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Category:Taxonomy - BirdForum Opus

Common Ostrich, the largest living bird, flightless
Photo by Leon
Vervain Hummingbird, one of the smallest birds on earth
Photo by Juan Estevez
Aves (all birds)


All birds are placed in the zoological class Aves. They are vertebrate, warm-blooded animals with wings, two feet and they lay eggs. They are characterised by some unique features:

  • Feathers
  • Laying of hard-shelled eggs
  • Beak without teeth
  • High metabolic rate
  • Strong but lightweight skeleton
  • Heart with four chambers
  • Unique respiratory and digestive systems

The accepted number of species varies in the different sources, but there are about 10'000 species worldwide, found on all continents.

The largest bird ever described had a wing span of about 5.2 meters and lived 5-10 million years ago[2]. The smallest probably is the Bee Hummingbird.


A number of traits are shared by both fossil dinosaurs and modern birds, such as the possession of a synsacrum and an open acetabulum have led to birds being classified within the Dinosauria. Birds are considered theropod dinosaurs, particularly maniraptorans, a group of theropods that includes famous fossil dinosaurs such as Velociraptor and Oviraptor.

Below is a list of all the orders in the class Aves that are recognized by Opus, which at this level of taxonomy follows the Clements Checklist of Birds of the World[1]. If you are looking for an order that you cannot find in this list, there may be a link to it at the end of this page; in the linked page you should find the families associated with that order as well as a link to the order under which those families are currently listed in Opus. Just typing in the name in the search field at the left probably will also find information about which orders currently hold the species associated with the order you are looking for

Class Aves viewedit
Struthioniformes Ostriches
Rheiformes Rheas
Tinamiformes Tinamous
Casuariiformes Cassowaries and Emu
Apterygiformes Kiwis
Anseriformes Ducks, geese and allies
Galliformes Fowl and allies
Phoenicopteriformes Flamingos
Podicipediformes Grebes
Columbiformes Pigeons and allies
Mesitornithiformes Mesites
Pterocliformes Sandgrouse
Otidiformes Bustards
Musophagiformes Turacos
Cuculiformes Cuckoos and allies
Caprimulgiformes Nightjars, frogmouths, swifts and hummingbirds
Opisthocomiformes Hoatzin
Gruiformes Cranes, rails and allies
Charadriiformes Shorebirds, gulls and allies
Eurypygiformes Kagu and Sunbittern
Phaethontiformes Tropicbirds
Gaviiformes Loons / divers
Sphenisciformes Penguins
Procellariiformes Petrels, shearwaters and allies
Ciconiiformes Storks
Suliformes Boobys, Frigatebirds and Coromorants
Pelecaniformes Pelicans, Herons and Ibises
Cathartiformes New World Vultures
Accipitriformes Buzzards, Eagles, Kites, Hawks, Vultures
Strigiformes Owls
Coliiformes Mousebirds
Leptosomiformes Cuckoo-Roller
Trogoniformes Trogons and allies
Bucerotiformes Hornbills, hoopoe and woodhoopoes
Coraciiformes Kingfishers, rollers and allies
Galbuliformes Jacamars and allies
Piciformes Woodpeckers and allies
Cariamiformes Seriemas
Falconiformes Falcons and Caracaras
Psittaciformes Parrots and allies
Passeriformes Passerines / perching birds (5,000+ species)


  1. Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2018. The eBird/Clements checklist of birds of the world: v2018. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
  2. Birdforum discussion about the so far largest bird described for planet earth