South Island Takahe
| South Island Takahe | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
South Island Takahe ( Porphyrio hochstetteri ) |
||||||||||
| Systematics | ||||||||||
|
||||||||||
| Scientific name | ||||||||||
| Porphyrio hochstetteri | ||||||||||
| ( AB Meyer , 1883) |
The takahē ( Porphyrio hochstetteri ) is a rare bird art of the South Island of New Zealand , which the family of rallidae belongs (Rallidae).
With an average height of 63 cm and an average weight of 2.650 kg, it is about the size of a domestic goose and the largest living rail in the world. She is completely incapable of flight , but can run very quickly.
The South Island Takahe had been considered extinct since 1894 and was not rediscovered until 1948. It was saved from extinction through a very extensive protection program supported by scientific studies and public relations work. The 2016 population consisted of 306 individuals.
As Takahe refers to two mutually very similar flightless birds of New Zealand: the recent takahē ( Porphyrio hochstetteri ) and the extinct North Island Takahē ( Porphyrio mantelli ). The name Takahe comes from the Māori language .
features
Appearance
The South Island Takahe has a very high and narrow beak with which it can bite very forcefully in order to snap off the stalks of its main food, the tussock grass of the genus Chionochloa, close to the ground. In relation to the body size, the beak is more than one and a half times as high as that of the closely related purple chicken .
The plumage has a loose and silky structure. The chest is dark blue in color, which becomes duller on the neck, head, abdomen and the feathered part of the legs. The legs are salmon red. The feathers on the back, the short wings and tail are olive green and shimmer almost metallic. The feathers under the short tail are white. If you look at the bird from the front, the plumage appears much clearer and more brightly colored than from behind. The eyes are auburn. The big beak is pink. Above the upper beak there is an unfeathered red front plate.
The South Island kahe resembles the purple chicken ( Porphyrio porphyrio ) in appearance , but has more vibrant colors. In addition, she is much bigger and more powerfully built. Males are taller and heavier at an average of 2.65 kg (2.3–3.25 kg) than females, which weigh an average of 2.30 kg (1.85–2.60 kg). They have the lowest weight during the rearing season in December. Despite the difference in size, the sexes are difficult to distinguish.
anatomy
If you compare these four species with each other, the purple hen is able to fly without restriction, while the regression that leads to the inability to fly from the Tasmanian grouse to the southern island takahe to the wekaralle continues to progress.
The rib cage of the South Island Takahe is shorter in relation to the body size than in the other three species. The sternum of the South Island Takahe is wide and flat and has only a weakly developed sternum ridge, to which hardly any flight muscles can attach. Part of the sternum has completely disappeared: the rostrum, which corresponds to the manubrium in humans, is missing on the front. The thickness of the collarbone is also much greater in the purple chicken than in the South Island kahe. The shoulder blade and collarbone decrease significantly in size.
The South Island Takahe has short wings that are unsuitable for flying, but are armed with a strong claw on the wrist. On the other hand, the pelvis and legs increase in size compared to the flying purple chicken. The pectoral muscle (M. pectoralis) is significantly smaller in relation to the body size of the South Islanders than that of the purple chicken, while the leg muscles (M. flexor cruris lateralis) are significantly longer.
nutrition
The wild South Islanders' diet consists primarily of grasses and herbs, and the animals spend much of the day grazing. In one study, family groups from the South Island nears spent around 70% of the observation time eating and foraging and 30% of their time doing other activities such as cleaning.
Adult South Islanders do not eat animal food, but do feed their young animals, which would starve to death with the food of the adults. Since the young birds have an increased need for such nitrogen compounds to build up their own protein, insects are indispensable in the first months of life.
One consequence of this diet is the large gizzard size and muscle mass of both adult and young South Islanders. Due to their nutrient-poor diet, South Islanders near the South Island produce feces around 8 m in total length per day. They also eat a lot of stones (240–440 pieces daily, an average of 18 mm 3 in size) in order to be able to break down the fiber-rich food in the gizzard.
Nevertheless, the grass in the excrement is sometimes so poorly digested that it can be mistaken for uneaten parts of the forage plants. Smaller herbivores are generally poor feed converters when they eat fiber-rich food, since cellulose is only digested by bacteria , which in the shorter gastrointestinal tract of smaller animals have less time to do their work than in large animals. The willow grouse is a comparatively poor feed processor, Canada geese , brent geese and emus are better feed converters than the South Island kahe. The South Island kahe only absorbs sugar well from its diet. Because it is such a bad feed processor, the South Islanders are very picky about their forage crops and only eat the most nutritious parts of a blade of grass or herb.
Diet in the Murchison Mountains
Summer food: rose grass and celmisia
The South Island nears in the Murchison Mountains , part of the Fiordland National Park , spend the snow-free time in the alpine Bültengraswiesen between 1110 m and 1430 m altitude. Although there are about 250 species of plants there and in the nearby mountain forests that could be used as feed in question, the summer food of Südinseltakahen October to January consists mainly of three types of typical New Zealand tuft, Tussock- or Bültengräser and the leaf bases of Celmisia petriei , a member of the daisy family .
Of each blade of grass, South Islanders eat only the water and nutrient-rich growth zone at the base of the stem. The more nutrient-rich the stalk, the more they eat of it. With their powerful beak, they bite off the stalk at the connection between stem and stalk, eat the lower 1–2 cm of the stalk and spurn the rest. Tussock grasses need such a force for this that a smaller bird would not be able to to get at this most nutritious part. The young birds are therefore dependent on the help of their parents for the first three months.
Before a bird eats a budgrass plant for a long time (they can grow up to 2.5 m high), it tries many plants in the area and selects its food according to their nutritional content. The preference for certain plants changes during the year: In spring and early summer they tend to eat nitrogen- and phosphorus-rich plants, in late summer and autumn they tend to choose foods rich in carbohydrates . The order of precedence in preference is: Chionochloa pallens > C. flavescens > C. crassiuscula > C. teretifolia . South Islanders prefer C. flavescens to C. pallens in November and December , after which the order is reversed until April. In terms of nutritional value, C. rigida belongs to a comparable category to C. crassiuscula , red tussock grass ( C. rubra ) has the lowest nutritional value, and South Island nears, for which almost only this grass is available as summer food in their territory, are significantly lighter and have the Winter significantly worse chances of survival than birds that could eat more nutrient-rich species. South Island nears have never been observed to eat C. acicularis and are very rare in the wetter areas to the west of their range in Fiordland , where it is the most common tussock grass.
Tussock grasses such as C. teretifolia and C. acicularis , which live on older, poorly drained soils, are rarely or never eaten. Birds with a significantly weaker beak than the South Island Takahe could only eat the slowly growing tussock grasses by digging up the plant and thereby destroying it. Grazing deer also kill the plant if they eat it. On the other hand, the South Island Takahe does not endanger the plant with its harvesting technique, as the stem bases regenerate.
Takahen eat the base of the young leaves of the Celmisia species, which belong to the Asteraceae among the daisy family. The leaf base of Celmisia petriei is particularly rich in calcium and sugar and is therefore popular.
