Country Owls Better Suited to the Suburbs?
for National Geographic News
|October 19, 2007|
For barred owls, suburban Charlotte, North Carolina, might as well be an ancient grove of trees.
At least that's the way it seems to a local ornithologist, who found that his city is saturated with the foot-and-a-half-tall (half-a-meter-tall) nocturnal predators, which have been long thought to thrive only in old-growth forests.
"I had read somewhere that barred owls need large tracks of old-growth forest to survive, but that didn't make sense," said Rob Bierregaard at the University of North Carolina at Charlotte.
"Turns out you can't swing a dead rat in suburban Charlotte without hitting a barred owl."
He and his graduate students have been studying the city's owls Since 2001. The research is ongoing, but the team is already making some significant finds about the birds' adaptibility.
"My guess is that as we get more data, we're going to find that the city birds are even doing better than the country birds," Bierregaard said.
Martha Desmond is an ornithologist at New Mexico State University in Las Cruces who is not involved in Bierregaard's work.
She said that the study is the first time she's heard of an urban population of these owls—but she's not surprised.
"If they're generalists and they can occupy different habitat types," she said, "they go where the prey is."
Barred owls are usually found in dense forests across North America. They feed on most things that come their way, from small mammals and birds to fish and small reptiles.
The birds favor older forests, because they rely on larger trees that have suitably sized holes to nest in.
In Charlotte, the barred owls tend to nest in the cavities of the numerous willow oak trees that line the city's streets.
The trees are old and large enough to offer good nesting sites, and the well maintained lawns below provide an open understory—creating perfect conditions for the raptors to hunt.
"The suburban habitat with mowed lawns, azalea bushes, and manicured gardens is really ideal" for the owls, Bierregaard said.
So far, he and his students have found 80 pairs of barred owls nesting in the city over the course of their study.
"There's virtually no place that looks like good habitat for them that doesn't have a pair of owls."
The biggest danger to urban owls seems to be fast-moving traffic: birds flying into cars is the number one cause of death among Charlotte's brood.
But Bierregaard's team has found that a healthy birth rate is keeping the owl population steady.
Scott Terrill is a biologist at H.T. Harvey and Associates, an ecological consulting group based in Los Gatos, California.
"Actually barred owls are doing really well everywhere," he said. "They've expanded their range tremendously in recent years."
Although the owls were traditionally found in the east, they have rapidly extended their range in the last several decades , moving north into Canada and west into California, Oregon, and Washington.
In some places where the barred owls have moved in, conservationists are worried about the effects their invasion might have on native species.
For example, surveys show that barred owls are interbreeding with the endangered northern spotted owls in the old-growth forests of the U.S. West Coast.
This creates sterile hybrids, hampering the endangered bird's reproductive success.
But the people of Charlotte have no qualms about their new neighbors.
"People love 'em," study leader Bierregaard said. "They're big and noisy and they're tame as can be."
The baby owls, he added, make a cute sight splashing around in peoples' birdbaths.
And with expanding human populations, the barred owl isn't the only country bird making a home for itself in cities.
"There seem to be a number of owl species that adapt quite well to urban areas," New Mexico State's Desmond said.
Great horned owls and screech owls are already very common in cities.
The ornithologist has even found burrowing owls nesting in roadside gutters in her hometown of Las Cruces, as well as sawhet owls wintering in downtown Manhattan.
"Because these birds are nocturnal," she said, "they're there, but you just don't notice them."
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