How to avoid becoming roadkill

And now for something else completely different.

Cliff swallows with nests which,  “dangle precariously from highway overpasses,” have less chance of becoming roadkill than in years past.

How come? Because, they have a shorter wingspan that  “lets them dodge oncoming traffic”.

At least,that’s the conclusion of a new study based on three decades of data collected on one population of the birds, says Science, adding.

“The results suggest that shorter wingspan has been selected for over this time period because of the evolutionary pressure put on the population by cars”.

The article is based on a study  in Current Biology.

Says the abstract »»»

SwallowsAn estimated 80 million birds are killed by colliding with vehicles on U. S. roads each year, and millions more die annually in Europe and elsewhere. Losses to vehicles are a serious problem for which various changes in roadway design and maintenance have been proposed.

Yet, given the magnitude of the mortality reported for some species we might expect natural selection to favor individuals that either learn to avoid cars or that have other traits making them less likely to collide with vehicles. If so, the frequency of road kill should decline over time.

No information is available for any species on whether the extent of road-associated mortality has changed.

During a 30-year study on social behavior and coloniality of cliff swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, we found that the frequency of road-killed swallows declined sharply over the 30 years following the birds’ occupancy of roadside nesting sites and that birds killed on roads had longer wings than the population at large.

(Cheers, Martin)

Jon Newton — myblogdammit

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