The Gansu leaf warbler (Phylloscopus kansuensis) is a small passerine bird known only from China. It belongs to the leaf warbler genus Phylloscopus within the family Phylloscopidae. It was formerly treated as a subspecies of Pallas's warbler (P. proregulus) but is now regarded as a separate species based on differences in voice and cytochrome-b gene sequences.[1]
It is 10 cm long, slightly larger than Pallas's warbler. It has greenish upperparts, pale underparts and a pale rump. The head has a long white supercilium and a pale stripe along the centre of the crown. The wings have one conspicuous wingbar, a slight second bar and whitish edges to the tertials.[2]
The song is very different from Pallas's warbler and consists of a thin, high-pitched note followed by a series of accelerating notes and finally a trill.[2]
It is known to breed only in Gansu and Qinghai provinces in northern China. Its wintering grounds are uncertain but probably lie in Yunnan province in southern China.[2] It is found up to 3,200 metres above sea-level in deciduous forest with some spruce and juniper.[2] [3] It is not currently known to be threatened with extinction and so is classed as a species of Least Concern by BirdLife International.[3]