Old World warbler

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.

They are of small to medium size, varying from 9 to 20 centimetres in length, with a slender, finely pointed bill.

[2] 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.

[4] 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.

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.

Clearly, the sheer extent of the groups concerned made it necessary to study a wide range of taxa.

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.

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.