Birds normally bring far more benefits than grief to gardeners because they eat large numbers of insects. However, they sometimes can be a problem for vegetable gardeners, especially when melons or corn are grown. They often are a problem for growers of grapes or strawberries, and nearly always are a problem to some degree for growers of stone fruits such as cherries and plums. A satisfactory harvest of blueberries is nearly impossible to attain without some protection from birds. Woodpeckers also may cause damage to wooden or wood-sided buildings, and one member of the group, the yellow-bellied sapsucker, may harm young trees.

Symptoms and Diagnosis

Corn exhibits partially eaten and damaged ears from the milk stage to maturity. Husks will be torn and partially removed. Melons show wounds that appear to have been made by very small daggers in the rind, with sizeable holes often evident, exposing the pulp. Stone fruits, such as cherries and plums, and grapes or strawberries will be partially eaten or missing, with damaged fruit left lying on the ground. The damage begins just as the fruit begins to ripen and continues throughout the ripening stage. Blueberries normally will be completely devoured, but some partially eaten fruits usually will be present on the ground around the plants. Woodpecker damage to buildings shows up as cavities or holes that appear to have been made in the wood with a fine chisel. Shavings or dust often will be present on flat surfaces under the damaged areas. Damage often is caused by birds searching for insect larvae originally in the tree or for some adult insects that overwinter in the wood. Woodpeckers also peck on siding to drum. In the spring, this behavior is the bird’s way of announcing its territory. Sapsucker damage normally does not threaten the tree, but always provides entry points to insects and disease organisms. Damage on small trees may threaten the plant. Sapsuckers peck vertical and horizontal rows of holes in the trunk and upper branches of trees, evenly spaced and identical. The geometric symmetry of sapsucker injury makes it easily distinguished from the random nature of damage by insect borers. Birds will continue to come back to the same trees during migration and peck in the same areas. Most damage is done during spring (April through May) or autumn (September and October) migrations through this area. Often, the birds are never observed. Except for this bird, the damage signs for which are distinctive, a definitive diagnosis of damage ultimately depends upon actual observation of birds active in the areas sustaining damage. Some species of birds feed on new buds and shoots in the tops of trees, including fruit trees, during spring migrations. However, damage from such feeding is nominal.

Integrated Pest Management Strategies

1. Tolerate the damage. If a satisfactory fruit or vegetable harvest is attained or in the case of woodpeckers, if damage to structures or trees is slight, tolerate the nuisance.

2. Exclude the birds. Many net and twine companies make netting that prevents bird damage. Installation sometimes is difficult with some types of netting because netting must be supported in some manner. A lightweight, commercially available, inexpensive acrylic webbing prevents damage. It is a spider web-like material that is draped directly over the plants and usually does not require support. It often is sold as floating row covering. The material does not interfere with water, sunlight, or plant growth and may retain its effectiveness for more than one year. Harvest is accomplished by carefully lifting the webbing. Any netting or webbing should be installed, if possible, after pollination and just before the beginning of fruit ripening. Netting is only practical with dwarf fruit trees and is not an effective deterrent to woodpeckers. Recurrent sapsucker damage may be prevented in susceptible trees by wrapping damaged areas with a loose, coarse material such as burlap. Such trees also should be fertilized and watered properly to stimulate growth and maintain overall health.

3. Repel birds with visual repellents such as whirlers; streamers; spinners; reflectors; and plastic hawks, owls, or snakes, etc. These methods may be helpful, but not be consistently effective. Under any circumstances, the techniques must be varied and devices moved, at most every other day, or birds soon learn that such items are harmless and ignore them. Woodpecker drumming sometimes can be stopped by frightening the bird whenever it begins drumming by using sudden loud noises, water from a garden hose, or flashing lights or mirrors.

4. Repel birds with chemicals. At least two products are labeled for bird control: RO-PEL Animal, Rodent and Bird Repellent (active ingredients Denatonium saccharide, Thymol) and Bird Shield Bird Repellent Concentrate (active ingredient Methyl anthranilate). Other products are also available. When using chemicals, read labels carefully and follow directions completely. Special Note. Almost all birds that can become pests to the home gardener are protected by federal and state wildlife codes.