Birds learn speed limits
As vehicles approach, birds in the road often appear unconcerned, until suddenly they take flight to avoid whizzing cars. The distance from an approaching car at which some birds take off varies depending on the local speed limit, according to a study published today (August 21) in Biology Letters.
Study coauthor Pierre Legagneux measured when birds took flight as he approached them at varying speeds while driving around the French countryside in a white Peugeot. He measured the takeoff distances of 134 birds including 21 species while traveling through zones with speed limits of 20, 50, 90, and 110 kilometers per hour (approximately 12, 31, 56, and 68 miles per hour).
The higher the speed limit, the sooner the birds flew away. But when Legagneux varied his speed, either driving above or below the speed limit, the birds’ responses didn’t change, indicating they were reacting to the speed of cars in each area in aggregate rather than gauging the speed of individual cars.
The authors said that the birds were likely varying their takeoff times in order to maximize time spent foraging while avoiding being struck. They said that the birds were not changing their behaviors due to natural selection, arguing instead that they were learning a variety of speed limits over a relatively small area and altering their behavior depending on their surroundings.
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