New Zealand duck
| New Zealand duck | ||||||||||||
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New Zealand duck |
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| Anas chlorotis | ||||||||||||
| Gray , 1845 |
The New Zealand duck ( Anas chlorotis ), also known as the green-eared duck , is a New Zealand duck bird that is counted among the swimming ducks . Like the Auckland duck and the Campbell duck , which have long been classified as a subspecies of the New Zealand duck, the population of the New Zealand duck is also threatened. The current population is estimated at 912 individuals. The IUCN classifies the New Zealand duck as endangered .
Appearance
The New Zealand duck reaches a body length of up to 48 centimeters. New Zealand ducks exhibit both seasonal and sexual dimorphism . In the magnificent dress, the male has a greenish shimmer on the head and neck. The face is brown. The white eye ring is striking. In some individuals, a pale white and not completely closed band runs down the neck. The body plumage is dark brown. The flanks are striped light and dark brown. The chest is dark maroon and the underside is light brown. The under tail-coverts are black with a white spot at the base of the tail. The greenish shimmering wing mirror is bordered by a narrow, white band. The greenish shimmer on the head is missing in the resting dress. The chest is then spotted more heavily. The flank feathers lack stripes and the white spot on the tail is almost invisible.
Females have a more uniformly brown plumage. Their feathers are brightly lined, which gives them a more scaled or spotted appearance. The chest is lightened towards the underside of the body. The eye ring is also noticeable in the female. Young ducks resemble females, but their plumage is darker. The body feathers and the breast feathers are broadly lightly lined.
The beak is steel gray with a black ridge, the legs and feet are dark gray. The eyes are black.
Possible confusion with other species
It can be confused with the Maori duck in its natural range . However, this floats significantly higher on the water and has a considerably stronger physique. Compared to the Maori duck, the New Zealand duck's body is slightly more elongated and their wing tips cross on their backs. The Maori duck also lacks the white eye ring, the forehead is significantly steeper. The males of the Maori duck are noticeably darker and have striking yellow eyes. Most female Maori ducks have white facial markings.
The Australian white-throated duck has a lighter throat and more scaled-looking plumage than the New Zealand duck. She also lacks the white eye ring. The similarly colored chestnut duck does not reach New Zealand even as a random visitor .
Distribution and existence
The New Zealand duck originally colonized both the South and North Islands and the Great Barrier Island, which adjoins the North Island . A very large number of the islands that are close to the coast of New Zealand and the Chatham Islands , a group of islands belonging to New Zealand and located around 800 km east of the main islands in the South Pacific, were also settled.
Today, the occurrence of the New Zealand duck is limited to the Great Barrier Island, three coastal islands, on which no more than ten pairs breed each, and to a small coastal region of the North Island. The population on the Great Barrier Island is currently around 600 ducks. At the beginning of the 1990s it was between 1,300 and 1,500 ducks. On the east coast, the population decreased to less than 100 individuals between 1988 and 1999. Here, however, the populations are increasing again and in 2004 were again 300 individuals. The number of New Zealand ducks reintroduced to the north of the Coromandel Peninsula was around 500 individuals in 2008 and is rising again. New Zealand ducks have been introduced to some of the smaller islands and have survived there for a decade or two. However, the islands are too small for this species to survive sustainably.
The New Zealand duck is largely extinct in the fjordland of the South Island. The few remaining New Zealand ducks hybridize with the eyebrow ducks and the mallards introduced to New Zealand .
The cause of the decline in the population was initially excessive hunting. The main cause, however, is the change in the habitat caused by humans. The drainage of numerous wetlands between 1890 and 1930 led to a very sharp decline and local extinction. On Stewart Island , New Zealand's third largest island off the coast of New Zealand's South Island, the disappearance is due to the introduction of domestic cats . The number of cats there increased sharply in the 1950s and no New Zealand ducks were found on the island after 1972.
habitat
Prior to the colonization of New Zealand by humans, the New Zealand duck was probably found very often in lakes and slow flowing waters. In the middle of the 19th century, when Europeans were already settling in New Zealand, they were only found in regions with tree-lined marshland.
Outside of the breeding season, the individual local populations gather at traditional moulting sites. These are usually estuaries. The ducks mostly stay above the zone up to which salt water penetrates. New Zealand ducks are resident birds that do not breed under unfavorable conditions, but stay close to their breeding area.
food
The New Zealand duck is a crepuscular to nocturnal duck. This seems to be an adaptation to protect against predators, of which before the arrival of humans there were mainly diurnal, such as the Haastadler or Skuas . It searches for its food carefully and also looks for areas that are some distance from its resting places. The diet consists mainly of aquatic invertebrates, insect larvae and small crustaceans. Mollusks also play a major role in their diet. Both small mollusks such as pee (Paphies australis) or larger ones such as Macomona liliana are swallowed whole. Cockles such as the New Zealand Austrovenus stutchburyi are eaten in a very specific way that other birds have not seen in this way before. The duck squeezes its actually rather soft beak between the cockle shells and pulls the meat out with pounding movements.
Reproduction
New Zealand ducks are territorial birds that vigorously defend their territory against other New Zealand ducks, especially during the breeding season. New Zealand ducks stay in pairs all year round in their territory, provided that there is sufficient water surface. Where this is not the case, the pairs migrate into the vicinity and return as soon as the water levels allow this. The districts are relatively large and, in addition to vegetation zones rich in cover, also have sufficient food spaces and breeding grounds.
With the exception of April and May, clutches are found in all months of the year. However, the peak of the breeding season is in the months of July to September. The nest is usually built under sedges or tufts of papyrus near the water. The nest is built from the surrounding grass and covered with down. The full clutch contains an average of 5.9 eggs. For New Zealand ducks kept in human care, the laying interval is one day. The female breeds alone. However, the male remains close to the nest. The breeding season in captivity is 27 to 30 days. The young ducks can fledge after 50 to 55 days.
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 (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe: The world's ducks. Ulmer Verlag, 1999, ISBN 3-8001-7442-1 .
Web links
- Birdlife Fact Sheet on the New Zealand Duck, uploaded February 14, 2009
- Anas chlorotis inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved February 6, 2014.
Individual evidence
- ↑ Birdlife Fact Sheet on the New Zealand Duck, uploaded February 14, 2009
- ^ Kear, p. 478
- ^ Kear, p. 477
- ↑ Higgins, p. 1289
- ↑ Birdlife Fact Sheet on the New Zealand Duck, uploaded February 14, 2009
- ↑ Birdlife Fact Sheet on the New Zealand Duck, uploaded February 14, 2009
- ^ Kear, p. 578
- ^ Higgins, p. 1290
- ^ Higgins, p. 1291
- ^ TH Worthy & RN Holdaway: The Lost World of the Moa. Indiana University Press, Bloomington 2002, ISBN 0-253-34034-9 .
- ^ Higgins, p. 1291
- ^ Kear, p. 579