Evidence of algae in the excrement of ducks. [Translation from: Hydrobiologia 1 22-27, 1948. ]

In the extremely severe winter of 1946-47 the surface of the Pfaffikersee (near Zurich) lay under an unbroken seal of ice for a full three months. The number of wild ducks resting in this location was estimated to be about 400. Six samples of excrements of ducks were microscopically analysed and fragments of algae were identified. These analyses allow the expert to specify with definite certainty the feeding areas under investigation of the studied birds.