Crested Serpent Eagle

The crested serpent eagle varies in total length from 41 to 75cm and in wingspan from 89 to 169cm. In the very small subspecies body masses were 420g in a male and 565g in a female, while in the Palawan form males weighed 688g and females 853g (Wikipedia, general species account).

These figures are for the species across its whole range, and the source read for the Bhutan guide gives nothing on the form found in Bhutan, nor any plumage, range, diet or breeding detail, so none is stated.