Birds of New Zealand
Like other isolated islands, New Zealand is home to some unique fauna. Most people will have heard of the kiwi. Two other endemic birds are the weka and the night parrot. Both are flightless.
The weka (Gallirallus australis) is a sturdy bird and a species of the rail family. Four subspecies are recognised. Apart from a few colonies on the mainland, the various subspecies are found mainly on islands.
Wekas are found in forests, sand dunes, rocky shores, sub-alpine grasslands and even semi-urban areas.
These rich brown birds are mottled with black and grey. Colours vary a little between subspecies. The males are 20 to 24 inches in length and weigh between 1 and 3 ½ pound. The hens are slightly smaller. The wingspan is 20 to 24 inches. They have a rather large, red-brown beak about an inch long. It tapers and is stout enough to be used as a weapon. The legs are strong. The pointed tail flicks almost constantly.
The weka is omnivorous, feeding mainly on invertebrates and fruit. Thirty percent of the diet is made up of animal food such as earthworms, beetles, ants, grubs, slugs, frogs, rats, mice and small birds. Leaves, berries, grass and seeds make up the rest of the diet. Weka play an important role as seed-dispersal agents. Although furtive, they are also curious and will fossick around houses and camps, often stealing shiny objects
If there is plenty of food, wekas may nest up to four times a year. Material such as grass will be formed into a bowl under cover of thick vegetation. Three or four eggs are normally laid. These are splotched creamy or pinkish in colour. Incubation takes four weeks. By the age of six to ten weeks, the chicks are fully grown. Both parents share incubation and feeding duties.
Populations of weka appear to adapt well to highly modified habitats but are very vulnerable to threats. They themselves can be a threat to other threatened species when introduced to offshore islands. Cats, dogs, ferrets, stoats and rats take eggs, chicks and adults. There is competition for food from introduced species; modification and degradation of wetlands and other habitats also impacts on the weka. Pest control measures can cause deaths among weka because of their foraging nature and some become roadkill. It is classed as vulnerable. Weka feature in Maori folklore and were used as a source of food, perfume, feathers and oil to treat inflammation. Curious, feisty and bold, they were relatively easy to catch.
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The Kakapo (Strigops habroptila) is also known as the night parrot. Like the weka, it is flightless and endemic to New Zealand. The yellow-green plumage is finely blotched. There is a distinct facial disc of whiskery feathers or vibrissae which have a sensory function. The beak is large and grey. It has short legs, relatively short tail and wings, and large feet.
A combination of features makes this bird unique among parrots. No other parrot is flightless. It is also the heaviest of the parrot species. It is nocturnal, herbivorous and one of the longest living birds in the world. Unlike the ratites which have no keel to the sternum, the night parrot has a diminished keel.
It is found in forests, scrublands, areas of tussocky grass and coastal regions.
It has a robust, rotund physique with reduced wing muscles and diminished keel. Males measure 24 inches and weigh between four and nine pounds when adult. The wings are used for support and balance. The birds accumulate body fat in large amounts. The mottled yellowy-green plumage gives good camouflage. The plumage is very soft and the tail feathers often become bedraggled from trailing on the ground. It walks with the head lowered, allowing it to sense the terrain with its vibrissae. The feet are large and scaly with two toes pointing forward and two back. The pronounced claws make climbing less hazardous. The bird has a musty odour which often alerts predators to its presence.
The kakapo is nocturnal. During the day it roosts in trees or on the ground. It is an excellent climber. It will 'parachute' down by leaping and spreading the wings. The strong legs enable the bird to keep up a fast jog-trot for miles. It is a curious bird and quite happy to interact with humans. When threatened the kakapo will freeze.
It has a low basal metabolic rate. The sense of smell is well developed, allowing it to discriminate when foraging. The beak is adapted for grinding. The gizzard is relatively small. Plants, pollens, seeds and fruits are eaten. The rimu fruit is a particular favourite. The bird often grabs a leaf with its foot and uses the beak to tear out the nutritious portions. Discarded clumps of plant fibres are clear evidence of the presence of the kakapo.
This is the only flightless bird to have a lek breeding system. The males gather together then compete to attract females. The hens listen to the males before choosing their mate. The males do not pursue the females and the pair come together only to mate. Each male has a court or lek consisting of several saucer-shaped depressions. These bowls may be established against anything that will help reflect the booming sound of the mating calls. Bowls are connected by trails which the males keep meticulously clear of debris.
The mating calls are made by inflating a thoracic sac. After around 20 loud booms, he finishes his display with a high frequency 'ching'. After a short rest, he begins the sequence again. The sound carries at least a kilometre on a still night. Males call for eight hours a night for three or four months. They may lose half their body weight during this time. The calling also attracts predators.
The female enters the court of her chosen male who then rocks from side to side while clicking his beak. He turns his back, spreads his wings and walks backwards towards her. Once the birds have mated, the hen departs, leaving the male to entice another female.
Nesting kakapo hens often have a bare patch on the belly. Up to three eggs are laid under cover or in hollow tree trunks. The females must go off to feed each night leaving the eggs vulnerable. The helpless chicks are just as vulnerable. Life expectancy is 95 years. The bird has a very low rate of reproduction, breeding only when trees fruit heavily. Females can alter the ratio of male and female chicks by varying her eating habits. Protein-rich food produces more male offspring.
The kakapo is considered critically endangered. Before the introduction of non-native predators, it was preyed on only by native birds of prey.
Predators include introduced cats, rats, stoats and ferrets. Surviving kakapo are now closely monitored on three islands which are free of predators. The bird was significant to the Maori people. It was hunted for its meat and its feathers. Clothing incorporating the feathers were highly valued. It was also kept as a pet. Between 1982 and 1997, surviving kakapos was transferred to predator-free islands. The Kakapo Recovery Plan, first developed in 1989, has been quite successful with numbers of birds increasing steadily.
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