Minecraft wiki entry for Egg_farming, associated text: The hopper egg farm is a relatively simple contraption, which does not require access to nether quartz: On the main floor, chickens are contained by water while they grow and lay eggs, which also wash the eggs into a hopper; from there the eggs go back into the system's supply chest. This chest feeds an automatic hatcher, which can refill the main floor after a harvest. The hatcher is controlled through a despawn timer, which prevents the system from spawning chickens ad infinitum (or at least until the server crashes).