Orders of Birds

A higher classification of modern birds (June 28, 2019)

Improving sets of DNA sequences are revolutionizing the Avian Tree of Life and call for substantial revisions of  the higher classification of birds, especially the sequence of the Orders (Hackett et al. 2008; Cracraft 2013; Jarvis et al. 2014; Prum et al. 2015; Suh et al. 2015; Kuhl et al. 2020).  The revised sequence of Orders below is a step towards our goal of representing the evolutionary history of the major groups of birds.  Species totals in parentheses are tallied from the IOC World Bird List, 12.1. Thanks to Steve Preddy for the cladogram pdf.  Updates following Kuhl et al. 2020 pending.

 PALAEOGNATHAE Ratites The ratites (paleognaths) are the sister group to the rest of living birds.
 Struthioniformes Ostriches (2)
 Rheiformes Rheas (2)
 Apterygiformes Kiwis (5) Kiwis are sister to tinamous/emus+cassowaries (Cracraft 2013, Prum et al. 2015).
 Casuariiformes Emu, cassowaries (4)
 Tinamiformes Tinamous (46) Tinamou relationships within the ratites are uncertain (Hackett et al. 2008,  Baker et al. 2010, Haddrath and Baker 2012), but are treated provisionally as sister to emus, cassowaries (Prum et al. 2015).
 NEOGNATHAE The neognaths are the sister group to the paleognaths
GALLOANSERES Landfowl (Galliformes) and Waterfowl (Anseriformes) together (Galloanseres) are sister to all other extant non-paleognath birds (Neoaves).
 Galliformes Landfowl: Grouse, quail, pheasants, francolins, guineafowl, moundbuilders (302) Landfowl (Galliformes) are sister to the Waterfowl (Anseriformes).
 Anseriformes Waterfowl: Ducks, geese, swans, screamers (178) Waterfowl (Anseriformes) are sister to the Landfowl (Galliformes).
NEOAVES Neoaves has a basal unresolved polytomy of at least 9 Orders, some of which (e.g. Telluraves,
Aequornithes) are supraordinal groups, and some of which (e.g. Opisthocomiformes) are orders with no close relatives (Prum et al. 2015, Suh et al. 2016).
 Caprimulgiformes Nightjars, frogmouths, potoos, oilbirds (121) The nocturnal caprimulgiform birds and related apodiforms define a  spectacular basal adaptive radiation of Neoaves.
Apodiformes Owlet-nightjars, treeswifts, swifts, hummingbirds (497) Swifts and hummingbirds and their relatives are ancient sister to the Caprimulgiformes and included together by some in that Order (Prum et al. 2015)
Musophagiformes Turacos (23) Turacos are sister to bustards (Otidiformes) and cuckoos (Cuculiformes) (Prum et al. 2015) or to bustards alone (Jarvis et al. 2014).
 Otidiformes Bustards (26) Now in their own Order, the bustards  are sister group to turacos (Musophagiformes)(Jarvis et al. 2014) or cuckoos (Cuculiformes) (Hackett et al. 2008, Prum et al. 2015).
 Cuculiformes Cuckoos (150) Cuckoos are sister to bustards (Otidiformes) (Prum et al. 2015) or the turacos (Musophagiformes) (Jarvis et al. 2014).
 Mesitornithiformes Mesites (3) Now in their own Order, the mesites of Madagascar are sister to sandgrouse (Pterocliformes) and in turn pigeons (Columbiformes) (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Pterocliformes Sandgrouse (16) Sandgrouse are sister to the mesites (Mesitornithiformes) (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Columbiformes Pigeons (351) Pigeons are the sister group to an Old World clade consisting of sandgrouse (Pterocliformes) and the  mesites (Mesitornithiformes). Together they form the clade Columbimorphae at or near the base of Neoaves (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Gruiformes Diverse terrestrial and marshbirds: rails and allies, flufftails, finfoots, cranes, limpkin, and trumpeters (188) Long recognized to be an artificial assemblage of taxa, the revised core Gruiformes represents on the branches of the basal polytomy. This Order now includes 7 families: rails (Rallidae), flufftails (Sarothruridae), finfoots (Heliornithidae),  trumpeters (Psophiidae), cranes (Gruidae), and Limpkin (Aramidae) (Hackett et al. 2008, Prum et al. 2015).
Podicipediformes Grebes (23) Grebes and flamingos (Phoenicopteriformes) are ancient sister taxa and members of the basal polytomy, potentially related to shorebirds (Charadriiformes) (Hackett et al. 2008, Mayr 2008, Prum et al. 2015).
 Phoenicopteriformes Flamingos (6) Flamingos and grebes (Podicipediformes) are ancient sister taxa, potentially related to shorebirds (Charadriiformes) (Hackett et al. 2008, Mayr 2008, Prum et al. 2015).
