
Photo: Firozhussain · CC BY-SA 4.0 (May be cropped or resized)
Locustella luteoventris
Habitat
Boreal forests when breeding; subtropical and tropical forest in the winter quarters
Range
Bangladesh, Bhutan, China, Hong Kong, India, Myanmar, Nepal, Thailand and Vietnam
The brown bush warbler is a songbird of the family Locustellidae, formerly placed among the Old World warblers. It is found in Bangladesh, Bhutan, China, Hong Kong, India, Myanmar, Nepal, Thailand and Vietnam. Its natural habitat is boreal forest during breeding and subtropical and tropical forest in the winter quarters (Wikipedia, general species account).
That short account is the only source read for the Bhutan guide. It gives no plumage, size, diet or nest information, so none is stated.