When the seeds of various smaller grasses ripen in the fall (January to March), they are also eaten by the South Island aha. This also applies to the seeds of C. pallens and other tussock grasses, which only bloom and produce fruit every three years and are then an important source of food.
Winter food: the fern Hypolepis millefolium and its addition to other plants
In winter, the alpine meadows are usually covered with a layer of snow up to one meter thick for at least two months. For a long time it was assumed that South Island nears migrate to lower elevations and overwinter in the forests on the shores of the Fiordland . By telemetry has now been demonstrated that they primarily in the shrub zone at or slightly above the timber line hibernate and there from deciduous fern Hypolepis millefolium feed, supplemented by Chionochloa species and other grass and herbs. Here, too, they live on plants that grow on young, nutrient-rich soils.
The rhizomes and stems of the fern Hypolepis millefolium , which is one of the spotted ferns, are eaten in Fiordland from late April (southern late autumn) to late September (early spring), where they form their most important winter forage with 60–80% food. This is also the time when the rhizomes of the fern have their highest starch content. This is then around 20% of the dry weight. This makes the fern one of the few good sources of carbohydrates available. The rhizomes are digested more completely by the South Islanders than the stalks of grass, as can be seen from the fine-grained blackish droppings at that time. Since the cold in winter makes South Islanders need more energy to maintain their body temperature, the starch content at this time of the year is more important than the content of other nutrients. South Islanders dig up the fern's rhizomes with their beak and pull them out of the ground.
While the Hypolepis -Rhizome a good source of strength, nitrogen and phosphorus are, they do not contain other nutrients in sufficient quantities. It is therefore necessary to supplement the winter forage with other plants, such as some forest grasses (e.g. Chionochloa conspicua ), sour grasses ( Uncinia affinus , U. clavata , Carex coriacea ) and rushes ( Juncus gregiflorus ). The forest rose grass species Chionochloa conspicua and the sedge species Carex coriacea contain a lot of phosphorus, magnesium and potassium. Carex coriacea is also high in nitrogen, soluble sugars and fats. The rush species ( Juncus gregiflorus ) contains a relatively large amount of soluble sugar and sodium. In addition, Fungus gregiflorus and the leaf bases of Schoenus pauciflorus are eaten.
The variety of food plants and their abundance decreases in the herb layer of the riparian forest at the foot of the Murchison Mountains towards the east. This is either due to the different densities of the deer population or to the slower recovery of the drier east after overgrazing by deer. In addition, the soil there freezes deeper, which makes it difficult to dig up the fern roots. In addition to the poor food quality of Chionochloa rubra in comparison to the other Chionochloa species, this is probably one of the reasons that South Island nears in the east of their range have lower weights and survival rates. This is also likely to cause the reduced breeding success due to smaller egg sizes in the following year.
Diet on the predator-free islands
Before people came to New Zealand, the South Islanders also lived in New Zealand's lower elevations. There is no doubt that she fed on different grasses and herbs there than she does in the Murchison Mountains today. What their diet was like back then can now be estimated based on what South Island kahs eat on the predator-free islands where they were released.
Since the main summer food of the South Island nears in the Murchison Mountains consists of some tussock grasses that normally only grow above the tree line, it was feared that the bird might not find adequate food on the islands. She proved this concern to be unfounded, as the South Island Takahe eats other types of grass there ( Poa , Dactylis ) and clover and in some cases they even offer her a better fodder basis.
Many meadows on Mana are dominated by bristles . In a study, the seeds of these plants were the main food for the South Islanders (72.5%). On Kapiti Island , the soft stalks of some species with smaller seeds (such as Poa sp.) Were their main diet (61.1%). Clover is a common component of food on both islands . In contrast to the purple grouse, adult South Islanders do not eat insects and other invertebrates, but do feed their young with them.
Way of life
Habitat and habitat behavior
South Island nears occupy territories of 0.8–80 hectares and defend them aggressively against intruders. On the islands there is an average of 0.8–2.1 ha with additional feeding and 4–34 ha when the animals had to look after themselves. In the Fiordland the districts were often much larger and could cover up to 80 ha. Pairs stay together all life, and the territories remain in possession of the same breeding pair as long as the pair persists. Only about 0.5 hectares around the nest are used during breeding. As soon as the juveniles are independent, territories are no longer defended as aggressively, and it happens that South Island sheds can be observed on neighboring territories. In the Murchison Mountains , part of Fiordland National Park , they sometimes hike in winter to lower elevations on the shores of Lake Te Anau , where there is less snow.
Takahen need habitats that offer enough grass for food as well as enough bushes to protect against birds of prey and that are well structured. Neither closed high forest nor open grassland are suitable habitats. They also need fresh water near the nesting site and like to be in swamps. The size of the district depends on the proportion of areas with a mosaic of grass and bushes in the district. The nutritional value of the forage plants available there also plays a role.
It was assumed that the South Island Takahe was actually a bird of the mountains that was only pushed into lower elevations by the snow in winter, where the known museum specimens were shot. In fact, it seems to have been pushed into habitats such as the Murchison Mountains by human hunting and predators, which offer it a rather poor livelihood, while the predator-free islands on which it was relocated offer much more suitable food, as the different territory sizes indicate. The research results on the area size without additional feeding also suggest that the habitat quality on the Mana, Maud and Kapiti Islands (on average 2.8, 8 and 5.5 ha) is better than on Tiritiri Matangi (without additional feeding, on average 25 ha) .
The maximum age that South Islanders can reach is not exactly known. However, some specimens lived to be over 14 years old in the wild.
Predators
One of the natural enemies of the South Island nears is the Marsh Harrier ( Circus approximans ), which has been observed several times trying unsuccessfully to hit a South Island Hawk. So far, since the South Island kahe is very rare, only one case is known in which the consecration was successful.
The individual areas in the area are used differently depending on the need for food and the threat from birds of prey. Forests are avoided because they do not contain enough forage crops. Only when the chicks are small in spring are they used more often to catch insects for the little ones. Open grasslands are avoided as far as possible, as the threat from birds of prey is particularly high there. Chicks often stayed under cover in mixed grass and bush habitats while the less endangered parents gathered food for them. With a higher population density, open grasslands are sought more often due to lack of food, which increases the risk of birds of prey.
Another natural enemy is the flightless Wekaralle . Wekas in Fiordland are known to eat eggs and young chicks from the South Island kahe. Obviously, this is not an innate behavior, but a learned one, because on Kapiti, one of the predator-free islands where the South Island nears were newly introduced, not a single case was known, while they do so elsewhere.
Ermines were only introduced by humans. They are the greatest threat of the known enemies of the South Islanders. They have been seen hunting adult South Island takahen, but radio telemetry studies show they pose little threat to adult takahen. The degree of danger to young animals is not fully known, but they are likely to be more at risk. The South Islanders react less to soil enemies than their closest relative, the purple hen . She is also much less afraid of people. This is a weakly pronounced island tameness exclusively against soil enemies, since there were originally birds of prey of all sizes in New Zealand.
Reproduction and rearing of young
South Islanders are monogamous and genetically monogamous. Once an animal has found a mate, it stays with him until one of the birds dies. South Island nears are among the few birds in which not only the pair bond lasts for years, but also do not mate with animals with which there is no pair bond (genetic monogamy).
Before the mating is done. A complete courtship sequence would be as follows: First, the birds take turns calling. Then they run towards each other and stand close to each other with their necks stretched upwards. Then they circle each other and peck at the partner's neck. Then the female turns away from the male, spreads her wings and lowers her head. Mutual cleaning, copulation. Often only part of these behaviors are shown during a courtship sequence.
Birds breed at the earliest when they are one year old, but usually only when they are over two or three years old. In the known cases of annual birds that hatched, no juveniles hatched from the eggs, and two-year-olds are probably even less successful than fully grown birds. The weather and the available food have a considerable influence on the frequency of broods and the success of the breeding. After heavy winters, both adults and young birds die in the Murchison Mountains. Cold and stormy weather during breeding reduces breeding success. In bad years, even couples who own a territory and have already successfully incubated do not breed. The number of successfully breeding pairs in good years is often four times as high as in bad years.
For nest building, a place near the water is sought where species such as New Zealand flax or tussock grass provide good cover. The nest is built by both animals. South Islanders often build multiple nests before laying eggs in one of them. The female only lays one to two eggs per clutch (average 1.78), and nests with 3 to 4 eggs are rare. 39–75% of the eggs are found to be sterile.
During the breeding season, both parent birds are never seen looking for food together, while the pair always stay close together outside the breeding season. It is therefore assumed that both parent birds take turns breeding. Females breed more often during the day while males do this more often at night. Young animals from the previous year sometimes help the parents with breeding.
If no young hatch from a clutch, the parents lay a second, sometimes a third clutch 4.5–8.5 weeks after the first. The time may be longer under natural conditions, as unfertilized eggs were removed during the observations and the nest was not destroyed, so that the birds lose as little time as possible before the next brood.
The rearing takes place in summer. Chicks less than a week old weigh around 100 g. They have an egg tooth when they hatch and a 3 mm long claw on each wing. Their black plumage looks almost like fur. The beak is black with a white border. The legs are dark with a purple tinge. At the age of about one month, the chick gets its juvenile plumage, which is similar to that of the adult animal, but is more dull in color. The crest and the beak are almost black, only the upper beak tip is a little lighter. Legs and feet are horn-colored. At this age it weighs around 440 g. Another moulting takes place soon afterwards, but only part of the feathers are changed. The colors of the plumage can now be seen more clearly, but still paler than in the adult bird. The legs, comb and beak begin to turn red. The first summer plumage of the annual birds that follows is a little paler than that of the adult birds.
Takahen are refugees. Both parents care intensely for the boys, keep in constant contact by calling and never go far from them. They feed the young animals with vegetable food. In addition, they hunt insects and other invertebrates for their young that they do not eat themselves. Sometimes there are mice or small reptiles.
When the chicks are young, the parents spend a lot of time looking for invertebrates in the forest and feeding them to their young. When the chicks are up to two months old, they only eat animal food. At the age of two to three months, parents also start feeding their young with plant-based food. When they are three months old, the chicks begin to forage for plants and invertebrates on their own. However, when the chicks are 2–5 months old, the South Island nears spend as much as 15% of their foraging time looking for invertebrates for the young in the forest. From the sixth month onwards, the young birds feed almost exclusively on vegetable food.
In the event of danger, the parents warn with an alarm call, and the young animals hide in dense vegetation. From a brood, South Islanders can only successfully raise one chick, even if several have hatched. This is a research result from the Murchison Mountains. The birds on the predator-free islands never got a chance to try two chicks, although the better feeding conditions and milder winters there might suggest that they might succeed. The birds reach their final weight between the seventh and twelfth month, depending on their nutritional status, and stay with their parents at least until the start of the next brood. Some stay with their parents for a year or less and help raise the young animals for the next year. Sometimes they also join a neighboring family group and help raise the young animals there. Three-year-olds have usually already left their parents' territory. Cubs that leave parents often have to travel far to find vacant territory.
In a study in Fiordland National Park , seven out of ten annuals were still with their parents, one was on the border of the parental territory, and one helped a neighboring couple raise their young. The tenth was already mated. Out of seven two-year-olds one was with their parents, three were probably already mated and one was dead. Three-year-olds are usually already mated.
Inventory development
Before the arrival of man
It was only about two million years ago that the South Island kahe separated from the purple hen . Like the purple hens, South Islanders are still dependent on nutrient-rich grasses and herbs that grow in good soil for their nutrition. However, they have developed a strong beak with which they can snap off the nutrient-rich growth zones of the tussock or cluster grass without destroying the forage plant and were therefore able to feed on plants that purple chickens cannot harvest and were common throughout New Zealand in the last ice age .
After the last ice age, forest cover increased in the lowlands of New Zealand from around 12,000 BC. Especially on soils with a high nutrient content, forests prevailed against mixed habitats where there is both cover and grassland. Grasses and herbaceous plants grew almost only on nutrient-poor soils or in areas that are too dry for the South Island Kakahs, but they are too nutrient-poor for the South Island Kakas. The number of the South Island nears therefore decreased even before the immigration of Europeans. Nevertheless, at that time the birds still lived in areas outside the Alpine zones to which they were later restricted.
Settlement by Māori
The South Island Takahe was spread all over the South Island when humans arrived. It was most common on the edges of forests and river banks with a lot of rain, but was completely absent in dry areas. When the Māori settled New Zealand 800–1000 years ago , about 75% of the island's area was forested. At the time, the South Island kahe population declined dramatically, presumably because the Polynesian settlers destroyed their habitat and hunted them at the same time.
Takahe bone finds from the east of the South Island of New Zealand are generally considered to be very old and probably date from the time of the moas hunter culture in New Zealand. The South Island of the island disappeared from there between 1100 and 1400 AD. In other areas of the island it survived much longer, but was gradually pushed back into more remote areas such as the Murchison Mountains, the Stuart Mountains, parts of the Kepler Mountains and the Hauroko-Poteriteri area.
From printed versions of Māori legends one can read that at the time of the settlement by Europeans they were only known from the Fiordland at the southern end of the South Island. On the shores of Lakes Te Anau and Manapouri , they were frequent enough that the Māori could still remember annual expeditions to hunt South Island hay in 1900. In 1949, the Māori still said that they knew the South Island Takahe as game that could be hunted.
Settlement by Europeans
When Europeans discovered New Zealand and colonized it from the late 18th century onwards, they brought with them further dangers, as well as additionally introduced food crops. They sown forage plants that the South Islanders eat today, but also brought animals with them that also eat these plants, for example the red deer as game. The fox kusu also eats plants similar to those of the South Island Takahe.
The ermine is an established predator of the South Island Takahe . Since South Island kahen are flightless and also react less strongly to enemies of the ground than purple chickens, such predators contribute significantly to the extinction of the South Island kahe.
