Passerine

Passerines
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)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Psittacopasserae
Order: Passeriformes
Linnaeus, 1758
Suborders

and see text

Diversity
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. Passerines are distinguished from other orders of Aves by 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.[1] 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.

Description

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).

Pterylosis or the feather tracts in a typical passerine

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. This is especially useful for passerine birds that develop nocturnal lifestyles.[2] [3]

Most passerine birds develop 12 tail feathers, although the superb lyrebird has 16.[4] 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.[5]

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.[6][7] 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.[8][9]

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 later 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 Corivida 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

Male superb lyrebird (Menura novaehollandiae): This very primitive songbird shows strong sexual dimorphism, with a peculiarly apomorphic display of plumage in males.

Perching bird osteology, especially of the limb bones, is rather diagnostic.[11] 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.[12] However, the material is too fragmentary and their affinities have been questioned.[13] 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).[14]

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[15] 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

Wieslochia fossil

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 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.[22] 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.

American fossils

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),[23] 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.[24] 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

New Zealand rock wren (Xenicus gilviventris), one of the two surviving species of suborder Acanthisitti

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,[25] based on the most modern and comprehensive studies.[26]

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.[27]

Suborder Acanthisitti

Javan banded pitta (Hydrornis guajanus), an Old World suboscine.
Andean cock-of-the-rock (Rupicola peruvianus) a New World suboscine

Suborder Tyranni (Suboscines)

Suborder Passeri (Songbirds or oscines)

Male regent bowerbird (Sericulus chrysocephalus, Ptilonorhynchidae)
Male stitchbird or hihi (Notiomystis cincta) showing convergence with honeyeaters
Tiny goldcrest (Regulus regulus) belongs to a minor but highly distinct lineage of Passeri
Reed warblers, such as this Blyth's reed warbler (Acrocephalus dumetorum), are now in the Acrocephalidae
blue tit (Cyanistes caeruleus) and its relatives stand well apart from rest of the Sylvioidea sensu lato
Brown-headed nuthatch (Sitta pusilla), nuthatches can climb downwards head-first
Hermit thrush (Catharus guttatus), like many Muscicapoidea a stout and cryptic bird with complex vocalizations.
Like these male (right) and female Gouldian finches (Erythrura gouldiae), many Passeroidea are very colorful
Gran Canaria blue chaffinch (male).

Phylogeny

Living Passeriformes based on the "Taxonomy in Flux family phylogenetic tree" by John Boyd.[27]

Footnotes

  1. ↑ Mayr, Ernst (1946). "The Number of Species of Birds" (PDF). The Auk. 63 (1): 67. doi:10.2307/4079907.
  2. ↑ Stefoff, Rebecca (2008), "The Bird Class", Marshall Cavendish Benchmark
  3. ↑ Brooke, Michael and Birkhead, Tim (1991) "The Cambridge Encyclopedia of Ornithology", Cambridge University Press ISBN 0521362059.
  4. ↑ Jones, D. (2008). Flight of fancy. Australian Geographic, (89), 18–19.
  5. ↑ 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. (May 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. PMID 15062790. doi:10.1016/j.ympev.2003.08.005.
  6. ↑ Dyke, Gareth J.; Van Tuinen, Marcel (June 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.
  7. ↑ Claramunt & Cracraft (2015)
  8. ↑ Ericson, P.G.; Christidis, L.; Cooper, A.; Irestedt, M.; Jackson, J.; Johansson, U.S.; Norman, J.A. (7 February 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): 235–241. PMC 1690883 Freely accessible. PMID 11839192. doi:10.1098/rspb.2001.1877.
  9. ↑ Claramunt & Cracraft (2015)
  10. ↑ Claramunt & Cracraft (2015)
  11. ↑ See e.g. Boles (1997), Manegold et al. (2004), Mayr & Manegold (2006)
  12. ↑ Boles (1997)
  13. ↑ Mayr, G (2013). "The age of the crown group of passerine birds and its evolutionary significance–molecular calibrations versus the fossil record. Systematics and Biodiversity". 11 (1). doi:10.1080/14772000.2013.765521.
  14. ↑ Worthy et al. (2007)
  15. ↑ The last common ancestor of all songbirds most likely had a decidedly longer tail. See del Hoyo et al. (2003, 2004).
  16. ↑ 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)
  17. ↑ Huguenet et al. (2003), Mayr & Manegold (2006)
  18. ↑ Specimens SMF Av 487–496; SMNS 86822, 86825-86826; MNHN SA 1259–1263: tibiotarsus remains of small, possibly basal Passeriformes: Manegold et al. (2004)
  19. ↑ 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)
  20. ↑ A humerus diaphysis piece of a swallow-sized passerine: Hír et al. (2001)
  21. ↑ Hír et al. (2001)
  22. ↑ Manegold et al. (2004)
  23. ↑ Distal right humerus, possibly suboscine: Noriega & Chiappe (1991, 1993)
  24. ↑ 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.
  25. ↑ del Hoyo et al. (2003–)
  26. ↑ 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)
  27. 1 2 John Boyd's. "Taxonomy in Flux family phylogenetic tree" (PDF). Retrieved 17 December 2015.
  28. ↑ Gill, F., Wright, M. & Donsker, D. (2008). IOC World Bird Names (version 1.6). Available at http://www.worldbirdnames.org/
  29. ↑ Lovette, I.J. (2008). "Convergent evolution: Raising a family from the dead". Current Biology. 18 (24): R1132–4. PMID 19108768. doi:10.1016/j.cub.2008.11.006.
  30. ↑ Fleischer R.C.; James H.F. & Olson S.L. (23 December 2008). "Convergent evolution of Hawaiian and Australo-Pacific honeyeaters from distant songbird ancestors". Current Biology. 18 (24): 1927–1931. PMID 19084408. doi:10.1016/j.cub.2008.10.051.

References

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