Old World warbler


The Old World warblers are a large group of birds formerly grouped together in the bird family Sylviidae. They are not closely related to the New World warblers. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into Cisticolidae and the kinglets into Regulidae. In the past 20–30 years they have been the subject of much research and many species are now placed into other families, including the Acrocephalidae, Cettiidae, Phylloscopidae, and Megaluridae. In addition some species have been moved into existing families or have not yet had their placement fully resolved. Only a small number of warblers, in just two genera, are now retained in the family Sylviidae.

Characteristics

Most Old World warblers are of generally undistinguished appearance, though some species are boldly marked. The sexes are often identical, but may be clearly distinct, notably in the genera Sylvia and Curruca. They are of small to medium size, varying from 9 to 20 centimetres in length, with a slender, finely pointed bill. Almost all species are primarily insectivorous, although many will also eat soft 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, a huge family, with few clear patterns of relationships recognisable. Though not as diverse as the Timaliidae, the frontiers were much blurred. The largely tropical warbler family Cisticolidae was at that time traditionally included in the Sylviidae. The kinglets, now a small genus in a monotypic family Regulidae, were also sometimes placed in this family, including by the influential List of Recent Holarctic Bird Species,. The American Ornithologists' Union then also included the gnatcatchers, as subfamily Polioptilinae, in the Sylviidae.
Sibley & Ahlquist 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 Sylviidae as initially defined was a form taxon which collected 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 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. These could only confirm that the Cisticolidae were indeed distinct, and suggested that bulbuls were apparently the closest relatives of a group containing Sylviidae, Timaliidae, cisticolids and white-eyes.
In 2003, a study of Timaliidae relationships 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 Sylviidae, turned out to be closer to taxa such as the yellow-eyed babbler and the wrentit, an enigmatic species generally held to be the only American Old World babbler. The parrotbills Paradoxornithidae of then 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, but this was rejected. 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. and Alström et al.. They determined that the late-20th-century Sylviidae united at least four, but probably as many as seven major distinct lineages. The authors propose the creation of several new families to better reflect the evolutionary history of the sylvioid group.

Species

Family Sylviidae ''sensu stricto''

Typical warblers. A fairly diverse group of smallish taxa with longish tails, now containing 33 species in two genera. Mostly in Europe and the Mediterranean region, with a few extending to central Asia and in tropical Africa.Genus Sylvia – typical warblers

Moved to family [Paradoxornithidae]

Source:
Image:Chrysomma sinense.jpg|thumb|right|Chrysomma sinense, the yellow-eyed babbler, used to be considered a sylviid closely related to parrotbills.Genus Lioparus – golden-breasted fulvettaGenus Chrysomma

Moved to family [Pellorneidae]

Genus Graminicola

Moved to family [Cisticolidae]

Genus Bathmocercus – rufous-warblers

Moved to family [Acrocephalidae]

Image:Hippolais icterina1.jpg|thumb|right|Icterine warbler, Hippolais icterina
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, reed beds or tall grass. Mainly southern Asia to western Europe and surroundings ranging far into Pacific, some in Africa.Genus Acrocephalus – marsh warblers Genus Iduna – olivaceous warblers Genus Hippolais – tree warblers Genus Arundinax – thick-billed warblerGenus Calamonastides – yellow warblers Genus Nesillas – brush warblers

Moved to [Malagasy warbler]s

See Cibois et al. Genus Thamnornis

Moved to family [Locustellidae]

Image:Fernbird.jpg|thumb|right|New Zealand's fernbird – probably belongs to the Locustellidae
Grass warblers and allies. Mid-sized and usually long-tailed species; sometimes strongly patterned but generally very drab in overall colouration. Often forage in dense low vegetation. Old World and into Australian region, centred on the Indian Ocean.Genus Bradypterus – megalurid warblers Genus Locustella – grass warblers Genus Megalurus – typical grassbirds Genus Amphilais – grey emutailGenus Elaphrornis – Sri Lanka bush warblerGenus Schoenicola – Genus Buettikoferella – buff-banded thicketbirdGenus Chaetornis – bristled grassbird

Moved to family [Donacobiidae]

The black-capped donacobius Donacobius atricapillus, which was long considered an aberrant wren or mockingbird is apparently quite closely related, and is the only South American species in the superfamily Sylvioidea.

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.Genus Pholidornis – formerly in Remizidae; tentatively placed here
Image:Cettia diphone.JPG|thumb|right|Uguisu, the Japanese bush warbler. See also uguisubari.Genus Erythrocercus – monarch-warblers. Formerly Monarchinae.

Moved to family [Aegithalidae]

Genus Leptopoecile – tit-warblers.

Moved to family [Phylloscopidae]

Leaf warblers. A group variable in size, generally dull to vivid green above and whitish or 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.
Image:Świstunka.jpg|thumb|right|Wood warbler, Phylloscopus sibilatrixGenus Phylloscopus – leaf warblers. Includes the former genus Seicercus.

Moved to family [Macrosphenidae]

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.Genus Sylvietta – crombecs

"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.Genus Phyllolais – Cisticolidae?

Not in [Sylvioidea]

Entirely unrelated songbirds hitherto placed in SylviidaeGenus Amaurocichla – Now placed in Passeroidea in the Motacillidae