Cross-seasonal effects in a sea ice-associated sea duck: do winter conditions affect breeding spectacled eiders?

Abstract

Climate change in the Arctic is more rapid than anywhere on the globe and changes in the marine environment can impact the distribution and abundance of Arctic and sub-Arctic species. Understanding how a species responds to climate change can aid conservation planning and recovery. Spectacled eiders (Somateria fischeri), sea ducks listed as "threatened" under the Endangered Species Act, winter at the Bering Sea and nest along the coastal areas of Alaska and Arctic Russia. Severity of winter conditions in the Bering Sea have been associated with both reduced annual survival and reduced breeding abundance and may have sublethal effects during the breeding season. In this study, we used 24 years of nesting data from Kigigak Island, a sub-Arctic site on the Yukon-Kuskokwim Delta, and 10 years from Utqiaġvik, on the Arctic Coastal Plain, to examine the hypothesis that winter conditions in the Bering Sea influence the reproductive performance of eiders in the following breeding season. For both sites, we examined the effects of winter ice conditions and spring temperature and wind on nest initiation date, clutch size, and nest survival. Nest initiation date was not strongly associated with conditions experienced prior to the breeding season. Estimates of nest initiation date following extreme high and extreme low winter ice conditions differed by only 2 days. In contrast, the difference in mean initiation dates between sites was 20 days. We found no evidence that winter and spring conditions preceding the breeding season explained variation in clutch size (mean clutch size = 4.8, 95% CI: 4.7, 4.8), suggesting that breeding propensity may buffer against variation in clutch size. Nest survival varied among years; annual estimates ranged from 0.11 (95% CI: -0.02, 0.24) to 0.95 (95% CI: 0.92, 0.98) at Kigigak Island and 0.40 (95% CI: 0.16, 0.63) to 0.83 (95% CI: 0.66, 0.99) at Utqiaġvik. At both sites, low days of high ice during winter were associated with lower nest survival and moderate to high counts of high ice cover conditions during winter were associated with higher nest survival. After accounting for the effect of days of high ice during winter, nest survival was higher at Utqiaġvik than Kigigak Island, potentially related to later nest initiation in the Arctic. We concluded that for breeding spectacled eiders, low sea ice winters are associated with reduced nest survival through reduced body condition, and we speculate that following winters with high sea ice more individuals may possibly decide not to breed. Delayed nest initiation at Arctic breeding sites may provide additional time for spectacled eiders to recover from low ice winters and contribute to higher nest survival at Utqiaġvik compared to the sub-Arctic breeding site. Associations between changing ice conditions on multiple demographic rates may lead to future population declines for spectacled eiders at rates higher than previously predicted.