Mrs. Gould's Sunbird (Aethopyga gouldiae) in Vietnam

Mrs. Gould's sunbird is a small sunbird. It has a down-curved and pointed beak, typical for a nectar feeder. The iris of the eye is usually deep brown, and the tarsus is black.

The male Mrs. Gould's sunbird is bright and colourful. The forehead to crown, supercilium and throat of the sunbird are deep violet. The lore, the auriculars and the malar region, the nape, mantle and side are bright red to deep scarlet. Bright blue patterns may be present on the auricular and the side. The coverts and wingbars to the primary feathers are brown or olive green. The belly and vent are yellowish-green. The tail covert is bright blue and fades to dark purple at the tip of the tail.

The female is dull in colour compared to the male. The female is covered by deep olive green on the dorsal side and greyish-yellow on the ventral side.

The colour and pattern may be different in different subspecies. For example, the breast of A. g. dabryii is purely scarlet, and A. g. gouldiae has a bright yellow breast, with or without a red stripe.[4]

The male weighs 4–12 g and measures 131–160 mm; wing length is 51–58 mm, tail length is 64–88mm, and tarsus length is 13–15.5 mm. The female weighs 5–8 g and measures 91–111 mm; wing length is 45–54 mm, tail length is 30.5–40 mm, and tarsus length is 12–16 mm. Both sexes have a beak 13–17 mm in length.