-- Robert Preidt
MONDAY, March 18 (HealthDay News) -- Cliff swallows in Nebraska
with shorter wingspans that help them take off more quickly and
pivot away from passing cars have a reduced risk of becoming
roadkill, a new study reports.
The findings suggest that cities can be hot spots of evolution,
said the authors of the study published March 18 in the journal
"Evolution is an ongoing process, and all this -- roads, SUVs and all -- is part of nature or 'the wild.' They exert selection pressures in a way we don't usually think about," Charles Brown, of the University of Tulsa, said in a journal news release.
He and his colleagues have been studying cliff swallows in
Nebraska since 1982. The birds build clusters of mud nests on
vertical walls under bridges, overpasses and railroad tracks. Their
colonies often number in the thousands.
Every year for the last 30 years, the researchers have traveled
the same roads to collect swallows that have been killed by
vehicles and compared them to swallows that suffered other types of
The data show a sharp decline in road deaths over the last 30
years, and the drop can't be attributed to declines in the swallow
population or in traffic volume. The researchers found that
swallows that continue to die on the roads have longer-than-average
"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," Brown said.
Wingspan may not be the only factor, said the researchers, who
noted that swallows can learn from one another. So although there
was an association between longer wingspans and road death in the
cliff swallows, the study did not prove a cause-and-effect
The fact that these swallows appear to be evolving to reduce
their risk of being hit by vehicles may be good news for other
species, such as turtles and snakes, that are frequent roadkill
victims, the authors noted in the release.
The Cornell Lab of Ornithology has more about
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