Marginal speed confinement resolves the conflict between correlation and control in collective behaviour.

Area of Science:

• Collective animal behavior
• Statistical physics
• Aerodynamics

Background:

• Individual bird flight speeds have moderate fluctuations due to physical constraints.
• Flock-wide spatial correlations in speed fluctuations are scale-free, enabling collective responses.
• Conflicting constraints exist between scale-free correlations and moderate speed fluctuations.

Purpose of the Study:

• To reconcile scale-free correlations with moderate individual speed fluctuations in bird flocks.
• To propose a mechanism controlling individual agent speeds within a collective system.
• To validate theoretical predictions with empirical data from starling flocks.

Main Methods:

• Statistical field theory approach to model flocking dynamics.
• Development of a marginal speed confinement model.
• Comparison of theoretical predictions with field experimental data.

Main Results:

• A marginal speed confinement mechanism effectively balances correlation and fluctuation.
• This model reconciles scale-free correlations with biologically acceptable group speeds.
• Theoretical predictions align with experimental observations across a wide range of flock sizes.

Conclusions:

• Marginal speed confinement is a viable mechanism for collective motion in biological systems.
• Scale-free correlations and moderate fluctuations can coexist in animal groups.
• The study provides insights into the physics of collective behavior in natural flocks.