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 Leonard R. Askham |
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Leonard R. Askham |
| A good way to control rodent pests in agricultural areas without using chemical pesticides is to attract hawks, owls, falcons and other birds of prey (raptors) into the area. Birds of prey will be attracted to a site they live near or migrate into if there are large numbers of prey, such as mice, voles, pocket gophers, moles or squirrels for them to feed on. Sometimes enhancing predator habitat helps attract the birds and keeps them in residence. | |
| Food Supply | |
| Predators almost never eliminate all of their prey. There are three reasons for this. First, the prey population increases faster and earlier than the predators (Figure 1). Predators eat a finite number of pests each day, and prey species are very prolific. Their large number of offspring replaces those lost to predators and adds new members to the breeding stock. Second, predators do not always hunt successfully. The more places the prey species has to hide, the easier it is for them to escape. Third, when the prey population declines because of disease, poor weather conditions or lack of food, the predators will either leave or die. |
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Figure 1. An Example of Predator and Prey Population Fluctuations Over Two Years |
| Perch and Nest Sites | |
| Perches and nesting sites are needed to attract birds of prey. You may grow trees or preserve them when they die for the birds to perch on and hunt from. Birds use less energy hunting from perches than flying in the air, so they use perches whenever they can. You may also build perches. You can add extensions to fence posts, or crossbars to sprinkler risers (Figure 2) throughout a field or orchard. Place a simple crossbar on top of a pole oriented so that birds can land on it against the prevailing wind. Where wind directions vary, use two crossbars. One perching pole every 200 ft. around a field or per acre provides the birds with enough perches for optimum hunting. |
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Figure 2. Bird perch attached to sprinkler riser (left). Bird perch added to poles or fence posts (right). |
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Figure 3. Combination bird perch and nest box. |
You can make nest boxes from a variety of materials (Figure 3). There are two basic styles, one for owls (Figure 4) and another for Sparrow hawks (or American kestrels) and falcons (Figure 5). Hawk nest boxes can be placed almost anywhere, such as open fields, groves of trees or on rocky ledges. Put owl nesting boxes in more protected areas, such as on barns. Always face the openings south or toward the sun to collect warmth during the early days of spring. Approximately one box per 20 acres is needed to attract predatory birds to an area. Remove unwanted birds, such as starlings, from the boxes as soon as possible if they begin to build nests in them. Clean and repair the nest boxes at the end of the breeding season. |
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Figure 4. Owl nest box plans. |
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Figure 5. Kestrel nest box plans. |
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Other Tips |
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Birds of prey have more successful hunts in open fields with short grass. When fields become overgrown, prey have more cover to hide in and escape from predators. For example, small rodents such as voles and mice can hide in six inches of thick grass. Keeping fields clear and grass short by frequent mowing helps the birds catch more pests. Experiment with these and other alternatives. Predators will not eliminate all rodent pests, but they can help by maintaining populations at manageable levels. |
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