fly briefly to explore their surroundings but generally do so only to flee perceived danger. Behavior Social behaviour Chickens are gregarious birds and live together in flocks. They have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a pecking order, with dominant individuals having priority for food access and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established. Adding hens, especially younger birds, to an existing flock can lead to fighting and injury. Chickens may occasionally gang up on a weak or inexperienced predator. At least one credible report exists of a young fox killed by hens. A group of hens have been recorded in attacking a hawk that had entered their coop. If a chicken is threatened by predators, stress, or is sick, it may puff up its feathers. Vocalizations When a rooster finds food, he may call other chickens to eat first. He does this by clucking in a high pitch as well as picking up and dropping the food. This behaviour may also be observed in mother hens to call their chicks and encourage them to eat. A rooster's crowing is a loud and sometimes shrill call and sends a territorial signal to other roosters. However, roosters may also crow in response to sudden disturbances within their surroundings. Hens cluck loudly after laying an egg and also to call their chicks. Chickens also give different warning calls when they sense a predator approaching from the air or on the ground. Crowing Roosters almost always start crowing before four months of age. Although it is possible for a hen to crow as well, crowing (together with hackles development) is one of the clearest signs of being a rooster. Rooster crowing contests are a traditional sport in several countries, such as Germany, the Netherlands, Belgium, the United States, Indonesia and Japan. The oldest contests are held with longcrowers. Depending on the breed, either the duration of the crowing or the times the rooster crows within a certain time is measured. Courtship To initiate courting, some roosters may dance in a circle around or near a hen (a circle dance), often lowering the wing which is closest to the hen. The dance triggers a response in the hen and when she responds