Duck-billed duck
| Duck-billed duck | ||||||||||||
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Hemlock duck - the dark membrane can be seen at the end of the beak |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Hymenolaimus | ||||||||||||
| Gray , 1843 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Hymenolaimus malacorhynchos | ||||||||||||
| ( Gmelin , 1789) |
The Saumschnabelente ( Hymenolaimus malacorhynchos ), and Blue Duck , Blue Scaup or onomatopoeic after the call of the male Whio called, is a species of the Order of the ducks . The duck, which mainly lives on insects, is the only species that belongs to the duck-billed genus and, together with the Laysan , Bernier and Madagascar ducks, is one of the rarest duck species in the world. Their occurrence is limited to fast flowing, clear and debris rich streams and rivers in New Zealand . The number of stocks has decreased significantly in recent years. The reasons include loss of habitat , increased enemy pressure from animal species introduced into New Zealand such as weasels , martens and feral domestic cats, and possibly food competition from the rainbow trout, which has also been introduced . The IUCN classifies the Saumschnabelente as endangered ( endangered ) and estimates the stock to 1,200 mature individuals.
Similar to other endangered New Zealand bird species such as the kakapo , the south island takahe and the kiwi , various measures are being taken in New Zealand to try to increase the numbers again.
Appearance
Appearance of fully grown fringed billed ducks
Saum-billed ducks are slightly lighter and smaller than the European mallard . The average body weight of an adult drake is 890 grams, that of an adult female 750 grams. The wing length is 23.5 to 25 centimeters.
The plumage of drakes and ducks is largely the same. The ducks are usually only slightly smaller than the drakes. The plumage on the front surface of the body, the so-called coat, is blue-gray with gray-brown speckles. The chest is spotted red-brown and blue-gray. In some individuals, the red-brown tones predominate. The blue-gray shoulder feathers, the so-called scapulars , are lined with thin black. The tail covers, the flanks and the wings are solid blue-gray. Neck and head plumage are uniformly dark blue-gray. The region between the eyes and the beginning of the beak shimmers green. The feet and legs are flesh-colored. The iris is yellow to orange. The beak is light flesh-colored to yellowish, the end of the beak is black.
Hem-billed ducks are adapted to their life in fast flowing waters through several characteristics. The long-billed duck's eyes are located in the skull in such a way that the field of vision for a species of duck is unusually directed forward. Some ornithologists see this as an adaptation for their hunt for aquatic insects. The beak of this species of duck has a dark and soft membrane at its end, which protects the beak from injuries when the ducks look for insects on the vegetation of stones.
Sea-billed ducks swim relatively high in the water. This allows them to stay up in very choppy waters.
Appearance of chicks and ducks not yet fully grown
The chicks are black-gray on the top of the head, back, wings, thighs and sides of the abdomen. The face is white-gray and the eyes, which are dark in color in contrast to the adult birds, have a dark rein. The white-gray over-eye stripes are separated on the forehead by a thin black stripe. The chest, the underside of the body, the front neck and the rear edge of the wing are also white-gray feathered. The chick's beak is still dark gray-blue in color. At around eight weeks of age, the chicks change into their first juvenile dress.
Not yet fully grown ducks can be distinguished from adult ducks by their overall duller plumage. With them, the reddish brown spots on the chest are still missing or less pronounced. The black feather edges of the scapulars are also missing. The beak is still light blue-gray, the iris dark brown in color. The flesh-colored beak coloration and the bright yellow to orange-colored iris, which are typical of adult ducks, are found in young ducks from the age of nine months.
Flight image
Black-billed ducks are considered to be one of the types of ducks that are very reluctant to fly. They move mostly swimming and continuously. However, even very young chicks have a high level of jumping power, which enables them to jump on boulders protruding out of the water. Despite the low inclination to fly, ducks are powerful fliers, where you can count up to 480 wing beats per minute. Individual observations of this so far insufficiently investigated duck species suggest that the ducks patrol their territory while flying at dusk. During the flight, stretch the Saumschnabelenten in flight image neck and head horizontally forward. They mostly fly just above the water surface.
voice
The drakes give out loud, shrill whistles that can be heard over the roar of the mountain streams and rivers. The calls resemble a "whio", which has coined the onomatopoeic name that the Maori have given this species of duck. These whistles cannot be heard from females. They respond to the males' calls with a quieter, darker rumble.
distribution
Greater billed ducks are limited in their distribution to New Zealand and occur on both the South and North Island.
Originally, breeding populations of the sea-billed ducks occurred on both New Zealand islands wherever the banks of clear, scree-rich, fast-flowing and shallow waters were densely overgrown with forest. Typical Saum-billed duck areas had a partly shaded watercourse and a largely stable water level, as strongly changing water levels and, above all, floods carry along with the algae and moss growth in which the aquatic insects that are important for food settle. If the rivers kept their fast flowing character and the banks were forested, the ducks colonized the rivers up to their mouth on the coast. Most rivers only had such suitable habitats on their upper and middle reaches. Black-billed ducks could be found here up to the alpine tree line. The forest that surrounded these sections or still surrounds them in natural regions was the endemic deciduous tree fern forest of New Zealand. The settlement density along such rivers and streams could be very high. In the 1960s, an employee of a New Zealand conservation agency who was traveling along two rivers that ran through pristine forests found breeding grounds every few hundred meters with a pair of black-tailed ducks.
Several factors have led to a significant reduction in the number of territories that can be used as habitat. Already the colonization of New Zealand by Maoris around eight hundred years ago resulted in New Zealand's forest cover being reduced by a quarter. With the Maori, dogs and the Polynesian rat came to New Zealand, both of which are potential predators of the pack-billed duck. Archaeological studies of Maori rubbish heaps suggest that pack-billed ducks were only occasionally among their prey.
