Temporal range: Eocene-Recent, 52.5–0 Ma
|Clockwise from top right: Palestine sunbird (Cinnyris osea), blue jay (Cyanocitta cristata), house sparrow (Passer domesticus), great tit (Parus major), hooded crow (Corvus cornix), southern masked weaver (Ploceus velatus)|
|Song of a purple-crowned fairywren (Malurus coronatus)|
and see text
|Roughly 100 families, around 5,400 species|
A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. A notable feature of passerines compared to other orders of Aves is the arrangement of their toes, three pointing forward and one back, which facilitates perching. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders, with over 5,000 identified species. It has roughly twice as many species as the largest of the mammal orders, the Rodentia. It contains more than 110 families, the second-most of any order of tetrapods (after Squamata, the scaled reptiles). The passerines contain several groups of brood parasites such as the viduas, cuckoo-finches, and the cowbirds. Most passerines are omnivorous, while the shrikes are carnivorous.
The names "passerine" and "Passeriformes" are derived from Passer domesticus, the scientific name of the eponymous species (the house sparrow) and ultimately from the Latin term passer for Passer sparrows and similar small birds.
- 1 Description
- 2 Anatomy
- 3 Eggs and nests
- 4 Origin and evolution
- 5 Systematics and taxonomy
- 6 Taxonomic list of Passeriformes families
- 7 Footnotes
- 8 References
- 9 External links
The order is divided into three suborders, Tyranni (suboscines), Passeri (oscines), and the basal Acanthisitti. Oscines have the best control of their syrinx muscles among birds, producing a wide range of songs and other vocalizations (though some of them, such as the crows, do not sound musical to human beings); some such as the lyrebird are accomplished imitators. The acanthisittids or New Zealand wrens are tiny birds restricted to New Zealand, at least in modern times; they were long placed in Passeri; their taxonomic position is uncertain, although they seem to be a distinct and very ancient group.
Most passerines are smaller than typical members of other avian orders. The heaviest and altogether largest passerines are the thick-billed raven and the larger races of common raven, each exceeding 1.5 kg (3.3 lb) and 70 cm (28 in). The superb lyrebird and some birds-of-paradise, due to very long tails or tail coverts, are longer overall. The smallest passerine is the short-tailed pygmy tyrant, at 6.5 cm (2.6 in) and 4.2 g (0.15 oz).
The foot of a passerine has three toes directed forward and one toe directed backward, called anisodactyl arrangement. This arrangement enables the passerine birds to perch upon vertical surfaces, such as trees and cliffs. The toes have no webbing or joining, but in some cotingas, the second and third toes are united at their basal third. The hind toe joins the leg at the same level as the front toes. The passeriformes have this toe arrangement in common with hunting birds like eagles and falcons.
The leg arrangement of passerine birds contains a special adaptation for perching. A tendon in the rear of the leg running from the underside of the toes to the muscle behind the tibiotarsus will automatically be pulled and tighten when the leg bends, causing the foot to curl and become stiff when the bird lands on a branch. This enables passerines to sleep while perching without falling off. This is especially useful for passerine birds that develop nocturnal lifestyles. 
Most passerine birds develop 12 tail feathers, although the superb lyrebird has 16. Certain species of passerines have stiff tail feathers, which help the birds balance themselves when perching upon vertical surfaces. Some passerines, specifically in the family Ploceidae, are well known for their elaborate sexual ornaments, including extremely long tails. A well-known example is the long-tailed widowbird.
Eggs and nests
The chicks of passerines are altricial: blind, featherless, and helpless when hatched from their eggs. Hence, the chicks require extensive parental care. Most passerines lay coloured eggs, in contrast with nonpasserines, most of whose eggs are white except in some ground-nesting groups such as Charadriiformes and nightjars, where camouflage is necessary, and in some parasitic cuckoos, which match the passerine host's egg. Vinous-throated parrotbill has two egg colours, white and blue. This can prevent the brood parasitic Common cuckoo.
