Many interesting native birds inhabit New Zealand’s wetlands – swamps, freshwater lakes and streams. They include grebes, bitterns, spoonbills, black swans, shelducks, dabbling and diving ducks (some flightless), rails, crakes, gallinules and coots, as well as kingfishers and fernbirds at wetland margins.
Some shags, herons, gulls, terns and wading birds also spend part of their time in freshwater wetlands.
An unusually high proportion of New Zealand’s native birds are wetland species – 30%, compared with less than 7% worldwide. This includes 15 species that have become extinct since humans first settled in New Zealand, around 1250–1300 AD.
Today some native wetland species are very rare, with less than 1,000 birds. New species have also become established, either by being deliberately introduced or arriving independently.
Loss of wetlands
Wetlands are areas of high biological productivity, and their fish and birds were important food for Māori. When Europeans arrived in New Zealand, freshwater wetlands covered around 672,000 hectares. But many areas have been drained for conversion to farmland or urban development – 87% have been lost since around 1800, and they now cover just 2% of New Zealand.
In some of the remaining wetlands, the water quality has declined. Eroded soil from disturbed land can build up in the water and choke aquatic organisms. Extra nutrients from fertiliser runoff can cause rapid algal growth, oxygen depletion and toxicity, which threaten the invertebrates, fish and plants that wetland birds depend on.
Many community groups, regional bodies and landowners are re-creating or restoring wetlands on private and public land. Organisations such as Ducks Unlimited rear native ducks in captivity and release them at suitable sites, and populations of some wetland bird species are starting to increase.