I've made enough mistakes this year to fill a book, so I want to make sure this one's right!
Together with what are undoubtedly Ferruginous ducks in the Parque Ambientale in Portugal (see my post of 1st November 2009) are a few birds as per the photo.
My book (Rob Hume's RSPB Complete Birds) only shows the male Ferruginous duck, but looking at pictures on the Web, the female is similar to the male. The bird in the picture seems right for ferruginous duck, (eye colour, beak, overall shape etc) but it's a different colour to the male. Is it a Ferruginous duck? Hybrid perhaps?