Clutches vary considerably in size: some larger passerines of Australia such as lyrebirds and scrub-robins lay only a single egg, most smaller passerines in warmer climates lay between two and five, whilst in the higher latitudes of the Northern Hemisphere, hole-nesting species like tits can lay up to a dozen and other species around five or six. The family Viduidae do not build their own nests, instead they lay eggs in other birds' nests.
Origin and evolution
The evolutionary history of the passerine families and the relationships among them remained rather mysterious until the late 20th century. In many cases, passerine families were grouped together on the basis of morphological similarities that, it is now believed, are the result of convergent evolution, not a close genetic relationship. For example, the wrens of the Americas and Eurasia; those of Australia; and those of New Zealand look superficially similar and behave in similar ways, and yet belong to three far-flung branches of the passerine family tree; they are as unrelated as it is possible to be while remaining Passeriformes.
Much research remains to be done, but advances in molecular biology and improved paleobiogeographical data gradually are revealing a clearer picture of passerine origins and evolution that reconciles molecular affinities, the constraints of morphology and the specifics of the fossil record. The first passerines are now thought to have evolved in Gondwana at some time in the Paleogene, maybe around the Late Paleocene some 60–55 million years ago. The initial split was between the Tyranni, the songbirds, the Eurylaimides, and the New Zealand "wrens", which must have diverged during a short period of time (some million years at most). The Passeriformes apparently evolved out of a fairly close-knit clade of "near passerines" that contains such birds as the Piciformes and Coraciiformes.
A little later, a great radiation of forms took place out of Australia-New Guinea: the Passeri or songbirds. A major branch of the Passeri, parvorder Passerida, emerged either as the sister group to the basal lineages and corvoids (parvorder Corvida), or more likely as a subgroup of it, and expanded deep into Eurasia and Africa, where a further explosive radiation of new lineages occurred. This eventually led to three major passeridan lineages comprising about 4,000 species, which in addition to the corvoidan clade and numerous minor lineages make up songbird diversity today. Extensive biogeographical mixing happens, with northern forms returning to the south, southern forms moving north, and so on.
Perching bird osteology, especially of the limb bones, is rather diagnostic. However, the early fossil record is poor because the first Passeriformes were apparently on the small side of the present size range, and their delicate bones did not preserve well. Queensland Museum specimens F20688 (carpometacarpus) and F24685 (tibiotarsus) from Murgon, Queensland, are fossil bone fragments clearly recognizable as passeriform; they represent two species of about 10 and 20 cm in overall length and prove that some 55 mya, barely into the Early Eocene, early perching birds were recognizably distinct.
A quite similar group, the Zygodactylidae (named for their zygodactylous approach to perching) independently arose at much the same time – and possibly from closely related ancestors – in the landmasses bordering the North Atlantic, which at that time was only some two-thirds of its present width.
Until the discovery of the Australian fossils mentioned, Palaeospiza bella from the Priabonian Florissant fossil beds (Late Eocene, around 35 mya) was the oldest known passeriform. However, it is now considered a nonpasseriform near passerine.
From the Bathans Formation at the Manuherikia River in Otago, New Zealand, MNZ S42815 (a distal right tarsometatarsus of a tui-sized bird) and several bones of at least one species of saddleback-sized bird have recently been described. These date from the Early to Middle Miocene (Awamoan to Lillburnian, 19–16 mya).
Modern knowledge about the living passerines' interrelationships (see the list of families below) suggests that the last common ancestor of all living Passeriformes was a small forest bird, probably with a stubby tail and an overall drab coloration, but possibly with marked sexual dimorphism. The latter trait seems to have been lost and re-evolved multiple times in songbird evolution alone, judging from its distribution among the extant lineages. Sexual dichromatism is very rare among the basal lineages of Passerida, and probably their plesiomorphic condition. But among the youngest passerid clade, the Passeroidea, extremely colorful males and drab females are common, if not the rule. On the other hand, among the basalmost Passeri a considerable number of strongly dimorphic lineages exist, too, such as the very ancient Menuridae, as well as many Meliphagoidea and Corvoidea. Sexual dimorphism is also not uncommon in the Acanthisittidae and prominent in some suboscines such as the Pipridae and Cotingidae.
