Minecraft wiki entry for Chicken, associated text: All baby zombie variants and baby zombified piglins have a 5% chance to spawn riding a chicken, forming a chicken jockey. Because a baby zombie occurs from 5% of zombie spawns, the chicken jockey spawns consist of 0.25% of all zombie spawns in a chicken-free environment; if chickens are present, the chance increases to 0.4875%. A chicken jockey can also be spawned by using the following command: