Madagascar bog duck
| Madagascar bog duck | ||||||||||||
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Madagascar bog duck ( Aythya innotata ) |
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| Aythya innotata | ||||||||||||
| ( Salvadori , 1894) |
The Madagascar bog duck ( Aythya innotata ) is an extremely rare diving duck of the genus Aythya , which was already believed to be extinct. In 2006 ducks of this species were observed again at one point in Madagascar. It cannot be ruled out that ducks of this species can also be found in other places in Madagascar. In any case, the species is considered to be directly threatened with extinction. The primary cause of the population decline is the introduction of a herbivorous cichlid (Oreochromis macrochir) . As a result, the vegetation of the breeding waters of the Madagascar bog duck was permanently changed.
features
Madagascar bog ducks reach a body length of 46 centimeters. It is the only diving duck in this region. The male's white iris, the white wing markings that exist in both sexes and the long start-up phase when it flies back up distinguish this species from other duck species native to Madagascar.
In its splendid plumage, the male has dark brown plumage with a white underside. The head and neck are black-brown with a faint green or purple sheen. The chest is dark red-brown. The flanks gray-brown. The wings have light vertical stripes over the wings. When resting, the male resembles the female, but then has the white iris color. The plumage in the female is a little more dull. Unlike the male, the female has a dark brown iris. In both sexes, the beak is lead gray with a black beak nail. The legs and feet are gray. Young ducks resemble the females, but appear a bit brown overall. Young male ducks very quickly develop a gray iris that turns white towards the end of the first year of life.
Distribution and existence
The Madagascar duck is an endemic species of duck from Madagascar. On this island it was limited to the region of Lac Alaotra , the one in the north of the central high plateau. This has an average height of 1,100 m and culminates in the Maromokotro , the highest mountain on the island at 2,876 m. Madagascar lies in the tropical climate of the south equatorial current. The annual average temperature is 25 ° C, with temperatures on the coasts being higher and in the inland highlands can drop below freezing point. Summer and winter correspond to the tropical rainy and dry seasons.
In the 1930s, the Madagascar bog duck was still relatively common on Lac Alaotra. In the 1940s and 1950s, stocks decreased dramatically. It has not been seen in the vicinity of Lac Alaotra since the 1960s. There was an unconfirmed sighting near Antananarivo in the 1970s. The species was therefore considered to be extinct until the early 1990s.
In August 1991, a single male was caught alive. In the time after that, the IUCN did not classify the species as extinct, but as critically endangered because it was not searched for nationwide. An intensive search was then initiated near Lac Alaotra. The search was accompanied by numerous PR campaigns in order to obtain information from the population about other Madagascar bog ducks. Both actions, which were repeated in 1993 and 1994, brought no further evidence of further ducks of this species. In 2006, however, nine adult Madagascar bog ducks and four young ducks were observed on a volcanic lake 330 kilometers north of Lac Alaotra. According to the statements of the population, the edge of this volcanic lake is unsuitable for rice cultivation. There are no fish in the lake either. The water is also relatively cool for Madagascar. Overall, this is seen as an indication that the Madagascar bog duck was able to survive here because it was exposed to relatively little human disturbance. In subsequent searches, a total of around 20 adult Madagascar bog ducks and nine young ducks were observed on the same lake. Five Madagascar bog ducks have also been observed at a second lake about three to four kilometers from the first observation site. But it is possible that these five ducks were among those that were already counted at the first volcanic lake.
Causes of the decline in stocks
The original habitat of the Madagascar bog duck was very plant-rich lakes with a high population especially of water lilies. Such lakes were mainly found at the southern end of Lac Alaotra, where the Madagascar bog duck was still common in the 1920s and 1930s. Much of this original habitat has been destroyed in Madagascar since then. Lac Alaotra is located in one of the most important rice-growing areas on the island. Of the 350 square kilometers that surround the lake, 250 square kilometers have been converted into rice-growing areas. The associated erosion has deteriorated the water quality of the lake and led to increasing siltation of the lake. In addition, there are changes in the bank area such as more intensive pasture management, the cultivation of rice , which is increasingly also taking place on marginal yield areas and the associated slash and burn on the banks. The number of rats near the lake has increased. These are potential nest and chick robbers. In addition, the water quality declined due to the spread of introduced plants such as the water hyacinth and floating ferns , which displaced the native floating leaf plants, clogged the waterways and led to an increasing oxygen depletion of the water. Largemouth bass introduced from North America in the 1960s may have ate the chicks of the Madagascar bog duck. The introduction of tilapia is considered to be the main cause of the decline in the population of both the Madagascar bog duck and other bird species on Lac Alaotra, which depend on rich aquatic vegetation . This species of fish was originally widespread in the Jordan, among others. The only requirement for breeding is a high water temperature (at least 18 to 20 ° C). In some development aid projects, tilapia are particularly suitable for all areas in which there is a lack of protein-rich nutrition. This also includes Madagascar with its rapidly increasing population.