Early European passerines
In Europe, perching birds are not too uncommon in the fossil record from the Oligocene onwards, but most are too fragmentary for a more definite placement:
- Wieslochia (Early Oligocene of Frauenweiler, Germany)
- Jamna (Early Oligocene of Jamna Dolna, Poland)
- Resoviaornis (Early Oligocene of Wola Rafałowska, Poland)
- Passeriformes gen. et sp. idet. (Early Oligocene of Luberon, France) – suboscine or basal
- Passeriformes gen. et spp. indet. (Late Oligocene of France) – several suboscine and oscine taxa
- Passeriformes gen. et spp. indet. (Middle Miocene of France and Germany) – basal?
- Passeriformes gen. et spp. indet. (Sajóvölgyi Middle Miocene of Mátraszőlős, Hungary) – at least 2 taxa, possibly 3; at least one probably Oscines
- Passeriformes gen. et sp. indet. (Middle Miocene of Felsőtárkány, Hungary) – oscine?
- Passeriformes gen. et sp. indet. (Late Miocene of Polgárdi, Hungary) – Sylvioidea (Sylviidae? Cettiidae?)
Wieslochia was possibly not a member of any extant suborder. That not only the Passeri expanded much beyond their region of origin is proven by an undetermined broadbill (Eurylaimidae) from the Early Miocene (roughly 20 mya) of Wintershof, Germany, and the indeterminant Late Oligocene suboscine from France listed above. Even very basal Passeriformes might have been common in Europe until the Middle Miocene, some 12 mya. Extant Passeri superfamilies were quite distinct by that time and are known since about 12–13 mya when modern genera were present in the corvoidean and basal songbirds. The modern diversity of Passerida genera is known mostly from the Late Miocene onwards and into the Pliocene (about 10–2 mya). Pleistocene and early Holocene lagerstätten (<1.8 mya) yield numerous extant species, and many yield almost nothing but extant species or their chronospecies and paleosubspecies.
In the Americas, the fossil record is more scant before the Pleistocene, from which several still-existing suboscine families are documented. Apart from the indeterminable MACN-SC-1411 (Pinturas Early/Middle Miocene of Santa Cruz Province, Argentina), an extinct lineage of perching birds has been described from the Late Miocene of California, United States: the Palaeoscinidae with the single genus Paleoscinis. "Palaeostruthus" eurius (Pliocene of Florida) probably belongs to an extant family, most likely passeroidean.
Systematics and taxonomy
Corvida and Passerida were classified as parvorders in the suborder Passeri; in accord with the usual taxonomic practice, they would probably be ranked as infraorders. As originally envisioned in the Sibley-Ahlquist taxonomy, they contained, respectively, the large superfamilies Corvoidea and Meliphagoidea, as well as minor lineages, and the superfamilies Sylvioidea, Muscicapoidea, and Passeroidea.
The arrangement has been found to be oversimplified by more recent research. Since the mid-2000s, literally dozens of studies are being published which try rather successfully to resolve the phylogeny of the passeriform radiation. For example, the Corvida in the traditional sense were a rather arbitrary assemblage of early and/or minor lineages of passeriform birds of Old World origin, generally from the region of Australia, New Zealand, and Wallacea. The Passeri, though, can be made monophyletic by moving some families about, but the "clean" three-superfamily-arrangement has turned out to be far more complex and it is uncertain whether future authors will stick to it.
Major "wastebin" families such as the Old World warblers and Old World babblers have turned out to be paraphyletic and are being rearranged. Several taxa turned out to represent highly distinct species-poor lineages, so new families had to be established, some of them – like the stitchbird of New Zealand and the Eurasian bearded reedling – monotypic with only one living species. In the Passeri alone, a number of minor lineages will eventually be recognized as distinct superfamilies. For example, the kinglets constitute a single genus with less than 10 species today, but seem to have been among the first perching bird lineages to diverge as the group spread across Eurasia. No particularly close relatives of them have been found among comprehensive studies of the living Passeri, though they might be fairly close to some little-studied tropical Asian groups. Treatment of the nuthatches, wrens, and their closest relatives as a distinct superfamily Certhioidea is increasingly considered justified; the same might eventually apply to the tits and their closest relatives.
