White-browed Bush Robin

The white-browed bush robin is a member of the Old World flycatcher family found from the Himalayas to south-central China and north Vietnam. Its natural habitat is rhododendron and conifer forest, and it performs altitudinal migration. It is an insectivore (Wikipedia, general species account).

White-browed bush robins show delayed plumage maturation: after becoming capable of breeding, first-year males retain their juvenile plumage, similar to adult females, to avoid direct competition with older males. The Taiwan bush robin was formerly regarded as a subspecies. The source read does not name Bhutan, and gives no size or breeding information.