Birds are two-legged, warm-blooded, egg-laying vertebrates which have a beak with no teeth, a four-chambered heart, a high metabolic rate, feathers, wings and a lightweight skeleton. These latter adaptions allow most birds to fly. Flight is the primary means of locomotion for most bird species and it distinguishes birds from most other vertebrates. The ability to fly allows birds to allude predators and to search large distances for both food and mates. Flight also allows many bird species to take advantage of global differences in the seasonal climates by migrating from one region to another as the seasons change. Flying has allowed birds to develop survival strategies, often unavailable to other animals so it is not surprising that birds are found in a variety of habitats on all seven of the world’s continents. Some birds have even adapted to live on the world’s oceans or within them, sometimes only coming ashore to breed.

There are approximately 10,000 different species of birds on the earth today. Scientist have classified these bird species into more than 200 different families which in turn are organized into 29 orders of birds. Birds are believed to have evolved from a dinosaur ancestor and are consider the closest living relative of dinosaurs. The fossil evidence suggests the early ancestor of birds may have been arboreal and had the ability to glide. Once the ability to fly evolved, birds, as a group, radiated into many different species occupying a wide range of ecological niches with the highest bird diversity occurring in the tropical regions of the world.

Unfortunately, human activity threatens about 1,200 bird species with extinction. Nearly 200 species of birds have already become extinct due to human activity, many of these flightless birds that were found on islands with no terrestrial predators.

Although flight was an evolutionary advantage for most birds, a few species of birds have actually lost the ability to fly. There seem to be three situations where flightless has tended to evolve. The best example of the first, would be penguins. Living in water made it necessary to trade flying for swimming. Or, to look at it another way, penguins can still fly, they just fly in water instead of air. The second situation where flightless birds seem to evolve is on isolated islands which have no land predators. Other examples of flightless birds are the unusually large birds, notably the Ostrich (Struthio camelus), Cassowary (Casuarius sp.), Emu (Dromaius novaehollandiae) and Rhea (Rhea sp.), where there appears to have been an evolutionary tradeoff of flight for large size.

Birds have a poor sense of smell and mainly rely on their sight and hearing to find food, detect predators and to find mates. Because of its importance for flight, vision is the most important sense in most birds. The most developed parts of the brain, in most birds, are the areas that control the flight-related functions and vision. Birds have both large nervous systems and large eyes relative to their body size. Within the animal kingdom, birds have the largest eyes relative to their size. Some birds can actual perceive ultraviolet light, as they are tetrachromatic, possessing ultraviolet sensitive cone cells in the eye as well as cone cells sensitive to green, red and blue light. In contrast, humans lack this ability since the lens of the human eye blocks most light of that wavelength range and most humans do not have ultraviolet sensitive cone cells. Nocturnal birds have eyes with large corneas relative to the eye’s length which optimizes their visual sensitivity at night. Birds can also detect very slow movement, such as the movement of the sun and the constellations across the sky, which is imperceptible to humans. This ability is believed to be used by migrating birds to orient themselves. Studies have suggested that some migratory birds can detect the earth’s magnetic fields with theirs eyes and also use this information to orient themselves during migrations.

