Population trends of king and common eiders from spring migration counts at Point Barrow, Alaska between 1994 and 2016

Polar Biology
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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.

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Publication type Article
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
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