This process is still continuing. Therefore, the arrangement as presented here is subject to change. However, it should take precedence over unreferenced conflicting treatments in family, genus, and species articles here.
Taxonomic list of Passeriformes families
This list is in taxonomic order, placing related species/groups next to each other. The Passerida subdivisions are updated as needed from the default sequence of the Handbook of the Birds of the World, based on the most modern and comprehensive studies.
Regarding arrangement of families
The families are sorted into a somewhat novel sequence unlike that in older works, where e.g. Corvidae are placed last. This is because so many reallocations have taken place since about 2005 that a definite taxonomy has not been established yet, although the phylogeny is by and large resolved. The present sequence is an attempt to preserve as much of the traditional sequence while giving priority to adequately addressing the phylogenetic relationships between the families. Based on John Boyd's Taxonomy in Flux Checklist 3.5.
- Acanthisittidae: New Zealand "wrens"
Suborder Tyranni (Suboscines)
- Infraorder Eurylaimides – Old World suboscines (or broad-billed suboscines), probably a separate suborder
- Infraorder Tyrannides – New World suboscines
- Superfamily Tyrannoidea – "bronchophones"
- Superfamily Furnarioidea – tracheophones
Suborder Passeri (Songbirds or oscines)
- Infraorder Menurida – the most ancient true songbirds, endemic to Australia, sometimes considered a superfamily "Menuroidea"[verification needed]
- Infraorder Climacterida – Possible superfamily "Ptilonorhynchoidea"[verification needed] – bowerbirds and Australian treecreepers, endemic to Australia, New Guinea, two very dissimilar families, one smallish and inconspicuous, the other sizeable, usually brightly colored and/or conspicuously vocal, and with extremely unusual mating habits
- Infraorder Meliphagida – mainly insectivores and nectarivores, distribution centered on Australo-Melanesian region extending into surroundings, notably the Pacific.
- Maluridae: fairywrens, emu-wrens and grasswrens
- Dasyornithidae: bristlebirds, formerly in Acanthizidae
- Meliphagidae: honeyeaters
- Pardalotidae: pardalotes
- Meliphagoidea incertae sedis
- Infraorder Orthonychida – logrunners and pseudo-babblers, insectivores, endemic to Australia, New Guinea, mid-sized and rather inconspicuous, wings short and round but tails well-developed plumage grey and brown with black and white markings, males and females look alike
- Infraorder 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.
- Campephagidae: cuckoo-shrikes and trillers
- Artamidae: woodswallows, butcherbirds, currawongs, and Australian magpie
- Machaerirhynchidae: boatbills
- Aegithinidae: ioras
- Pityriaseidae: Bornean bristlehead, tentatively placed here
- Malaconotidae: puffback shrikes, bush shrikes, tchagras, and boubous
- Platysteiridae: wattle-eyes and relatives, formerly in Passerida, probably paraphyletic
- Vangidae: vangas
- Corvoidea incertae sedis
- Vireolanius: shrike-vireos, usually included in Vireonidae, possibly a monotypic family
- Erpornis: white-bellied erpornis, formerly in Yuhina (Passerida: Timaliidae); possibly a monotypic family, possibly in Vireonidae
- Colluricinclidae: shrike-thrushes, often included in Pachycephalidae, but perhaps recognizable as a subfamily at least
- Pitohuidae: pitohuis, usually included in Pachycephalidae, but seem closer to Oriolidae and best considered a distinct family including Oreoica and possibly other Pachycephalidae sensu lato.
- Infraorder Passerida
- Melanocharitidae (berrypeckers and longbills)
- Cnemophilidae (satinbirds)
- Picathartoidea – rockfowl and allies, eat large arthropods and sometimes small vertebrates. Relictual distribution in three areas of the Old World tropics, mid-sized to large songbirds with strong legs, adapted to move long distances on foot across rough ground, males and females look alike
- Paroidea – titmice and allies, might be included in Sylvioidea, feed mainly on arthropods, seeds, and berries, widely distributed but absent from South America and the Australian region[verification needed], smallish round-bodied acrobatic birds, often brightly colored with large patches of yellow, blue, green, black and white, males and females usually look quite alike
- Stenostiridae: ("flycatcher-tits"), a newly assembled family.
