When do chickens usually establish a pecking order?

In poultry farming, the establishment of a pecking order—a social hierarchy that dictates access to resources like food and nesting sites—varies by sex:1

• Female chicks: The pecking order is typically established within groups by the 10th week of life.1
• Male chicks: Fights for dominance are more persistent and can continue into adulthood.1

When new birds are introduced to an existing flock, they often challenge established members, which can lead to aggressive altercations involving pecking, wing-pummeling, and scratching. While these hierarchies are natural, it is important to note that in industrial settings, management practices such as debeaking are sometimes employed to mitigate injuries from aggressive behaviors like cannibalism or feather picking.12