About Hymenolaimus malacorhynchos (J.F.Gmelin, 1789)
The blue duck, Hymenolaimus malacorhynchos (J.F.Gmelin, 1789), is 53 cm (21 in) long, with weight that differs by sex. Females are smaller than males: females weigh 680–870 g (24–31 oz), while males weigh 820–970 grams (29–34 oz). Its plumage is dark slate-grey, with a greenish sheen on the head and a chestnut-flecked breast. Outer secondary feathers have white tips, and inner secondaries have black margins. Male and female plumage is mostly the same, though females have slightly less chestnut on the chest. The pinkish-white bill has fleshy flaps of skin hanging from the sides of its tip. When the bird hatches, the beak is green, and it develops its final color eight hours later.
