Swallows Evolve Shorter Wings in 30 Years

Started by stromboli, March 21, 2013, 11:58:35 AM

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stromboli

http://www.sciencenews.org/view/generic ... d_highways

QuoteCrossing the road has gotten easier for cliff swallows. Over generations, the mortal threat of speeding cars may have shortened their wings.

Over the last 30 years, the number of cliff swallows killed along roads in southwestern Nebraska has plunged, and the birds' average wing length has shrunk, researchers report March 18 in Current Biology.

The data are "jaw dropping," says animal behaviorist Colleen Cassady St. Clair of the University of Alberta in Edmonton, who was not involved with the work. The results suggest that years of smacking into SUVs forced swallows to adapt to the road.

In the absence of roads, cliff swallows — sparrow-sized birds with orange rumps and white foreheads — tuck their nests under overhangs on cliff faces. But in the last few decades, many birds have traded ancestral homes for modern real estate — highway bridges and overpasses.
Cliff swallows can plaster thousands of cantaloupe-sized mud nests to the undersides of these structures, says study author Charles Brown of the University of Tulsa in Oklahoma. These colonies are less likely than cliff nests to be washed away in storms but come with a different risk: They perch near roads — and fast-moving traffic.

As graduate students in the 1980s, Brown and study coauthor Mary Bomberger Brown didn't set out to study swallows' adaptations to cars. They were interested in the birds' social behavior. But because the team drove thousands of kilometers among colonies, they saw a lot of roadkill.

Every summer for the next 29 years, the team trekked to the colonies, counted nests and picked up dead birds. In total, the Browns gathered more than 2,000 swallows.

Starting in 1983, the researchers collected fewer birds killed by cars each year, until they found only four in 2012. And when Charles Brown measured preserved specimens' wing lengths, he saw that, compared with the rest of the population, swallows that died on the road had wings that were a few millimeters longer.

A few millimeters — about the width of a Tic Tac — might seem like a small change, but for birds' wings, "a little bit can make a big difference," says evolutionary biologist Ronald Mumme of Allegheny College in Meadville, Pa.

Petite wings let birds take off quickly and maneuver deftly through the air. Like quail, which have short, rounded wings and can explode off the ground almost vertically, Brown says, swallows might be better served by short wings that help them whiz up and out of harm's way.

He thinks the population's shorter average wing lengths could help explain why roadkill numbers are going down. "It's amazing what natural selection can do," he says.

The team ruled out other potential explanations, such as declining swallow populations or an increase in avian scavengers stealing carcasses. Still, Charles Brown says, factors other than wing length may also be involved. Cars may have killed off daredevil swallows, for example, leaving more cautious birds behind.

Give this one to your Creationist friends. This is adaptation in real time, a key component of evolution. Love it.

Hydra009

[creationist]Proof of microevolution, not macroevolution.   [-(  Show me a dog giving birth to cats or waterbears turning into bears and then I'll accept evolution as true.[/creationist]

Brian37

No they didn't you are just making this up. God made bananas you know.
"We are a nation of Christians and Muslims, Jews and Hindus -- and nonbelievers." Obama
Poetry By Brian37 Like my poetry on Facebook Under BrianJames Rational Poet and also at twitter under Brianrrs37

stromboli

The nature trail where I walk my dog and ride my bike goes under an overpass at one point, and there are numerous Cliff Swallow nests there. I think its cool, because they are awesome little birds. Yeah, fuck creationists.

NitzWalsh

Neato. Evolution in action, gotta love it.
Any sufficiently advanced technology is indistinguishable from magic.
~ Arthur C. Clarke

caseagainstfaith

But they are still swallows!  Checkmate atheists!

 :Hangman:
Please visit my site at http://www.caseagainstfaith.com  featuring critiques of Lee Strobel and other apologetics.

NitzWalsh

And people are still apes.
Any sufficiently advanced technology is indistinguishable from magic.
~ Arthur C. Clarke

Atheon

Gaaawd intervened and made their wings shorter. Intelligent design!!
"Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful." - Seneca

NitzWalsh

I think that'd qualify as intelligent redesign.
Any sufficiently advanced technology is indistinguishable from magic.
~ Arthur C. Clarke

aitm

it's technically not re-design if it was planned all along. See here son, *spits tabakky*  Gawd nu a couple thousand year ago that around this here time he would shortened the wings of our feathered breathern so's they'n could survive better. Ole gawd is an awesome gawd.
A humans desire to live is exceeded only by their willingness to die for another. Even god cannot equal this magnificent sacrifice. No god has the right to judge them.-first tenant of the Panotheust

Brian37

Quote from: "NitzWalsh"Neato. Evolution in action, gotta love it.

LIES LIES ALL OF IT LIES! Ok, before you comment lead paint is part of my diet.
"We are a nation of Christians and Muslims, Jews and Hindus -- and nonbelievers." Obama
Poetry By Brian37 Like my poetry on Facebook Under BrianJames Rational Poet and also at twitter under Brianrrs37