The White-faced Heron, Ardea (Egretta) novaehollandiae, self introduced from Australia, began nesting here in the late 1940s so as a consequence is classified as a native. It is now the most common heron, having benefited from the widespread conversion of forest to farmland. They are found throughout Australia, except for the dry hinterland, and also occur in Indonesia, New Guinea and New Caledonia.
They feed in aquatic environments and damp pastures, taking fish, tadpoles, frogs, insects, spiders, worms and even mice. They will also, like the legendary white heron, raid suburban fish ponds. Food is obtained in a variety of ways, such as walking and disturbing prey, searching among damp crevices or simply standing in the water and watching for movement. There is apparently no official count on these birds and since the virtual disappearance of the introduced Australian bell frog, they have reduced in numbers.
As with other herons, male and female white-faced herons share in the raising of their young. They build the nest together, usually high in trees, and take turns to incubate the eggs and feed the nestlings. Breeding takes place any time between June and October, bringing about three to five pale blue-green eggs, usually with only two young birds surviving. 
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Ref:  NZ BIRDS.COM

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