The Social Lives of Birds

Flocks, Communes, and Families

By: Joan E. Strassmann

An exploration of all the ways in which birds are social creatures—from breeding to nesting to babysitting

In The Social Lives of Birds, evolutionary biologist and author of Slow Birding 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 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, tick infestations, and more. Strassmann exposes the conflicts birds face and the many ways in which they resolve these conflicts.

With stories of birds from around the world—from broad-winged hawks that migrate south together in the fall, tree swallows that roost together in the thousands, and guira cuckoos that nest in communes—The Social Lives of Birds explores the different kinds of bird groups and what to look for when watching them. Above all, it reveals this fact: solitary life, it seems, is not for the birds.

©2025 Joan E. Strassmann (P)2025 Penguin Audio

Critic reviews

“For those of us drawn to watch birds, few aspects are more awe-inspiring and mind-blowing than their propensity to live with others of their clan. Strassmann digs deep into the fascinating social world of birds, bringing a scientist's critical eye and a novelist's sharp pen to interpret and understand its dizzying diversity.”—John M. Marzluff, author of Gifts of the Crow

"Joan Strassmann knows the social life of birds almost as well as birds do. A delightful and informative flight into sociality in our avian friends."—Lee Dugatkin, author of How to Tame a Fox (and Build a Dog)

"The main features of birds most of us are interested in concern their feathers, flight, nesting, feeding, foraging, mating, predator evasion, migration, and group vs. solitary behavior. If I were to read any book on what birds are all about, I could not recommend one more than this one. I know of no other book that so thoroughly covers the hugely extensive scientific literature from the experts who spend their lives and fortunes on their work. This book is a must-read for all birders and a clear-eyed pleasure for anyone interested in Nature."—Bernd Heinrich, author of Mind of the Raven

“In this elegant and masterful treatment of avian life, the biologist Joan Strassmann makes it abundantly clear that the proverb ‘birds of a feather flock together’ is one massive understatement. Birds variously pair up, lek, roost, form colonies, team up to assist the parent, breed communally, and turn super-social. She will intrigue the novice while transporting even the most knowledgeable bird lover in fresh and unexpected directions.”—Mark Moffett, author of The Human Swarm

“Why do birds join flocks, nest in sprawling colonies, or tend to eggs that are not their own? Using global examples, from mixed-species groups in Finland to families of Pinyon jays in the American southwest, Strassmann carefully unpacks the motivations behind avian social behaviors. A mix of personal observation, interviews with experts, and a review of the scientific literature, this is a fascinating and informative read.”—Jonathan C. Slaght, author of Owls of the Eastern Ice