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 (Old World babblers; another "wastebin taxon" containing more thrush-like forms), 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 (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 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 (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 Sylviidae, 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 Paradoxornithidae (roughly, "puzzling birds") 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 (Cibois 2003b), 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. (2005) and Alström et al. (2006). 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 (Phylloscopidae, Cettiidae, Acrocephalidae, and Megaluridae, this last turning out to be a synonym of the older-published Locustellidae) to better reflect the evolutionary history of the sylvioid group.
Species
Family Sylviidae sensu stricto Typical warblers (or sylviid 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 (6 species) Eurasian blackcap, Sylvia atricapilla Garden warbler, Sylvia borin Dohrn's warbler, Sylvia dohrni Abyssinian catbird, Sylvia galinieri Bush blackcap, Sylvia nigricapillus African hill babbler, Sylvia abyssinica Genus Curruca – 27 species. Formerly in Sylvia (Sylviidae) Barred warbler, Curruca nisoria Layard's warbler, Curruca layardi Banded parisoma, Curruca boehmi Chestnut-vented warbler, Curruca suboerulea Desert whitethroat, Curruca minula Lesser whitethroat, Curruca curruca Hume's whitethroat, Curruca althaea Brown parisoma, Curruca lugens Yemen warbler, Curruca buryi Arabian warbler, Curruca leucomelaena Western orphean warbler, Curruca hortensis Eastern orphean warbler, Curruca crassirostris African desert warbler, Curruca deserti Asian desert warbler, Curruca nana Tristram's warbler, Curruca deserticola Menetries's warbler, Curruca mystacea Rüppell's warbler, Curruca ruppeli Cyprus warbler, Curruca melanothorax Sardinian warbler, Curruca melanocephala Western subalpine warbler, Curruca iberiae Moltoni's warbler, Curruca subalpina Eastern subalpine warbler, Curruca cantillans Common whitethroat, Curruca communis Spectacled warbler, Curruca conspicillata Marmora's warbler, Curruca sarda Dartford warbler, Curruca undata Balearic warbler, Curruca balearica
Moved to family Paradoxornithidae Source:
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