Trees evolved fruits to aid in seed dispersal. The sweet, nutrient-rich fruit covered a seed that, when consumed by a bird or animal, would be carried away from the tree and dispersed in the animal's droppings. When you plant fruit trees, you don't usually want you precious fruits robbed by birds doing what they have evolved to do. Several methods exist for protecting your fruit trees from bird damage.
Many common bird species cause damage to fruit trees, including finches, sparrows, jays and starlings. According to the University of California Cooperative Extension, birds damage both ripe fruits and new buds. Damage to fruit tends to be primarily an aesthetic issue, but damage to buds can reduce the yields of your trees.
Exclusion methods prevent birds from accessing the fruit trees. The most practical exclusion method is plastic netting, which can cover all or part of the tree. In orchards, front-end lifts are used to access the tops of tall fruit trees, but this is impractical for trees in the home garden.
Other than exclusion, the iconic scarecrow represents the primary method of bird control for you fruit trees--frightening them away. According Glen Dudderar and Gary L. Heilig of the Michigan State University Extension, when used properly, frightening devices are the most cost-effective way to protect a few trees from bird damage. Frightening devices may be as advanced as motion-sensitive sound players to as simple as a plastic snake draped along a branch. As the Arizona Cooperative Extension notes, birds quickly learn that a frightening device won't harm them if it is not moved frequently or used in an unpredictable manner.
The University of California Cooperative Extension recommends employing control methods at the first signs of birds congregating near fruit trees. It suggests monitoring the area around trees for bird activity rather than waiting for damage. It is easier to observe bird activity than early stages of damage, and control methods are more effective if the birds haven't already associated your trees with an easy source of food.
Some experts, such as Dudderar and Heilig, recommend trapping methods for controlling birds. However, as they and the University of California Cooperative Extension caution, gardeners who plan to use methods other than simply deterring avian pests should check with the local extension office first to ensure the birds don't have any special protected status.