On zebra mussels and tufted ducks

One of the most common diving ducks around here is the handsome Tufted Duck (Aythya fuligula). The male striking black and white plumage, long tuft of feathers at the back of their heads and yellow eyes makes them quite distinctive. Females are all brown and have only a tiny, but clear tuft. Reading about tufted ducks I came across some research suggesting that the spread of a non-native invasive species, the Zebra Mussel (Dreissena polymorpha) in the UK in the last couple of centuries could be linked to the increase in Tufted Duck numbers.
 Tufted ducks dive up to 5 m of depth to feed. They eat mostly zebra mussels where they are available, whereas in places where zebra mussels are not widespread, their diet is more varied, with crustaceans, insects, seeds and some molluscs. The mussels, which are of small size are swallowed whole and crushed in the muscular gizzard. The small mussels are sucked and filtered, while the larger ones require more manipulation.

and down it goes!

More information
Olney, P. J. S. (1963). The food and feeding habits of tufted duck Aythya fuligula. Ibis, 105(1), 55-62. here.

Joep J. De Leeuw and Mennobart R. van Eeerden 1992. Size selection in diving tufted ducks Aythya fuligula explained by differential handling of small and large mussels Dreissena polymorpha. Ardea 80:353-362. here