The green pygmy goose (Nettapus pulchellus) is a small perching duck which breeds in southern New Guinea and northern Australia. Ranging from 30 to 36 cm in length, the green pygmy goose is one of the smallest species of duck. It has a 48 to 60 cm wingspan. It has a small bill and a compact form. The breeding male has a predominantly dark green back and neck, and a dark gray crown. The cheeks are white, and the underparts are pale grey and white scalloped. The tail, primary flight feathers and primary coverts are black, while the secondary flight feathers are white. The secondary coverts are a dark iridescent green. This iridescence is lost outside of the breeding season and the plumage becomes duller. The species exhibits a degree of sexual dimorphism — the female has a barred rather than green neck but otherwise resembles the non-breeding male. Immature birds are less brightly coloured, and have mottled dark brown heads. The male has a high-pitched whistle and the female a lower-pitched call.