We know a lot about how birds navigate over long distances, yet little about how they steer through small-scale, cluttered environments like forests and city streets. How, for example, do they decide on a course that won’t lead to a nasty crash? To address this question, researchers constructed randomized obstacle courses of vertical poles, through which four pigeons—trained to fly between two perches—could traverse. A series of ceiling-mounted, high-speed cameras were used to monitor the animals, which wore pairs of LED markers—on the head (pictured) and on the body—so they could be tracked. From these, the scientists constructed 3D maps of the birds’ flight paths. Pigeons seem to use a reactive approach to navigating obstacles , the researchers report online today in the Journal of the Royal Society Interface, with the birds first adjusting their flight path when only 1.5 meters from the entry to the artificial forest—rather than planning out their path in advance. By combining data on each run of the course with the respective layout of obstacles, the team was then able to reconstruct a literal bird’s-eye view along the flight, breaking down the journey into sections to determine, at each point, how the pigeons might decide on a path to take based on the obstacles they encounter. Rather than solely attempting to minimize the extent of their course corrections (by aiming for the nearest gaps between obstacles lying in their path), pigeons seem to prefer steering toward larger gaps, if available, when making rapid steering decisions: a behavior that the researchers call “a surprisingly simple strategy for such sophisticated behavior,” and one that might inform the development of controllers for guiding flying robots in the future.
ScienceShot: Why Pigeons Don't Crash