Since the colonization of New Zealand by Europeans about 200 years ago, the forest has declined by a further quarter. In addition, logging has changed the structure of these forests, and the construction of hydropower plants has destroyed a number of habitats. The introduction of a large number of neozoa in connection with the European settlement has had an impact on the fauna of New Zealand at least as seriously as the reduction in the forest. Among the introduced species are among the red fox , marten, weasel, Domestic Cat, Deer , the opossum , the possum , domestic sheep , -schwein and goats , Canada goose and rainbow trout.
The introduction of these species and changes in forest populations are threatening a number of animal species endemic to New Zealand . The best-known examples include the owl parrot or kakapo, whose survival is attempted by trying to settle the remainder of the population on islands that are still free from imported animals.
Duration
Until the 1990s, the pack-billed duck was one of the endemic species of New Zealand, whose potential settlement area had indeed been reduced and whose populations had declined significantly. Saum-billed ducks, however, were not regarded as a species that was directly threatened with extinction. The continued existence of the species was seen as certain because there was apparently still a sufficient number of suitable habitats. The ornithologist Hartmut Kolbe, who specializes in ducks, gave the population of this species for 1995 as 2,000 to 4,000 individuals and the inland area of the North Island of New Zealand and the entire western half of the South Island as the distribution area. Hartmut Kolbe already pointed out, however, that suitable territories increasingly remained unoccupied when the adult birds died.
Since the beginning of the new millennium, the assessment of the stock status of the black-billed ducks has changed. In 2003 the World Conservation Union classified the species as critically endangered. The decisive factor for this assessment is the knowledge that fringed-billed ducks exist today in isolated populations, between which there is no longer any exchange. Each of these isolated populations is threatened with extinction due to natural disasters such as forest fires or further habitat destruction. The increased pressure from introduced predators and food competitors has also led to a change in the habits of the duck-billed ducks, which endangers a recovery of the population. This also applies to the New Zealand areas, which apparently have largely been preserved in their original state and are now considered to be the areas with the densest sea-billed duck population. These include the Te-Urewera National Park , the largest area of untouched forests on the North Island and New Zealand's largest national park, the Tongariro National Park , the west coast of the South Island and the New Zealand Fjordland as well as the area around Mount Taranaki and the Kahurangi National Park .
Way of life
Sea-billed ducks belong to the so far relatively little researched duck species. The British ornithologist Janet Kear , who belonged to the Wildfowl Trust , carried out the first more intensive field studies towards the end of the 1960s . Most of the findings that are still valid today can be traced back to these investigations.
Food and subsistence
Greater billed ducks eat the larvae of quiver flies , stone flies and mayflies . They partially collect these underwater from the rubble stones in the river or stream bed. Greater billed ducks are also able to catch adult and airworthy insects from the air. They also eat a number of different berry fruits during the New Zealand winter months.
The aquatic insects, which make up the largest part of the sea-billed duck's diet, are also preferred to be eaten by the rainbow trout introduced into New Zealand. However, the impact of rainbow trout on the stock of frilled billed ducks has not yet been adequately investigated.
Systematics
The pack-billed duck, together with the mirror geese , the humped goose , the kasarkas , the spatula-billed duck , the red-billed duck and the steamship ducks , belong to the subfamily of the half-geese .
Footnotes, literature and web links
literature
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683
- Janet Kear : The Blue Duck of New Zealand. In: Living Bird, No. 11, 1972, pp. 175-192.
- Janet Kear and PJK Burton: The Food and Feeding Apparatus of the Blue Duck Hymenolaimus , Ibis, No. 113, 1971, pp. 483-493
- Janet Kear and Tom H. Steel: Aspects of Social Behavior in the Blue Duck , Notornis, Volume 18, 1971, pp. 187-198
- Hartmut Kolbe; Die Entenvögel der Welt , Ulmer Verlag 1999, ISBN 3-8001-7442-1
- David Young: Whio - Saving New Zealands's Blue Duck , Craig Potton Publishing, Nelson 2006, ISBN 978-1-877333-46-0
Web links
- Videos, photos and sound recordings of Hymenolaimus malacorhynchos in the Internet Bird Collection
- BirdLife factsheet about the duck-billed duck
- Hymenolaimus malacorhynchos inthe IUCN Red List of Threatened Species 2013.1. Listed by: BirdLife International, 2012. Retrieved October 12, 2013.
Footnotes
- ↑ BirdLife Factsheet on the Saum-billed Duck , accessed April 10, 2011
- ↑ Kolbe, p. 160 The drakes of the European mallard, on the other hand, weigh 1100 grams, the females 970 grams
- ^ Higgins, p. 1255
- ↑ Young, p. 36
- ↑ Kolbe, p. 161
- ↑ Kolbe, p. 161
- ↑ Young, p. 17
- ↑ This high jumping force, even in young chicks, is also found in the chicks of the South American tomb duck , which inhabit raging mountain rivers
- ↑ Young, p. 15
- ↑ Young, p. 15
- ↑ Kolbe, p. 160
- ↑ Higgins, p. 1256
- ↑ Kolbe, p. 161
- ↑ Young, p. 14
- ↑ Young, p. 16
- ↑ Young, S. 8f
- ↑ see also the detailed article about the kakapo , where these exceptions are described in detail
- ↑ Young, p. 10
- ↑ Kolbe, p. 334 (distribution map) and p. 161
- ↑ Young, p. 11
- ↑ Janet Kear has published her observations in several articles in professional journals, see literature list
- ↑ Kolbe, p. 161
- ↑ Higgins, p. 1256
- ↑ Kolbe, p. 11