The Pacific black duck is a dabbling duck found in the northern hemisphere. It has a dark body and a paler head with a dark crown and facial stripes. In flight, it shows a green speculum (a patch on the secondary wing feathers) and pale underwing. All plumages are similar. Males tend to be larger than females, and some island forms are smaller and darker than the main populations.
Pacific black ducks are found in much of Indonesia, New Guinea, Australia, New Zealand, and many islands in the southwestern Pacific, reaching to the Caroline Islands in the north and French Polynesia in the east. These birds live in a variety of wetland habitats, flooded grasslands, fresh or brackish lagoons, estuaries, streams, and small ponds.
Pacific black ducks are social birds and are often seen in pairs or in small groups. They feed by 'dabbling' mainly at night. Dabbling is the way of obtaining food in which the bird plunges its head and neck underwater and upends, raising its rear end vertically out of the water. Occasionally, Pacific black ducks may feed on land in damp grassy areas. Like their relatives mallards and American black ducks, Pacific black ducks are one of a number of duck species that can quack. Females produce a sequence of raucous, rapid quacking which decreases in volume, while males may utter soft hiss or long quacking.
Pacific black ducks are monogamous and males and females stay only with one partner. During the breeding season pairs usually perform courtship displays which include mutual preening, bobbing, and wing flapping. Pacific black ducks nest near water. Their nests are usually hidden in tall grasses or in a tree hollow. Females lay 8 to 12 greenish eggs and may produce two broods per season. Eggs are incubated within 26-30 days, mainly by the female. Ducklings are born fully developed (precocial). They fledge at 48-58 days of age and are ready to breed for the first time when they are 1 year old.
The main threats to Pacific black ducks include competition and hybridization with mallards, habitat loss and hunting.
According to the IUCN Red List, the total Pacific black duck population size is 180,000-1,200,000 individuals. In 1993, the New Zealand population of the Pacific black duck included around 80,000-150,000 individuals. Another subspecies of the Pacific black duck that breeds on the southwest Pacific islands and northern New Guinea included around 10,000-25,000 birds. Overall, currently, Pacific black ducks are classified as Least Concern (LC) on the IUCN Red List.