How to tell a Grey Duck apart from a Mallard

The New Zealand grey duck population is believed to be extensively hybridised with introduced mallards to such an extent that few pure grey ducks may now exist, hence its “nationally vulnerable” conservation status. The Grey Duck is also native to Australia where it is known as the Pacific Black Duck.
Grey ducks are easily confused with female Mallard from which they can be distinguished by: mallards have bright orange legs and feet, orange-and-brown bills, more diffuse eye and bill stripes and mottled face, and a blue speculum edged with white both at front and back.
Grey ducks have olive coloured legs and feet, a leaden grey to black coloured bill, and a iridescent green speculum with a black border and thin white trailing edge.

Видео How to tell a Grey Duck apart from a Mallard канала Mr Gedge's Geography Channel