bird, beaker, water
The bird's fuzzy head must be soaked to serve as the heat sink. As the head cools by evaporation, the centre of gravity of the bird shifts as coloured liquid from its tail rises. The bird pivots at the hips, leaning forward and dipping its head into the water reservoir.
The drinking bird is a heat engine, showing a conversion of energy: thermal to mechanical.
PIRA 4C31.30, 4F30.01