Sex-specific survival of adult common eiders in Nova Scotia, Canada

Milton, G. Randy; Iverson, Samuel A.; Smith, Paul A.; Tomlik, Molly D.; Parsons, Glen J.

doi:10.1002/jwmg.21135

Cited by 14 publications

(18 citation statements)

References 45 publications

(58 reference statements)

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“…For Söderskär, we had no access to raw data and therefore, we estimated annual apparent survival of adult females directly from annual capture–recapture records on nesting females reported in [ 32 ], while for Tvärminne, we used a time-dependent Cormack–Jolly–Seber (CJS) model with a linear trend in recapture probability, applied to the capture-recapture data collected by our research team (see 19 for details). As no demographic data were available for males from the study sites, we adopted male survival estimates (mean = 0.92, CI = 0.87–0.95) from a Canadian population of eiders [ 33 ]. To consider uncertainty in male survival obtained from the literature, we used three different survival rates (88%, 90% or 92%) for males in age classes 1–5 in each population; the two lowest survival rates were chosen based on our long-term experience of the study populations.…”

Section: Methodsmentioning

confidence: 99%

Increased male bias in eider ducks can be explained by sex-specific survival of prime-age breeders

et al. 2018

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In contrast to theoretical predictions of even adult sex ratios, males are dominating in many bird populations. Such bias among adults may be critical to population growth and viability. Nevertheless, demographic mechanisms for biased adult sex ratios are still poorly understood. Here, we examined potential demographic mechanisms for the recent dramatic shift from a slight female bias among adult eider ducks (Somateria mollissima) to a male bias (about 65% males) in the Baltic Sea, where the species is currently declining. We analysed a nine-year dataset on offspring sex ratio at hatching based on molecularly sexed ducklings of individually known mothers. Moreover, using demographic data from long-term individual-based capture-recapture records, we investigated how sex-specific survival at different ages after fledgling can modify the adult sex ratio. More specifically, we constructed a stochastic two-sex matrix population model and simulated scenarios of different survival probabilities for males and females. We found that sex ratio at hatching was slightly female-biased (52.8%) and therefore unlikely to explain the observed male bias among adult birds. Our stochastic simulations with higher survival for males than for females revealed that despite a slight female bias at hatching, study populations shifted to a male-biased adult sex ratio (> 60% males) in a few decades. This shift was driven by prime reproductive-age individuals (≥5-year-old), with sex-specific survival of younger age classes playing a minor role. Hence, different age classes contributed disproportionally to population dynamics. We argue that an alternative explanation for the observed male dominance among adults–sex-biased dispersal–can be considered redundant and is unlikely, given the ecology of the species. The present study highlights the importance of considering population structure and age-specific vital rates when assessing population dynamics and management targets.

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Section: Methodsmentioning

confidence: 99%

Increased male bias in eider ducks can be explained by sex-specific survival of prime-age breeders

et al. 2018

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“…A unique collaboration with down harvest crews has provided annual nest counts and allowed the implementation of a banding program across most of the major common eider colonies in Quebec. This has complemented other extensive banding programs of adult females caught on colonies across the breeding range since the 1970s (Milton et al 2016, Allen et al 2019). Based on expert opinion, post‐hatching survival, which affects recruitment, may be the most important factor limiting the common eider population in eastern North America (Noel et al 2021).…”

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confidence: 90%

“…Furthermore, this species faces many threats from natural (e.g., disease outbreaks, predation) and anthropogenic sources (e.g., disturbance during nesting, marine oil spills, commercial exploitation of mollusks, climate change; Noel et al 2021). Although there is no long‐term and large‐scale monitoring program for common eider, waterfowl managers are concerned about the status of this population, especially across the southern portion of its breeding range (e.g., Maine, Nova Scotia) where numbers are declining (Bowman et al 2015, Milton et al 2016, Allen et al 2019).…”

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Estimating Population Growth and Recruitment Rates Across the Range of American Common Eiders

et al. 2021

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Sound management of bird populations rests upon an adequate understanding of their population dynamics. Our study evaluated recruitment and population growth rates of 14 American common eider (Somateria mollissima dresseri) colonies from Labrador, Nova Scotia, Quebec, Canada, and Maine, USA, during various periods between 1970 and 2019. We used Pradel mark‐recapture models to estimate colony‐specific growth rates and the relative contributions of survival and recruitment on growth. We also validated this approach using annual nest counts (~8,000 pairs) conducted between 2003 and 2019 during down harvest operations in 3 colonies located in the Saint Lawrence estuary in Quebec. There was generally a good agreement between estimates derived using the 2 approaches. We considered that capture‐recapture data were suitable to estimate population trends of common eiders in other colonies, especially for colonies where accurate nest monitoring is impaired by dense vegetation. The breeding abundance declined at major colonies in Maine and Nova Scotia and increased or was stable in Quebec and Labrador. Female survival contributed the most to population growth, but variation in recruitment among colonies was more important than variation in survival to explain population growth. Management measures should thus strive to maximize local recruitment in colonies with declining populations. The assumption that apparent survival probabilities were homogeneous throughout an individual capture history was violated at several colonies in Quebec and Labrador. Using recaptures and band recoveries, we showed that the lower apparent survival for newly marked individuals compared to females that had been recaptured at least once was caused by a difference in site fidelity rather than true survival. But <1% of recaptured females dispersed to another colony for breeding, indicating that the lower site fidelity could be related to heterogeneity in capture probability among individuals. © 2021 The Wildlife Society.

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“…Such estimates should be temporally and spatially explicit, as Common Eider survival rates can vary markedly over time (Milton et al . 2016) and also between adjacent subpopulations (Öst et al . 2016).…”

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confidence: 99%

“…Obtaining improved estimates of adult survival rates to inform the conservation and management of Common Eiders (and other seaducks) has therefore been identified as a research priority (Austin et al 2014, Koneff et al 2017. Such estimates should be temporally and spatially explicit, as Common Eider survival rates can vary markedly over time (Milton et al 2016) and also between adjacent subpopulations (Öst et al 2016).…”

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confidence: 99%

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

Wood

Thorstensen²,

Lúðvíksson³

et al. 2020

Ibis

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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.

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Sex-specific survival of adult common eiders in Nova Scotia, Canada

Cited by 14 publications

References 45 publications

Increased male bias in eider ducks can be explained by sex-specific survival of prime-age breeders

Increased male bias in eider ducks can be explained by sex-specific survival of prime-age breeders

Estimating Population Growth and Recruitment Rates Across the Range of American Common Eiders

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

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