Definitions

chamaea fasciata

Old World warbler

The "Old World Warblers", family Sylviidae are a family of small passerine bird species; the names sylviid warblers or true warblers may be more appropriate. The Sylviidae mainly occur as breeding species, as the name implies, in Europe, Asia and, to a lesser extent Africa. However, most birds of temperate regions are strongly migratory, and winter in the latter continent or tropical Asia. Many are accomplished songbirds, though perhaps not as much as other warblers or some thrushes.

The American wood warblers (Parulidae), the Olive Warbler (Peucedramidae) and the stenostirid warblers or "flycatcher tits" (Stenostiridae) are not closely related to the sylviids. The Australian warblers (Acanthizidae), apart from also being Passeri, are entirely unrelated.

Characteristics

Most Old World Warblers are of generally undistinguished appearance, though some Asian species are boldly marked. The sexes are often identical, but may be clearly distinct, notably in the genus Sylvia. They are of small to medium size, varying from 9 to 16 centimetres in length, with a small, finely pointed bill. Almost all species are primarily insectivorous, although some will also eat fruit, nectar, or tiny seeds.

The majority of species are monogamous and build simple, cup-shaped nests in dense vegetation. They lay between two and six eggs per clutch, depending on species. Both parents typically help in raising the young, which are able to fly at around two weeks of age.

Systematics

In the late 20th century, the Sylviidae were thought to unite nearly 300 small insectivorous bird species in nearly 50 genera. They had themselves being split out of the Muscicapidae. The latter family had for most of its existence served as perhaps the ultimate wastebin taxon on the history of ornithology. By the early 20th century, about every insectivorous Old World "songster" known to science had at one point been placed therein, and most continued to do so.

Only after the mid-20th century did the dismantling of the "pan-Muscicapidae" begin in earnest. However, the Sylvidae remained a huge family, with few clear patterns of relationships recognisable. Though by no means as diverse as the Timaliidae (Old World babblers) (another "wastebin taxon" containing more thrush-like forms), the frontiers between the former "pan-Muscicapidae" were much blurred. The largely southern warbler family Cisticolidae was traditionally included in the Sylviidae. The kinglets, a small genus in a monotypic family Regulidae, were also frequently placed in this family. The American Ornithologists' Union includes the gnatcatchers, as subfamily Polioptilinae, in the Sylviidae.

Sibley & Ahlquist (1990) united the "Old World warblers" with the babblers and other taxa in a superfamily Sylvioidea as a result of DNA-DNA hybridisation studies. This demonstrated that the Muscicapidae as initially defined were a form taxon which collected entirely unrelated songbirds. Consequently, the monophyly of the individual "songster" lineages themselves was increasingly being questioned.

More recently, analysis of DNA sequence data has provided information on the Sylvioidea. Usually, the scope of the clade was vastly underestimated and only one or two specimens were sampled for each presumed "family". Minor or little-known groups such as the parrotbills were left out entirely (e.g. Ericson & Johansson 2003, Barker et al. 2004). These could only confirm that the Cisticolidae were indeed distinct, and suggested that bulbuls (Pycnonotidae) were apparently the closest relatives of a group containing Sylviidae, Timaliidae, cisticolids and white-eyes.

In 2003, a study of Timaliidae relationships (Cibois 2003a) using mtDNA cytochrome b and 12S/16S rRNA data indicated that the Sylviidae and Old World babblers were not reciprocally monophyletic to each other. Moreover, Sylvia, the type genus of the Sylvidae, turned out to be closer to taxa such as the Yellow-eyed Babbler (Chrysomma sinense) (traditionally held to be an atypical timaliid) and the Wrentit (Chamaea fasciata), an enigmatic species generally held to be the only American Old World babbler. The parrotbills, formerly considered a family Paradoxornithidae (roughly, "puzzling birds") of unclear affiliations also were part of what apparently was a well distinctive clade.

Cibois suggested that the Sylviidae should officially be suppressed by the ICZN as a taxon and the genus Sylvia merged into the Timaliidae (Cibois 2003b), but doubts remained. Clearly, the sheer extent of the groups concerned made it necessary to study a wide range of taxa. This was begun by Beresford et al. (2005) and Alström et al. (2006). They determined that the late-20th-century Sylviidae united at least 4, but probably as much as major 7 distinct lineages. The authors propose the creation of several new families (Phylloscopidae, Cettiidae, Acrocephalidae, Megaluridae) to better reflect the evolutionary history of the sylvioid group.

The Sylviidae, in turn, receive several taxa from other families. Nonetheless, the now-monophyletic family has shrunk by nearly 80% for the time being, now containing 55 species in 10 genera at least. It is entirely likely however that with further research, other taxa from those still incertae sedis among its former contents, the Timaliidae, the Cisticolinae, or even the Muscicapidae will be moved into this group.

Species

Family Sylviidae sensu stricto

True warblers (or sylviid warblers) and parrotbills. A fairly diverse group of smallish taxa with longish tails. Mostly in Asia, to a lesser extent in Africa. A few range into Europe; one monotypic genus on west coast of North America.

