Old World warblers are a large group of birds formerly grouped together in the bird family
Sylviidae. 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 ten 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. A smaller family of warblers, together with some babblers formerly placed in the family
Timaliidae and the
parrotbills, are retained in a much smaller family
Sylviidae.