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Can birds read speed signs?

Researchers say that birds on roads adapt to speed limits as they fly off to avoid oncoming cars

BIRDS seem to be adapting to speed limits when they land on roads, with researchers saying that the birds flew to safety if traffic was moving at normal speeds – but took off too late if the vehicle was going too fast and got hit.

Pierre Legagneux and Simon Ducatez did 134 tests across the west of France on various roads with speed limits varying from 20, 50, 90 to 110kph and with 21 different bird species.

They found that when vehicles approached the birds took off roughly in accordance with the speed limit – as if they could read the signs – and not in accordance with the real speed of the vehicle.

They did their tests by measuring the distance at which the birds decided to take off when a vehicle approached – the called this the Flight Initiation Distance (FID) – and found that the FID varied according to the speed limit on the road, not with the speed of the vehicle.

Birds took off earlier on a 110kph road than they did on a 50kph road – even if the test vehicle is doing just 30kph.

The researchers concluded that the birds were aware of typical speeds on the roads and these became characteristics of the habitat, like the roadside vegetation or the possibility of finding road-kill.

Writing in the Royal Society’s Biology Letters, Legagneux and Ducatez, both from Canada, said birds were also known to adapt to their environment in towns – where they would stop singing if local noise levels were too high.
Photo: B4bee/Flickr

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