Effects of a Hazing-Light System on Migration and Collision Avoidance of Eiders at an Artificial Oil-Production Island, Arctic Alaska

Abstract

During migration, Common and King Eiders (Somateria mollissima and S. spectabilis) cross the Beaufort and Chukchi Seas of Arctic Alaska. Because they may become attracted to lights, eiders are susceptible to collision with structures, including offshore oil facilities. We used ornithological radar in 2001 – 04 to characterize the behavior of eiders migrating past Northstar Island, an oil-production island near Prudhoe Bay, Alaska, and to assess the effects of a hazing-light system on migrating eiders. “Eider” radar targets exhibited pulsed, irregular periods of movement; movement rates were higher when sea ice was present, without precipitation, and during tailwinds and crosswinds but were not affected by lights. Velocities (ground speeds) were higher when ice was present and with strong tailwinds. They were lower at night when the lights were on, but higher during the day when the lights were on. Radar targets exhibited little variation in flight behavior as they passed the island; the proportion of non-directional behavior was larger when ice was present, with tailwinds, with weak winds, and near the full moon when it was not visible. Lights had no effect on flight behavior. Birds tended to exhibit more course changes as they approached the island, greater angular changes when they changed course, and larger net increases in passing distance as a result of those course changes when the lights were on; however, none of these differences were statistically significant. Overall, the hazing lights at Northstar did not disrupt the birds’ migratory movements but resulted in increased avoidance of the island.

Effect of anthropogenic light on bird movement, habitat selection, and distribution: a systematic map protocol

“…Even sub-lethal effects of aggregation and disruption to flight paths may ultimately reduce survival during migration by reducing energy stores and delaying arrival at breeding or wintering grounds [2]. Despite documented effects of light, some studies show no significant effect of light on bird flight behavior, density, or mortality at illuminated man-made structures [20,21]. Describing the numbers of studies and contexts associated with different kinds of light effects is a necessary first step toward potential mitigation.…”

“…Such factors may explain why one study reported that red lights are less likely to cause aggregation of nocturnal migrants [22], while another study found that green and blue lights were less disruptive to birds than red ones [23]. Similarly, ambient light may explain why migrating eiders (Somateria mollissima and S. spectabilis) exposed to artificial light increased flight velocity during the day, but decreased velocity at night [20]. Bird aggregation and mortality is often documented during nights of low cloud cover [23,24], but sometimes occurs in clear weather as well [19].…”