Cliff swallows are evolving shorter wingspans to avoid becoming roadkill, according to new research.
Though cliff swallows are named for their habit of building nests on
cliffs, they also nest on man-made structures such as bridges. Roadkill
is an unfortunate consequence of animals living in close proximity to
traffic, but very few studies have looked at how roadkill numbers change
over time.
While conducting a
survey on American cliff swallow colonies, Charles and Mary Bomberger
Brown (University of Nebraska, USA) collected dead swallows to preserve
as additional specimens. Over the 30 years, they felt like they were
finding fewer and fewer dead swallows.
When they looked at
their statistics, they found roadkill numbers really were falling. Even
more interesting was that birds killed by cars had longer wingspans than
those killed by nets (who were representative of the general
population). Spurred on by this initial result, they measured live
swallows' wings and found they had become shorter over the course of the
study.
"Longer-winged swallows sitting on a road probably
can't take off as quickly, or gain altitude as quickly, as
shorter-winged birds, and thus the former are more likely to collide
with an oncoming vehicle," explained Brown. Shorter wings also allow the
bird more maneuverability in the air and make quicker turns possible.
Though they have tried to rule out other causes, the Browns acknowledge
that behavioural changes could be responsible for the reduced roadkill
rates. Nonetheless, the study does show roadkill numbers can decline
even when the population and traffic do not.
Photo credit: Glenn Bartley/All Canada Photos/Corbis.
http://www.nature.com/news/
http://news.sciencemag.org/
http://phys.org/news/
http://www.livescience.com/
Cliff swallows are evolving shorter wingspans to avoid becoming roadkill, according to new research.
Though cliff swallows are named for their habit of building nests on cliffs, they also nest on man-made structures such as bridges. Roadkill is an unfortunate consequence of animals living in close proximity to traffic, but very few studies have looked at how roadkill numbers change over time.
While conducting a survey on American cliff swallow colonies, Charles and Mary Bomberger Brown (University of Nebraska, USA) collected dead swallows to preserve as additional specimens. Over the 30 years, they felt like they were finding fewer and fewer dead swallows.
When they looked at their statistics, they found roadkill numbers really were falling. Even more interesting was that birds killed by cars had longer wingspans than those killed by nets (who were representative of the general population). Spurred on by this initial result, they measured live swallows' wings and found they had become shorter over the course of the study.
"Longer-winged swallows sitting on a road probably can't take off as quickly, or gain altitude as quickly, as shorter-winged birds, and thus the former are more likely to collide with an oncoming vehicle," explained Brown. Shorter wings also allow the bird more maneuverability in the air and make quicker turns possible.
Though they have tried to rule out other causes, the Browns acknowledge that behavioural changes could be responsible for the reduced roadkill rates. Nonetheless, the study does show roadkill numbers can decline even when the population and traffic do not.
Photo credit: Glenn Bartley/All Canada Photos/Corbis.
http://www.nature.com/news/
http://news.sciencemag.org/
http://phys.org/news/
http://www.livescience.com/
Though cliff swallows are named for their habit of building nests on cliffs, they also nest on man-made structures such as bridges. Roadkill is an unfortunate consequence of animals living in close proximity to traffic, but very few studies have looked at how roadkill numbers change over time.
While conducting a survey on American cliff swallow colonies, Charles and Mary Bomberger Brown (University of Nebraska, USA) collected dead swallows to preserve as additional specimens. Over the 30 years, they felt like they were finding fewer and fewer dead swallows.
When they looked at their statistics, they found roadkill numbers really were falling. Even more interesting was that birds killed by cars had longer wingspans than those killed by nets (who were representative of the general population). Spurred on by this initial result, they measured live swallows' wings and found they had become shorter over the course of the study.
"Longer-winged swallows sitting on a road probably can't take off as quickly, or gain altitude as quickly, as shorter-winged birds, and thus the former are more likely to collide with an oncoming vehicle," explained Brown. Shorter wings also allow the bird more maneuverability in the air and make quicker turns possible.
Though they have tried to rule out other causes, the Browns acknowledge that behavioural changes could be responsible for the reduced roadkill rates. Nonetheless, the study does show roadkill numbers can decline even when the population and traffic do not.
Photo credit: Glenn Bartley/All Canada Photos/Corbis.
http://www.nature.com/news/
http://news.sciencemag.org/
http://phys.org/news/
http://www.livescience.com/
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