A key question in collective behaviour is how among-individual differences structure animal groups, affect the flow of information, and determine leadership roles1,2. Leadership does not necessarily arise ‘intentionally’3. For instance, if certain individuals maintain cohesion with a group by more closely following others than vice versa, then leadership in collective movement emerges spontaneously. Since leaders can increase but also decrease a group’s navigational accuracy, the mechanisms behind leadership are important for understanding its evolutionary significance1.
In elucidating mechanisms of animal navigation, homing pigeons (Columba livia, hereafter pigeons) have been a paradigmatic study species for many decades4. The University of Oxford has extensive experience in studying avian navigation, and has been at the forefront of elucidating the dynamics of collective decision-making. Using GPS tracking devices2,5, mounted to the backs of pigeons, Oxford researchers have shown that the birds develop idiosyncratic routes6, and resolve conflicts over route choice by integrating information from group members7. Interestingly, this mechanism gives certain birds’ input more weight in the group’s decision, revealing a hierarchical arrangement of leadership within flocks2,8.
What places birds into leadership positions poses a crucial challenge in understanding how navigating flocks are structured. Recent experiments revealed that leadership correlates with how quickly pigeons learn more efficient routes1. This result opens up novel questions on the causality of the correlation. For instance, do leaders become better because they are compelled to learn as they take a more active role in navigational decisions? This possibility – a form of the so-called passenger/driver effect9 – is particularly interesting as it suggests a hitherto unexplored causal interaction between leadership and learning. Alternatively, it may be that leadership and learning capacities are naturally linked as ‘personality’ traits: individuals that emerge as leaders in groups may also possess superior competence at processing or memorising information.
To study cause and effect of leadership within groups of navigating pigeons, I work with Dr Dora Biro from the Oxford Navigation Group at the Department of Zoology, University of Oxford. Using the group’s established facilities, I will experimentally elucidate whether leaders are naturally the best learners, or if, through the experience of leading, they are ‘forced’ to make navigational decisions that promote faster learning.
Untangling the causal feedback loop between leadership and learning could have implications that extend beyond navigation by pigeons to a wide range of contexts10 and species including humans3. Leadership is essential in many human group activities, and it is important to understand not only how competence affects leadership but also how leadership may feed back to affect competence. In other words, even if leaders may not be the most knowledgeable individuals at the outset, through the experience of leading they can develop into increasingly competent leaders.
My experiments involve state-of-the-art GPS-devices2,5 mounted to the backs of pigeons. Tagged birds are released, away from their loft, either alone or in pairs. The GPS-devices provide time-stamped positional data on the birds’ return-tracks to the loft with high spatiotemporal resolution, i.e. five location-fixes per second, with a spatial accuracy of <4 m. These data provide instantaneous flight speed and, using cutting-edge quantitative techniques8, allow accurately distinguishing leaders and followers. Additionally, I collect environmental data such as wind speed to control for external factors influencing route efficiency.
To test whether leadership itself promotes quicker learning of a more efficient route, I manipulate leadership of 20 naïve focal birds by manipulating the level of experience relative to their respective partners. To obtain a baseline measure of route- efficiency, I first provide focal birds with a learning trial at two different release locations (east and west of the loft). I then run group trials: At one location, I make half of the birds the leader (by pairing them with an inexperienced partner) and the other half followers (by pairing them with a highly experienced partner)11. At the other location, I reverse the treatment. Then, for each release location, each bird flies alone again and I compare this route-efficiency with its original solo-flight from that location. If route-efficiency has increased more in the leader than in the follower treatment, we can conclude that leadership itself promotes learning. In turn, this will allow me to gain important insights into the informational consequences of leadership.
Pettit B, Ákos Z, Vicsek T, Biro D. Speed determines leadership and leadership determines learning during pigeon flocking. Current Biology 25(2015): 1-6.
Nagy M, Ákos Z, Biro D, Vicsek T. Hierarchical group dynamics in pigeon flocks. Nature 464(2010): 890-893.
King AJ, Johnson DDP, Van Vugt M. The origins and evolution of leadership. Current Biology 19(2009): R911-R916.
Wiltschko R, Wiltschko W. Avian navigation: from historical to modern concepts. Animal Behaviour 65(2003): 257-272.
Biro D, Guilford T, Dell'Omo G, Lipp H-P. How the viewing of familiar landscapes prior to release allows pigeons to home faster: evidence from GPS tracking. Journal of Experimental Biology 205(2002): 3833-3844.
Biro D, Meade J, Guilford T. Familiar route loyalty implies visual pilotage in the homing pigeon. Proceedings of the National Academy of Sciences 101(2004): 17440-17443.
Biro D, Sumpter DJT, Meade J, Guilford T. From compromise to leadership in pigeon homing. Current Biology 16(2006): 2123-2128.
Nagy M, Vásárhelyi G, Pettit B, Roberts-Mariani I, Vicsek T, Biro D. Context-dependent hierarchies in pigeons. Proceedings of the National Academy of Sciences 110(2013): 13049-13054.
Burt de Perera T, Guilford T. The social transmission of spatial information in homing pigeons. Animal Behaviour 57(1999): 715-719.
Sih A, Mathot KJ, Moirón M, Montiglio PO, Wolf M, Dingemanse NJ. Animal personality and state–behaviour feedbacks: a review and guide for empiricists. Trends in Ecology & Evolution 30(2015): 50-60.
Flack A, Pettit B, Freeman R, Guilford T, Biro D. What are leaders made of? The role of individual experience in determining leader–follower relations in homing pigeons. Animal Behaviour 83(2012): 703-709.