Pecking Order

Pecking order or just peck order is the colloquial term for a hierarchical system of social organization in chickens. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste and introduced into English in 1927.

The original usage of "pecking order" referred to the expression of dominance of birds. Dominance in chickens is expressed in various behaviours including pecking which was used by Schjelderup-Ebbe as a measure of dominance and leadership order. In his 1924 German-language article he noted that "defense and aggression in the hen is accomplished with the beak".

This emphasis on pecking led most subsequent studies on fowl behaviour to use it as a primary observation. However, it was also noted that roosters tended to leap and use their feet in conflicts. The term dominance hierarchy is often used for this phenomenon in other animals.

It is a basic concept in social stratification and social hierarchy that has its counterpart in other animal species, including humans. Still, the term "pecking order" is often used synonymously; the "pecking order" was the first studied example of the social hierarchy among animals.

The basic concept behind the establishment of the pecking order among, for example, chickens, is that it is necessary to determine who is the 'top chicken,' the 'bottom chicken' and where all the rest fit in between. The establishment of the dominance hierarchy is believed to reduce the incidence of intense conflicts that incur a greater expenditure of energy. The dominance level determines which individual gets preferential access to resources such as food and mates.

Chickens held in intensive poultry farming operations are often confined with up to 40,000 other birds in a single shed, making natural pecking order impossible.