1. When water evaporates from the fuzz on the Dippy Bird’s head, the head is cooled.
2. The temperature decrease in the head condenses the methylene chloride vapor, decreasing the vapor pressure in the head relative to the vapor pressure in the abdomen.
3. The greater vapor pressure in the abdomen forces fluid up through the neck and into the head.
4. As fluid enters the head, it makes the Dippy Bird top-heavy.
5. The bird tips. Liquid travels to the head. The bottom of the tube is no longer submerged in liquid.
6. Vapor bubbles travel through the tube and into the head. Liquid drains from the head, displaced by the bubbles.
7. Fluid drains back into the abdomen, making the bird bottom-heavy.
8. The bird tips back up.

Credit: How Stuff Works

• Wet the head and beak of the bird with cold water. The bird will sway back and forth. A cup of cold water can be placed under the bird’s beak to keep the beak moist and to simulate drinking. The bird can also function without a cup of water.
• The cup should be tall enough that the liquid can drain back into the body after tipping over (about the height of the supports). Using a softer cup than a glass beaker can lessen the impact when the bird drops forwards.
• It may take some time to set up the system just right. The first cycle will take the most time. Take 10 minutes to set up before the lecture.