Madagascar bog ducks have also been hunted. Occasionally they also got caught in the fishing nets. It is symptomatic that the Madagascar bog duck caught in 1991 got tangled in a fishing net. The introduction of carnivorous fish species in Lac Alaotra also has a negative impact on the waterfowl population on this lake. Chicks in particular fall victim to them. However, it is assumed that at the time these species were introduced, the Madagascar bog duck on Lac Aloatra was already extinct.
At the two lakes where the Madagascar bog duck was rediscovered, the factors that led to the decline and disappearance of this species of duck at Lac Alaotra are currently missing. However, the population there is so small that inbreeding depression must be feared. With a population spread across so few lakes, there is also a significant risk that they will be made extinct by unusual events such as a cyclone or a disease outbreak. The strict protection of the lakes is one of the main measures to preserve the species. Both hunting and all other human activities must be avoided near the lake.
During a census in 2009 only 19 individuals were found.
Way of life
Very little is known about the way of life of the Madagascar bog duck from field observations. Most of the knowledge about this species comes from the first half of the 20th century, when some bog ducks were kept in human care.
The Madagascar bog duck prefers waters that are rich in vegetation. It was mainly found in calm waters near Lac Alaotra, which have a dense vegetation of water lilies. According to today's knowledge, it neither formed large flocks nor socialized with other duck species. She looked for her food by diving. The food composition is unknown. Presumably she mainly ate seeds from aquatic plants, presumably especially those of the water lilies. Their diet also presumably included aquatic invertebrates. Their courtship repertoire is unknown. But it probably resembles that of the Australian bog duck .
The Madagascar bog duck probably breeds between October and January. The location of the nests is unknown. The eggs are oval and brownish white. The full clutch consists of six to eight eggs. The female breeds alone. The breeding season is 26 to 28 days.
Keeping in human care
Madagascar bog ducks were first imported to Clères, France in 1929. There were five ducks with which one bred very successfully. In 1935 some animals were imported to Clères a second time. Great breeding successes were also achieved with these ducks. From there, the animals end up in a number of other zoos and have also been sold to some private owners. In Great Britain, for example, the offspring of these ducks was first bred in 1935. However, conservation breeding with these ducks came to a complete standstill in the years of the Second World War. In 2009 a new conservation breeding program was initiated, supported by the Durrell Wildlife Conservation Trust, the Wildfowl & Wetlands Trust (WWT), the Peregrine Fund and the Malagasy government. In November 2009 the first 8 chicks were reported since the rediscovery.
swell
literature
- Dominic Couzens : Rare Birds - Survivors, Evolution Losers and the Lost. Haupt Verlag, Bern 2011, ISBN 978-3-258-07629-4 .
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 8487334105 .
- Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0198546459
- Hartmut Kolbe: The world's ducks . Ulmer Verlag, 1999, ISBN 3-8001-7442-1
Web links
- Aythya innotata inthe IUCN 2012 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved January 3, 2013.
Individual evidence
- ↑ a b c Birdlife Fact Sheet about the Madagascar Moor Duck, uploaded on February 14, 2009
- ↑ a b Kolbe, p. 277
- ↑ Kear, p. 657
- ↑ a b Kear, p. 658
- ↑ Aythya innotata in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2009. Accessed November 16, 2011th
- ↑ Couzon, p. 208
- ↑ Couzon, pp. 208-210
- ↑ Couzon, p. 210
- ↑ nzz.ch:A protection program for the “rarest duck in the world” (accessed on August 31, 2009)
- ↑ Wildlifeextra.com: Madagascar Pochard - The world's rarest ducklings hatched in captive breeding program