Birds – Aves

Struthioniformes

– Africa and Australasia; 2 species

Struthionidae: Ostrich

Rheiformes

– South America; 2 species

Rheidae: rheas

Tinamiformes

– South America; 45 species

Tinamidae: tinamous

Casuariiformes

– Australasia; 4 species

Casuariidae: cassowaries

Dromaiidae: Emu

Apterygiformes

– Australasia; 5 species

Apterygidae: kiwis

Anseriformes

– Worldwide; 150 species

Anhimidae: screamers

Anseranatidae: Magpie-goose

Anatidae: ducks, geese, and swans

Galliformes

– Worldwide; 250 species

Megapodidae: megapodes

Cracidae: chachalacas, curassows, and guans

Phasianoidea: pheasants and allies

Odontophoridae: New World quail

Numididae: guineafowl

Phasianidae: pheasants and relatives

Podicipediformes

– Worldwide; 19 species; sometimes grouped with Phoenicopteriformes

Podicipedidae: grebes

Phoenicopteriformes

– Worldwide; 6 species

Phoenicopteridae: flamingos

Mesitornithiformes

– Madagascar, Neotropics, New Caledonia; 5 species

Mesitornithidae: mesites

Rhynochetidae: Kagu

Eurypygidae: Sunbittern

Pteroclidiformes

– Africa, Europe, Asia; 16 species; sometimes grouped with Columbiformes

Pteroclididae: sandgrouse

Columbiformes

– Worldwide; 300 species

Columbidae: pigeons and doves

Phaethontiformes

– Oceanic; 3 species

Phaethontidae: tropicbirds

Caprimulgiformes

– Worldwide; 90 species

Steatornithidae: Oilbird

Podargidae: frogmouths

Nyctibiidae: potoos

Caprimulgidae: nighthawks and nightjars

Eurostopodidae: eared-nightjars

Apodiformes

– Worldwide; 400 species

Trochilidae: hummingbirds

Apodidae: swifts

Hemiprocnidae:treeswifts

Aegotheliformes

Oceania; 10 species; sometimes grouped with Apodiformes

Aegothelidae: owlet-nightjars

Cuculiformes

Worldwide; 126 species

Cuculidae: cuckoos and relatives

Opisthocomiformes

– South America; 1 species

Opisthocomidae: Hoatzin

Musophagiformes

– Africa; 23 species

Musophagidae: turacos and relatives

Gruiformes

– Worldwide; 191 species

Otididae: bustards

Grui: cranes and allies

Gruidae: cranes

Aramidae: Limpkin

Psophiidae: trumpeters

Ralli: rails and allies

Rallidae: rails and relatives

Sarothruridae: flufftails

Heliornithidae: finfoots

Gaviiformes

– North America, Eurasia; 5 species

Gaviidae: loons

Sphenisciformes

– Antarctic and southern waters; 17 species

Spheniscidae: penguins

Procellariiformes

– Pan-oceanic; 120 species

Diomedeidae: albatrosses

Procellariidae: petrels and relatives

Pelecanoididae: diving petrels

Hydrobatidae: storm petrels

Ciconiiformes

– Worldwide; 19 species

Ciconiidae: storks

Pelecaniformes

– Worldwide; 108 species

Balaenicipitidae: Shoebill

Scopidae: Hamerkop

Pelecanidae: pelicans

Ardeidae: herons and relatives

Threskiornithidae: ibises and spoonbills

Suliformes

– Worldwide; 59 species

Phalacrocoracidae: cormorants and shags

Fregatidae: frigatebirds

Sulidae: boobies and gannets

Anhingidae: darters

Charadriiformes

– Worldwide; 350 species

Scolopacidae: sandpipers and relatives

Thinocori: jacana-like waders

Rostratulidae: painted snipes

Pluvianidae: Egyptian Plover

Jacanidae: jacanas

Thinocoridae: Seedsnipes

Pedionomidae: Plains-wanderer

Turnicidae: buttonquail

Lari: gulls and allies

Laridae: gulls

Rhynchopidae: skimmers

Sternidae: terns

Alcidae: auks

Stercorariidae: skuas and jaegers

Glareolidae: coursers and pratincoles

Dromadidae: Crab-Plover

Chionidi: thick-knees and allies

Burhinidae: thick-knees and relatives

Chionididae: sheathbills

Pluvianellidae: Magellanic Plover

Ibidorhynchidae: Ibisbill

Recurvirostridae: avocets and stilts

Haematopodidae: oystercatchers

Charadriidae: plovers and lapwings

Accipitriformes

– Worldwide; 200 species

Cathartidae: New World vultures

Pandionidae: Osprey

Accipitridae: hawks, eagles, buzzards, harriers, kites and Old World vultures

Sagittaridae: Secretarybird

Strigiformes

– Worldwide; 130 species

Tytonidae: barn owls

Strigidae: true owls

Coliiformes[edit]

Sub-Saharan Africa; 6 species.

Coliidae: mousebirds

Trogoniformes

Sub-Saharan Africa, Americas, Asia; 35 species.

