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Tuesday, 05 February 2013 10:31

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The Black swan (Cygnus atratus) is native to Australia and it was introduced in Europe in the early nineteenth century for private and ornamental use in gardens and ponds. As it happens with  a lot of other exotic species of animals, these swans escaped or were set free in the environment becoming a real problem for the native fauna.

Cygnus atratus ostrera

Black Swans in Kanala

It is a very territorial species and they defend it with aggressiveness, becoming also in a big threat for other water birds in the wetlands where it is introduced. In this way, there are described competitions with other ducks displacing them from their breeding areas. And in some places they have been the cause of the reduction of some reproductive populations of native birds.

It is confirmed their breeding in several European countries such as Austria, United Kingdom, Italy and France and there are also some quotations in the Iberian Peninsula; there is also confirmed in the Zurbano's pond in Salburua, Vitoria-Gasteiz (Onrubia, 2002), where it caused serious problems because it stopped the breeding of other species in the surroundings of their nests. In studies made by B.T.O (British Trust for Ornithology) for United Kingdom, but they can be extrapolated to other countries, it is seen that the number of the locations where exists any Black swan has been doubled in the last five years and that the number of breeding centers has been trebled; for this reason the release and escapes have been increasing. In some European countries, being aware of the risk of this species, they have set in motion a eradication programme, and for example in Austria it is believed that is has been completely eradicated.

Cygnus atratus busturi

We must not forget, that the protection of breeding native birds helps to achieve one of the biggest environmental challenge of our century: the conservation of biodiversity.

In Urdaibai there is the evidence of some individual loose since some years, probably escaped from a private pond; but it was not until three years ago when the number has increased and currently can be seen four specimens between Murueta and Axpe in the middle marsh. Furthermore, we can confirm that they have been seen next to a group of Brent Gooses these days and sometimes also disturbing and displacing them from their resting and feeding areas.

Brantak eta beltxarga beltzak

Black swans and Brent gooses in the middle marsh

Therefore, although this elegant and great bird is beautiful in our eyes, it can be a serious problem for the conservation of water birds in Urdaibai.

 
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