FAMILY CLASSIFICATION (2010)
The original version of the IOC World List (Gill and Wright 2006) mostly followed the classification and sequence of families in the third edition of the Howard and Moore Complete Checklist of the Birds of the World (Dickinson 2003). That classification reflected the phylogenies based on DNA data available at that time, summarized in the chapter on "Avian Higher-Level Phylogenetics" by Cracraft, Barker, and Cibois.
We now have the ability to to distinguish taxa of similar rank that are reciprocally monophyletic. This lets us redefine some groups of species that in hindsight were paraphyletic. Changes in taxonomy follow, especially splitting of orders, families, and genera to create monophyletic taxa that can be reconnected to their closest relatives in the classification.
In addition, DNA sequences clarify (or erase) some of the connections between the deepest historical branches of avian evolution (Hackett et al 2008). Accordingly, we can revisit the compositions of the classical Orders of birds and the relationships among them. Some groups (clades) of bird species are not as closely related to each other as previously thought. DNA-based resolutions of the phylogenetic relationships among world birds have increased dramatically in the past few years, and will continue to multiply. Many of the latest results are available on the web as part of the Tree of Life (TOL) project. Other excellent resources include Don Roberson’s tracking of family classifications and John Boyd's website Taxonomy in Flux .
Version 2.0 of the IOC World List included the first substantial updates of the higher classification of the birds of the world. Summarized below are the major features of the 2.0 updates, and supplements:
- Separation of 9 (+1) additional Orders, bringing the total recognized to 40 (details below)
- Separation of 8 (+2) additional families of nonpasserine birds, and 25 (-1) families of passerine birds (4 [-1]suboscine, 21 oscine), bringing the total number of families (excluding 7 incertae sedis) recognized to 224 (details below).
- Resequencing of families of suboscine passerines to match the sequence of these families in the SACC classification, and reorganization of the Old World warbler taxa, but we defer major sequence changes to a future update.
Orders
Phaethontiformes |
Tropicbirds |
| Suliformes (v2.5) | Frigatebirds, boobies, cormorants, anhingas |
Falconiformes |
Falcons |
Otidiformes |
Bustards |
Mesitornithiformes |
Mesites |
Cariamiformes |
Seriemas |
Eurypygiformes |
Kagu and Sunbittern |
Pteroclidiformes |
Sandgrouse |
Leptosomiformes |
Cuckoo-Roller |
Bucerotiformes |
Hoopoes and hornbills |
NOTE: We refrain from adding Cathartiformes (New World vultures) and Galbuliformes (jacamars and puffbirds) adopted by Clements 6.1.
Nonpasserine families
The families of nonpasserine birds added to the list are
Sagittariidae |
Secretarybird |
Pandionidae |
Osprey |
Pluvianellidae |
Magellanic Plover |
Pluvianidae |
Egyptian Plover |
Strigopidae (formerly Nestoridae) |
New Zealand parrots |
Cacatuidae |
Cockatoos |
Megalaimidae |
Asian barbets |
Lybiidae |
African barbets |
| Capitonidae (v2.6) | New World barbets |
| Semnornithidae (v2.6) | Prong-billed barbets |
Recognition of the Sagittariidae, Pandionidae, Pluvianellidae, Nestoridae, and Cacatuidae is consistent with other classifications.
The Egyptian Plover is assigned to a monotypic family (Pluvianidae) because it is not a member of the Glareolidae as previously defined, but instead constitutes a separate lineage that is the outgroup to plover complex including stilts and ibisbill etc (Baker et al. 2007, TOL).
The phylogeny of world barbets and toucans distinguishes the African barbets, Asian barbets, and New World barbets (and toucans) as separate and equivalent evolutionary groups. The Asian barbets are a monophyletic lineage that is sister/outgroup to the rest of the world’s barbets and toucans. In turn, the African barbets are sister to the New World barbets. We initially included all New World barbets in a single family (Ramphastidae) that was given equivalent status to the two families of Old World barbets. As of v2.6, we recognize the Capitonidae and Semnornithidae following SACC.