The South Island Takahe must have been widespread in almost all of the Fiordland , which lies at the southwestern end of the South Island, before 1900 , as shown by the places where the four specimens known before the bird was rediscovered were shot. The last sighting of a South Island kahe was reported in 1894, and it was believed to be extinct until its rediscovery in 1948. There were a few unconfirmed sightings between 1898 and 1948, but they were ignored for a long time, as most of the time only individual birds were sighted. They show that in the Fiordland, existing islands were preserved in some isolated places for a long time.
Presumably, the South Island Takahe also survived in the Nelson District and near the Cook Strait , which separates the North Island from the South Island, into European times. In any case, four unconfirmed sightings were reported between 1866 and 1935.
After the rediscovery
Although the species was rediscovered in 1948 and it was already suggested at that time to ring South Island kahs in order to be able to recognize them individually, it was only started four years later. You didn't want to disturb the birds more than was absolutely necessary.
In 1963, the investigation of ringed South Island Ahaen suggested that the mortality of the adult South Island Ahae was greater than the number of the regrowing pups. But an investigation in the following years showed that the population was stable. It was estimated to be around 500 based on bird tracks, but the true number of birds was probably half that because they were not counted and neither were seasonal migrations nor how much droppings such a bird produced.
Population size counts showed that between 1966 and 1967 and between 1968 and 1969 the population size decreased significantly. In contrast, it decreased only slightly between 1969 and 1970 and between 1973 and 1974. The distribution of the bird decreased and the birds slowly but hardly noticeably disappeared from the less good habitats of their limited remaining distribution area. In 1973/74 there were about 170-200 breeding pairs.
The population was lowest in 1981 with around 120 birds. 1981-1994 it varied between 100 and 180 birds. Between 1990 and 1994 the number of takahen in the Murchison Mountains decreased to 160 and then rose to nearly 250 in 2004 due to an adjustment of the protection measures. In 2016 the population was 306 individuals, one third of them in the Murchison Mountains, two thirds in introduced populations in predator-free areas, mainly on islands.
In 2004, South Islanders lived mainly in two habitats in the Murchison Mountains in Fiordland National Park . One is dominated by the Chionochloa pallens , which provides the South Island Takahe with a fairly good nutritional basis, while the South Island Takahe Valley and Point Burn are predominantly overgrown by Red Tussock Grass Chionochloa rubra , which has a much lower nutritional value, and leads to the affected South Island Takahe are significantly lighter and have significantly less success in the production and rearing of young animals. The soil vegetation in the forests on the edge of the lake in the east of the Murchison Mountains, where the deciduous fern Hypolepis millefolium is an essential winter food, also offers the South Islanders a rather poor livelihood. In general, the Murchison Mountains are not an optimal habitat for the South Islanders.
South Islanders and purple chickens in comparison
To understand how the flightless South Island kahe has changed compared to its flightless ancestor, it makes sense to compare it to its closest living relative, the purple hen.
South Islanders and purple chickens are so similar that they sometimes treat birds of the other species as conspecifics. It has been observed several times that South Islanders and purple chickens defended their territory against birds of the other species when they approached very closely. In such cases, the larger South Island kahe usually wins. It was once observed how a South Island kahe who had not found a partner took care of the cubs of a purple hen couple for one summer before they were brought together with a suitable partner on another island, with whom he raised his own kittens. Courtship behavior was not observed between the species and is also unlikely.
800–1000 years ago the population of the South Island nears in New Zealand declined dramatically. Around the same time, the purple hen immigrated from Australia.
There are several reasons why the purple hen was successful when the South Island kahe was pushed back by humans and its cultural followers: First, the purple hen is able to fly, pays more attention to predators and is also more skilled at protecting itself from them. In addition, it can reproduce much faster than the South Island kahe: it lays an average of five eggs per clutch and can have several broods in one breeding season. On the other hand, the flightless South Island kahe only has another clutch if the first one fails and only raises one chick per year.
As long as this low reproduction rate is sufficient to allow the population to grow, the South Island Takahe is superior to the Purple Grouse in the long run: In direct disputes, the South Island Takahe almost always wins. As soon as the settlement density is so high that there is a lack of food and the vast majority of young animals die in the first winter, the second strength of the South Island Takahe comes into play: their young animals have a size advantage due to the larger eggs from hatching. Since both parents only care for one chick together, it is logically better fed and the advantage over the purple chicken chicks is increased.
South Islanders and purple hens choose the most nutritious herbs and grasses in their habitat and have the same preferences. However, the South Island kahe is a slightly better feed processor than the purple chicken and with its much more powerful beak it can use the cluster grasses as a source of food, the most nutrient-rich parts of which are not accessible to the purple chicken. Conversely, adult purple chickens also eat smaller amounts of insects and other small animals while they are only used to feed their young while shores in the South Island.
So if the main danger for South Islanders and purple chickens lies in the food competition between the two species and the competition within the species, the South Island kahe will prevail against the purple chickens.
Protective measures
Since it was rediscovered in 1948, measures have been taken to protect the South Islanders. In 1972 a comprehensive research program was started covering many areas such as the population dynamics of South Islanders, their diet and reproduction. Their food plants, predators and food competitors were also examined. In the 1980s, the research results that had been collected up to then were used to design a comprehensive plan for the protection of the South Island kahe, which was published in 1982. This included the intensive care of the wild population in order to maximize the breeding success, improvement of the quality of the habitat through various measures, the establishment of a further wild population in Fiordland, the establishment of a breeding station for South Island kahen for this population and the release of South Island kahen on predator-free islands . In 1994 a new plan for the protective measures was drawn up. The long-term goal of the measures planned is to establish at least two large wild populations of at least 500 animals each and many smaller populations on predator-free islands.
An attempt is made to do this:
- ensure that the Murchison Mountains population remains stable.
- that the wild population in Fiordland is spreading again
- that at least three other populations remain on islands and in captivity
- that enough is known about the behavior and diseases of South Islanders to be able to plan the protective measures sensibly.
Murchison Mountains Special Area
The highest priority for the protection of the South Island kahe is the population in the Murchison Mountains, where the last South Island kahe survived. The aim is to increase the population there to 500 animals through protective measures and releases and to achieve that they colonize the entire Fiordland again in the meantime. This number should also correspond to the carrying capacity of this area for South Island nears. 500 km 2 of the Murchison Mountains within Fiordland National Park were designated as a sanctuary for the South Islanders shortly after their rediscovery. This area is not allowed to be visited by tourists. Visits in which South Islanders are filmed in order to raise awareness of the population are only permitted in exceptional cases.
Control of red deer and other food competitors
Five introduced herbivorous mammals have spread to the habitats of the South Island Takahe. These include the red deer , the Rocky Mountain elk , the fox kusu , the chamois and the brown hare . Chamois and hares are only found in very low densities, fox cusus are also rare and prefer different habitats than the South Island kahe. This leaves the two species of deer as the only serious threat.
As a ruminant, the red deer is a considerably better feed processor than the South Island Khae and can therefore live on food crops that do not contain enough nutrients for the South Island Khao. Nevertheless, the deer have similar food preferences as the South Island kahe - they also like the most nutrient-rich plants. If both species live in the same habitat as food competitors, the red deer can graze the area to such an extent that the South Island kahe can no longer feed itself adequately.
