Sounds of the forest
A New Zealand forest filled with birds is alive with sounds, as birds find food, defend their territory, attract mates and guard chicks. Some small forest birds are easier to track by ear than by eye.
Today, many forests have fallen quiet as introduced predators take their toll. The best places to hear the hubbub are predator-free areas – offshore islands, and fenced or managed ‘island’ reserves on the mainland.
It is illegal for people to hunt any native forest birds.
Nearly all of New Zealand’s small native forest birds are endemic – found nowhere else. Many belong to families that only exist in New Zealand, and have unusual characteristics such as very strong legs and limited flight. Only the silvereye and shining cuckoo are not endemic.
Most of the small forest birds are passerines – belonging to the order Passeriformes. Sometimes called perching birds, they have four toes (three pointing forwards and one backwards) with which they cling to branches. Passerines are the largest bird group worldwide, and probably originated on the Gondwana supercontinent.
New Zealand began to drift away from Gondwana around 85 million years ago. At least one passerine family has probably evolved in isolation ever since – Acanthisittidae, the New Zealand wrens (not related to northern hemisphere wrens). Surviving members are the tiny rifleman and the rock wren.
Another ancient passerine family is Callaeidae, the New Zealand wattlebirds, which are unrelated to Australian wattlebirds. Its members are the saddlebacks, the kōkako (larger birds) and the extinct huia. The stitchbird is thought to be related to this group, in a family of its own. A third endemic passerine family is Mohouidae, which includes the yellowhead, whitehead and brown creeper.
Other small forest species have ancestors that arrived later, across the sea from Australia. Some came via islands in the north Tasman Sea, probably when more of the Norfolk Ridge was above water. Later arrivals include the ancestors of parakeets, honeyeaters (bellbirds and tūī), warblers, robins and tomtits. The silvereye is a more recent immigrant – it is also found in Australia.
New Zealand forests also have two species of migratory cuckoos.
Most of the small forest birds have a possible life span of 12 to 15 years, but in a typical forest with predators, their life expectancy is about three years.