bianchi's warbler Phylloscopus valentini

One of a number of mind-numbingly similar Seicercus warblers. Greenish-yellow above and bright yellow below, with a faint wingbar, a yellow eyering, and a grayish crown marked by two black stripes. Gray of the crown is weaker than that of White-spectacled and Plain-tailed Warblers, but this feature is difficult to see in the shade of the understory, where it usually forages. Breeds in submontane and montane forest up to the treeline; averages higher Martens’s Warbler. Descends into submontane and hill forest in the non-breeding season. Song is an unremarkable but lively burst of whistled notes, lower in pitch than that of Plain-tailed Warbler.