"Pecking order or just peck order is a hierarchical system of social
organization in animals. 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 1925. The peck
order referred to the refusal of birds to feed until the more dominant
individuals had finished. The term dominance hierarchy is more 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 as well, including
humans. Still, the term "pecking order" is often used synonymously as
well, because 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. Consequently, this also determines which chicken gets to eat
first or which chicken gets to peck on any other chickens they want.
The top chicken is one which can peck any chicken it wants. The bottom
chicken is one that lets all the other chickens peck on it and stands
up to none. There are chickens in the middle, who peck on certain
chickens but are, in turn, pecked on by other chickens higher up on
the scale."
http://en.wikipedia.org/wiki/Pecking_order
