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Do black and white swans interbreed?

Sent in by Janet Fearns, London

As a general rule, no. Mute and black swans won’t breed or hybridise, although as with everything, there are always exceptions to this rule!

Wild black swans are native to southwestern and eastern Australia. They have been introduced to New Zealand and are popular as ornamental birds in Europe, and localised areas of blighty!

Mute swans on the other hand are native to Europe, Asia and parts of Northern Africa and were introduced to the Americas and Australasia. Therefore, in the wild they are far less likely to encounter one another. When selecting a mate they will preferentially select a mate of the same species. However, if a given area is void of others swans of the same species, but does have other closely related wildfowl of the opposite sex they are perhaps more likely to pair up and attempt to breed. The black swan is a nearer relative to the mute swan than any other swan species.

Black swans have therefore been recorded as producing hybridised young with mute swans, producing large mottled grey and white offspring. Not to be confused with juvenile mute swans! In addition, both black and mute swans have also hybridised with tundra, whooper and trumpeter swans and even greylag, snow and Canada geese!

First generation wildfowl can produce viable offspring and this often leads to problems with correct identification. Where dominant wildfowl species hybridise with more passive species, this can lead to conservation threats as was seen with the native white-headed duck population following the introduction of ruddy ducks to the UK. 

Check out this discussion on our Community: http://www.rspb.org.uk/community/forums/p/7342/53975.aspx#53975

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