Siberian Rubythroat

The Siberian rubythroat is a small chat, formerly classed with the thrushes but now considered an Old World flycatcher. It is plain brown above except for a distinctive black tail with red side patches, and has a strong white supercilium. The male has a red throat edged with a narrow black and then a broad white border, while females lack the brightly coloured throat and borders (Wikipedia, general species account).

It is a migratory insectivorous species breeding in mixed coniferous forests with undergrowth in Siberia, nesting near the ground. The male's song is similar to a harder version of the garden warbler's. The source read does not name Bhutan, so its occurrence there is flagged for checking.