Bird feather picking results most often from a caged bird's sexual isolation and frustration. It is easy for bird owners to ignore the sexuality of their pet birds because they may not know the gender of their birds. Caged birds don't have external genitalia or other physical characteristics that would, at a glance, indicate their sexual identity. They do, however, have gonads (testes or a single ovary) located inside their bodies. Male and female bird organs in fact produce exactly the same sex hormones (testosterone or estrogens) that human gonads produce.
Bird sex hormones are extremely potent, and can change a bird's behavior. In the wild, these hormone induced behavioral changes would result in the selection of a mate and the pursuit of courtship and mating behaviors. Unfortunately, in the home, solitary pet birds are rarely free to engage in these pursuits. The frustration that often follows can result in feather picking. Some investigators believe that hormone-influenced (sexual) feather picking is the result of a bird's attempt to create a "brood patch." This completely featherless area of the breast allows very efficient transfer of heat from the bird's body to the egg(s) it is incubating. In captivity and nonbreeding situations, the feather picking and pulling is, of course, nonproductive and becomes an obsessive vice, even when hormone levels wane. Some of these birds exhibit a favorable response to progesterone drugs in the early stages.
Providing an appropriate mate is obvious, but not always practical. Reducing sexual stimulation (removing mirrors and masturbatory toys, placing birds of opposite sex that are caged separately out of sound range from each other) may be helpful. In multiple-bird households, feather picking may result when a bird is housed near other birds. Under these circumstances, moving this individual out of sight and beyond hearing from the others may educe the level of stress experienced by the bird and the severity of its feather picking.