53 cm; Male 900 g, Female 750 g. Blue-grey duck with a pale pink bill, tipped with black flaps. Adult has yellow eyes, breast spotted reddish chestnut. Sexes similar. Juvenile has dull grey bill and eyes, and fewer breast spots. Uniformly grey in flight. Male call a whistling ''whio, whio'' (fee-o, fee-0); female call a rattling growl; often call together in flight. Remain in territorial pairs all year. Seen standing on rocks or feeding with head and neck underwater. Habitat: Fast-flowing mountain streams and rivers, mainly in native forest or tussock grassland, occasionally on lakes. Breeding: Jul-Jan.