Hierarchical group dynamics in pigeon flocks

TL;DR

This study uses high-resolution GPS data to analyze the hierarchical dynamics of pigeon flocks, revealing leader-follower roles, positional influences, and eye-based response differences, providing insights into collective animal movement.

Contribution

First detailed high-resolution tracking of natural pigeon flocks revealing hierarchical structures and differential response behaviors during flight.

Findings

Identified a clear hierarchy based on pairwise interaction delays.

Found a correlation between flock position and hierarchical rank.

Discovered birds respond faster to conspecifics seen with the left eye.

Abstract

Animals that travel together in groups display a variety of fascinating motion patterns thought to be the result of delicate local interactions among group members. Although the most informative way of investigating and interpreting collective movement phenomena would be afforded by the collection of high-resolution spatiotemporal data from moving individuals, such data are scarce and are virtually non-existent for long-distance group motion within a natural setting because of the associated technological difficulties. Here we present results of experiments in which track logs of homing pigeons flying in flocks of up to 10 individuals have been obtained by high-resolution lightweight GPS devices and analyzed using a variety of correlation functions inspired by approaches common in statistical physics. We find a well-defined hierarchy among flock members from data concerning leading roles in pairwise interactions, defined on the basis of characteristic delay times between birds' directional choices. The average spatial position of a pigeon within the flock strongly correlates with its place in the hierarchy, and birds respond more quickly to conspecifics perceived primarily through the left eye - both results revealing differential roles for birds that assume different positions with respect to flock-mates. From an evolutionary perspective, our results suggest that hierarchical organisation of group flight may be more efficient than an egalitarian one, at least for those flock sizes that permit regular pairwise interactions among group members, during which leader-follower relationships are consistently manifested.