Abstract：
While seabirds are well-known for making a living under some of the harshest conditions on the planet, their capacity to buffer against unfavourable conditions can be stretched in response to ecosystem change. During population increases, overlap between conspecifics can limit population growth through competition for breeding or feeding resources. What is less well understood is the role that intrinsic processes play during periods of population decline or under a changing environment. We interrogate key demographic parameters and their biophysical drivers to understand the role of intrinsic and extrinsic drivers during a recent near halving of a large Adélie penguin (Pygoscelis adeliae) metapopulation. The loss of 154,000 breeding birds along the 100-km East Antarctic coastline centred around 63°E over the last decade diverges from a sustained increase over preceding decades and is contrary to recent models that predict a continued increase. The decline was initially triggered by changed environmental conditions: more extensive near-shore sea ice caused a reduction in breeding success. The evidence suggests this decline was exacerbated by feedback processes driving an inverse density-dependent decrease in fledgling survival in response to smaller cohort size. It appears that the old adage of safety in numbers may shape the fledgling penguins\' chances of survival and, if compromised over multiple years, could exacerbate difficulties during population decline or if feedback processes arise. The likely interplay between demographic parameters meant that conditions were more unfavourable and negative effects more rapid than would be expected if demographic processes acted in isolation or independently. Failure to capture both intrinsic and extrinsic drivers in predictive population models may mean that the real impacts of climate change on species\' populations are more severe than projections would lead us to believe. These results improve our understanding of population regulation during periods of rapid decline for long-lived marine species.
摘要：
虽然海鸟以在地球上最恶劣的条件下谋生而闻名，他们缓冲不利条件的能力可能会随着生态系统的变化而扩大。人口增长期间,物种之间的重叠可以通过争夺育种或饲养资源来限制种群的增长。人们不太了解的是内在过程在人口减少或环境变化期间所起的作用。我们询问关键的人口统计学参数及其生物物理驱动因素，以了解在最近将大型Adélie企鹅（Pygoscelisadeliae）种群减半期间内在和外在驱动因素的作用。在过去十年中，沿100公里的东南极海岸线的154,000种繁殖鸟类的损失集中在63°E附近，与前几十年的持续增长不同，并且与最近预测持续增长的模型相反。下降最初是由环境条件的变化引起的：更广泛的近岸海冰导致繁殖成功率降低。证据表明，由于较小的队列规模，反馈过程导致新生生存率的反向密度依赖性下降，从而加剧了这种下降。看来，在数量上安全的古老格言可能会塑造羽翼未丰的企鹅的生存机会，如果多年来妥协，可能会在人口减少期间或出现反馈过程时加剧困难。人口统计参数之间可能的相互作用意味着，如果人口统计过程孤立或独立地发挥作用，条件比预期的更不利，负面影响更快。无法在预测人口模型中捕获内在和外在驱动因素，可能意味着气候变化对物种种群的真正影响比预测更严重。这些结果改善了我们对长寿海洋物种迅速下降期间种群调节的理解。
