Bird Migration

Speed leads the way

Print edition : December 11, 2015

Pigeons in flight. Photo: Zsuzsa Akos

MANY birds travel in flocks, sometimes migrating over thousands of miles. But how do the birds decide who will lead the way? On the basis of studies with homing pigeons, researchers have gained some insight; for pigeons, it seems, leadership is largely a question of speed. The research has been published in Current Biology.

The new findings offer an elegantly simple explanation for the phenomenon of leadership in birds, with important implications for how spatial knowledge is generated and retained in navigating flocks.

While many birds travel in flocks, homing pigeons are domestic and more easily studied than most. “We can control the composition of the flocks and the starting points for their homeward journeys,” said Benjamin Pettit of the University of Oxford, and the first author of the new study. “We also have a good understanding of their individual spatial cognition, in particular how their homing routes develop over repeated flights in the same area.”

Recent developments in sensor technology also make it possible to explore with exquisite precision how pigeon flocks are coordinated. The latest global positioning system, or GPS, loggers allow researchers to track not only the birds’ overall routes, but also the sub-second time delays with which they react to each other while flying as a flock.

In the new study, the researchers compared pigeons’ relative influence over flock direction with their solo flight characteristics. Their studies showed that a pigeon’s degree of leadership could be predicted by its speed in earlier flights.

In solo flights, leaders were no better than followers in forging a straight path. In other words, they did not excel in navigation ability, at least not at first. When the researchers tested the birds individually after a series of flock flights, however, they found that leaders had learned straighter homing routes than followers.

“Some birds are naturally faster and consistently get to the front, where they end up doing more of the navigation, which means on future flights they know the way better,” said Dora Biro, also of Oxford University.

While it’s often tempting to take an anthropocentric view of leadership, the findings come as a reminder that leadership can arise as an unavoidable consequence of individual differences within a population. A very simple, self-organising mechanism —such as that based on variation in speed—is sufficient for leadership to arise. In addition, the new findings offer a mechanism through which leaders can improve in their roles over time, making increasingly better decisions that others can follow.

R. Ramachandran

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