- Hyliotidae: (hyliotas), recently split from the Sylviidae, basal to/in Passerida, restricted to the Afrotropics, resemble "Old World warblers", but quite colorful
- Remizidae: (penduline tits), sometimes included in the Paridae
- Paridae: (tits, chickadees, and titmice)
- Sylvioidea: – "Old World warblers/babblers" and allies, generally insectivores, sometimes supplemented with berries, distribution centered on the Indo-Pacific region, few occur in the Australian region and fewer still in the Americas, usually slender and drab birds, few have pronounced sexual dimorphism
- Nicatoridae: (nicators), have been classed as bulbuls in the past, but appear to have no close relatives
- Panuridae: (bearded reedling), formerly classed as a parrotbill, but seems to be closest to the larks
- Alaudidae: (larks)
- Macrosphenidae: African warblers such as longbills and crombecs, a recently proposed family whose composition is still uncertain
- Cisticolidae: cisticolas and allies
- Acrocephalidae: marsh- and tree-warblers, recently split from the Sylviidae
- Pnoepygidae: pygmy wren-babblers, apparently unrelated to other babblers
- Locustellidae: grass-warblers and allies, recently split from the Sylviidae
- Donacobiidae: the black-capped donacobius, previously classed as a wren, but probably closest to the Locustellidae or Bernieridae
- Bernieridae: Malagasy warblers, a newly assembled family
- Hirundinidae: swallows and martins
- Pycnonotidae: bulbuls
- Phylloscopidae: leaf-warblers and allies, recently split from the Sylviidae
- Cettiidae: ground-warblers and allies, recently split from the Sylviidae
- Aegithalidae: long-tailed tits or bushtits
- Sylviidae: Sylvia warblers and allies
- Zosteropidae: white-eyes and allies
- Timaliidae: tree babblers
- Pellorneidae: ground babblers
- Leiothrichidae: laughingthrushes and allies
- Regulidae (kinglets), tiny forest-dwelling insectivores, found only in the Northern Hemisphere, greenish above, whitish below and striking (at close range) head pattern of black and yellow to red stripes, sexual dimorphism slight
- Bombycilloidea – waxwings and allies, included in the Muscicapoidea if Sittoidea/Certhioidea are also included there, omnivores but strongly prefer juicy fruit and nectar, Laurasian, essentially[verification needed] limited to the Northern Hemisphere, mid-sized and typically fairly inconspicuous except for their habit of roaming around in noisy flocks, plumage typically grey-hued and with silk-like texture, but many have a conspicuous black face and/or yellow ornaments, several melanic lineages, sexual dimorphism slight if any. Hylocitrea might be included here as monotypic family.
- Certhioidea – wrens, treecreepers and allies. Sometimes included in Muscicapoidea. Occur in the Americas and Eurasia, though mostly north of the Alpide belt. Distribution and the basal fossil Certhiops indicates the Certhioidea probably originated around the end of the Paleogene somewhere around the North Atlantic. Small, often tiny, tend to be conspicuously plump but nimble; many accomplished climbers. Plumage extremely cryptic or somewhat colorful, in the latter case typically blue-grey at least on the upperside. Sexes look identical or almost so, but may differ strongly in vocalizations.
- Tichodromadidae: wallcreeper: Traditionally placed as a subfamily of the nuthatches and more rarely of the treecreepers, no study has been able to verify either placement this far. Thus it is better considered a monotypic family, at least for the time being.
- Sittidae: nuthatches
- Certhiidae: treecreepers
- Salpornithidae: spotted creepers. Tentatively placed here; often considered a subfamily of the Certhidae.
- Troglodytidae: wrens
- Polioptilidae: gnatcatchers
- Muscicapoidea – "Old World flycatchers", starlings and allies. 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 robust 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, the most aquatic members of the whole clade.
