individual bird species don't like, but at night the light beam is visible over a large distance and can cause widespread (non-species specific) disturbance. Lasers use can be limited due to safety concerns of the beam and some nations have laws which prohibit lasers above a certain power from being used. Lasers should be looked at as an additional scaring system to add to a wildlife management program. Manually operated laser torches and automated laser bird deterrent robots that move the laser automatically towards the birds are available on the market. Research conducted at Wageningen University shows the potential of laser technology to prevent the spreading of Avian Influenza. When the laser was used at a poultry farm, a 99.7% wild bird reduction rate was recorded. Dead birds The use of model or actual dead birds is used to signal danger to others. Initially, birds often approach the corpse but usually leave when they see the unnatural position of the bird. This approach has been frequently used in attempts to deter gulls from airports. Pheasant feed sacks often have an image of an owl with large eyes so that when empty they can be strung up to scare predators. Balloons Balloons are an inexpensive deterrent. However, this method relies on the movement of balloons, which is something that birds can become used to. The addition of eye illustrations on the balloons has been shown to increase this method's effectiveness as it combats the birds' ability to adapt. Commercially available "scare-eye" balloons have holographic eyes that follow birds wherever they go. The long-term effectiveness of this method can be increased by periodically moving the placement of the scare devices. In the United Kingdom the use of balloons is subject to approval from the Civil Aviation Authority, especially around airfields. Auditory scarers Audible bird scarers use noise stimuli that makes birds uncomfortable. However, once birds realize these pose no real threats, they can easily become habituated to sounds that seemed initially frightening. If just being placed in situ and left, audible bird scarers can easily become ineffective bird control solutions, however when managed on an ongoing basis or used as part of a greater bird deterrent system, sound methods can deliver quality results. Sōzu (shishi odoshi) One very old design is the Japanese sōzu, known metonymically as a shishi odoshi (although the term shishi odoshi properly refers to any method of scaring