By Frank James
If you're a scientist and you want to learn which birds lead the flock during flights and which follow, there's probably no better way to research that question than to fit the birds with little backpacks containing GPS devices and track them. Really.
So that's exactly what some scientists did. They strapped GPS-bearing backpacks onto homing pigeons, then followed their flight patterns in minute detail.
And what they learned was that though dominant birds tended to get a lot of time in the lead position, other, lower-ranking birds contributed to how the flocks maneuvered as well.
But the flocks they studied definitely seemed to key off the higher-ranked birds. That led the researchers to conclude the following in the abstract of their research paper in the British science journal Nature:
From an evolutionary perspective, our results suggest that hierarchical organization 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.
In other words, evolution figured out that true democracy wasn't necessarily good for the survival of the species. Often it takes a strong leader, whether it's a man on a horseback or in this case a bird with a backpack, to get things done, apparently.
NPR's Nell Greenfieldboyce has a piece on All Things Considered Wednesday and an article on the NPR.org website. An excerpt:
Without the GPS tracking, it would have been impossible to figure out who was leading the flock just by watching the birds as they veered through the air, says Dora Biro of the University of Oxford in the U.K.
"If you tried to work out who it is within the flock who's making the decisions about, you know, what the flock should do from one moment to the next, it's very difficult to actually see this," says Biro, "because the decisions that are made and that spread through the group are made at such short time scales that it's really not visible easily to the naked eye."
And don't assume that birds in the front are the leaders, she says, because "birds have a very wide angle of vision, so for them, it is possible that they would be responding to birds who are flying behind them."
The GPS data, however, allowed Biro and her colleagues at Eotvos University in Hungary to detect clear leader-follower relationships within the flock.
For any given pair of birds, Biro says, "you can accurately work out which of them is the leader and which one of them is the follower."
Some birds had more followers than others. This demonstrates a hierarchy of influence within the flock. "You can actually rank birds in terms of the influence that they have on others within the group," Biro says. "Basically every individual gets a kind of a vote in what the flock does, but the weight of your vote depends on your rank, your position in the hierarchy."
And it did turn out that highly influential birds tended to fly out in front, according to a report on the study in the journal Nature.
Biro isn't sure what qualities make a bird a leader in the air -- maybe some birds just fly faster, or have a better sense of direction -- and says that's something she'd like to investigate further.