Why do birds fly so low to the ground when crossing roads? Whenever I’m driving they fly right in front of my car when they could fly at any other height?
In: Biology
I heard about a study that looked at Cliff Swallows, who used to be fairly rare, but was growing in population as we started building highways in their habitat (1983-2012). They relied on cliffs for nesting sites, but readily adopted to using overpasses instead.
An ornithologist studying them over a few decades started compared the wingspans and found that the wingspan of these birds was shortening. This gave them increased agility at the expense of range. This makes sense, since their nesting sites were much less rare, but you needed to be able to dodge traffic.
Birds have literally evolved in the last century to be able to bob in and out of traffic. This gives them an unnaturally protected habitat and access to the bounty of food source (roads create an “edge”, like you’d normally find in a clearing in the wood, where insects and quick growing plants flourish).
[https://www.cell.com/current-biology/fulltext/S0960-9822(13)00194-2](https://www.cell.com/current-biology/fulltext/S0960-9822(13)00194-2)
I’m sure that this extends beyond just wingspan but also reaction time. If you’ve ever seen a bird drop out of the sky onto a pile of seeds, you know they have incredible reaction times to begin with. They may seem close to your car to you – but I imagine they have a faster reaction time than you, and they get a bit more of a heads up, as they are probably very sensitive to changes in air current caused by your car (which also give added energy to move them out of the way).
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