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Response of Water Birds to Hazing with a Red Laser

  • Author(s): Gorenzel, W. Paul
  • Salmon, Terrell P.
  • Imai, Randy
  • et al.
Abstract

The use of lasers to prevent oiling of waterbirds at a spill is a new concept. Little is known about how some species that could occur at a spill would respond. The objectives of this study were to: 1) identify species that respond to the laser, 2) document the immediate response of waterbirds to the laser, 3) determine if laser treatment during the early evening reduces bird numbers over the course of a night, and 4) determine if the laser treatment has any lasting effect over the short term after treatment has ended. The study was conducted in 2 parts. In Part 1, we used 5 locations in the Sacramento Valley of California. We visited the sites at dusk from October 2007 - March 2008 and opportunistically used the laser on any birds encountered. At each test session, we recorded ambient light levels and the species and number of birds. We fired the laser, then recorded the immediacy and type of responses and the number of birds remaining. A response was considered favorable if the bird left the site. For Part 2, we used a 20-ha marsh in Woodland, Yolo County, California. The study, conducted in March 2008, was divided into 3 periods (pretreatment, treatment, and post-treatment) of 5 days each. We counted birds in the morning and at dusk each day. During the treatment period, we counted the birds at dusk, fired the laser, and then counted any remaining birds. We recorded the same information as described above for the random tests. In part 1, we tested the laser on 18 evenings and fired the laser 129 times at 2,000 birds consisting of 25 species. Overall, 1,212 (61%) birds responded favorably. High proportions of pelicans and cormorants (100%), herons and egrets (99%), geese (93%), and diving ducks (85%) responded favorably. No grebes, coots, shorebirds, gulls responded favorably. Only 10% of the dabbling ducks responded favorably to treatment. In Part 2, we fired the laser 74 times at 3,036 birds consisting of 16 species. Overall, 2,251 (74%) birds responded favorably. High proportions of herons (98%) and dabbling ducks (93%) responded favorably, but only 46% of the diving ducks responded favorably. No coots responded favorably. There was a significant decrease in bird numbers immediately after laser treatment. Bird numbers recorded the next morning were not significantly different from the levels present just before the laser treatment the evening before. There was a significant decrease of 47% in the average number of birds on the treated area from the pretreatment period (x-bar = 873.7; SD = 151.8) to the treatment period (x-bar = 463.9, SD = 171.3). Thereafter, the number of birds during the 5-day post-treatment period (x-bar = 530.8, SD = 206.6) was not significantly different from that during the treatment period. Suggestions are provided on using the laser at a spill event.

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