Bats can be an important weapon in a chemical-free arsenal for bug control. One big, brown bat can eat 3,000 to 7,000 insects in a night. Attract bats to your yard by building and placing bat houses in your yard.
Birds will generally not be scared away by scarecrows. Instead try tying pieces of glass, colored cloth or tin to loose strings so the wind can blow them and clash them together. Random motion is the key to alarming the birds away from the garden. See also, Birds and Hummingbirds.