The Water Bird is a static decor item that can be bought for 1,400 Bells and sold for 350 Bells at Re-Tail (280 Bells at Nooklings). Although it is a static decor item, it bobs back and forth on it's own. This item can be placed on surfaces.
More commonly known as a drinking bird, this toy is a heat engine that mimics the motions of a bird drinking from a water source. It is made of two glass bulbs joined by a glass tube. Inside is a colored fluid, which is usually methylene chloride. First the head is wetted with water. This evaporates from the felt that is on the head. The temperature of the head lowers, which causes condensation of the methylene chloride in the head. This causes the pressure to drop. The higher pressure in the warmer base pushes liquid up the neck, which makes the bird top-heavy, thus tipping it over. The bottom end of the neck is then over the surface of the liquid, which makes a bubble of warm vapor rise through the gap. Liquid flows back to the bottom bulb, which brings the bird back to its original position. This can be repeated indefinitely as long as the head stays wet, which is why it is commonly seen dipping its head into a glass of water.