Two apparent females engaged in what appears to be out-of-season and same-sex copulation in October. Birds of North America Online describes Acorn Woodpecker behavior that "mimics normal copulatory behavior in many respects but serves a more social function because sperm is not transferred between individuals." Birds "mount each other," which "may involve any group member mounting any other, including both heterosexual and homosexual combinations." This most often takes place in communal gatherings at dusk, before the birds roost for the night, but also occurs at other times of day and apart from any group, as was the case here -- a single pair of females, early in the morning. Thanks to Walt Koenig, co-author of the BNA article on Acorn Woodpeckers, for information on this behavior.