The heirarchy within a group or organization. There's definitely a pecking order in this company, and you're not going to do well if you don't know your place.
The hierarchy of authority in a group, as in On a space mission, the astronauts have a definite pecking order. This expression, invented in the 1920s by biologists who discovered that domestic poultry maintain such a hierarchy with one bird pecking another of lower status, was transferred to human behavior in the 1950s.