- Turdidae: thrushes and allies. Monophyly needs confirmation.
- Muscicapidae: Old World flycatchers and chats. Monophyly needs confirmation.
- Buphagidae: oxpeckers. Formerly usually included in Sturnidae.
- Sturnidae: starlings and possibly Philippine creepers. Placement of latter in Muscicapoidea seems good, but inclusion in Sturnidae requires confirmation; possibly distinct family Rhabdornithidae.
- Mimidae: mockingbirds and thrashers
- Passeroidea – "finches", "New World warblers/blackbirds" and allies. Mostly herbivores including many seed-eaters but some specialized insectivores; 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.
- Promeropidae (Sugarbirds), living fossils with a nondescript "honeyeater" or "warbler" phenotype, a Capensis relict lineage only found in Africa south of the Equatorial region, Include keystone species for fynbos and some Afromontane forest ecosystems, sexual dimorphism does not appear pronounced, but includes many little-studied species
- Arcanatoridae (Dapplethroat & allies)
- Dicaeidae (flowerpeckers), sunbirds and flowerpeckers, might be included in Passeroidea, eat mostly nectar, pollen, and berries, supplemented with arthropods, generally restricted to the Old World tropics, plumage usually extremely colorful at least in males, usually a few contrasting hues (commonly including black and/or white, and usually including red) and in some with metallic sheen, sexual dimorphism usually pronounced, females in most species greenish above, lighter below
- Nectariniidae: sunbirds
- Chloropseidae: leafbirds
- Irenidae: fairy-bluebirds.
- Urocynchramidae: Przewalski's finch. Recently split from Fringillidae; tentatively placed here.
- Peucedramidae: olive warbler
- Prunellidae: accentors
- Ploceidae: weavers. Certain members of Ploceidae, such as the long-tailed widowbird are well known for their elaborate sexual ornaments.
- Viduidae: indigobirds and whydahs
- Estrildidae: estrildid finches (waxbills, munias and allies)
- Passeridae: true sparrows
- Motacillidae: wagtails and pipits
- Nine-primaried oscines:
- Passerida incertae sedis
- Passeroidea – "finches", "New World warblers/blackbirds" and allies. Mostly herbivores including many seed-eaters but some specialized insectivores; 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.
Living Passeriformes based on the "Taxonomy in Flux family phylogenetic tree" by John Boyd.
- Mayr, Ernst (1946). "The Number of Species of Birds" (PDF). The Auk. 63 (1): 67. doi:10.2307/4079907.
- Stefoff, Rebecca (2008), "The Bird Class", Marshall Cavendish Benchmark
- Brooke, Michael and Birkhead, Tim (1991) "The Cambridge Encyclopedia of Ornithology", Cambridge University Press ISBN 0521362059.
- Jones, D. (2008). Flight of fancy. Australian Geographic, (89), 18–19.
- The name wren has been applied to other, unrelated birds in Australia and New Zealand. The 27 Australasian "wren" species in the family Maluridae are unrelated, as are the New Zealand wrens in the family Acanthisittidae; the antwrens in the family Thamnophilidae; and the wren-babblers of the families Timaliidae, Pellorneidae, and Pnoepygidae. For the monophyly of the "true wrens", Troglodytidae, see Barker, F. K. (2004). "Monophyly and relationships of wrens (Aves: Troglodytidae): a congruence analysis of heterogeneous mitochondrial and nuclear DNA sequence data" (PDF). Molecular Phylogenetics and Evolution. 31 (2): 486–504. doi:10.1016/j.ympev.2003.08.005. PMID 15062790.
- The context is summarised in Dyke, Gareth J.; Van Tuinen, Marcel (2004). "The evolutionary radiation of modern birds (Neornithes): Reconciling molecules, morphology and the fossil record". Zoological Journal of the Linnean Society. 141 (2): 153–177. doi:10.1111/j.1096-3642.2004.00118.x.
