Gansu Leaf Warbler Phylloscopus kansuensis

Small, confusing leaf warbler with olive-yellow upperparts, yellow brow, double wing bars, and a pale crown stripe. Extremely similar to many other small leaf warblers: Pallas’s Leaf Warbler has a brighter yellow brow stripe, and Chinese Leaf Warbler has an incrementally weaker head pattern and a small hook at the rear end of the black eye stripe. Lemon-rumped Warbler is extremely similar visually but averages paler on the brow stripe and darker on the underparts. Listen for the song, an accelerating series of sharp chips followed by a trill; its calls include a tinkling series of chips. Inhabits mid-altitude forests, usually bushy poplar and birch groves; found at lower altitudes than Chinese Leaf Warbler.