David Wright writes:


> Somewhere I read that Ruddy Ducks introduced somewhere in Spain (?)

Actually, these guys have been introduced in the UK a while ago.
The population is now something like 1000 pairs, if I remember well.
This population is doing so well that it has reached France at least
10 years ago, and Spain at least 5 years ago, where he is threatening
the native species, the White-headed Duck _Oxyura leucocephala_.

> are threatening the status of a native population of another oxyurine
> duck, because Ruddy males are mating with the Spanish oxyurine females
> quite frequently (more so than the natives, I think). Whether this is
> attributable to females choosing the Ruddies because of their stunning
> good looks (or other attributes), or the Ruddies being more agressive
> than the native males I don't recall.

The "common wisdom," as Dennis says, is that male Ruddy Ducks are more
aggressive than the Europian native male White-headed Duck.
The net result is either a dilution of WHDU genes (when RUDU succeeds
in mating with females) or simply no reproduction for WHDU (because
RUDU will disrupt the courtsip of males WHDU).

These darn RUDU! Almost as imperialist as McDonald and Coca-Cola...

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