Data from: Hidden survival heterogeneity of three common eider populations in response to climate fluctuations

(1) Understanding how individuals and populations respond to fluctuations in climatic conditions is critical to explain and anticipate changes in ecological systems. Most such studies focus on climate impacts on single populations without considering inter- and intra-population heterogeneity. However, comparing geographically dispersed populations limits the risk of faulty generalizations and helps to improve ecological and demographic models. (2) We aimed to determine whether differences in migration tactics among and within populations would induce inter- or intra-population heterogeneity in survival in relation to winter climate fluctuations. Our study species was the Common eider (Somateria mollissima), a marine duck with a circumpolar distribution, which is strongly affected by climatic conditions during several phases of its annual cycle. (3) Capture-mark-recapture (CMR) data were collected in two arctic (northern Canada and Svalbard) and one subarctic (northern Norway) population over a period of 18, 15 and 29 years, respectively. These three populations have different migration tactics and experience different winter climatic conditions. Using multi-event and mixture modelling, we assessed the association between adult female eider survival and winter conditions as measured by the North Atlantic Oscillation index. (4) We found that winter weather conditions affected survival of female eiders from each of these three populations. However, different mechanisms seemed to be involved. Survival of the two migrating arctic populations was impacted directly by changes in the NAO, whereas the subarctic resident population was affected by the NAO with time lags of two to three years. Moreover, we found evidence for intra-population heterogeneity in the survival response to the winter NAO in the Canadian eider population, where individuals migrate to distinct wintering areas. (5) Our results illustrate how individuals and populations of the same species can vary in their responses to climate variation. We suspect that the found variation in survival response of birds to winter conditions is partly explained by differences in migration tactic. Detecting and accounting for inter- and intra-population heterogeneity will improve our predictions concerning the response of wildlife to global changes.

(1) 解析个体与种群对气候波动的响应规律，对于阐释并预测生态系统动态至关重要。现有同类研究多聚焦于气候对单一种群的影响，却未考虑种群间与种群内异质性（inter- and intra-population heterogeneity）。然而，对比地理分布离散的种群，可降低错误泛化的风险，同时助力优化生态模型与种群统计模型。(2) 本研究旨在探究种群间及种群内部的迁徙策略差异，是否会引发与冬季气候波动相关的存活率种群间与种群内异质性。本研究的受试物种为普通绒鸭（Common eider, Somateria mollissima），这是一种环极地分布的海鸭，其年度生活史的多个阶段均受气候条件的显著影响。(3) 研究分别在两个北极种群（加拿大北部与斯瓦尔巴群岛）及一个亚北极种群（挪威北部）收集了标记重捕（Capture-mark-recapture, CMR）数据，各采样时长分别为18年、15年与29年。这三个种群具有不同的迁徙策略，且所处冬季气候环境各异。本研究采用多事件模型与混合模型，以北大西洋涛动指数（North Atlantic Oscillation index, NAO）表征冬季气候条件，评估了成年雌性绒鸭的存活率与冬季气候之间的关联。(4) 本研究发现，冬季气候条件对这三个种群的雌性绒鸭存活率均存在显著影响，但背后的作用机制各不相同。两个迁徙型北极种群的存活率直接受NAO变化的调控，而亚北极居留型种群的存活率则受NAO影响，且存在2至3年的时间滞后。此外，在加拿大绒鸭种群中，个体会迁徙至不同的越冬区域，本研究发现该种群内存在针对冬季NAO的存活响应异质性证据。(5) 本研究结果表明，同一物种的不同个体与种群，对气候波动的响应模式存在显著差异。我们推测，鸟类对冬季气候的存活响应差异，部分可由迁徙策略的不同加以解释。识别并纳入种群间与种群内异质性因素，将有助于优化我们对野生动物响应全球变化的预测能力。