 Charadriiformes Shorebirds and relatives: sandpipers, plovers, phalaropes, stilts, jacanas, painted snipes, pratincoles, gulls and terns, seedsnipes, sheathbills, skimmers, skuas, auks (390) Shorebirds and diving birds in the Charadriiformes are an ancient and diverse adaptive radiation of waterbirds.
 Eurypygiformes Sunbittern, Kagu (2) The Sunbittern and Kagu are removed from the Gruiformes to a new Order Eurypygiformes, which with tropicbirds (Phaethontiformes) is sister to the Core Waterbirds (Aequornithes)  (Hackett et al. 2008, Prum et al. 2015).
 Phaethontiformes Tropicbirds (3) Tropicbirds together with Sunbittern and Kagu (Eurypygiformes) are sister to Core Waterbird clade (Prum et al. 2015).
Aequornithes  Core Waterbirds
 Gaviiformes Loons (5) Loons are the sister group to penguins (Sphenisciformes) + tube-nosed seabirds (Procellariiformes) (Prum et al. 2015).
 Sphenisciformes Penguins (18) Penguins are sister to the tube-nosed seabirds (Procellariiformes).
 Procellariiformes Tube-nosed seabirds: petrels, shearwaters, albatrosses, storm petrels, diving petrels (147) The tube-nosed seabirds are sister to penguins (Sphenisciformes).  Albatrosses are  the sister group to all other tubenoses (Prum et al. 2015, cf Hackett et al. 2008).
 Ciconiiformes Storks (19)  The Order Ciconiiformes includes only the storks (Ciconiidae). Ibises and spoonbills (Threskiornithidae) and herons (Ardeidae) are members of the Pelecaniformes (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Suliformes Totipalmate water and diving birds: frigatebirds, cormorants, anhingas, and boobies (61) The  Suliform waterbirds are sister to the herons and pelicans (Pelecaniformes) (Prum et al. 2005).
 Pelecaniformes Ibis, herons, pelicans,  Hammerkop, Shoebill (118)  The relationships among Pelecaniform bird families remain uncertain (Hackett et al. 2008, Prum et al. 2015).
Opisthocomiformes Hoatzin (1) The Hoatzin is one of the most ancient, living bird lineages possibly sister to the Caprimulgiformes (sensu lato (Kuhl et al. 2020)
Telluraves Core Landbirds
 Accipitriformes Raptors including New World Vultures (266) Raptors (Accipitriformes) are a basal member of the Core Landbirds clade. New World vultures are a deep basal split and sister to the rest of the Accipitriformes (Prum et al. 2015).
 Strigiformes Owls (255)  Owls are basal members of the Core Landbirds.
Coliiformes Mousebirds (6)  Mousebirds are basal members of the Core Landbirds.
 Leptosomiformes Cuckoo Roller (1)  Formerly included in the Coraciiformes, the Cuckoo Roller is the only member of an ancient lineage that is the sister group to Trogoniformes, Bucerotiformes, Coraciiformes and Piciformes (Hackett et al. 2008, Prum et al. 2015).
 Trogoniformes Trogons, quetzals (43) Trogons are embedded in the Core Landbirds as the sister group to the Bucerotiformes, Coraciiformes, and Piciformes (Prum et al. 2015).
 Bucerotiformes Hornbills, hoopoes, wood hoopoes (74) Separation of the hornbills and  hoopoes  from the Coraciiformes as the Order Bucerotiformes maintains monophyly of the Coraciiformes (Hackett et al. 2008, Prum et al. 2015).
 Coraciiformes Kingfishers and allies: rollers, todies, motmots, bee-eaters (184) The kingfishers, rollers and allies form the sister group to the Piciformes (Prum et al. 2015).
 Piciformes Woodpeckers and allies (449) The diverse Piciformes includes jacamars, puffbirds  honeyguides, wrynecks, barbets and toucans as well as woodpeckers worldwide (Hackett et al. 2008, Prum et al. 2015).
Australaves  Terminal Landbird Clade
 Cariamiformes Seriemas (2) Seriemas are moved from the traditional Gruiformes to their own Order, basal member of the terminal landbird clade Australaves  (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Falconiformes Falcons (65) The falcons and caracaras (Falconiformes) are not relatives of other raptors in the Accipitriformes, but rather are a separate lineage and Order in the terminal landbird clade Australaves which includes parrots and the Passeriformes (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Psittaciformes Parrots (403) Parrots (Psittaciformes) are the sister group to the Passeriformes (Hackett et al. 2008, Jarvis et al. 2014, Prum et al. 2015).
 Passeriformes Perching birds (6533) The Passeriformes, or perching birds, include the majority of all world bird species. The New Zealand Wrens (Acanthisittidae) are the sister group to all passerines, including both suboscines and oscines.