching birds. Most of them are small in size, and most can sing very well. Their main suborder is the Passeri, the songbirds.
Adaptations
The passerines have a number of adaptations which, taken together, have made them highly successful, with many species around the world.
Perching. All passerines have four toes on each foot. Three of the toes point forwards. The other toe points backwards. This means that passerines can easily hold onto trees or rocks. Because of this, they are also known as perching birds. A tendon in the rear of the leg makes the foot curl and grip when the bird lands on a branch. This is more than just a convenience for the birds: it is a tendon locking mechanism so they can sleep without falling off.
All passerine chicks are born in an undeveloped state (altricial): they need parental help. Their eyes are closed, and they are bald, with little or no down. They cannot leave the nest, and must be fed by the parents. The advantage of this is that their brains grow larger during the fledgling stage. In birds which leave the nest early, their brains depend mainly on material in the egg. Passerines have significantly large brains compared to body size, and many passerines are comparatively intelligent.
The use of song for communication. This is the most obvious adaptation.
Almost all passerines have 12 tail feathers. This is a basal trait, a feature inherited from their past. It leads biologists to think this large group originally had one common ancestor.
Evolution
Evidence on their evolution comes from comparative anatomy, the fossil record and molecular biology.
It is thought that the first passerines evolved in the southern continent of Gondwana in the Palaeogene. This might have taken place around the Upper Palaeocene some 60-55 mya. The latest opinion on passerine evolution is that that passerines originated on the Australian landmass ~47 mya.
The early fossil record is poor because the first Passeriformes were on the small side, and their delicate bones did not preserve well. Two specimens from Queensland, Australia are fossil bone fragments clearly recognizable as passeriform. They are two species of about 10 and 20 cm in overall length. This proves that some 55 mya, barely into the early Eocene, early perching birds were recognizably distinct. It also suggests that the origin of this great order of birds was in the southern continent.
Taxonomy
There are three sub-orders: Acanthisitti, Tyranni and Passeri. There are only two bird species in the sub-order Acanthisitti. They are known as New Zealand wrens. The sub-order Tyranni are also known as the suboscines. Many of these birds are found in tropical areas. The sub-order Passeri has the most bird species. They are also known as the oscines.
Suborder Acanthisitti
Acanthisittidae: New Zealand "wrens"
Suborder Tyranni
Suboscines
Infraorder Eurylaimides broadbills and allies
Infraorder Tyrannides - New World suboscines
Suborder Passeri
Songbirds or oscines
Basal Passeri - the oldest 'true' song birds. They live in Australia.
Menuridae: lyrebirds
Atrichornithidae: scrub-birds
Superfamily Meliphagoidea - mainly insectivores and nectarivores, distribution centered on Australo-Melanesian region extending into surroundings, notably the Pacific.
Superfamily Corvida - a highly diverse group of global distribution, but most plentiful in the Australasian region and surroundings. The oldest truly globally successful group of passerines, they include among them what may well be the most intelligent and the most spectacular of the order.
Melanocharitidae: berrypeckers and longbills.
Callaeidae: New Zealand wattlebirds
Stitchbirds
Cnemophilidae: satinbirds
Neosittidae: sittellas
Vireonidae: vireos
Campephagidae: cuckoo-shrikes and trillers
Pachycephalidae: whistlers and allies
Oriolidae: orioles and figbirds
Paramythiidae: tit berrypecker and crested berrypecker.
Artamidae: woodswallows, butcherbirds, currawongs and Australian Magpie
Malaconotidae: puffback shrikes, bush shrikes, tchagras and boubous
Platysteiridae: wattle-eyes
Aegithinidae: ioras
Pityriaseidae: Bornean bristlehead.
Prionopidae: helmetshrikes and woodshrikes
Vangidae: vangas
Dicruridae: drongos
Monarchidae: monarch flycatchers
Rhipiduridae: fantails
Paradisaeidae: birds of paradise
Corcoracidae: white-winged chough and apostlebird
Laniidae: shrikes
Corvidae: crows, ravens and jays
Corvoidea (?)
Passeri
Ptilonorhynchoidea: bowerbirds and Australian treecreepers
Logrunners and pseudo-babblers
Petroicidae: Australian robins
Rockfowl, rock-jumpers and rail-babblers
Regulidae: kinglets
Hyliotas
Irenidae: fairy-bluebirds
Chloropseidae: leafbirds
Infraorder Passerida
Superfamily Sylvioidea - mostly insectivores, distribution centered on the Indo-Pacific region. Few occur in the Australian region and fewer still in the Americas. Usually sleek and drab birds, few have pronounced sexual dimorphism.
Alaudidae: larks
Hirundinidae: swallows and martins
Phylloscopidae: leaf-warblers and allies.
Aegithalidae: long-tailed tits or bushtits
Cettiidae: ground-warblers and allies
Megaluridae: grass-warblers and allies
"Bernieridae": Malagasy warblers. A new family.
Acrocephalidae: marsh- and tree-warblers
Pycnonotidae: bulbuls
Cisticolidae: cisticolas and allies
Sylviidae: "true warblers" and parrotbills.
Zosteropidae: white-eyes
Timaliidae: (Old World) babblers.
Sylvioidea (?)
Superfamily Muscicapoidea - mostly insectivores, near-global distribution centered on Old World tropics. One family endemic to Americas. Nearly absent (except introductions) from the Australian region. Usually rather stocky for their size, most are quite dark and dull though Sturnidae are commonly iridescent and/or colorful. Sexual dimorphism often absent, sometimes pronounced.
Cinclidae: dippers
Muscicapidae: Old World flycatchers and chats.
Turdidae: thrushes and allies.
Buphagidae: oxpeckers. Formerly usually included in Sturnidae.
Sturnidae: starlings and possibly Philippine creepers.
Mimidae: mockingbirds and thrashers
Superfamily Certhioidea - wrens and allies
Sittidae: nuthatches
Tichodromadidae: wallcreepers
Certhiidae: treecreepers
Salpornithidae: spotted creeper
Troglodytidae: wrens
Polioptilidae: gnatcatchers
Superfamily Passeroidea - mostly herbivores including many seed-eaters, near-global distribution centered on Palearctic and Americas. Includes the Nine-primaried oscines (probably a subclade). A very high proportion of colorful and highly sexually dimorphic forms.