Just because some features eliminate the other species you've mentioned, and because claudiae should be the one occuring in this part of Sichuan. I don't have the features to separate reguloides from claudiae, maybe some others could confirmed.
claudiae is a common phylloscopus in the mountain of NW Hunan, where it can be found above 1200 meter.
Below a link where you could find a good set of claudiae pictures.
http://www.netfugl.dk/pictures.p ... es&birdid=17529
Cheers,
Jonathan
