Speed limits affect birds’ behavior

When speed limits change, birds pay attention. That’s the conclusion of a study in Biology Letters, which shows that European birds fly away from cars sooner on roads with higher speed limits.

The researchers conducted the study on roads in France, “mostly on our way home from the laboratory,” they write. Speed limits in the area varied from 20 to 110 kilometers per hour. During their drives, the authors looked for birds along the side of the road and recorded the animals’ “flight initiation distance” — how close the bird allowed the car to approach before flying away.

The team observed 134 flights by birds from 21 species, mainly carrion crows, house sparrows, and common blackbirds. The higher the speed limit on the road, the longer the flight initiation distance, the researchers found. The car’s actual speed didn’t affect the birds’ flights.

The results suggest that birds have learned to link average car speeds along a road with the risk of being hit, the authors say. The animals might also assess danger based on how crowded and noisy the roads are. Roberta Kwok | 21 August 2013

Source: Legagneux, P. and S. Ducatez. 2013. European birds adjust their flight initiation distance to road speed limits. Biology Letters doi: 10.1098/rsbl.2013.0417.

Image © Sean Nel | Shutterstock