Few things are more heartbreaking for a gardener than watching birds feasting on the nearly ripe fruit in her unprotected fruit trees. One reason, among many, not to harm the birds is that they eat many garden pests. There are a few things you can do to keep birds out of fruit trees that are much more effective than using a traditional scarecrow.
Hang compact disks from the branches. Hang from wire threaded through the center hole and formed into a hook at the other end, or tie them to the tree limbs with string. The flashes of sunlight reflecting off the compact disks frightens the birds. Space the compact disks about a foot apart. You will need several dozen for a dwarf tree, even more for a larger tree.
Hang monofilament fishing line from the ends of the branches like tinsel on a Christmas tree. The strands should be about 18 inches long. Monofilament fishing line reflects light as the birds approach the tree and frightens them away from it. It's not necessary to hang them from all of the branches; space them so there appears to be no opening large enough for the birds to easily fly into when the sunlight reflects off the tree.
Hang disposable aluminum pie pans from the limbs. These also reflect light to unnerve the birds, but they also make noise. As the wind blows they crash into the tree branches, further unnerving the birds. Poke holes near one edge of the pans and hang them from the tree limbs with a piece of string.
Move the bird bath and feeder away from the fruit trees. This may be less effective than other methods, but the birds may be distracted by another food source closer to the bird bath or feeder.
Plant another source of food, such as a mulberry tree. Birds often eat mulberries to the exclusion of all other fruit. Mulberries fruit from midsummer through early fall, depending on the amount of sun they receive. Mulberries planted in full sun fruit early in the summer, while those growing in partial or full shade produce fruit much later. Mulberries produce their berries over several weeks so by planting one in full sun and one in a shaded position, you will have fruiting mulberry trees for most of the growing season.
Encase the entire tree in protective netting. Use the black plastic netting labeled and sold for this purpose at garden centers. It is sometimes sold as trellis netting for growing crops vertically, but works well to protect fruit trees from birds. This method is nearly 100% effective, but somewhat cumbersome to install around full size fruit trees. It is a good solution for dwarf fruit trees, because the netting can easily be installed using only step ladders. Completely cover the leafy crown of the tree with the netting and secure around the trunk beneath the canopy. Most birds will move on to another food source when confronted with a netted tree, but check it daily in case a wily bird finds its way under the netting.