When deer colonize an area, they first eat various herbs, and after they have been pushed back, they then eat the main food of the South Islands, the tussock grass, and prefer the same species and plants as the South Islands. Repeated grazing by deer on the same tussock plants severely weakens the plants and can kill them. In areas where there are too few meadows or where the plants growing on them were already almost too nutrient-poor for the South Island Takahe, the South Island Takahe disappeared faster than in better habitats.
In particular, Chionochloa conspicua and some Uncinia species are no longer sufficiently available in some winter habitats of the South Islanders due to overgrazing to meet the bird's nitrogen and phosphorus needs. The fact that South Islanders survived in the Murchison Mountains is also due to the fact that the red deer immigrated there later than in most other areas.
The disappearance of the South Island kahe usually soon followed red deer colonization of an area. The red deer of the Murchison Mountains are descended from animals that were released as game animals between 1901 and 1910 in the South Fiordland near Manapouri . The deer spread to the Kepler Mountains, where their largest population was in the 1950s. In 1962 the last South Island Takahe was observed there. They spread over the Kepler Range along the shores of Lake Te Anau . The first animals reached the Murchison Mountains around 1930. That is why the hunt for red deer is considered the most important protective measure for the South Island kahe.
The elk were released on George Sound around 1905 and began colonizing the northwestern Murchison Mountains around 1940. While they were quite common in the beginning, their numbers are negligible compared to the red deer today.
Measures to reduce the deer population began in 1948 and were stepped up in the 1960s and 1970s. Between 1969 and 1973 the deer population remained the same at around 2040, then decreased to around 815 in 1975. The deer began to avoid open areas and withdrew into the forests, so that they could only compete with the South Islanders in the winter habitats. The decline in the deer population was followed by an increase in the takahe population in the Murchison Mountains, which has stabilized at around 160–170 since 1981.
Also in the 1994 plan for the protection of the South Island of the island, the hunt for red deer from the helicopter and from the ground was still planned. In order to limit the consequences of overgrazing by the red deer, some areas were fertilized, but with little success, so this measure is no longer carried out.
Control of predators
Stoat
Ermines and Wekarall have been seen eating South Island kahen. How great their impact on the total population is is unknown, but any loss of animals and eggs is a serious hazard with such a small population of slowly reproducing animals. The number of stoats fluctuates and is heavily dependent on the increases in the mouse populations that occur in the years in which the grasses, for example the Chionochloa species, produce seeds. In addition, the ermine population could have been artificially increased by the deer hunt, since the shot animals were left lying and ermines also eat carrion. Ermines are caught with traps to protect the South Island Takahe.
On Maud, where ermines remained in small quantities for many years, no case has been recorded of a South Island kahe being torn by an ermine. Ermines do not seem to attack the healthy and well-nourished South Islanders there.
Weka
It is a learned behavior that wekarallen eat eggs and young chicks from the South Island kahen. Not a single case of this kind has been reported on Kapiti Island , one of the predator-free islands where the South Island nears were newly introduced. It has therefore been recommended that solitary animals that eat South Island chicks and eggs be relocated to areas where there are no South Island kahs.
Kusu bait
The fox kusu itself does not pose a threat to the South Islanders, but it was poisoned with hydrocyanic acid compounds to protect other native birds. It could have happened that South Islanders were poisoned as well. There is no definite evidence for this, but it would be a possible explanation for some otherwise inexplicable population declines in areas where these poison baits were used. To avoid this, traps have been constructed to keep the poison bait off the ground so that the South Island kahe cannot reach them. The main reason why the hunt for fox kusus is permitted in the Murchison Mountains is so that the animals are not illegally hunted using methods that also endanger the South Islanders.
Egg swap
Depending on the place and year, around one to two thirds of the eggs in the South Island nears are sterile. At the same time, the clutches only have one or two eggs, so it can easily happen that not a single chick hatches from a clutch. But when two young birds hatch from a clutch, the parents only raise one successfully because young South Island kahans need a great deal of care in order to eat enough fat to survive the winter in the Murchison Mountains.
In order to increase the number of successfully reared young animals, nesting sites are therefore sought in the Murchison Mountains and the eggs are x-rayed, measured and weighed. This can be used to estimate the likely hatch date. Pigeon eggs are removed. Some of these eggs are replaced by wax eggs in order to later replace them with a healthy egg from another couple. In the case of clutches of two live eggs, one is taken from the nest and, if possible, placed in a taka nest without live eggs. This is intended to ensure that, if possible, every pair raises a single healthy chick. If no suitable foster parents are available, the young are raised by hand.
Only the clutches of couples that have been occupying their territory for at least two years are examined so as not to disturb the birds during the establishment phase in their territory. Dogs that are used to find the nests receive special training and are tested, and in the Murchison Mountains they must not be let off the leash.
In addition, according to the management plan of 1994, a few pairs are selected every year from which an entire clutch is removed in order to have eggs for the artificial rearing of South Islanders. In bad years, couples are selected that are almost always unsuccessful in rearing their young. In good years, the clutches of very successful breeding pairs are chosen, which have a chance of successfully raising the young of a second clutch.
Offspring in captivity
Mount Bruce and Te Anau Wildlife Park
Between 1957 and 1963, four eggs, four chicks and three adult South Island kittens were removed from the wild for captive breeding. This happened in what is now called the National Wildlife Center on Mount Bruce.
At first the success was only irregular. After the deaths of two South Islanders in 1973, it was found that they had been infected with bacteria of the Campylobacter genus , causing hemochromatosis . While these bacteria are common in bird populations in many parts of New Zealand, they were not detected at the Weka in Fiordland, and it was therefore suspected that the wild South Island kahe does not come into contact with them and therefore may not have sufficient defenses against them. Since then, care has been taken not to introduce this disease or any other bacteria into Fiordland. Even today, a small number of South Island shahs are kept at Te Anau Wildlife Park and at Mt. Bruce. The birds there mainly serve to show the population the birds and are therefore presented in as natural an environment as possible.
Hand-raised in Burwood
In Burwood, South Island Taka eggs are hatched in an incubator and raised by hand so that there are enough animals available for release in Fiordland. Individual birds are only made available for this purpose if it is necessary to expand the genetic base of the South Island aahs on the predator-free islands. Four breeding pairs are to be kept there to lay the eggs for artificial rearing. You shouldn't have any contact with people.
Enclosed incubators and enclosures with one-sided transparent observation windows and feeding hatches were developed for the young animals. The calls of the adult birds are played to them from the tape. In order for them to develop the eating habits that they need to survive in the wild, the young are kept in enclosures where they can find suitable wild plants, especially the fern, to eat.
Establishment of a second population in the Stuart Mountains
The population in the Murchison Mountains grew rapidly at the beginning of the release program, and therefore no additional birds appeared to be needed there. It was also feared that the released South Island nearer birds could introduce bird diseases into the habitat of the existing population. A separate population in the largest suitable habitat - the Stuart Mountains - outside the Murchison Mountains would then have meant a kind of natural quarantine. It is also known that the South Island nears survived there for a long time.
