
Photo: Kelly Abram (iNaturalist) · CC0
Chalcoparia singalensis
Habitat
Subtropical or tropical moist lowland forest, mangrove forest and moist montane forest
Range
Bangladesh, Bhutan, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand and Vietnam
The ruby-cheeked sunbird is found in Bangladesh, Bhutan, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand and Vietnam. Its natural habitats are subtropical or tropical moist lowland forest, mangrove forest and moist montane forest (Wikipedia, general species account).
That short account is the only source read for the Bhutan guide. It gives no plumage, size, diet or breeding information, so none is stated.