Diving ducks face the strongly cooling properties of aquatic environments.
In experiments with Tufted Ducks Aythya fuligula feeding on zebra mussels Dreissena polymorpha in outdoor cages, we measured changes in food consumption and diving behaviour in rel Diving ducks face the strongly cooling properties of aquatic environments. Tufted Ducks swallow mussels whole and crush the shells in the gizzard. Water efflux was 6.5 to 13 times higher than allometrically predicted, with a maximum of 1.1 l.d-1. At lower temperatures, dive duration was shorter and less time was spent selecting small mussels at the bottom, while more larger mussels were brought up and were ingested at the water surface. Thereby, the energy costs of crushing shells probably increased in favour of reducing diving costs.