The plan was to increase the population in the Stuart Mountains until it eventually combined with the population in the Murchison Mountains. The first eight artificially reared birds were released there in October 1987, and three of those birds have since been known to have died. Every year between six and eight birds have been released there, a total of 58 animals by December 1992, and at least one pair has raised chicks. The program was then interrupted until it was possible to check whether the birds were able to establish themselves there successfully.
As the population size in the Murchison Mountains fell between 1990 and 1993, hand-reared birds were released into the Murchison Mountains in 1993.
Maxwell et al. found in a 1997 study that South Island kahen raised in captivity had at least as good survival rates as their wild counterparts in the first five years after release in the Murchison Mountains. Wild specimens often do not survive the first year because they lack sufficient fat stores to survive the nutrient-poor winter in cold temperatures. Of the nine female South Islanders released, eight were mated after the observation period, while only two of the eight males had found a partner. This suggests that there are too few females living in the wild in Fiordland.
Relocation to predator-free islands
The 1982 management plan and some research recommended releasing South Island kahens on a trial basis on suitable rat- and predator-free islands off the coast of New Zealand, since natural reproduction on the islands is cheaper than rearing in captivity. Kapiti , Tiritiri Matangi, Maud and Mana were selected for this . This is unique because the islands differ considerably from the alpine habitat from which the birds are known from historical times.
Between 1984 and 1993 a total of 24 South Island nears were released on the islands. The first attempt at breeding was established in 1986, in 1991 eight pairs brooded on the islands, in 1997 there were already 19 breeding pairs. From the beginning of the reintroduction until 1991, birds were exchanged between the islands in order to ensure that the same number of male and female animals were present on each island, so that as many breeding pairs as possible can form. The number of birds was still increasing in 2003.
Since South Island nears have occasionally been observed to eat wetas and various lizards, and since it was feared that they might eat the Auckland duck chicks , it is feared that South Island nears could adversely affect other protected species.
1991 was the last year that South Island shells were brought to Maud and Tiritiri from Mount Bruce and Te Anau Wildlife Center (as of 1994). The later South Island aahs of Maud and Tiritiri are all from Burwood. To avoid the spread of disease, until 1993 it was not allowed to bring birds from Kapiti and Mana to Maud and Tiritiri. It was then shown that essentially the same diseases are common in all four populations and the ban was lifted. The 1994 management plan called for birds to be exchanged between the islands to increase genetic variability and limit the risk of disease as much as possible.
The South Island nears on the islands have a much lower breeding success than the animals living in the mountains. Nevertheless, the number of island animals increased steadily as adults have high survival rates. In one year 83% of all birds survived, in four other years there was no death of an adult bird.
The island animals have been fed since 1994/95 in order to increase breeding success.
In a study published in 1998 it was calculated that the islands are occupied with so many breeding pairs between 1997 and 2009, depending on the estimate for the carrying capacity, that no further South Island nears can live there.
Infertility of the eggs and poor breeding and rearing success in the island nears
The low breeding success of the South Island Ahaen relocated to the islands is mainly due to the fact that a large proportion of the eggs do not hatch, a significant proportion of which do not survive the first two weeks, partly due to deformities. In Fiordland, 39% of eggs are found to be sterile; on the predator-free islands it is 60–75%. Although animal inbreeding is increasing, egg sterility and the number of malformations do not by and large increase. However, female birds whose parents were very closely related lay more deaf eggs and less of their young to grow than other South Island kahe females.
The southern islands on the islands of Maud and Tiritiri have a much lower breeding success than the animals living in the mountains. This low breeding success has existed since the first founder animals began to breed on the islands in 1986. Pesticides, poisons from plants infected by fungi, excessive water loss by the eggs during incubation were examined and excluded as the cause.
An examination of the sterile eggs on the islands showed that their composition hardly differed from those in the Murchison Mountains and that the widespread sterility cannot be attributed to malnutrition. In addition, the fertility of the eggs increases in the second and third broods compared to the first brood, which would not be expected in the case of malnutrition, since fewer nutrients would then have to be available for the later clutches because the parents already have their supplies of the scarcest nutrients had largely used up the first clutch. Other than that, the infertility problem does not exist in the closely related purple chicken, which feeds almost the same diet.
The fact that fertility increases in later clutches is probably due to the fact that fewer territorial fights then take place. Territorial fights could also be responsible for part of the fertility problems on the islands, which are more densely populated with southern islands compared to the Fiordland. However, they cannot fully explain this problem.
For decades, the population of the South Island nears was small and spatially limited, so that it has little genetic variability. Young animals leave their parents' territory, but usually do not move very far. The additional inbreeding after relocation to the islands obviously hardly plays a role in the problem, because no connection can be proven between the pedigree data of the birds there and their breeding success. This is confirmed by the fact that the genes of the birds on the islands have been shown to differ even more than the birds from the Fiordland population examined. The breeding success of kakapos and South Islanders on the predator-free islands is very low compared to birds in the Northern Hemisphere, but also compared to birds of other small populations with probably high inbreeding, but which remained in their original habitat. It has been shown that populations with high levels of inbreeding do as well as populations with high intraspecific variability, as long as the environmental conditions do not differ from those to which they were exposed during the phase when the population was smallest. As soon as living conditions change significantly, both fertility and survival rates decrease significantly. It can therefore be assumed that the relocation of the South Island kahe to the significantly different island habitats is responsible for the problem with the reproductive rate, although the adult birds survive there much more successfully and the habitats appear more suitable overall for the South Island kahe than in the Fiordland.
Maud
Maud Island is the first island to be released into the wild on South Island nears. Five male and four female juvenile birds were released on Maud Island in a total of 1984 and 1985. The first attempt at breeding took place in 1986.
Mana
Of the islands, Mana has the largest areas with meadows. Originally (1987 or later) four birds were released there. In 1995 there were five pairs and a group of three of one male and two females on the island and according to the estimates of Ryan and Jamieson at the time, the island would have been so densely populated with 22 breeding pairs in 2000 that it could no longer feed any more pairs. If the island had been modified for the South Islanders to include additional water points and nesting sites, it would not have been fully populated until 2004.
Tiritiri Matangi
Tiritiri Matangi is a 2.7 km long island that averages 700 m wide. The country has some gentle slopes that rise up to 191 m above sea level. There are no dry seasons and the average rainfall is 1026 mm per year. The vegetation consists of bushland and grass, as well as mowed meadows, on which both native and introduced plants grow, and a small piece of farmland. There are also some bare corners with ponds or small streets. The island was used for agriculture until 1970 and was then designated as a protected area in 1987. In the 120 years of agricultural use, the island lost 94% of its original forest. Between 1984 and 1994, 250,000 to 300,000 trees were planted and the Pacific rat was wiped out, leaving no introduced mammals to hunt native species. Many endangered and threatened birds have since been introduced here and have developed self-sustaining populations. As a result of the succession, the forest will increase, which will worsen the living conditions for the South Island kahe.