Trogonidae: trogons and quetzals

Coraciiformes

– Worldwide; 144 species

Meropidae: bee-eaters

Coraciidae: rollers

Brachypteraciidae: ground rollers

Todidae: todies

Momotidae: motmots

Alcedines: kingfishers

Alcedinidae: river kingfishers

Halcyonidae: tree kingfishers

Cerylidae: water kingfishers

Bucerotiformes

= Old World, New Guinea; 64 species

Bucerotidae: hornbills

Upupidae: Hoopoe

Phoeniculidae: woodhoopoes

Leptosomatiformes

– Madagascar; 1 species

Leptosomatidae: Cuckoo-roller

Piciformes

– Worldwide except Australasia; 400 species

Galbulidae: jacamars

Bucconidae: puffbirds

Lybiidae: African barbets

Megalaimidae: Asian barbets

Ramphastidae: toucans

Semnornithidae: Toucan barbets

Capitonidae: American barbets

Picidae: woodpeckers

Indicatoridae: honeyguides

Falconiformes

– Worldwide; 60 species

Falconidae: falcons and relatives

Cariamiformes

– South America; 2 species

Cariamidae: seriemas

Psittaciformes

– Pan-tropical, southern temperate zones; 330 species

Nestoridae: Kea and kakas

Strigopidae: Kakapo

Cacatuidae: cockatoos

Psittacidae: African and American parrots

Psittrichasiidae: Pesquet’s parrot, vasa parrots

Psittaculidae: Australasian parrots

Passeriformes

– Worldwide; 5000 species

Acanthisittidae: New Zealand wrens

Eurylaimidae: broadbills

Philepittidae: asities

Pittidae: pittas

Sapayoidae: Sapayoa

Tyrannidae: tyrant flycatchers

Tityridae: becards and tityras

Furnariidae: ovenbirds

Thamnophilidae: antbirds

Formicariidae: ground antbirds

Rhinocryptidae tapaculos

Grallariidae: antpittas

Conopophagidae: gnateaters

Cotingidae: cotingas

Pipridae: manakins

Melanopareiidae: crescent-chests

Passeri: oscines

Atrichornithidae: scrub-birds

Menuridae: lyrebirds

Superb Lyrebird (Menura novaehollandiae)

Albert’s Lyrebird (Menura alberti)

Alaudidae: larks

Hirundinidae: swallows and martins

Motacillidae: wagtails and pipits

Campephagidae: cuckoo-shrikes

Eupetidae: Rail-Babbler

Pycnonotidae: bulbuls

Regulidae: kinglets

Hyliotidae: hyliotas

Chloropseidae: leafbirds

Aegithinidae: ioras

Ptilogonatidae: silky-flycatchers

Bombycillidae: waxwings

Hypocoliidae: Hypocolius

Dulidae: Palmchat

Cinclidae: dippers

Troglodytidae: wrens

Donacobiidae: Donacobius

Mimidae: mockingbirds and thrashers

Prunellidae: accentors

Turdidae: thrushes and relatives

Cisticolidae: cisticolas and relatives

Sylviidae:true warblers

Stenostiridae: fairy warblers

Macrosphenidae: African warblers

Cettiidae: bush warblers

Phylloscopidae: leaf warblers

Megaluridae: grass warblers

Acrocephalidae: marsh warblers

Bernieridae: malagasy warblers

Pnoepygidae: pygmy wren-babblers

Polioptilidae: gnatcatchers

Muscicapidae: flycatchers and relatives

Platysteiridae: wattle-eyes and batises

Petroicidae: Australasian robins

Pachycephalidae: whistlers and relatives

Colluricinclidae: shrike-thrushes and relatives

Picathartidae: rockfowl

Chaetopidae: rock-jumpers

Timaliidae: babblers and relatives

Panuridae: Bearded Reedling

Nicatoridae: nicators

Pomatostomidae: Australasian babblers

Orthonychidae: logrunners

Cinclosomatidae: whipbirds and quail-thrushes

Aegithalidae: bushtits

Maluridae: Australasian wrens

Neosittidae: sittellas

Climacteridae: Australasian treecreepers

Paridae: chickadees and true tits

Sittidae: nuthatches

Tichodromidae: Wallcreeper

Certhiidae: treecreepers

Rhabdornithidae: Philippine creepers

Remizidae: penduline tits

Nectariniidae: sunbirds

Melanocharitidae: berrypeckers

Paramythiidae: painted berrypeckers

Dicaeidae: flowerpeckers

Dasyornithidae: bristlebirds

Pardalotidae: pardalotes

Acanthizidae: Australasian warblers

Zosteropidae: white-eyes

Promeropidae: sugarbirds

Meliphagidae: honeyeaters and relatives

Notiomystidae: Stitchbird

Oriolidae: Old World orioles

Irenidae: fairy-bluebirds

Laniidae: shrikes

Malaconotidae: bushshrikes and relatives

Prionopidae: helmetshrikes and relatives

Vangidae: vangas

Dicruridae: drongos

Rhipiduridae: fantails

Monarchidae: monarch flycatchers

Callaeidae: wattlebirds

Corcoracidae: mudnesters

Artamidae: woodswallows and butcherbirds

Pityriaseidae: bristlehead

Paradisaeidae: birds-of-paradise

Cnemophilidae: satinbirds

Ptilonorhynchidae: bowerbirds

Corvidae: jays and crows

Sturnidae: starlings and mynas

Buphagidae: oxpeckers

Passeridae: Old World sparrows

Ploceidae: weavers and relatives

Estrildidae: weaver finches

Viduidae: whydahs and indigobirds

Vireonidae: vireos and relatives

Fringillidae: finches and relatives

Urocynchramidae: Pink-tailed Bunting

Peucedramidae: Olive Warbler

Parulidae: wood warblers

Coerebidae: Bananaquit

Thraupidae: tanagers and relatives

Emberizidae: Old World buntings and New World sparrows

Cardinalidae: cardinals, grosbeaks, and New World buntings

Icteridae: New World blackbirds and New World orioles