Bird flocks exhibit scale-free correlations, where the behavioral state of one individual influences and is influenced by all others, regardless of flock size. By analyzing the three-dimensional positions and velocities of starlings, researchers found that velocity fluctuations are correlated over distances scaling with flock size, indicating scale-free correlations. These correlations extend the effective perception range of individuals, compensating for short-range interactions and enhancing global response to environmental perturbations. Scale-free correlations suggest that flocks behave as critical systems, poised to respond maximally to environmental changes. The study shows that both orientation and speed correlations are scale-free, with the correlation length growing linearly with flock size. This implies that information can be transmitted across the flock without damping, enabling collective response. The findings highlight the importance of scale-free correlations in achieving efficient collective behavior in animal groups.Bird flocks exhibit scale-free correlations, where the behavioral state of one individual influences and is influenced by all others, regardless of flock size. By analyzing the three-dimensional positions and velocities of starlings, researchers found that velocity fluctuations are correlated over distances scaling with flock size, indicating scale-free correlations. These correlations extend the effective perception range of individuals, compensating for short-range interactions and enhancing global response to environmental perturbations. Scale-free correlations suggest that flocks behave as critical systems, poised to respond maximally to environmental changes. The study shows that both orientation and speed correlations are scale-free, with the correlation length growing linearly with flock size. This implies that information can be transmitted across the flock without damping, enabling collective response. The findings highlight the importance of scale-free correlations in achieving efficient collective behavior in animal groups.