On Tiritiri Matangi Island, South Island nears were only released into the wild in 1991. Between 1994 and 1995 there were 10 animals living in the wild, belonging to three different family groups. In March 2002 there were 20 South Islanders living on Tiritiri. The 2000/2001 breeding season was largely unsuccessful because the number of territorial conflicts had increased too much.
Purple chickens as foster parents for South Island kahe chicks
The Chatham flycatcher was saved from certain extinction by shoving its eggs under a closely related species, the Maori flycatcher . Since the species-specific behavior of South Islanders and purple hens is similar enough, an attempt was made to slip eggs of the South Island hens under the non-threatened purple hens. Since the real parents of the chicks lay a second clutch when the eggs are removed from them, it was to be assumed that more young South Island cows would grow up as a result. The breeding success of the purple foster parents in this experiment was less than that of the South Island kahe chicks, which remained with their real parents. In the former, 2 out of 8 hatched chicks survived the first year, in the latter two out of five chicks. This difference is presumably due to chance, since it is not statistically significant and an observation of the behavior of the purple chickens compared to the young Takahen does not reveal any reason for the difference.
The purple hens have accepted the South Island kahe eggs, hatched them successfully, and look after the South Island kahe chicks as if they were their own young. Young South Islanders raised by purple hens react much more violently to predators than those raised by their own parents. This could be an advantage if you want to reintroduce South Island nears from the predator-free islands to the South Island.
When humans approach, purple chickens flee and leave their chicks alone, while with the Takahen at least one adult bird always stays with the young. Young purple hens hide in the understory when their parents flee. When purple chickens flee while their South Island kahe chicks stay behind, it is not quiet, but often utters a cry of fear that you never hear when South Island kahe are looking after their own young.
Informing the population
Care is taken to make the bird known to the population so that the population in the areas in which there are South Island nears does not hinder the protective measures for these animals out of ignorance or indifference. For this purpose, some breeding pairs are kept in the National Wildlife Center (Mount Bruce) and in the Te Anau Wildlife Park and shown to the public. Visits to the islands where takahen have been released are also encouraged. In addition, news about protective measures for the South Islanders and their successes are regularly brought to the public.
research
In order to be able to optimally protect the South Island kahe, it is necessary both to check the effectiveness of the protective measures and to know the needs of the bird. That is why research on the South Island akahe is given high priority. Care should be taken not to disturb the bird more than is absolutely necessary, but the Murchison Mountains Special Area can be visited for research purposes, which otherwise only a few people are allowed to enter. These research measures include an annual determination of the number of birds present, which is used to assess the effects of weather conditions, predators and protective measures and to adjust the measures accordingly. The living conditions of the bird and its forage plants are observed and the bird's biology and way of life are intensively researched.
See also
Web links
- Porphyrio hochstetteri in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 9 of 2008.
- Videos, photos and sound recordings of Porphyrio mantelli in the Internet Bird Collection (old name together with North Island kahe, but of course all videos refer to the still living South Island kahe)
- "Rediscovery of an extinct species" in "scineXX Das Wissensmagazin"
swell
- ↑ Takahē population crosses 300 milestone. Department of Conservation, December 2, 2016, accessed March 28, 2017 .
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y J. A. Mills, RB Lavers, WG Lee: The Takahe - A Relict Of The Pleistocene Grassland Avifauna Of New Zealand. In: New Zealand Journal of Ecology. Volume 7, 1984, pp. 57-70.
- ↑ a b c d e J. M. Suttlie, PF Fennessy: Organ Weight And Weight Relationships In Takahe And Pukeho. In: Notornis. Volume 39, 1992, pp. 47-53.
- ^ A b Walter L. Buller : On the Ornithology of New Zealand. In: Transactions and Proceedings of the Royal Society of New Zealand 1868-1961. Volume 31, 1898, Art. 1
- ↑ a b c d e f g h i j k l m n o G. R. Williams: The Takahe (Notornis mantelli Owen, 1848): A General Survey. In: Transactions and Proceedings of the Royal Society of New Zealand 1868-1961. Volume 88, pp. 1960-1961.
- ↑ a b c d e f g h i J. S. Bunin, IG Jamieson: A cross-fostering experiment between the endangered Takahe (Porphyrio mantelli) and its closest relative, the pukeko (P. porphyrio). In: New Zealand Journal of Ecology. Vol. 20, No. 2, 1996, pp. 207-213.
- ↑ a b c d e f g h i j k l m n Porphyrio hochstetteri in the Red List of Threatened Species of the IUCN 2011.2. Listed by: Birdlife International, 2008. Retrieved November 19, 2011.
- ↑ a b c d Ian G. Jamieson, Graham P. Wallis, James V. Briskie: Inbreeding and Endangered Species Management: Is New Zealand Out of Step with the Rest of the World? In: Conservation Biology. Volume 20, No. 1, February 2006, pp. 38-47. doi: 10.1111 / j.1523-1739.2005.00282.x
- ↑ a b c d e f g Brian Reid: Faeces Of Takahe (Notornis mantelli): A General Discussion Relating The Quantity Of Faeces To The Type Of Food And To The Estimated Energy Requirements Of The Bird. In: Notornis. Vol 21, Part 4, December 1974.
- ↑ a b c d e f g h i j k G. R. Williams, KH Miers: A Five-Year Banding Study Of The Takahe (Notornis imntelli Owen). In: Notornis . Vol. VIII, Part 1, 1958.
- ↑ Daryl Eason, Graig D. Millar, Alison Cree, Joy Halverson, David M. Lambert: A comparison of five methods for assignment of sex in the Takahe (Aves: Porphyrio mantelli). In: Journal of Zoology. (Cambridge University Press). Volume 253, No. 3, March 2001, pp. 281-292. doi: 10.1017 / S0952836901000267
- ^ A b c T. Jeffery Parker: On the Skeleton of Notornis Mantelli. In: Transactions and Proceedings of the Royal Society of New Zealand 1868-1961. Volume 14, 1881, Art. XXXII.
- ^ A b c J. Cowan: Notes on some South Island Birds, and Maori Associations connected therewith. In: Transactions and Proceedings of the Royal Society of New Zealand 1868-1961. Volume 38, 1905, Art. XLII.
- ↑ a b c d e f g h J. A. Mills, RB Lavers, WG Lee, MK Mara: Food Selection by Takahe Notornis mantelli in Relation to Chemical Composition. In: Ornis Scandinavica . Vol. 22, No. 2, Apr-Jun 1991, pp. 111-128. doi: 10.2307 / 3676542
- ↑ a b c d e f g h i Kerry AC James, Peter J. Moore, James A. Mills, John P. Koolaard, Roger B. Lavers, Christine A. Butts, Bryan P. Treloar, Neville D. Grace, Lynne M. Bang: The nutritional value of cocksfoot (Dactylis glomerata L.), midribbed snow-tussock (Chionochloa pallens Zotov), and red tussock (Chionochloa rubra Zotov) for the takahe (Porphyrio hochstetteri Meyer). In: Journal of the Royal Society of New Zealand. Volume 34, Number 4, December 2004, pp. 333-345.
