Passerine

Passerines Temporal range: Eocene-Recent, 52.5–0 Ma PreЄ Є O S D C P T J K Pg N
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)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Clade:	Psittacopasserae
Order:	Passeriformes Linnaeus, 1758
Suborders
Acanthisitti Tyranni Passeri and see text
Diversity
Roughly 100 families, 6,409 species

A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or – less accurately – as songbirds, passerines are distinguished from other orders of birds by the arrangement of their toes (three pointing forward and one back), which facilitates perching. With more than 110 families and some 6,409 identified species,^[1][2] Passeriformes is the largest order of birds and among the most diverse orders of terrestrial vertebrates.^[3]

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 terms "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, which refers to sparrows and similar small birds.

Description

The order is divided into three suborders, Tyranni (suboscines), Passeri (oscines), and the basal Acanthisitti^[4]. 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).

Anatomy

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.^[5][6]

Most passerine birds develop 12 tail feathers, although the superb lyrebird has 16.^[7] 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, while 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.^[8]

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.^[9][10] The first passerines are now thought to have evolved in the Southern Hemisphere in the late Paleocene or early Eocene, around 50 million years ago.^[11][10]

The initial split was between the New Zealand wrens (Acanthisittidae) and all other passerines, and the second split involved the Tyranni (suboscines) and the Passeri (oscines or songbirds). The latter experienced a great radiation of forms out of the Australian continent. A major branch of the Passeri, parvorder Passerida, expanded deep into Eurasia and Africa, where a further explosive radiation of new lineages occurred.^[10] This eventually led to three major Passerida lineages comprising about 4,000 species, which in addition to the Corvida 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.

Fossil record

Earliest passerines

Perching bird osteology, especially of the limb bones, is rather diagnostic.^[12] 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 initially assigned to Passeriformes.^[13] However, the material is too fragmentary and their affinities have been questioned.^[14] Several more recent fossils from the Oligocene of Europe that are more complete definitely represent early passeriforms, although their exact position in the evolutionary tree is not known.

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).^[15]

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^[16] 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 onward, 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. indet. (Early Oligocene of Luberon, France) – suboscine or basal^[17]
• Passeriformes gen. et spp. indet. (Late Oligocene of France) – several suboscine and oscine taxa^[18]
• Passeriformes gen. et spp. indet. (Middle Miocene of France and Germany) – basal?^[19]
• Passeriformes gen. et spp. indet. (Sajóvölgyi Middle Miocene of Mátraszőlős, Hungary) – at least 2 taxa, possibly 3; at least one probably Oscines^[20]
• Passeriformes gen. et sp. indet. (Middle Miocene of Felsőtárkány, Hungary) – oscine?^[21]
• Passeriformes gen. et sp. indet. (Late Miocene of Polgárdi, Hungary) – Sylvioidea (Sylviidae? Cettiidae?)^[22]

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.^[23] Extant Passeri super-families 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.

American fossils

See also: Late Quaternary prehistoric birds

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),^[24] 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 that try rather successfully to resolve the phylogeny of the passeriform radiation. For example, the Corvida in the traditional sense was 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.^[25] 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 super-family 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,^[26] based on the most modern and comprehensive studies.^[27]

Suborder Acanthisitti

• Acanthisittidae: New Zealand wrens

Suborder Passeri (songbirds or oscines)

• Infraorder Menurides – the most ancient true songbirds, endemic to Australia, sometimes considered a superfamily "Menuroidea"
  • Menuridae: lyrebirds
  • Atrichornithidae: scrub-birds

• Infraorder Climacterides – Possible superfamily "Ptilonorhynchoidea" – 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
  • Climacteridae: Australian treecreepers
  • Ptilonorhynchidae: bowerbirds
• Infraorder Meliphagides – 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
    • Acanthorhynchus: spinebills, usually included in Meliphagidae, might be considered a monotypic family if Pardalotidae are considered valid too
    • Acanthizidae: scrubwrens, thornbills, and gerygones
• Infraorder Orthonychides – 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
  • Orthonychidae: logrunners
  • Pomatostomidae: pseudo-babblers
• Infraorder Corvides – 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.
  • Mohouoidea
    • Mohouidae
  • Pachycephaloidea
    • Pachycephalidae: whistlers
    • Oreoicidae: Australo-Papuan bellbirds
    • Falcunculidae: crested shriketits
    • Psophodidae: quail-thrushes & jewel-babblers
  • Orioloidea
    • Eulacestomidae: Wattled ploughbills
    • Neosittidae: sittellas
    • Oriolidae: Old World orioles & figbirds
    • Paramythiidae: painted berrypeckers
    • Psophodidae: whipbirds & wedgebills
    • Vireonidae: vireos
  • Campephagoidea
    • Campephagidae: cuckoo-shrikes and trillers
  • Malaconotoidea

