Oriental Dollarbird

The Oriental dollarbird is a roller, named for the distinctive pale blue or white coin-shaped spots on its wings. It is 27 to 32cm long and dark brown heavily washed with a bluish-green sheen on the back and wing coverts, with a light belly, glossy bright blue on the throat and undertail, and a short, wide, orange-red bill with a black tip in adults (Wikipedia, general species account).

It ranges from Australia to Korea, Japan and India. At least two subspecies are migratory, one breeding in north-eastern Asia and wintering in south-eastern Asia. The birds prefer open wooded areas with hole-bearing trees for nesting. The sources read do not name Bhutan, so its occurrence there is flagged for checking.