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Providing evidence to improve practice

Individual study: Lasers directed at roost trees after sunset are effective in dispersing double-crested cormorants Phalacrocorax auritus from night roosts, the delta region of Mississippi and Alabama, USA

Published source details

Glahn J.F., Ellis G., Fiornelli P. & Dorr B. (2001) Evaluation of moderate- and low- power lasers for dispersing double-crested cormorants from their night roosts. Proceedings of the Eastern Wildlife Damage Management Conference, 9, 34-45


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Disturb birds at roosts Bird Conservation

Replicated before-and-after trials in January-March 2003 at double-crested cormorant Phalacrocorax auritus night roosts (with 2,500 to 34,000 individuals) near catfish farms in Mississippi and Alabama, USA (Glahn et al. 2001), found that hand-held lasers reduced cormorant numbers by 94% to 100%. The time required to achieve success varied (the most effective was 16 min to achieve 100% success at one roost; the least effective 113 min to achieve 94% success at another), but cormorants typically abandoned roosts after three nights of harassment. Six trials (at six sites) were conducted using a Desman™ Laser and five using a Laser Dissuader™. From sunset to 1 hour after sunset (on one to three consecutive evenings), a laser beam was directed at roosting cormorants, from 100-1,000 m distant. Birds were counted before and after treatment. (Note: Laboratory trials found no ocular damage to cormorants exposed to the Desman Laser at distances to the minimum of 1 m tested).