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
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.
Double-crested cormorants Phalacrocorax auritus are a major predator of catfish at fish farms in the Mississippi delta region (southern USA). As a non-lethal deterrent method, the use of commercially available hand-held lasers was trialled to assess efficacy in dispersing double-crested cormorants from night roosts near aquaculture facilities in Mississippi and Alabama.
During January-March 2003, trials were undertaken at roosts with over 1,000 cormorants. Laser harassment was undertaken for one to three consecutive evenings; roosts were approached on foot or by boat to 100-1,000 m of roost trees. From sunset to 1 hour after sunset, a laser beam was directed where cormorants were roosting.
Roost sizes prior to laser treatment varied from around 2,500 to 34,000 birds (dependent on site). Both lasers were consistently effective at reducing cormorant numbers by 94% to 100%, although the time required to achieve success varied considerably (e.g. the most effective was 16 min to achieve 100% success at one roost; the least effective 113 min to achieve 94% success at another). Cormorants typically abandoned roosts after three nights of harassment.