page_title: Acorn woodpecker
section_title: Pairs and communities
hierarchical_section_title: Acorn woodpecker / Breeding / Pairs and communities
context_page_description: The acorn woodpecker is a medium-sized woodpecker, 21 cm long, with an average weight of 85 g.
context_section_description: Field studies have shown that breeding groups range from monogamous pairs to breeding collectives, sometimes called "coalitions". Cooperative breeding, defined as more than two birds taking care of nestlings in the nest, is a relatively rare evolutionary trait that is thought to occur in only nine percent of bird species. 
  With the acorn woodpecker, cooperative breeding occurs in two ways: coalitions and family groups. Coalitions of adult acorn woodpeckers nest together, localizing to storage granaries. Additionally, adult offspring often stay in their parents' nest and help raise the next generation of woodpeckers. It is generally believed that limited territories drive cooperative breeding behavior in birds, and in the case of the acorn woodpecker, this limited territory is the acorn storage granary.
  Breeding coalitions consist of up to seven co-breeding males and up to three joint-nesting females. However, most nests are made up of only three males and two females. Nesting groups can also contain up to ten offspring helpers. These breeding coalitions are typically closely related. The males are often brothers, and the females are usually sisters. Inbreeding is rare, however, meaning that co-breeders of the opposite sex are almost never related.
  In groups with more than one breeding female, the females put their eggs into a single nest cavity. A female usually destroys any eggs in the nest before she starts to lay. Once all the females start to lay, they stop removing eggs. Young from a single brood have been found with multiple paternity.
caption: Acorn hoarded by acorn woodpecker
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