Not included in the IOC list (2.0) are 8 other families that are recognized in some classifications, as follows:
Oceanitidae: The two subfamilies of “storm petrels” are not sister taxa (Nunn and Stanley 1996, TOL) and may merit recognition as separate families (see Christidis and Boles 2008). Initial DNA analyses indicate that the Hydrobatidae is basal to the other members of the Procellariiformes, while the Oceanitidae separated from the Procellariidae at a later stage in the evolution of the tube-nosed seabirds. We propose to recognize the Oceanitidae when this phylogeny is confirmed.
Rynchopidae: The current phylogeny of the members of the Laridae doesn't support recognition of the skimmers as a separate family (Baker et al 2007; TOL). The genus Rhynchops is paraphyletic in relation to three lineages of terns that occupy different positions in this phylogeny
Batrachostomidae: The latest phylogeny of frogmouths separates Rigidipenna inexpectata from the genus Podargus (Cleere et al. 2007). Recognition of the Asian frogmouths (Batrachostomus) as a separate family (Christidis and Boles 2008) would require treating Rigidipenna as a monotypic family. We prefer to retain the Podargidae as a monophyletic taxon that includes the three genera.
Eurystopodidae: The eared-nightjars (Eurystopodus) are sister to rest of the Caprimulgidae and are treated as a separate family in some classifications (Sibley and Monroe 1990; Christidis and Boles 2008) but they are not equal in rank to Podargidae.
Cerylidae and Dacelonidae: The kingfishers of the world include three reciprocally monophyletic groups (Alcedininae, Cerylininae and Daceloninae) which are sometimes treated as separate families (Sibley and Monroe 1990; Christidis and Boles 2008). These three clades, however, are not at the same rank as the other families in the Coraciiformes.
Suboscine families
The Eurylaimidae is expanded, tentatively, to include both the asities of Madagascar (formerly Philepittidae) and Sapayoa of the New World (Irestedt et al. 2006; Moyle 2006a). Both the NACC and SACC treat Sapayoa as a member of the Eurylaimidae. But we retain the Pittidae as sister to the Eurylaimidae (see Hackett et al. 2008).
Some colleagues advocate including all of them in a single family that embraces this spectacular radiation of colorful Old World suboscines. An alternative classification would be to recognize 4 separate families of “broadbills” – Philepittidae, Sapayoaidae, Eurylaimidae and Calyptomenidae (Calyptomena and Smithornis) as well as the Pittidae. The exact, but currently uncertain position of Sapayoa relative to pittas versus broadbills will guide future revisions of this classification.
The IOC list (2.0) sequence of New World suboscine families follows that of the SACC (2008), with four additional families in bold font (below). Note that Sharpbill is transferred provisionally to the Tityridae. Genetic data place the Sharpbill in the Tityridae (Ohlson et al. 2008, Tello et al 2009); SACC may retain as a separate family Oxyruncidae along with Myiobius, Terenotriccus, Onychorhynchus ; Tree of Life does not (Harshman 2009).
The relationships of Swallow-tailed Cotinga remain open. Piprites, however, are basal tyrannids, as is Kinglet Calyptura, which forms a clade with Platyrinchus and Neopipo (Ohlson et al, MS/Poster at IOC 2010).
