I have this drinking bird on my desk and the kids can’t stop watching it. It keeps drinking the water all day long. As long as I keep adding water to the beaker, the bird will keep drinking. It’s not really drinking the water, just dipping its beak in the water. The water evaporates and cools the beak, thus the liquid moves up.
From Wikipedia
- The water evaporates from the felt on the head.
- Evaporation lowers the temperature of the glass head (heat of vaporization).
- The temperature decrease causes some of the dichloromethane vapor in the head to condense.
- The lower temperature and condensation together cause the pressure to drop in the head (ideal gas law).
- The pressure differential between the head and base causes the liquid to be pushed up from the base.
- As liquid flows into the head, the bird becomes top heavy and tips over during its oscillations.
- When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid.
- A bubble of vapor rises up the tube through this gap, displacing liquid as it goes.
- Liquid flows back to the bottom bulb (the toy is designed so that when it has tipped over the neck’s tilt allows this), and vapor pressure equalizes between the top and bottom bulbs
- The weight of the liquid in the bottom bulb restores the bird to its vertical position
