Understanding the factors that drive the dynamics of populations of long‐lived species presents a unique challenge for conservation management. Here, we investigated long-term change in the body condition of adult northern rockhopper penguins Eudyptes moseleyi at Amsterdam Island, southern Indian Ocean, which hosts 5–10% of the global population of this endangered species. Analysis of a long‐term dataset (1994–2016), concurrent to the population's rapid decline, revealed no trend in adult northern rockhopper penguin body condition over time at the stages considered in this study, i.e. breeding and moulting. However, body condition varied between years and sexes and part of this variation was explained by environmental factors. Males were on average in better condition than females whatever the stage and individuals on average were in better condition during the moulting compared to the breeding period. The environmental conditions [sea surface temperature anomaly (SSTa), Subtropical Indian Ocean Dipole (SIOD) and Southern Annular Mode (SAM)] appeared to impact non-linearly the body condition. Overall, females were in better condition for negative values of SAM, SIOD and SSTa. The body condition of males exhibited similar but less complex and more significant patterns, with decreasing body condition for increasing SAM, SIOD and SSTa. The absence of long-term trends in male and female body condition suggests that the very low reproductive output and declining population since 1997 is probably not the result of environmental conditions during pre-breeding and pre-moult and necessitates further research into possible drivers during the breeding season.

了解驱动长寿物种种群动态的因素对保护管理提出了独特的挑战。在这里，我们调查了印度洋南部阿姆斯特丹岛北部成年北部rock蝉企鹅Eudyptes moseleyi的身体状况的长期变化，该岛拥有该濒危物种全球人口的5-10％。长期数据集（1994年至2016年），同时人口的快速下降的分析，揭示了成人北部跳岩企鹅的身体状况没有趋势随着时间的推移在这项研究中考虑的阶段，即育种和换羽。但是，身体状况因年龄和性别而异，部分这种变化是由环境因素引起的。男性平均在更好的条件比女性无论阶段和平均个人期间，在更好的条件换羽相比，养殖期。环境条件[海面温度异常（SSTa），亚热带印度洋偶极子（SIOD）和南部环形模式（SAM）]似乎对身体状况产生非线性影响。总体而言，女性的SAM，SIOD和SSTa阴性值处于更好的状态。男性的身体状况表现出相似但较不复杂且更显着的模式，随着身体状况的降低，SAM，SIOD和SSTa升高。缺乏男性和女性身体状况的长期趋势，表明自1997年以来极低的生殖产量和人口下降可能不是繁殖前和换羽前的环境状况造成的，因此有必要进一步研究生育过程中可能的驱动因素。繁殖季节。