The female has duller chocolate brown plumage, brown eyes and has a white face patch during breeding season. A white wing bar can be seen in both sexes when in flight, and both sexes have a grey bill. The young are initially covered in pale brown and white down, and juveniles look like the female, except with no white at the base of the bill. The males have a high pitched whistle call and the females 'quack'. Distribution and habitat It is found throughout both the North and South Island of New Zealand in deep freshwater lakes and ponds, and recently, hydroelectric lakes and oxidation ponds. Despite being widespread, they have a patchy distribution, and most scaups are on suitable habitat areas in Northland, the upper Waikato, Rotorua, Taupō, Hawke's Bay, West Coast, North Canterbury, and the Southern Alps. Unlike other members of this genus, the scaup is not migratory, although it does move to open water from high country lakes if they become frozen in winter. A recent population expansion has happened in Christchurch thanks to predator control and suitable habitat. Behaviour and ecology New Zealand scaups are usually seen in flocks during autumn in winter, with flocks of over 200 birds seen at traditional moulting and wintering sites such as Lake Rotorua, Lake Taupō, Lake Tūtira, the Bromley sewage ponds, and the Ashburton Lakes. Breeding New Zealand scaups typically leave their wintering flocks by September, and the males become territorial. The nest is a bowl of grass, sedges and other similar plants, lined with down, and in dense cover close to water. Sometimes scaups breed in loose colonies if suitable breeding habitat is scarce. Egg laying is mostly from late October to December, but some late or replacement clutches are laid until February. The clutch of can contain 2–15 creamy-white coloured eggs, although the typical range is 6–8 eggs, and clutches of 12 eggs or more are probably laid by multiple female scaups. The eggs are around 65mm x 45mm (2.56in x 1.77in) in size, and weigh around . The eggs are laid in an interval of 1.2–1.4 days, and are incubated by the female for around 30 days. The female broods the ducklings on the nest for up to 24 hours before leading the ducklings to water. The ducklings are immediately capable of diving to feed. The female guards the brood during the fledging period of around