Helpers at the nest is a term use in behavioural ecology and evolutionary biology to describe a social structure in which juveniles, of one or both sexes, remain in association with their parents and help them in raising subsequent broods or litters, instead of dispersing and beginning to reproduce themselves. This phenomenon was first studied in birds, and is found, for example, in the Common Moorhen, also species of woodpeckers-(example Acorn Woodpecker), but it is now known in animals of many different groups. It is a simple form of co-operative breeding.