(Common) Pochard x Rosybill Pochard
Aythya ferina x Netta peposaca

This unusual hybrid is a cross of a common wild species (Pochard) and a non-native species (Rosybill Pochard). The pink bill-base of the Rosybill is somewhat subdued here and the overall effect is to produce a bird that looks a bit like a large Aythya. Thanks to Jörn Lehmhus for help with the identification.
 

1: Thun, Switzerland, 08/02/2009.