    

    • 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
    • Rhipiduridae: fantails
    • Dicruridae: drongos
    • Ifritidae: blue-capped ifrit
    • Melampittidae: melampittas
    • Corcoracidae: white-winged chough and apostlebird
    • Paradisaeidae: birds-of-paradise
    • Monarchidae: monarch flycatchers
    • Laniidae: shrikes
    • Corvidae: crows, ravens, and jays
  • 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 Passerides
  • Melanocharitida
    • Melanocharitidae (berrypeckers and longbills)
  • Cnemophilida
    • Cnemophilidae (satinbirds)
  • Petroicida
    • Callaeidae (New Zealand wattlebirds)
    • Notiomystidae (stitchbird)
    • Petroicidae (Australian robins)
  • Eupetida – 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
    • Picathartidae (rockfowl)
    • Chaetopidae (rock-jumpers), recently split from the Turdidae
    • Eupetidae (Malaysian rail-babbler), recently split from the Cinclosomatidae
  • 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, 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
    • Hyliidae
    • Aegithalidae: long-tailed tits or bushtits^[29]
    • Sylviidae: Sylvia warblers and allies
    • Zosteropidae: white-eyes and allies
    • Timaliidae: tree babblers
    • Pellorneidae: ground babblers
    • Leiothrichidae: laughingthrushes and allies
  • Reguloidea
    • 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 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.
    • Elachuridae: spotted elachura
    • Mohoidae^[30][31]

      

    • Ptiliogonatidae: silky flycatchers, tentatively placed here
    • Bombycillidae: waxwings
    • Dulidae: palmchat, tentatively placed here
    • Hypocoliidae: hypocolius, tentatively placed here
  • 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, some species (especially of Cinclidae, Buphagidae and Mimidae) are quite dark and dull while others are commonly colorful or/and iridescent. 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:
      • Fringillidae: true finches and Hawaiian honeycreepers. Possibly polyphyletic.
      • Calcariidae: longspurs and snow buntings
      • Emberizidae: buntings
      • Passerellidae: American sparrows
      • Icteridae: grackles, New World blackbirds, and New World orioles
      • Parulidae: New World warblers
      • Thraupidae: tanagers and allies
      • Cardinalidae: cardinals
  • Passerida incertae sedis
    • Scotocercidae: streaked scrub warbler
    • Rhagologidae: mottled whistler
    • Prionopidae: helmetshrikes and woodshrikes

Footnotes

References

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• 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 503738. 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 1599865. PMID 15888418. Electronic appendix
• Boles, Walter E. (1997). "Fossil Songbirds (Passeriformes) from the Early Eocene of Australia". Emu. 97 (1): 43–50. doi:10.1071/MU97004.
• Cibois, Alice; Slikas, Beth; Schulenberg, Thomas S. & Pasquet, Eric (2001). "An endemic radiation of Malagasy songbirds is revealed by mitochondrial DNA sequence data" (PDF). Evolution. 55 (6): 1198–1206. doi:10.1554/0014-3820(2001)055[1198:AEROMS]2.0.CO;2. Archived from the original (PDF) on 21 May 2006.
• Claramunt, S.; Cracraft, J. (2015). "A new time tree reveals Earth history's imprint on the evolution of modern birds". Science Advances. 1 (11). doi:10.1126/sciadv.1501005. PMC 4730849. PMID 26824065.
• del Hoyo, J.; Elliot, A. & Christie, D. (eds.) (2003): Handbook of the Birds of the World (Vol. 8: Broadbills to Tapaculos). Lynx Edicions. ISBN 84-87334-50-4
• del Hoyo, J.; Elliot, A. & Christie, D. (eds.) (2004): Handbook of the Birds of the World (Vol. 9: Cotingas to Pipits and Wagtails. Lynx Edicions). ISBN 84-87334-69-5
• del Hoyo, J.; Elliot, A. & Christie, D. (eds.) (2005): Handbook of the Birds of the World (Vol. 10: Cuckoo-Shrikes to Thrushes. Lynx Edicions). ISBN 84-87334-72-5
• del Hoyo, J.; Elliot, A. & Christie, D. (eds.) (2006): Handbook of the Birds of the World (Vol. 11: Old World Flycatchers to Old World Warblers). Lynx Edicions. ISBN 84-96553-06-X
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External links

The Wikibook Dichotomous Key has a page on the topic of: Passeriformes

• The dictionary definition of passerine at Wiktionary
• Media related to Passeriformes at Wikimedia Commons
• Data related to Passeriformes at Wikispecies