Owls to the rescue: Nesting boxes attract the predatory birds that control rodents
January 30, 2016 12:00 AM
A barn owl enters one of Mark Browning's nesting boxes.
A barn owl provides a more environmentally friendly way to control rodents in farms and in orchards.
By John Hayes / Pittsburgh Post-Gazette
Illuminated by flickering firelight at a West Virginia park, Mark Browning asked fellow campers if they wanted to have a little fun. He set up a boombox on a picnic table and pushed play.
Instead of the folk-rock that could be expected from a songwriter and co-founder of the Pittsburgh jam band Sandoz, the tape broadcast a long series of eerie hoots and caterwauls.
“Just wait,” he whispered.
In a few minutes, a reply rose from a dark wooded hillside — the distinctive howl and “who-cooks-for-you?” of a barred owl. As the campers marveled at another reply from the opposite direction, a dark shape swooped low over the campsite, and the hoot-hoot-hooting continued from high in a nearby tree.
“Works every time,” Mr. Browning said.
A longtime fascination with the natural world and an entrepreneurial conservation ethic have propelled the biologist and former Pittsburgh Zoo & PPG Aquarium animal trainer into a new career using nature’s ways to address a major agricultural and environmental problem.
This month, Mr. Browning launched a national marketing campaign to promote his line of nesting boxes specially designed to establish colonies of barn owls on farms and orchards in desperate need of rodent control.
“When farmers plant acres of fruits or grains or sugar cane, they attract a density of voles, mice and other rodents that is astounding — beyond belief,” he said. “But this monoculture does not provide homes for predators; the system is set out of balance. The farmers suffer huge financial losses, and traditionally they’ve used poisons to kill the pests. Those chemicals are costly, time-consuming to spread and are transferred up the food chain and get into the water table, causing broader environmental problems.”
Inspired by an Israeli nest box conservation experiment, Mr. Browning devoted several years to researching rodent predators, their mating habits and the cost effectiveness of attracting a specific predator species to individual agricultural areas.
“A lot of predators eat rodents, but we were looking for population sustainability, low maintenance, tolerance to human activity and measurable results,” he said.
Enter the distinctive white heart-shaped face of the common barn owl: 13 to 15 inches in height, wingspan of nearly 3 feet, the world’s most common owl species and one of the most widespread of all birds.
“The barn owl suited our purposes very well,” said Mr. Browning. “They’re cavity nesters, fledge four to seven young and have low mortality rate when food is abundant. And — this was important for us — barn owls tend to form colonies in places where there is a lot of food. My idea was establish barn owl colonies in agricultural areas as an alternative means of rodent control.”
With funding grants, he set up a three-year study near a 100-acre vineyard in California’s Sacramento Valley. Starting with 18 breeding pairs and 66 young living in prototype boxes monitored by video cameras, Mr. Browning and his researchers watched some 25,000 voles, mice, rats and pocket gophers being consumed in 2011 and 2012.
“In one box we had 316 deliveries to three chicks over one eight-week period,” he said. “That’s 105 deliveries per chick.”
The nest box trial in Israel found that the deterioration of wooden boxes forced farmers back to those sites every several years. Mr. Browning and a Wisconsin polyethylene manufacturer experimented with designs for durable boxes with entry holes and interior space suited to the specific needs of barn owls. Mounted on poles or secured to buildings, the boxes needed to be cool in direct sunlight.
“I experimented with all kinds of wackadoodle ideas like solar fans until I realized that the best way to keep heat out of something is to keep it from going in,” he said.
The final design uses exterior plastic impregnated with reflective white pigment, and a dark vented interior box to restrict the light and release the heat.
Mr. Browning’s Barn Owl Box was patented in 2014. It has been used for rodent control by state wildlife agencies in Illinois, Wisconsin, Missouri and South Carolina, as well as several Audubon chapters and thousands of private vineyards and orchards. Substantially cheaper than pesticides, and safer and easier to use, the boxes have been featured in agricultural trade magazines and an episode of PBS’s “American Heartland.”
The success of the Barn Owl Box led Mr. Browning to design additional nest boxes that attract screech owls, sparrow hawks, bluebirds and other songbirds.
“Residential users have a different set of needs,” he said. “We developed boxes that repel house sparrows [with the hole size] and are resistant to black fly invasions, which disrupt nesting. Black flies are attracted to the carbon dioxide exhaled by the birds. We provide plugs for the vent holes.”
Mr. Browning’s boxes are priced from $34.50 to $185 for industrial products. For more information and purchases, visit www.barnowlbox.com.
John Hayes: 412-263-1991, email@example.com.
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