Acorn woodpeckers: Helping at the nest, polygynandry, and dependence on a variable acorn crop

Th e acorn woodpecker ( Melanerpes formicivorus ) plays an important role in the history of cooperative breeding. It was one of the earliest species for which cooperative breeding was noted with more than two individuals feeding at a single nest as well as apparent mate-sharing (Myers 1915 ; Leach 1925 ; Michael 1927 ). Subsequently, in his classic Animal Dispersion in Relation to Social Behaviour , V. C. Wynne-Edwards singled out the acorn-storing habits of this species as a means by which birds assessed the food supply and adjusted their breeding so as to avoid overexploitation of resources. Indeed, Wynne-Edwards suggested that acorn storing was “the perfect example of an epideictic rite, combining as it does a sampling of the Acorn woodpeckers: Helping at the nest, polygynandry, and dependence on a variable acorn crop