acorn woodpeckers (Melanerpes formicivorus). In this species, two female woodpeckers share a single nest and will even feed and care for each other’s young. But before that occurs, the nestmates may also destroy and consume each other’s eggs if one bird should lay an egg first. Presumably this is because the oldest hatchling would be the most likely to survive. To eliminate this advantage, the birds will keep eating each other’s eggs until they both lay their eggs on the same day, a process that can take weeks.
