Buff-barred Warbler Phylloscopus pulcher photos Sid Francis
Small with typical fine bill - like ashy-throated with tail outers - very noticeable white and tail splaying - best ID pointer. On fresh birds a wing bar with an almost orange coloured wing bar - on worn far more faded and can look almost white. Has faint coronal stripe and light rump but these are not highly distinctive features - dirtier looking underparts than most other smaller warblers.
Similar species - .most likely to confused with other small species found in same habitat, especially Sichuan, and especially when bird is worn - however lack of strong coronal stripe and rump is a clincher and of course those white outers and tail splaying.
Habitat - one of the higher warblers, at treelines at 3,500m and beyond in taller bush and shrub habitat down to 2,500m - most likely seen in bushy/shrubby/secondary growth type situations.
Vocalizations - a very distinctive short trill - slightly abrasive rather than sweet sounding. Like the outer tail feathers a very distinctive and sure ID pointer. Call single note high pitched chips - much like ashy-throated.
Song here Sid Francis iNaturalist