From local collective behavior to global migratory patterns in white storks

TL;DR

This study investigates how juvenile white storks coordinate during migration, revealing leader-follower dynamics and the costs and benefits of collective movement in natural conditions.

Contribution

It provides detailed insights into the social interactions and movement strategies of migrating white storks using high-resolution tracking data.

Findings

Leaders explore thermals and guide followers.

Followers benefit but leave thermals earlier and flap more.

Followers migrate less far annually than leaders.

Abstract

Soaring migrants exploit columns of rising air (thermals) to cover large distances with minimal energy. Employing social information while locating thermals may be beneficial, but examining collective movements in wild migrants has been a major challenge. We investigated the group movements of a flock of 27 naturally migrating, juvenile white storks using high-resolution GPS and accelerometers. Analyzing individual and group movements on multiple scales reveals that birds ahead navigate to and explore thermals, while followers benefit from their movements. Despite this benefit, followers often leave thermals earlier and at lower height, and consequently must flap considerably more. Followers also migrated less far annually than did leaders. We provide insights into the interactions between freely-flying social migrants and the costs and benefits of collective movement in natural populations.