
Photo: William Stephens · CC BY 4.0 (May be cropped or resized)
Phylloscopus magnirostris
Habitat
Dense vegetation; occasionally seen in urban areas
Range
Breeds in central China and the Himalaya; winters in Sri Lanka, the Western Ghats and associated hills
The large-billed leaf warbler is a fairly large leaf warbler with a single wing bar, a yellowish-white eyebrow, a broad dark eye stripe, a dark crown, greyish ear-coverts and a large dark upper bill. It can be confused with the Arctic warbler. It was described by Edward Blyth in 1843 (Wikipedia, general species account).
It is usually heard rather than seen: its two-note call has a higher second note, and it also gives a faint single note followed by evenly descending paired notes, repeated often at regular intervals. It is a migrant that breeds in central China and the Himalaya and winters in Sri Lanka and the Western Ghats. The source does not mention Bhutan (Wikipedia, general species account).