Drinking bird

      Almost everyone remembers this hard to find toy with at least a twinge of nostalgia. Now, the Drinking Bird is back, disguised as a great demonstration of thermodynamics.

     When the head of the bird is moistened with water it will repeatedly tip over and appear to be drinking from a cup placed in front of it. The dunking is due to the evaporating water, which cools the head reducing the pressure of the gas inside. The liquid inside the bird rises up from his tail towards his head, causing the bird to tip and appear to be drinking. As the bird dunks, the liquid returns to its tail, and the process begins again. In essence this is a small, cleverly designed thermodynamic engine which only needs water to run.