Long‐term trends in the survival rates of adult female Common EiderSomateria mollissimaat three colonies in Iceland

Abstract

Identifying temporal and spatial patterns in demography is critical to understanding long‐term fluctuations in population size. Common Eider Somateria mollissima numbers have shown a long‐term decline, resulting in the species being uplisted in 2015 to ‘Endangered’ within European Union countries. Obtaining improved estimates of survival rates of Common Eiders (and other seaducks) has been identified as a priority to improve our understanding of the demographic causes of the observed global decreases in population size and to inform conservation efforts. In this study, we used long‐term (1982–2017) mark–recovery data on 3018 individuals from three breeding colonies in Iceland to quantify the spatial and temporal variation in the annual true survival rates of adult female Common Eider. Model comparison using an information‐theoretic approach indicated that true survival and recovery rates varied between years and colonies but showed no consistent temporal pattern across the three colonies. Geometric mean (± se) annual true survival across our three breeding colonies was 0.916 ± 0.017 (95% confidence interval (CI) = 0.819–0.961), with a mean life expectancy of 11.8 years (95% CI 5.4–25.2). Our survival estimates were relatively high compared with those reported previously for many other Common Eider populations, which may reflect their protected status, low predation pressure and high food availability on Iceland and its surrounding waters. Our findings provide spatially and temporally explicit demographic information needed to help conservationists understand the local and global declines in Common Eider populations.

Eiders, nutrients and eagles: Bottom‐up and top‐down population dynamics in a marine bird

“…However, the relative contribution of these factors remains unknown. Adding to this uncertainty, the drivers of the decline may show geographic variation (Öst et al., 2016), and eider demographic rates vary also between breeding colonies within the same region (Wood et al., 2021).…”

Long-term responses of Icelandic Arctic foxes to changes in marine and terrestrial ecosystems

“…Although the separation between the two groups of marine resources is not strongly supported by the mixing model (high correlation between the posterior distributions and overlap of credibility intervals), it appears likely that marine resources like common eiders, which are the most common waterfowl available throughout the year and are widely distributed in coastal areas, could represent an important part of the diet of Icelandic Arctic foxes. However, predation on eiders in Iceland is thought to be lower than for other populations in other areas since their protection is one of the reasons for the Icelandic fox culling program [26, 57]. A high importance of common eider in Arctic fox diet is also contrary to findings from prey remains at dens [20], where fulmars were the most common species.…”

Adult survival and annual movement patterns of common snipe in Iceland

“…Clair et al 2010). For context, we recently examined adult survival in Arctic terns (Sterna paradisaea) and common eiders nesting on Flatey, and estimated rates were amongst the highest reported for each species (Petersen et al 2020;Wood et al 2021). The snipe apparent survival rate on Flatey could be a bit higher than elsewhere on mainland Iceland, where nesting birds may experience predation pressure from feral American mink (Neovison vison) and Arctic fox (Vulpes lagopus).…”