Bird controls using aural and visual signals are currently in widespread use for crop control, at airports, and similar locations where the presence of birds is undesirable. Although some of these methods have met with limited success, quite often the birds are either harmed or tend to become accustomed to and subsequently ignore the false threats. Birds also can, through consistent and varied stimulation, change their habit patterns to defeat the repelling devices.
Research into bird behavior and the effects of various repelling methods discloses that birds are very habitual creatures, requiring great persistence to effectuate a change in habit. Although birds become accustomed to non-lethal threats and learn to ignore them, they are responsive to alarm and distress calls of their own species. Birds generally are frightened by loud explosions, bright colors, and distress signals from other birds.
Utilizing the research results, a shotgun, acetylene and similar explosions have been used as well as recordings of the pest birds in distress played over loudspeakers. Also, pictures or models of predators with prevalent predator eyes had some deterent effect. Not withstanding short-term successes, the birds have tended to become accustomed to the lack of variety in the application of these repelling means and have tended to ignore the same.