Correcting for within-season demographic turnover to estimate the island-wide population of King Penguins (Aptenodytes patagonicus) on South Georgia
Correcting for within-season demographic turnover to estimate the island-wide population of King Penguins (Aptenodytes patagonicus) on South Georgia
复制标题
校正季节内人口流动，以估计南乔治亚岛全岛王企鹅 (Aptenodytes patagonicus) 的数量
作者：
C. Foley;W. Fagan;H. Lynch
王企鹅（Aptenodytes patagonicus）生活在偏远的地方，在异步繁殖的大殖民地。这三个因素阻碍了王企鹅人口普查的设计和进行，对趋势的评估往往需要将不同人口组成部分的不匹配调查拼凑在一起。这项研究介绍了一种新的方法来远程普查这些人口全年和正确的人口估计国王企鹅的独特繁殖物候。我们结合实地地面计数和基于高分辨率卫星图像的估计，对南大西洋南格鲁吉亚岛的繁殖群体分布进行了编目，并估计了种群丰度。虽然大多数王企鹅的数量预计将在下一个世纪显着下降，南格鲁吉亚预计将经历更有利的条件，并代表了该物种的重要避难所，尽管调查王企鹅的挑战已经排除了全面的人口普查。由于在原地和远程计数的可变时间，我们开发了一个离散的时间，年龄和阶段结构的人口模型，提供特定阶段和特定日期的校正因子的标准化普查计数。我们估计南格鲁吉亚的王企鹅目前的人口为405，425（95%CI 102，624 - 2，375，061）繁殖对，并发现人口趋势，不占物候偏差持续低估人口增长率。校正因子是高度敏感的年度鸡蛋死亡率和总繁殖人口最好的估计使用巢计数的早期繁殖对。未来对王企鹅种群进行普查的努力可能会通过更精确地估计蛋的存活率和优化地面和卫星普查的时间来最大限度地减少不确定性，以便在早期育种者定居期间进行。考虑到与模型参数当前不确定性相关的误差，需要18-32年的人口普查数据才能准确检测10%增长率的人口趋势。虽然异步繁殖的物种提出了一个独特的挑战，人口监测，仔细核算的季节内动态可以用来组装一个自洽的时间序列从异质性的调查数据。
King Penguins (Aptenodytes patagonicus) live in remote locations, in large colonies with asynchronous breeding. These three factors hinder the design and conduct of King Penguin censuses, and assessments of trend often require piecing together mismatched surveys of different demographic components. This study introduces a new method to remotely census these populations year-round and correct population estimates for the King Penguin’s unique breeding phenology. We combined in situ ground counts with estimates based on high-resolution satellite imagery to catalog the distribution of breeding colonies and estimate population abundance across the island of South Georgia, in the south Atlantic. While most King Penguin populations are forecast to decline significantly over the next century, South Georgia is expected to experience more favorable conditions and represents an important refugium for the species, though the challenges of surveying King Penguins have precluded a comprehensive census. Due to the variable timing of both in situ and remote counts, we developed a discrete time, age- and stage-structured population model that provides stage- and day-specific correction factors for standardization of census counts. We estimate the current population of King Penguins on South Georgia as 405,425 (95% CI 102,624–2,375,061) breeding pairs and find that population trends that do not account for phenological biases persistently underestimate the population growth rate. Correction factors are highly sensitive to annual egg mortality and the total breeding population is best estimated using nest counts of early-breeding pairs. Future efforts to census King Penguin populations may minimize uncertainty by capturing more precise estimates of egg survival and optimizing the timing of ground and satellite censuses to occur during the settlement of early breeders. Accounting for the error associated with current uncertainty in model parameters, 18–32 years of census data would be required to accurately detect trends of a population with a 10% growth rate. While asynchronously breeding species present a unique challenge to population monitoring, careful accounting of within-season dynamics can be used to assemble a self-consistent time series from heterogeneous survey data.