Many birds, fish and invertebrates depend on wetlands for their survival.
Wetlands usually contain a variety of habitats that provide food, shelter and breeding sites for many native birds.
Pūkeko (swamp hens), white-faced herons, little shags and some waterfowl (dabchicks, grey teal, paradise ducks, scaup and New Zealand shovelers) are fairly common. Banded rails, Australasian bitterns, spotless and marsh crakes and fernbirds are secretive, seldom seen as they hide among raupō and rushes.
Introduced game birds (black swans and mallards) are common on lakes and wetlands and are hunted in the winter months, between May and July.
Species in decline
Grey duck numbers have declined throughout the country as wetland habitats disappear. The once common brown teal is seriously endangered, with remnant populations surviving only in Fiordland (the far south) and Northland (the far north).
Longfin and shortfin eels are found throughout New Zealand’s wetlands. The shortfin eel is most common in lowland and coastal sites. Longfin eels travel further inland and may be found at higher altitude.
New Zealand’s five species of mudfish (Neochanna) are specialised for life in wetlands and pools that dry up in summer. During droughts they burrow into the mud, and survive curled up in the damp sediment. They remain there for weeks until the rains arrive and their pools fill with water again.
Common whitebait (Galaxias) species of wetlands include īnanga and the giant kōkopu. The rare gollum galaxias inhabits swamps and shallow lakes of Stewart Island and Southland, and in the Catlins and the Nevis River in Otago.
Perch are the most widespread introduced species. Tench and rudd are common in wetlands of the Waikato and northern North Island.
The three introduced frog species are associated with lowland wetlands, in particular at their tadpole stage. Green and whistling frogs are common throughout the country. The green and golden bellfrog is restricted to the northern half of the North Island.
Insects abound in and around wetlands and provide food for the fish and birds there. In summer swarms of gnats are commonly seen flying above wetlands, and dragonflies and damsonflies sun themselves on rushes. Many species of moth – such as flax loopers, wirerush loopers, cabbage tree moths and wetland oranges – flit about day and night.
Freshwater snails are common, and include the ubiquitous dark snail (Potamopyrgus antipodarum), the left-handed water snail (Glytophysa variabilis) and Lymnaea tomentosa, the host for liver-fluke, which affects grazing stock.