EVOLUTION NEWS -

TOP SPEED BIRD EVOLUTION

 

CAUSED BY MOTORISTS AND MAN-MADE STRUCTURES

It's a mystery that turns into a fascinating evolution story.  Here are the facts:

 

-  American Cliff Swallows need cliffs to live and reproduce.

-  Nebraska has no respectable-sized cliffs. It's all flat terrain.

-  Cliff swallows then use man-made structures as cliff-substitutes. 

 

-  Plot thickens.

 

-  Although the cliff swallows population is thriving, there are fewer road kills. 

-  Scientists were puzzled but determined to solve this mystery.

-  They noticed that while the road kill had longer wings,  the majority of the survivors had developed shorter wings.
 

-  Mystery solved. 

Long-winged swallows are getting decimated because they have more difficulty evading approaching cars than shorter-winged swallows.

 

-  The problem?

 

-  Short-winged swallows will have a harder time during their long migrations, and they'll tire more easily.

DISCOVER MAGAZINE:  A lot of birds, including most swallows, have long wings for their body size because they spend a lot of time catching flying prey like insects, and longer wings reduce the effort needed to glide and maneuver in the air.   But while short wings are less efficient once in flight, they provide a bigger boost from the ground, allowing birds a near-vertical takeoff.   When you’re trying to jump out of the way of a speeding car, the faster you can get out of range of the vehicle, the better.    Not only roadkill birds had longer wings, but over time the overall wingspan of the cliff swallow population in Nebraska has been declining.

 http://blogs.discovermagazine.com/science-sushi/?p=2658