Humans may not be the only ones heeding speed limits. Birds apparently take this information into account to avoid being hit by traffic as they forage near roads. Canadian researchers traveled stretches of road with various speed limits and tested how close a bird on or beside the road would allow the advancing car to come before fleeing. As soon as the scientists saw a bird ahead of them fly away, they recorded how long it took them to reach the spot where the bird had been.
When they calculated the distance at which birds bailed for safer ground, they found that this distance was greater on roads with higher speed limits. It seems that the birds didn't judge the speed of a specific oncoming vehicle, but instead associated each stretch of road with a degree of risk based on the speed limit and took extra precautions on faster roads, the researchers reported.