The method relies on birds being startled by the strong contrast between the ambient light and the laser beam. During low light conditions this technique is very selective and can be tuned to frequencies and wavelengths that 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.
The method uses birds being startled by the significant contrast between ambient light and laser beams. In low-light situations, this technique is highly selective and can be tuned to frequencies and wavelengths that particular bird species find unpleasant, but at night, the beam becomes visible over a large area and may disturb non-specific groups of birds.