Relationships: Long-tailed tits Aegithalidae

The family Aegithalidae contains only four genera: long-tailed tits Aegithalos (four species), tit-warblers Leptopoecile (two species), Bushtit Psaltriparus minimus and Pygmy Tit Psaltria exilis. This last is endemic to Java and is one of the smallest passerines in the world, while Bushtit is the only representative of the family in the New World, being found in Mexico and the southern United States. The tit-warblers are restricted to Asia, while Long-tailed Tit A caudatus is widespread across Europe and Asia and has been spilt into as many as 17 subspecies.

From the results of genetic studies, Martin Päckert et al (2010) have concluded that Long-tailed Tit subspecies A caudatus glaucogularis of central China diverged relatively early from A caudatus and warrants full species status. It is a sister taxon to Sooty Tit A fuliginosus and Black-browed Tit (also known as Rufous-fronted or Blyth’s Long-tailed Tit) A iouschistos.

The authors suggest that the Long-tailed Tit taxa A caudatus bonvaloti and A c sharpei are actually subspecies of Black-browed Tit. The genetic difference between the latter and Sooty Tit is much lower than would be expected for different species and the two are likely to be just morphological variations, or morphotypes, of the same species.