Chinese Leaf Warbler Phylloscopus yunnanensis     photos Nigel Goodgame

A very cryptic species that's best identified by very distinctive song/call - another small warbler, fine bill, with crown stripe, wing-bars and rump similar to Sichuan and Pallas's, but all of these features not as distinct  - pictured bird looks worn showing greyer tones to nape and head but fresher birds are greener and have more of a typical sichuan look, with grey tone mainly concentrated in a band around the nape. Yellow base to bill.

Similar species - during breeding season can be confused with other small warblers with rumps and crown-stripes, especially sichuan - lack of light outer tail feathers will separate it from buff-barred.- during passage pallas's could also be confused, but its a far brighter bird and like sichuan has very well defined crown stripe and easier to see light rump. Also note, has yellow base to lower bill which will be shown on good photos (shared feature with possible Sichuan species Gansu Leaf Warbler) - Sichuan and Pallas's are all black bills.

Habitat - despite field guides giving lower elevations, in Sichuan can be found at over 3,000m (Baxi area) - otherwise prime habitat around 2,000m in mixed forest - a forest rather than a secondary growth species. 

Vocalizations - by far the best means of identification - unique sounding song, a mechanical repeated single phrase, very bush warbler like but coming from high branches of a tree. Call is high pitched single note but can be used in a distinctive, unique manner where the note is repeated until it becomes a high pitched trill - this is more often heard than the mechanical song and a good way of picking up the bird.

Song here     Sid Francis iNaturalist

Call here - xeno-canto     Peter Boesman, XC916509. Accessible at www.xeno-canto.org/916509