The type and amount of damage caused, effective control methods, and legal protection vary among bird species. As a result, it is very important for a grower to be able to identify the birds causing damage. A number of field guides for identifying birds are available at bookstores or libraries. Listed below are the species that most often cause damage to fruit, along with a brief description of each bird and the type of damage it causes
For best results in reducing bird damage, growers should use a variety of simultaneous techniques and start the control program before birds have established a habit of feeding on the fruit. Control is much more difficult after feeding patterns have become established. Growers also should keep records of attempted control methods and their success rates. The methods listed are only suggestions.
Species of Birds
The American crow, Corvus brachyrhynchos, is a problem primarily for apples. It pecks deep triangular holes in the apples, often destroying the fruit or leaving it susceptible to disease.
The common grackle, Quiscalus quisula, has a black body, an iridescent head, and a keel-shaped tail. Grackles consume small fruit such as blueberries whole. They often slash large fruit such as cherries and apples and leave it damaged.
The house finch, Carpodacus mexicanus, is a relative newcomer to the eastern United States--its historic range is in the western part of the country. In the 1940s, it was released on Long Island, New York, and has been spreading in numbers and distribution since that time. The house finch has brown streaks and looks like a sparrow. The male has patches of orange or red under its chin and on its sides. The house finch starts at the top of a blueberry bush and pecks berries in rapid succession. Many are left damaged. It also pecks grapes open and feeds on the juice and pulp within. It leaves small irregular nicks on apples, which often make the fruit susceptible to disease. The house finch causes extensive damage to fruit in the western United States. In the eastern United States, it is not a major problem but might become one in the future.
The house sparrow, Passer domesticus, is also an exotic species introduced from Europe. The male can be recognized by his black bib and white cheeks. The female is drab brown. House sparrows damage grapes, cherries, and other small fruit, generally by pecking holes. The house sparrow is not protected by law.
The American robin, Turdus migratorius, is a common and well-known bird. It is probably the species most frequently reported as consuming small fruits and cherries. Robins consume whole cherries, grapes, blueberries, and other small fruit and frequently cause substantial damage.
The European starling, Sturnus vulgaris, is an exotic (nonnative) species introduced into North America from Europe. It has a black-speckled appearance, short tail, and wings that appear triangular when the bird is in flight. Starlings are not protected by law. They can cause extensive damage to fruit because they often descend on orchards in huge flocks. Starlings eat small fruit such as grapes whole, and slash large fruit such as cherries. They peck holes in apples, consume the inside of the fruit, and leave the apple hollowed out.
A number of other species might cause problems, depending on the time of year and the habitat surrounding the orchard or garden. Species include the cedar waxwing (Bombycilla cedrorum), gray catbird (Dumetella carolinensis), northern mockingbird (Mimus polyglottos), and Baltimore oriole (Icterus galbula).
Damage to fruit does not occur randomly. By being familiar with patterns of damage, a grower may be able to reduce damage or the cost of control by concentrating control methods in particular areas and at times of the season when damage is most severe.
Although all farms and orchards are susceptible to damage, it usually is greatest on farms in close proximity to town environments where birds such as robins and starlings are abundant. Damage is generally higher in orchards isolated from other orchards. In large areas of orchards, so much fruit is available that the amount of damage on any one site is fairly low. The size of the orchard also influences the amount of damage. As a pattern, small orchards generally experience a greater degree of damage than large orchards because they have fewer trees. Thus, damage can be an important problem for those who produce fruit on a small scale.
The time at which the fruit matures appears to influence the amount of damage. For apples, bird damage is highest on early maturing varieties. Late varieties that experience damage are primarily ones that turn red early in the season. These patterns suggest that birds are responding to the color change in apples. Bird damage to cherries and grapes is also greatest to early ripening varieties. Early ripening fruit might be damaged more frequently because it matures at a time when other fruits are not available.
Federal law protects all species of birds except starlings, house sparrows, and pigeons. All other species are protected and cannot be trapped or shot without a permit. The only exceptions to this rule are blackbirds, cowbirds, crows, and grackles, which may be killed without a permit when they are observed committing or about to commit damage. When controlling birds through lethal methods, use extreme care in identifying the species causing damage.
The type of control you choose will depend on a number of factors. Use your knowledge of damage patterns and species behavior to decide when and where to use control methods and the types of control methods to use.
For many types of fruit, netting is the most effective way to reduce bird damage. Cover, cage, or surround trees, vines, and bushes with nylon or plastic mesh, closely woven wire, or cheesecloth before the fruit begins to ripen and throughout the harvest period.
In most cases, netting is placed directly over the plants or bushes, but for some fruits such as highbush blueberry, a framework is built and the netting is suspended over the frame. The major disadvantages of netting include the high initial cost, the time necessary to apply it, and the inconvenience of working around it. Although netting is expensive, it can be reused for a number of years if it is removed carefully and stored over winter. When deciding whether to use netting, growers should consider the costs of purchasing and installing it relative to the losses from bird damage. Although netting is the most effective means of bird control for small fruits and isolated trees, other methods are available.
Scare Tactics and Noise Devices:
Many growers use visual scare devices and noisemakers to frighten birds away from fruit crops. Visual scare devices include streamers, spinners, aluminum pie tins, plastic owl and snake models, and scare-eyes (large balloons with eyes painted on them). They are most effective when used in conjunction with sound devices. Because birds learn quickly that visual scare devices are harmless, they should be used only during short damage periods and should be changed regularly. Varying locations, colors, and types of scare devices enhances their effectiveness.
A number of noise devices are available. Cannons, exploders, sirens, and other noisemakers work best when the sound is presented at irregular intervals and the sound source is moved frequently. Taped distress calls are more effective, but the calls are usually species specific, so a grower must obtain a tape of the distress calls of the type of bird causing the damage. A problem with both visual and scare tactics is that birds become accustomed to them over time.
One chemical repellent, methyl anthranilate (MA), currently is registered for use on small fruits in Pennsylvania. In the past, the repellent methiocarb (Mesurol) was registered for use on cherries and blueberries; however, this product is no longer registered in Pennsylvania.
Methyl anthranilate is a colorless to pale-yellow liquid with a grape-like odor. It has been used as a food and drug flavoring for humans for years. In preliminary tests, fruit treated with MA were consumed significantly less than untreated fruit. In addition, human consumers could not detect a difference in taste between fruit that had been treated earlier in the season and fruit that had not been treated. MA should not be applied to blueberry plants, however, because it has been known to cause foliar burns in field studies and has not been cost effective. Methyl anthranilate is currently registered for use on fruits and turf.