The breakup of Gondwanaland, about 60 million years ago, caused New Zealand to become the most isolated landmass of its size. Isolation is the dominant theme in the origin and evolution of New Zealand’s birds.
Isolation has limited the spread of land birds to New Zealand and prevented snakes and land mammals from spreading here of their own accord. What our land birds lack in numbers is made up for by the interest that attaches to them for having evolved for so long in such isolation.
Evolution without mammals
In New Zealand, evolution proceeded without any predatory mammals. There were no mice, rats, mustelids, or any other mammals except for tiny short and long-tailed bats. In the absence of mammals, our birds evolved to fill those ecological niches.
Many birds became larger and heavier than their ancient ancestors, and many became flightless, as the need to fly from predators was gone. This worked well in prehistoric New Zealand, but had disastrous results when humans introduced predators.
Flightlessness
Flying uses a great deal of energy and the ability to fly is lost very quickly where it is no longer needed. New Zealand is renowned for its number of flightless birds – 38 species originally. The number is large, because New Zealand lacked predatory mammals until the arrival of humans 1000 years ago.
Moa becomes extinct
Among New Zealand birds there were seven endemic families, 37 endemic genera of birds and 120 endemic species. Forty-eight species or 40 per cent of these endemic birds are now extinct. These include Moas that are extinct flightless birds, unique to New Zealand and the only known birds to have no wings at all. Before man, the only predator of the moa was the majestc New Zealand eagle, Harpagornis or Haast’s Eagle – the largest known bird of prey in the world. Moa succumbed to the ecological disruption that came with settlement, including hunting, habitat loss from land clearance, and rat predation of eggs and chicks.
Harpagornis or Haast’s Eagle
Harpagornis, New Zealand’s now extinct eagle, were massive birds. The female had an estimated wingspan of 2.4m and weighed about 14.5 kilograms. Males were slightly smaller. It’s believed that these eagles still existed when the Maori came to New Zealand, but habitat destruction and the hunting to extinction of the moa, led to the loss of their main prey species and their eventual decline.
Kiwi survive settlement
Kiwi are New Zealand’s best known flightless birds, the oldest surviving family of New Zealand birds, and the only ones that are nocturnal. All five species of Kiwi are endemic to New Zealand. They have soft hair-like feathers on their body, and bristle-like sensory feathers around the face.
Kiwi are the only bird with nostrils at the end of their long bill. As they probe in the soil for prey, they snuffle noisily as they exhale to clear dirt from their nasal passages. Unlike most other land birds they have an excellent sense of smell.
The Little Spotted Kiwi is the smallest and rarest of the Kiwi and now survives only on sanctuary islands. Other species of Kiwi are in decline, but conservation programmes are helping to protect habitat and control their main threat – the introduced stoat.
All five species of Kiwi can be seen by keen bird watchers at various locations around the country. The best time of day to see Kiwi and hear their loud piercing calls is an hour after sunset when they emerge from their day burrows and call to locate their mate.
Flightless swamp hen
The South Island Takahe or Notornis, is a giant flightless swamp hen – the world’s largest living rail, weighing 2-3kg. There were two separate species of Takahe in New Zealand, but the taller North Island species was extinct before European settlement. South Island Takahe were believed to be extinct until they were rediscovered in a remote mountain valley in Fiordland in 1948. Both species are closely related to the modern swamphen, the Pukeko, but research suggests they may have arisen independently after separate colonisations by ancestors of the Pukeko.
Nocturnal, heavy and flightless
The Kakapo is the heaviest parrot in the world and the only flightless species of parrot.
It is also unusual among parrots in being solitary, nocturnal and in having an owl-like facial disc of hair-like feathers. The male Kakapo attracts females by booming from a track and bowl system that he has cleared on a prominent ridge-top. These large flightless parrots feed on the ground and by clambering up shrubs and small trees, using their wings for balance.
Kakapo were found throughout New Zealand up to the early period of Maori settlement, when they began to decline. After European settlement and the introduction of stoats, Kakapo numbers fell rapidly and there are now only about 120 Kakapo left. This number has been increased due to intensive conservation efforts.
Unique Avian Fauna
New Zealand has a very unique avian fauna that includes two species of flightless ducks, (the Auckland Island Teal and Campbell Island Teal), wattlebirds like the extinct Huia and the endangered Kokako and Saddleback (or Tieke), and honeyeaters like the rare Stitchbird (Hihi), Tui and Bellbird.
The introduction of mammals (such as the rat, possum, stoat, weasel, ferret, goat, pig, deer) by early settlers had a disastrous impact on populations of New Zealand’s birds.
These birds, having evolved without the presence of mammals, had no defenses for repelling them.
Pest free Islands
Pest-free island sanctuaries are New Zealand’s response to this destruction by mammals.
New Zealand leads the world in developing techniques for eradicating pests from islands, and developing island sanctuaries, both on the mainland and on off-shore islands.
These range from open island sanctuaries like Tiritiri Matangi in the Hauraki Gulf near Auckland, to mainland islands that are fenced with predator proof fencing to prevent mammals re-colonising an area.
These are a successful means of conserving New Zealand's precious rare, endemic birdlife.
References
Gibbs G, 2007, 'Ghosts of Gondwana' , Craig Potton Publishing, New Zealand.
Holdaway RN and Worth TH, 2003, 'The Lost World of the Moa', Indiana University Press, Indiana.
Tennyson A and Martinson P, 2006, 'Extinct Birds of New Zealand', Te Papa Press, Wellington.
