Birds kept as companion animals require adequate flight space for physical and psychological health, yet most pet bird housing provides far less space than needed for flight.
Birds evolved for flight are physiologically and psychologically dependent on it. The cardiovascular and respiratory systems of birds are adapted for the demands of sustained flight, and permanent deprivation leads to muscle deterioration and cardiovascular insufficiency. Psychologically, the inability to flee from stressors — a fundamental avian coping mechanism — causes chronic anxiety in cage-bound birds. Flight also allows birds to express natural foraging, exploration, and courtship behaviors that are profoundly suppressed by small cages.