Furnariidae |
Ovenbirds, woodcreepers |
Thamnophilidae |
Antbirds |
Formicariidae |
Antthrushes |
Grallariidae |
Antpittas |
Conopophagidae |
Gnateaters |
Rhinocryptidae |
Tapaculos |
Melanoparaeiidae |
Crescentchests |
Tyrannidae |
Tyrant flycatchers |
Oxyruncidae (to Tityridae v2.3) |
Sharpbill |
Cotingidae |
Cotingas |
Pipridae |
Manakins |
Tityridae |
Tityras, becards |
Incertae sedis |
Phibalura, Calyptura (see above) |
Oscine families
The 21 added families of oscine passerines are:
Paramythiidae |
Painted Berrypeckers |
Notiomystidae |
Stitchbird |
Tephrodornithidae |
Woodshrikes |
Prionopidae |
Helmet Shrikes |
Psophodidae |
Whipbirds, quail-thrushes |
Hypocoliidae |
Hypocolius |
Ptilogonatidae |
Silky-flycatchers |
Hylocitreidae |
Hylocitrea; previously Yellow-flanked Whistler |
Mohoidae |
Oos |
Stenostiridae |
Fairy warblers |
Panuridae |
Bearded Reedling |
Nicatoridae |
Nicators |
Cettiidae |
Cettia warblers and allies |
Phylloscopidae |
Leaf warblers and allies |
Acrocephalidae |
Reed warblers and allies |
Megaluridae |
Grassbirds and allies |
Donacobiidae |
Donacobius |
Bernieridae |
Malagasy warblers |
Hyliotidae |
Hyliotas |
Buphagidae |
Oxpeckers |
Calcariidae |
Longspurs and snow buntings |
Phylogenetic revisions of the oscine passerines are arguably the most extensive and complex of those underway in ornithology. The ongoing revelations about waxwings and their allies are one case in point. Several (oddball) species in monotypic families are known as allies of the waxwings and silky-flycatchers, e.g. palmchat (Dulidae) of Hispaniola, Hypocolius (Hypocoliidae) of the Middle East. Adding to them is the revelation that the Oos (Moho) of the Hawaiian Islands are bombycillids, not honeyeaters (Meliphagidae) as traditionally believed (Fleischer et al 2008). And – the Yellow-flanked Whistler (Hylocitrea) of Sulawesi is yet another surprising relative of the waxwings (Spellman et al. 2008).
Further, the Rail-babbler (Eupetes) of Southeast Asia is not related to the Papuan whip-birds and quail-thrushes (Psophodidae). Instead it is related to the rockfowl (Picathartes) and rockjumpers (Chaetops) of Africa (Jønsson et al. 2007) . Consequently we restrict the family Eupetidae to this species. Linking Africa and southeast Asia is the network of shrike allies that include bushshrikes (Malaconotidae), helmetshrikes (Prionopidae), vangas (Vangidae), woodshrikes and allies (Tephrodornithdae), Bristlehead (Pityriasidae), and their outgroup relatives, the ioras (Aegithinidae) (Moyle et al 2006).
The shrike-babblers (Pteruthius) and White-bellied Yuhina (Erpornis) of southeast Asia are relatives of the vireos, not babblers (Reddy and Cracraft 2007, Reddy 2008). And conversely, the Black-capped Donacobius of South America is neither a mockingbird (Mimidae) nor a wren (Troglodytidae). Adding to the list of New World representatives of Old World families, Donacobius is a New World representative of the sylvioid grassbirds (Megaluridae) or perhaps the Malagasy warblers (Bernieridae). The IOC list (2.0) incorporates all such revelations known to us on December 31, 2008. Other revisions include the resorting of the Old World Warblers into five families additional to the Cisticolidae, namely the Cettidae, Phylloscopidae, Megaluridae, Acrocephalidae, Bernieridae following Cibois et al (2001, Alström et al (2006), Jøhansson et al (2006), Ryan et al (2006).
More is to come. We have not yet addressed the revision of the babblers (Timaliidae) that is underway including integration of Sylvia warblers, which are babblers, of white-eyes (Zosteropidae), which are probably sister to Yuhina babblers, and other lineage revisions (see Cibois 2003, Gelang et al. 2009). The resorting of the taxonomic boundaries of New World buntings, tanagers, warbler, finches, and grosbeaks also will be addressed in a future update.