- Ericson, PG; Christidis, L; Cooper, A; Irestedt, M; Jackson, J; Johansson, US; Norman, JA (2002). "A Gondwanan origin of passerine birds supported by DNA sequences of the endemic New Zealand wrens". Proceedings of the Royal Society B. 269 (1488): 235–41. doi:10.1098/rspb.2001.1877. PMC . PMID 11839192.
- Johansson & Ericson (2003);
- See e.g. Boles (1997), Manegold et al. (2004), Mayr & Manegold (2006)
- Boles (1997)
- Worthy et al. (2007)
- The last common ancestor of all songbirds most likely had a decidedly longer tail. See del Hoyo et al. (2003, 2004).
- Specimen SMF Av 504. A flattened right hand of a passerine perhaps 10 cm long overall. If suboscine, perhaps closer to Cotingidae than to Eurylaimides: Roux (2002), Mayr & Manegold (2006)
- Huguenet et al. (2003), Mayr & Manegold (2006)
- Specimens SMF Av 487–496; SMNS 86822, 86825-86826; MNHN SA 1259–1263: tibiotarsus remains of small, possibly basal Passeriformes: Manegold et al. (2004)
- A partial coracoid of a probable Muscicapoidea, possibly Turdidae; distal tibiotarsus and tarsometatarsus of a smallish to mid-sized passerine that may be the same as the preceding; proximal ulna and tarsometatarsus of a Paridae-sized passerine: Gál et al. (1998–1999, 2000)
- A humerus diaphysis piece of a swallow-sized passerine: Hír et al. (2001)
- Hír et al. (2001)
- Manegold et al. (2004)
- Distal right humerus, possibly suboscine: Noriega & Chiappe (1991, 1993)
- The former does not even have recognized subspecies, while the latter is one of the most singular birds alive today. Good photos of a bearded reedling are for example here and here.
- del Hoyo et al. (2003–)
- Lovette & Bermingham (2000), Cibois et al. (2001), Barker et al. (2002, 2004), Ericson & Johansson (2003), Beresford et al. (2005), Alström et al. (2006), Jønsson & Fjeldså (2006)
- John Boyd's. "Taxonomy in Flux family phylogenetic tree" (PDF). Retrieved 17 December 2015.
- Gill, F., Wright, M. & Donsker, D. (2008). IOC World Bird Names (version 1.6). Available at http://www.worldbirdnames.org/
- Lovette, I.J. (2008). "Convergent evolution: Raising a family from the dead". Current Biology. 18 (24): R1132–4. doi:10.1016/j.cub.2008.11.006. PMID 19108768.
- Fleischer R.C.; James H.F. & Olson S.L. (2008). "Convergent evolution of Hawaiian and Australo-Pacific honeyeaters from distant songbird ancestors". Current Biology. 18 (24): 1927–31. doi:10.1016/j.cub.2008.10.051. PMID 19084408.
- Alström, Per; Ericson, Per G.P.; Olsson, Urban & Sundberg, Per (2006). "Phylogeny and classification of the avian superfamily Sylvioidea". Mol. Phylogenet. Evol. 38 (2): 381–397. doi:10.1016/j.ympev.2005.05.015. PMID 16054402.
- Barker, F. Keith; Barrowclough, George F. & Groth, Jeff G. (2002). "A phylogenetic hypothesis for passerine birds: taxonomic and biogeographic implications of an analysis of nuclear DNA sequence data" (PDF). Proceedings of the Royal Society B. 269 (1488): 295–308. doi:10.1098/rspb.2001.1883. PMC . PMID 11839199.
- Barker, F. Keith; Cibois, Alice; Schikler, Peter A.; Feinstein, Julie & Cracraft, Joel (2004). "Phylogeny and diversification of the largest avian radiation". PNAS. 101 (30): 11040–11045. doi:10.1073/pnas.0401892101. PMC . PMID 15263073. Supporting information
- Beresford, P.; Barker, F.K.; Ryan, P.G. & Crowe, T.M. (2005). "African endemics span the tree of songbirds (Passeri): molecular systematics of several evolutionary 'enigmas'" (PDF). Proceedings of the Royal Society B. 272 (1565): 849–858. doi:10.1098/rspb.2004.2997. PMC . PMID 15888418. Electronic appendix
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