Recruit owls to control gophers
If you're trying to attract owls, avoid exposing them to harmful products.
Cabinetmaker Tuck Contreras (right) discusses birdhouses with Dave Case, an orchardist in Chelan, Washington, while Mike Wacker of The Dalles, Oregon, inspects an owl box.
Orchardists in the Pacific Northwest are installing owl boxes in the hope that owls will help control gophers, but it can take time for the birds to move in.
Ray Fuller, an organic grower at Chelan, Washington, who spends a considerable amount of time trapping gophers, bought four owl boxes this year. His orchard is surrounded by natural habitat.
Without some kind of control, the gophers would inflict serious damage on his orchard, he said. "They'd almost wipe us out."
Tim Dahle, a grower at The Dalles, Oregon, started putting up owl boxes about ten years ago, and now has between 40 and 50. Though there's a resident population of owls in the area, Dahle said growers shouldn't have high hopes that owls will move into the boxes immediately. "I think by three years, if we have 10 percent occupancy, I would regard that as a success."
Though Dahle can't quantify what effect the owls might be having on gophers, he believes the investment in owl boxes is a sound one. One owl can eat hundreds of gophers each year.
"I think the potential is too valuable to not make the investment in finding out just what they can do," he said.
Cherry grower Mike Omeg of The Dalles, Oregon, has tried trapping, smoke bombs, and poison, and, despite spending around $43 per acre to combat gophers, he felt he was just keeping his head above water. If a gopher girdles and kills the tree, the grower loses not just the $17.50 per tree it costs to establish a planting, but also faces the cost of putting a new tree in the ground.
All that prevents owls from aiding growers in the fight against gophers is a lack of housing, Omeg believes. So, last year, he introduced the idea of building bird boxes to Tuck Contreras, a local wildlife enthusiast and artist who has been a cabinetmaker for 40 years. Though more used to building custom kitchens, Contreras eagerly turned her talents to making boxes for barn owls. In the past year, she's made more than 200 boxes for customers as far away as Oroville, Washington. The sturdily built boxes are designed to last for at least 10 to 15 years. Omeg bought 30 of them.
Normally, it can take anywhere from one to five years for owls to locate the boxes and move in, Contreras said, but she is now working with a raptor rescue center in Oregon that rescues baby barn owls from nests in hay stacks when the bales are sold and moved. Her plan is to rear and release the owls, and while doing so familiarize them with the owl boxes to increase the chances that they will use them.
Omeg warned that when growers are trying to attract owls to orchards, they should avoid exposing the birds to harmful products. Normal orchard sprays are probably not harmful, he said, but rodenticides can be. For example, Ramik green, which contains the anticoagulant diphacinone, can be toxic if the owl preys on rodents that have eaten some of the bait.
However, Omeg acknowledged that an orchardist can't just put out owl boxes and do nothing about the gophers until the owl population builds up. Rozol (chlorophacinone) is cheaper and not toxic to barn owls, yet is effective against rodents, he said.
Smaller birds can also play a role in controlling orchard pests.
A couple of years ago, Fuller installed 18 kestrel boxes, hoping that kestrels would stop smaller birds from eating his cherries. "Our bird damage has gone down to almost zero," he said. A bonus is that the kestrels also help control mice.
Dahle has more than a hundred bluebird and swallow houses, and wrens are using some of the swallow houses. All those bird species are insectivores, and Dahle thinks they're probably eating obliquebanded leafroller larvae and other pests—though, again, he says it's hard to quantify.
"I've got wrens and bluebirds that live off my deck, and as I watch them, they're a constant stream of coming and going to feed their chicks," he said. "Judging by watching their activity, I think they have a considerable effect."
This year, he is beginning a three-year study, in collaboration with the Oregon Watershed Enhancement Board, to monitor occupancy and trespass for each of his birdhouses, which will give him a better idea of how effective they are. They can't be checked until the fall for fear of scaring away the mother birds, he said.
Meanwhile, Dahle continues to install more birdhouses in his orchard. He'll have 200 by the end of this year.
"We don't know what the potential is," he said. "But it's not expensive to do, and it's interesting and fun to see what the results are. I think it makes a lot of sense for growers to put out just a few owl houses and put a few bluebird and wren houses up. It's going to take some field observations from many growers for us as an industry to get a good grasp on the potential."