RESEARCH ARTICLE Coordinated Behaviour in Pigeon Flocks

We analysed pigeon flock flights using GPS trajectory data to reveal the most important kine-matic aspects of flocking behaviour. We quantitatively investigated the internal motion of the flock based on pairwise statistics and found the following general relationships in all data-sets: i) the temporal order of decisions characterised by the delay between directional changes is strictly related to the spatial order characterised by the longitudinal relative posi-tion within the flock; ii) during circling motion, pigeons use a mixture of two idealised and fun-damentally different turning strategies, namely, parallel-path and equal-radius type turning. While pigeons tend to maintain their relative position within the flock on average, as in the parallel-path approximation, those who turn later also get behind as in the equal-radius case. Equal-radius type turning also tends to be expressed more during smaller radius turns