Population trends of king and common eiders from spring migration counts at Point Barrow, Alaska between 1994 and 2016
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Abstract
Most king (Somateria spectabilis) and common eiders (S. mollissima v-nigra) breeding in the northwestern Nearctic migrate past Point Barrow, Alaska. Spring migration counts have been conducted there since 1953; during 1976–1996, both species declined > 50% for unknown reasons. To evaluate population trends, counts in 2003, 2004, 2015, and 2016 were compared to earlier counts. King eider estimates were 304,966 (95% CI ± 76,254) in 2003, 591,961 (± 172,011) in 2004, 796,419 (± 304,011) in 2015, and 322,381 (± 145,833) in 2016. Common eider estimates were 114,998 (± 28,566) in 2003, 110,561 (± 32,087) in 2004, 96,775 (± 39,913) in 2015, and 130,390 (± 34,548) in 2016. The 2016 estimate was likely biased low for king eiders due to weather (causing large pulses of king eiders to pass within 2 days) and early ice break-up (causing observers to count at greater distances from the flocks). Using all estimates, populations of both species were statistically stable during 1994–2016. Excluding the 2016 count for king eiders indicated a significant increase of 18.63%/year in that population. Photo analysis of flocks in 2016 indicated that observer counts averaged 4% lower, species detection was not different, but females’ counts were underestimated by 25%. Methods should be refined to reduce bias and variability. Ice-based spring counts are becoming more difficult due to earlier break-up, less stable ice, and new techniques or locations; or a switch to land-based summer/fall migration counts are needed. Population monitoring is needed to ensure sustainability of harvests for these valuable subsistence resources.
Study Area
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Population trends of king and common eiders from spring migration counts at Point Barrow, Alaska between 1994 and 2016 |
Series title | Polar Biology |
DOI | 10.1007/s00300-019-02581-6 |
Volume | 42 |
Year Published | 2019 |
Language | English |
Publisher | Springer |
Contributing office(s) | Coop Res Unit Atlanta |
Description | 10 p. |
First page | 2065 |
Last page | 2074 |
Country | United States |
State | Alaska |
Other Geospatial | Point Barrow |
Google Analytic Metrics | Metrics page |