Chickens are highly social birds that synchronize their behavior with flock-mates, meaning welfare conditions affecting some birds cascade through the flock via behavioral copying.
Flock behavioral synchrony means that the welfare of individual chickens affects the welfare of those around them. A frightened bird spreads fear through the flock; a dustbathing bird invites others to join. This social welfare contagion has practical implications: reducing individual stressors improves flock-wide welfare beyond the direct effect on the individual. It also means that welfare assessment must account for social dynamics, not just individual conditions.