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

Robert H Day,Alexander K Prichard,Ted Swem,John R Rose,Bill Streever

doi:10.14430/arctic4628

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.

Highlights

If all of the 928 radar targets that we studied in 2001 – 04 had an average size similar to that of flocks we located visually (23.4 ± 95% CI 6.5 birds/flock), we would have collected data on ~21 750 ± 6032 migrating eiders in the vicinity of Northstar Island
Movement rates varied substantially among nights, indicating pulses of migratory movement and presumably reflecting conditions favorable or unfavorable for migration. This pulsed movement pattern of eider migration has been seen at Barrow (Thompson and Person, 1963; Suydam et al, 1997; Day et al, 2004) and along the Beaufort Sea coast of Alaska (Johnson and Richardson, 1982)
Many eiders migrated past Northstar Island at night, a pattern similar to that seen at Barrow (Day et al, 2004) and in the Baltic Sea (Alerstam et al, 1974) under good migration conditions

Summary

Introduction

Large numbers of migrating Common and King Eiders (Somateria mollissima and S. spectabilis) cross the Beaufort and Chukchi Seas of Arctic Alaska (Thompson and Person, 1963; Johnson, 1971; Richardson and Johnson, 1981; Johnson and Richardson, 1982; Woodby and Divoky, 1982; Divoky, 1984a; Suydam et al, 1997, 2000b; Quakenbush and Suydam, 2004). Migrating eiders are susceptible to collision with human-made structures in the nearshore zone because they fly low over the water (Thompson and Person, 1963; Johnson and Richardson, 1982; Day et al, 2004), fly rapidly (Day et al, 2004), and may be attracted to bright lights Common and King Eider populations in the Beaufort Sea have declined substantially (Suydam et al, 2000a), so any additional source of mortality is of concern

Methods

Results

Conclusion