Posts Tagged Eyes
So says a current television commercial trying to convince drivers to slow down. A recent study indicates that this will save not only human lives but avian ones as well. It seems that birds are able to calculate the average speed that cars travel along certain stretches of road and adjust their flight initiation distance accordingly (http://www.sciencenews.org/view/generic/id/352603/description/Birds_know_road_speed_limits).
On stretches of road with a speed limit of 20 kilometres per hour, birds waited to fly until the car was about 10 metres away. That distance increased to roughly 25 metres on roads with a 90 km/h limit and around 75 metres at a 110 km/h limit. Consequently a speeding car will reach the bird earlier than it expects, making it more likely to be struck. Yet another reason to slow down and stick to the speed limit.
Over the years I have seen many avian road trauma victims. Recently I have begun peering into the eyes of these injured birds. Intriguingly a number of them have long standing retinal damage presumably reducing their visual acuity and field of vision. I wonder if many of the birds that are struck on roads become victims because their eyesight is compromised. To study this properly I would need to compare the injured birds with a sample of healthy wild caught birds. Something for the future.
Dr. F. Bunny
Legagneux, P., and S. Ducatez. 2013. European birds adjust their flight initiation distance to road speed limits. Biology Letters. Published online August 21, 2013. doi: 10/1098/rsbl.2013.0417.