In The Social Lives of Birds, evolutionary biologist Joan Strassmann examines what it means for birds of a feather to flock together. Some birds sleep together. Some join the foraging groups of other species. Some are only social during the breeding season, forming nesting colonies in trees, cliffs, and sandbanks. Some are altruistic, helping to rear young that are not their own. Some males perform mating dances together. Strassmann explains how flocks provide safety in numbers, roosts offer warmth and shelter, and colonies allow for protected breeding. But group behavior is not without its costs-including increased competition, infidelities, tick infestations, and more. Strassmann exposes the conflicts birds face and the many ways in which they resolve these conflicts.