Flashing Rotating
Flashing, rotating, strobe and searchlights are a novel stimulus to birds, which encourage an avoidance response. Although a steady light source such as searchlights have been known to attract birds at night, particularly when it is cloudy or foggy, strobe lights, revolving lights and amber barricade lights might be useful for deterring night-feeding birds such as herons at fisheries.
The lights have a blinding effect which causes the birds to become confused and restricts their ability to fish. However, birds can quickly become habituated and black-crowned herons (Nycticorax nycticor) have been known to avoid the glare by landing with their backs to the lights. Lawrence et al. reviewed strobe lights particularly in relation to their use on airfields, and concluded that strobe lights had some deterrent effect though they were more effective at deterring lapwings than gulls. Pilo et al. showed that birds such as kites, vultures and pigeons were affected by a high intensity strobe light, which could encourage them to take evasive action and move away. They also showed no habituation. Green and Bahr recommended a randomised selection of at least two strobe frequencies in order to deter a broader range of bird species. However, Theale investigated the use of strobe lights to drive house sparrows from the interior of buildings.
In an experimental situation, such lights failed to disturb the birds feeding activities. Numbers of night-feeding black-crowned night-herons and great blue herons at a trout hatchery were reduced by the use of bright rotation lights, but only by moving them a short distance to an unlit part of the hatchery. However, they caught fish just as effectively in both lit and unlit sections, so the lights had no effect on fish losses.
A floating solar-powered rotating beacon was successful in reducing the number of ducks visiting a sewerage pond by 90%. The device was most effective when rotating slowly and operated only during the night. Although lights are easy to deploy and require very little maintenance, they should not be used where they might cause a visual nuisance to neighbouring properties. They may not be effective during daylight hours and their ability to scare birds at night varies with the bird species. Lights are best used with other deterrent methods.
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