Auckland Duck
| Auckland Duck | ||||||||||||
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Auckland duck (front right, back left a New Zealand duck ) |
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| Systematics | ||||||||||||
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| Anas aucklandica | ||||||||||||
| ( Gray , 1844) |
The Auckland duck ( Anas aucklandica ) is a flightless duck bird that is counted among the swimming ducks. This duck is an endemic species of the sub-Antarctic Auckland Islands . It is a very small species of duck with noticeably short wings. The IUCN classifies the Auckland duck as endangered ( vulnerable ) and estimates the population at 600 to 2,000 sexually mature birds.
Appearance
The Auckland duck is a small, dark brown, flightless species of duck. The males weigh an average of 551 grams. Females weigh an average of 480 grams during the breeding season, while non-breeding females weigh an average of 410 grams.
The Auckland duck shows a sexual dimorphism . The males resemble the New Zealand ducks in their magnificent dress , but are a little darker overall. The head and neck are dark brown. The neck feathers shimmer slightly green. The white eye ring is striking. The body plumage is dark brown. The flank feathers have light brown transverse stripes. The breast plumage is dark maroon. The under tail cover is black. However, the feathers are dirty white at their base. The wing mirror is shiny green with a white border. The beak, legs and feet are dark gray. The eyes are dark brown. In the resting plumage the head plumage lacks the greenish sheen. The breast plumage is then a dull chestnut brown. The flank springs have no stripes.
The females are uniformly dark brown, only the underside of the body is a little lighter. The white eye ring is also very noticeable on them. Young ducks are like females.
Distribution and existence
The Auckland duck occurs exclusively on the Auckland Islands. These islands are located about 465 km south of the South Island of New Zealand between 50 ° 30 'and 50 ° 60' south latitude and 165 ° 50 'and 166 ° 20' east longitude. The total area of the archipelago is 606 km². Of this, the main island of Auckland Island accounts for 510 km². The second largest island in the group is Adams Island, south of the main island . The islands are uninhabited today.
Originally the Auckland duck was found on all islands of this archipelago. It is now missing on the main island of Auckland Island after it was exterminated there by introduced mammals. The population is estimated at a little over 1500 ducks. Bird counts are difficult because they can hide well in the thick vegetation. Hartmut Kolbe, for example, gives only 260 to 300 ducks for 1990. In fact, however, the stock was probably underestimated at this point in time.
The population is considered stable. The spread on six islands of the archipelago reduces the risk that this species of duck will become extinct due to a natural disaster or a strong negative influence such as a tank accident off the coast. The islands of the archipelago now populated have reached their limit of Auckland ducks. The main island, Auckland Island, is to be freed from the imported mammals - pigs and cats - in the coming years. This would make it possible for the Auckland duck to colonize this island again.
Habitat and diet
The Auckland duck prefers to stay in the coastal area covered with bluegrass . She prefers areas that are moist in the soil, where sedges also grow. However, it is also found in ironwood forests along streams. On the island of Ewing, some breeding pairs also live in olearia forests.
The Auckland duck is mostly crepuscular and nocturnal. During the day it seeks protection in dense vegetation, in earthworks of other bird species or in crevices. It feeds primarily on animals such as small marine invertebrates, amphipods , insect larvae and small mollusks. The formation of small flocks is very rare and can only be observed on the coastline, where the ducks find plenty of food in the washed up kelp.
Reproduction
Social courtship has not yet been observed in the Auckland duck and is unlikely to occur. During the breeding season, the ducks are extremely aggressive. This includes threatening with an open beak and attacks on other birds. Only pairs that have successfully occupied a territory and are able to defend it will breed. The area size on Ewing is 1000 to 3700 square meters on grassland and 200 to 550 square meters for areas whose area also includes a piece of coastline.
Egg laying begins in late October. Since chicks can still be observed in March and April, Auckland ducks apparently raise a replacement clutch if the first clutch cannot be successfully incubated. The nest is built on the ground under thick vegetation. The hollow is covered with plants from the area and down. Nesting sites are used again. The eggs are pale brown and larger than those of the New Zealand duck or the Campbell duck .
The female breeds alone. However, the male stays nearby and accompanies the partner during the breeding breaks. The incubation period is 30 to 35 days. Both parent birds lead and defend the chicks. After about sixty to seventy days, they will have reached the weight and size of the parent birds. The mortality rate of the chicks is very high: of the average 3.4 chicks that hatch per clutch, only about 14 percent reach an age of 70 days. In 66 percent of the breeding pairs, none of the hatched chicks survived.
Keeping in human care
The first European holder was the London Zoo, which acquired an Auckland duck back in 1895. The British Wildfowl Trust bought three ducks in 1955, but they all died during the acclimatization period. More extensive breeding programs for these ducks ran since 1984, but they were abandoned after some time in favor of the Campbell Duck, as the stock of Auckland ducks was considered sufficient.
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 factsheet on the Auckland Duck
- Anas aucklandica onthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2013. Retrieved February 6, 2014.