A drinking duck

The duck, whose head is wet, leans forward and tries to drink water from the glass. When the duck touches the rim of the glass it moves back to the vertical position and then again leans forward.

The red hat covers one of the two glass bulbs joined by a small tube (the bird's neck). There is a liquid inside that evaporates easily. The level of the liquid in the tube slowly rises till the bird leans forward. Then the liquid flows down to the lower bulb.

The movement of the liquid is the result of the pressure difference in the bottom and top bulbs. While the water evaporates from the wet hat, the temperature of the hat falls and, subsequently, the pressure in the top bulb decreases. The pressure difference sucks the liquid from the bottom bulb and the bird's centre of gravity moves up until the bird leans forward. While the bird is leaning, the pressures become equal and the liquid flows down. It seem to be example of perpetual motion.

The duck moves faster if it dips its head in alcohol. You start nodding off when you are tipsy...