- ↑ a b c d e f g P. A. Williams, P. Cooper, P. Nes, KF O'Connor: Chemical composition of tall-tussocks in relation to the diet of the takahe (Notornis mantelli Owen), on the Murchison Mountains, Fiordland , New Zealand. In: New Zealand Journal of Botany. Vol. 14, 1976, pp. 55-61.
- ↑ a b c d e f g h M. J. Baber, JL Craig: The relationship between foraging behavior and habitat use by South Island Takahe (Porphyrio hochstetteri) on Tiritiri Matangi Island. In: Notornis. Vol. 50, 2003, pp. 59-66.
- ↑ a b c d e f Steve Trewick: Short Note: The diet of Kakapo (Strigops habroptilus), Takahe (Porphyrio mantelli) and Pukeko (P. porphyrio melanotus) studied by faecal analysis. In: Notornis. Volume 43, June 1996, pp. 79-84.
- ↑ a b c d e f g h i M. J. Baber: Home range size and carrying capacity of the South Island Takahe (Porphyrio hochstetteri) on Tiritiri Matangi Island. In: Notornis. Vol. 50, 2003, pp. 67-74.
- ↑ a b c d e J. A. Mills, AF Mark: Food Preferences of Takahe in Fiordland National Park, New Zealand, and the Effect of Competition from Introduced Red Deer. In: The Journal of Animal Ecology. Vol. 46, no. 3, Oct 1977, pp. 939-958. doi: 10.2307 / 3651
- ↑ a b c d e f J. A. Mills, WG Lee, AF Mark, AB Lavers: Winter use by takahe (Notornis mantelli) of the summer-green fern (Hypolepis millefolium) in Relation to its annual cycle of Carbohydrates and Minerals. In: New Zealand Journal of Ecology. Vol. 3, 1980, pp. 131-137.
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap Dave Crouchley: Takahe Recovery Plan ( Porphyrio [Notornis] mantelli). Threatened Species Unit, Department of Conservation, Wellington, New Zealand 1994, ISBN 0-478-01465-1 .
- ↑ a b c d e f g h C. J. Ryan, IG Jamieson: Estimating the home range and carrying capacity for takahe (Porphyrio mantelli) on predator-free offshore islands: implications for future management. In: New Zealand Journal of Ecology. Volume 22, No. 1, January 1998, pp. 17-24.
- ↑ a b c d e f g h i j k l Brian Reid: Some features of recent research on the takahe (Notornis mantelli). In: New Sealand Journal of Ecology. Volume 14, 1967, pp. 79-87.
- ^ MN Clout, JL Craig: The conservation of critically endangered flightless birds in New Zealand. In: Ibis. Vol. 1, supplement 1, 1995.
- ↑ a b c d e f g h i j Christine Ryan: Observations on the breeding behavior of the Takahe (Porphyrio mantelli) on Mana Island. In: Notornis. Volume 44, 1997, pp. 233-240. notornis.osnz.org.nz (PDF; 363 kB).
- ↑ a b c Marieke Lettink, Ian G. Jamieson, Craig D. Millar, David M. Lambert: Mating system and genetic variation in the endangered New Zealand Takahe. In: Conservation Genetics. Volume 3, Number 4, December 2002, pp. 427-434. doi: 10.1023 / A: 1020567701633
- ↑ a b c d e f g h i j k Ian G. Jamieson, Christine J. Ryan: Increased egg infertility associated with translocating inbred takahe (Porphyrio hochstetteri) to island refuges in New Zealand. In: Biological Conservation. Vol. 94, No. 1, June 2000, pp. 107-114. doi: 10.1016 / S0006-3207 (99) 00158-5
- ^ A b Judah S. Bunin: Preliminary observations of behavioral interactions between Takahe (Porphyrio mantelli) and Pukeko (P. porphyrio) on Mana Island. In: Notornis. Volume 42, 1995, pp. 140-143 Short notes.
- ^ Susan M. Timmins, Ian AE Atkinson, Colin C. Ogle: Conservation Opportunities On A Highly Modified Island: Mana Island, Wellington, New Zealand. In: New Zealand Journal of Ecology. Vol 10, 1987, pp. 57-65.
- ↑ Trevor H. Worthy, Stephen EJ Swabey: Avifaunal changes revealed in Quaternary deposits near Waitomo Caves, North Island, New Zealand. In: Journal of The Royal Society of New Zealand. Volume 32, Number 2, June 2002, pp. 293-325.
- ↑ a b c d Judah S. Bunin, Ian G. Jamieson: New Approaches Toward a Better Understanding of the Decline of Takahe (Porphyrio mantelli) in New Zealand. In: Conservation Biology. Volume 9, No. 1, 1995, pp. 100-106. doi: 10.1046 / j.1523-1739.1995.09010100.x
- ^ A b Brian Reid: Sightings And Records Of The Takahe (Notornis mantelli) Prior To Its "Official Rediscovery" By Dr GB Orbell In 1948. In: Notornis. Vol 21, Part 4, December 1974.
- ↑ Richard N. Holdaway, Martin D. Jones, Nancy R. Beavan Athfield: Late Holocene extinction of Finsch's duck (Chenonetta finschi), an endemic, possibly flightless, New Zealand duck. In: Journal of The Royal Society of New Zealand. Volume 32, Number 4, December 2002, pp. 629-651.
- ↑ a b J. A. Mills, RB Lavers: Preliminary Results Of Research Into The Present Status Of Takahe (Notornis mantelli) In The Murchison Mountains. In: Notornis. Vol 21, Part 4, December 1974.
- ↑ Takahē population crosses 300 milestone. Department of Conservation, December 2, 2016, accessed March 28, 2017 .
- ↑ a b c d J. Parkes, K. Tustin, L. Stanley: The History And Control Of Red Deer In The Takahe Area, Murchison Mountains Fiordland National Park. In: New Zealand Journal of Ecology. No. 1, January 1978, pp. 145-152.
- ↑ Jane M. Maxwell, Ian G. Jamieson: Survival and Recruitment of Captive-Reared and Wild-Reared Takahe in Fiordland, New Zealand. In: Nueva Zelanda Conservation Biology. Volume 11, No. 3, June 1997, pp. 683-691. doi: 10.1046 / j.1523-1739.1997.95432.x
- ↑ a b J. S. Bunin, IG Jamieson, D. Eason: Low reproductive success of the endangered takahe Porphyrio mantelli on offshore island refuges in New Zealand. In: Ibis. Vol. 139, no. 1, Jan 1997, pp. 144-151.
- ^ A b Ian G. Jamieson, Michael S. Roy, Marieke Lettink: Sex-Specific Consequences of Recent Inbreeding in an Ancestrally Inbred Population of New Zealand Takahe. In: Conservation Biology. Volume 17, No. 3, 2003, pp. 708-716. doi: 10.1046 / j.1523-1739.2003.01400.x
- ^ A b Ian G. Jamieson: No evidence that dietary nutrient deficiency is related to poor reproductive success of translocated takahe. In: Biological Conservation. Volume 115, 2003, pp. 165-170.