This drinking bird is so cute and a perfect addition to your desk. The glass bird belly is filled with a temperature sensitive liquid. The head and beak is covered in felt. When the bird dips its head into a cup of water, the felt soaks it up. Then, as the water slowly evaporates, the liquid in its belly moves up into the neck changing the weight and the balance of the bird. When enough liquid moves up to offset the weight, the bird dips its beak back into the water to start the process over again. (Cup not included) Tips: Move the bird up or down to make it so it can dip its beak in a cup of water. Use this in warmer temperatures so the evaporation works better. 75 degrees is ideal. Colder temperatures will cause it to not move as fast.