Editor’s Note: This article was originally published by the Oregon State University Extension Service. Contributors include: Shilah Olson and Karen Lamson, conservation planners with Wasco County Soil & Water Conservation District, OR; Mike Omeg, grower, Omeg Orchards, Wasco County, OR; Brian Tuck, Oregon State University Extension Service, Wasco County; Susan Kerr, Washington State University Extension, Klickitat County; and Ellen Hammond, water quality specialist, Oregon Department of Agriculture.
Rodents are common pests for growers. Most farmers who have tried growing a crop know the damage these pesky creatures cause.
Conventional methods of rodent control include trapping, poison baits, or destroying tunnels. These techniques are labor intensive and costly, and can harm non-target species. They may even be outlawed in some areas.
As environmental awareness increases, many people are looking for other methods of rodent control. One excellent option in areas where there are large rodent populations is to attract their natural predators.
Raptors are a group of predatory birds including hawks, owls, eagles, and falcons. These birds often prey upon rodents. Raptors alone don’t completely eliminate a rodent problem. But, attracting raptors as part of an integrated pest management strategy can reduce the cost of conventional control methods. And, it’s a rewarding, environmentally-friendly way to reduce rodent populations.
There are many important and useful predatory birds. Two of the most important for controlling rodents in agricultural lands are barn owls and kestrels. Kestrels hunt by day, and barn owls hunt at night.
The barn owl has been called the “cat with wings.” This beneficial bird preys on rodents, particularly gophers, mice, and voles. A family of barn owls eats about 3,000 gophers each year. An adult will catch and eat 10 to 12 gophers per night while brooding, between March and July.
Barn owls are about the size of a small cat, but only weigh a pound. Their wings have soft fringe-edged feathers and a slow, silent flight that makes them especially efficient at catching unsuspecting rodents.
Barn owls have adapted to man-made structures like barns, attics, silos, and nest boxes. They don’t show strong territorial instincts and sometimes nest in colonies. That means you can put up barn owl nest boxes as close as several yards apart.
Barn owls will not harm game birds like pheasants or quail and are not a threat to chickens or cats.
You can find more information about the habits and needs of barn owls at these websites:
• Cornell Lab of Ornithology: http://www.allaboutbirds.org/guide/Barn_Owl/lifehistory
• Audubon Society: http://birds.audubon.org/species/barowl
• State of Montana Field Guide: http://fieldguide.mt.gov/detail_ABNSA01010.aspx
The American kestrel is the smallest falcon in North America (about the size of a mourning dove). It has a diverse diet, but its main foods are rodents and insects. It also eats small birds, so if you are attracting songbirds to your land, kestrels are not the best choice.
Kestrels readily take to nest boxes, but they are highly territorial. Be sure to place nest sites at least half a mile apart.
For more information on the American kestrel, refer to these publications:
• USDA Natural Resources Conservation Service: http://www.mn.nrcs.usda.gov/technical/ecs/wild/kestrel.pdf
• Oregon State University Extension Service: http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19715/ec1578.pdf
Attract, Maintain Raptors
Suitable habitat for raptors includes food, cover and nest sites, water, and perches from which to hunt. The key factor that limits most raptor populations is suitable nest sites.
Nest boxes and perches can increase raptors’ success in places that lack nest, roosting, and hunting sites. For centuries, humans have successfully attracted raptors to help control pests by providing perches and nest boxes in areas that offer enough food, cover, and water.
For more information, refer to “The Wildlife Garden: Build Nest Boxes for Wild Birds,” a publication of the Oregon State University Extension Service: http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19668/ec1556.pdf
Once you have a plan to attract raptors, be sure to monitor the plan’s success and keep your nest boxes in good condition. Also, monitoring and maintenance can help you take care of problems before they become serious, such as starlings taking up residence in nest boxes intended for raptors.
If you want to attract wild raptors, be careful with rodenticides. Poison baits that contain anticoagulants will kill a rodent in three to ten days due to internal bleeding. During this time, the poisoned rodent may be eaten by a raptor. Depending on how many poisoned rodents a raptor eats, it too can become ill and die.
If you decide to use poisonous baits, then take all necessary precautions to ensure that children, domestic animals, and non-target wildlife can’t eat or come in contact with the poisonous bait or poisoned rodents.
All things considered, if you want to attract and rely on raptors for rodent control, it’s safest to forego the use of poison baits altogether.
Health and Safety
It’s best to clean out nest boxes at least once a year, but be sure to take precautions to avoid exposure to germs. Barn owls regurgitate owl pellets that contain the undigested hair and bones of their prey. Along with pellets, nest boxes may hold uneaten rodents. This debris in an owl nest box can be infected with diseases harmful to humans. Be sure to wear rubber gloves and a dust mask when cleaning out a nest box.
If you think you’ve found a sick or injured raptor, don’t approach it. Instead, contact your local state wildlife agency or U.S. Fish and Wildlife Service office. All owls, hawks, and eagles are federally-protected species. Only licensed individuals may handle or keep them, although most states have “good Samaritan laws” that allow the public to transport injured wildlife to a licensed rehabilitation facility.
Keep in mind that it’s common in spring to see fledgling raptors on the ground or on low branches, because they are still learning how to fly. The parents keep feeding them outside of the nest at this stage. They are not abandoned and are usually not in any physical distress. It’s best to leave them alone and let the parents keep feeding them. It’s an important part of their early learning and development of hunting skills.