Moved to family Timaliidae

Moved to family Cisticolidae

Moved to family Acrocephalidae

Marsh- and tree warblers or acrocephalid warblers. Usually rather large "warblers", most are olivaceous brown above with much yellow to beige below. Usually in open woodland, reedbeds or tall grass. Mainly southern Asia to western Europe and surroundings ranging far into Pacific, some in Africa. The genus limits are seriously in need of revision; either most species are moved into Acrocephalus, or the latter is split up though there is presently insufficient knowledge as to how.

Moved to Malagasy warblers

See Cibois et al. (2001)

Moved to family Megaluridae

Grass warblers and allies or megalurid warblers. Mid-sized and usually long-tailed species; sometimes strongly patterned but generally very drab in overall coloration. Often forage on the ground. Old World and into Australian region, centred around Indian Ocean; possibly also one species in South America. A not too robustly supported clade that requires further study.

Moved to family Cettiidae

Typical bush warblers and relatives or cettiid warblers. Another group of generally very drab species, tend to be smaller and shorter-tailed than Megaluridae. Usually frequent shrubland and undergrowth. Continental Asia, and surrounding regions, ranging into Africa and southern Europe.

Moved to Family Aegithalidae

Moved to family Phylloscopidae

Leaf-warblers or phylloscopid warblers. A group very variable in size, often vivid green coloration above and yellow below, or more subdued with greyish-green to greyish-brown plumage. Catch food on the wing fairly often. Eurasia, ranging into Wallacea and Africa.

"African Warblers"

Also "Sphenoeacus group". An assemblage of usually species-poor and apparently rather ancient "odd warblers" from Africa. Ecomorphologically quite variable. Monophyly requires confirmation.

"Sylviidae" ''incertae sedis

Taxa that have not been studied. Most are likely to belong to one of Sylvioidea families listed above. Those in the Australian-Pacific region are probably Megaluridae. These taxa are listed in the sequence used in recent years.

Not in Sylvioidea

Entirely unrelated songbirds hitherto placed in Sylviidae

References

  • Alström, P., Ericson, P. G. P., Olsson, U., & Sundberg, P. (2006). Phylogeny and classification of the avian superfamily Sylvioidea. Molecular Phylogenetics and Evolution 38 (2): 381–397.
  • Baker, K. (1997). Warblers of Europe, Asia, and North Africa. Helm ISBN 0-7136-3971-7.
  • Barker, F. K., Cibois, A., Schikler, P. A., Feinstein, J., & Cracraft, J. (2004): Phylogeny and diversification of the largest avian radiation. Proceedings of the National Academy of Sciences 101 (30): 11040-11045. PDF fulltext 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'. Proc. Roy. Soc. Lond. B 272 (1565): 849–858. PDF fulltext Electronic appendix
  • Cibois, A. (2003a). Mitochondrial DNA Phylogeny of Babblers (Timaliidae). Auk 120 (1): 1-20. DOI: 10.1642/0004-8038(2003)120[0035:MDPOBT]2.0.CO;2 HTML fulltext without images
  • Cibois, A. (2003b). Sylvia is a babbler: taxonomic implications for the families Sylviidae and Timaliidae.Bull. B. O. C. 123: 257-261.
  • Cibois, A., Slikas, B., Schulenberg, T. S., & Pasquet, E. (2001). An endemic radiation of Malagasy songbirds is revealed by mitochondrial DNA sequence data. Evolution 55 (6): 1198-1206. DOI:10.1554/0014-3820(2001)055[1198:AEROMS]2.0.CO;2 PDF fulltext
  • del Hoyo, J.; Elliot, A. & Christie D. (editors). (2006). Handbook of the Birds of the World. Volume 11: Old World Flycatchers to Old World Warblers. Lynx Edicions. ISBN 849655306X.
  • Ericson, P. G. P. & Johansson, U. S. (2003). Phylogeny of Passerida (Aves: Passeriformes) based on nuclear and mitochondrial sequence data. Molecular Phylogenetics and Evolution 29 (1): 126–138 PDF fulltext
  • Fuchs, J., Fjeldsa, J., Bowie, R. C. K., Voelker, G., & Pasquet, E. (2006). The African warbler genus Hyliota as a lost lineage in the Oscine songbird tree: Molecular support for an African origin of the Passerida. Molecular Phylogenetics and Evolution 39 (1): 186-197.
  • Shirihai, H., Gargallo, G., & Helbig, A. J. (2001). Sylvia Warblers. Helm ISBN 0-7136-3984-9.
  • Sibley, C. G. & Ahlquist, J. E. (1990). Phylogeny and classification of birds. Yale University Press, New Haven, Conn.
  • Simms, E. (1985). British warblers. Collins, London. ISBN 0-00-219404-X.
  • Yamagishi, S., Honda, M., Eguchi, K., & Thorstrom, R. (2001). Extreme endemic radiation of the Malagasy Vangas (Aves: Passeriformes). Journal of Molecular Evolution 53 (1): 39-46. (HTML abstract)

Notes

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