Managing Bird Damage
Wildlife damage management has become more of a problem as large areas are planted to single crops, such as blueberries, and use restrictions for repellents and toxins have increased. While it is seldom possible to prevent total damage, much can be done to reduce impact on wildlife within legal and economic constraints.
Of all the wildlife that blueberry growers have to contend with, birds rank as one of the most important. Each year about 10 percent (range 0 to 60 percent) of a blueberry crop can be lost to bird depredation. Although many species of birds will feed on blueberries, the principal species that cause losses are starlings, robins, and finches.
Birds are difficult to manage because they are the most mobile of all wildlife. They move quickly from one area to the next. They have also learned to take advantage of new crops that replace natural food sources within their range. These crops become important supplements to their native food and, like blueberries because of their high protein and sugar content, often are preferred over their normal diets.
Birds feed on different food patches throughout the year. They move from one to another, sometimes feeding on two or more patches as they ripen. They also explore potential food sources by periodically testing the crop. As it matures, the birds begin feeding, often before the fruit is fully ripe.
Once birds begin feeding on, or become habituated to, a crop they are very difficult to manage. Control strategies must be started before the fruit begins to ripen and must continue through harvest.
Little can be done within the plantation. The removal of ground cover will not affect the birds’ feeding behavior. Removing nesting, perching, and roosting sites around the perimeter of the field will reduce the number of congregating birds that tend to flock when they feed. The removal of alternative food sources, such as sunflowers and grains, from nearby fields will also reduce the number of birds that tend to congregate in an area.
Repellents and toxicants (poisons) can-not currently be used to control birds in blueberries because none are registered for agricultural production areas.
Trapping can be used to remove some birds, such as starlings and sparrows, but cannot be used for protected species, such as robins and cedar waxwings. The latter, if caught, must be removed and released. Moving them to another area, miles away from the trap site, will only slow down their return.
Various hazing or herding techniques or scare devices can be used to move birds. Few, however, work well by themselves over an extended period of time.
Stationary objects, such as flashing pie tins and ribbons, owl and hawk silhouettes, rubber snakes, and scare-eye balloons will frighten birds for a few days until they become used to them. Scare-eye balloons have an effective range of about 12 yards and thus need to be placed at a high density per area. These, also, need to be moved frequently to be effective. Noisemakers, such as firecrackers, exploding shells, gas-fired cannons, and distress calls, fare equally well.
When the techniques are combined, however, and moved within the plantation to different locations on a regular basis, they can reduce the number of birds feeding on the crop. For example, propane-fired cannons can be mounted on swivels so that they move to a different location each time they ignite. They can also be timed so that they become active during different times of the day, particularly early in the morning and late in the afternoon when the birds tend to be more actively feeding. Distress calls or “avilarms” can similarly be programmed for the same periods.
During the remainder of the day, exploding firecrackers can be fired from pistols as people work around the field. Other examples could be drawn, all involving activity and change, to prevent bird habituation to the scare method.
Netting is the only strategy that will completely reduce bird damage. It is, however, expensive, time-consuming, and difficult to work around.
One-quarter-inch plastic nets are commonly used for small fields. Wire or cables are suspended from poles at the ends of each row and often in rows. The nets are then rolled out along these wires and secured to the ground so that birds will not work their way under them. During the remainder of the year, the net should be re-rolled and stored.
Netting on large fields may be impractical and may interfere with machine harvesters.
This fact sheet is adapted from Oregon State University Extension Publication PNW215, Highbush Blueberry Production. The authors of Highbush Blueberry Production are – Oregon State University: Bernadine Strik, Glenn Fisher, John Hart, Russ Ingham, Diane Kaufman, Ross Penhallegon, Jay Pscheidt and Ray William; Washington State University: Charles Brun, M. Ahmedullah, Art Antonelli, Leonard Askham, Peter Bristow, Dyvon Havens, Bill Scheer, and Carl Shanks; University of Idaho: Dan Barney. PNW215, Highbush Blueberry Production can be purchased from the Department of Extension & Experiment Station Communications, Oregon State University. How to Order