Using inter-colony variation in demographic parameters to assess the impact of skua predation on seabird populations
Using inter-colony variation in demographic parameters to assess the impact of skua predation on seabird populations
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利用种群间人口参数的变化来评估贼鸥捕食对海鸟种群的影响
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
R. Furness
中科院分区：
文献类型：
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作者：
S. Votier;M. Heubeck;R. Furness
大型贼鸥和海鸥是海洋生态系统中的顶级掠食者，以浅水鱼类、渔业丢弃物和小型海鸟的寄生虫为食。作为多面手的掠食者，它们可能对海鸟的猎物种群产生有害影响，特别是在替代食物稀缺的情况下。丢弃物和富含脂质的浅滩鱼类的减少可能导致这些大型食腐鸟类转向捕食海鸟以满足其营养需求，但我们对海鸟捕食者-猎物动态的了解相对较少。英国黑腿三趾鸥里萨的减少是由于Sandeel Ammodytes marinus的可用性减少，但也可能是由于大贼鸥Stercorarius skua在其部分地区的捕食。我们调查是否在两个人口统计参数（繁殖成功率和人口增长率）的变化，整个设得兰群岛的Kittiwake殖民地解释贼鸥人口密度在增加的空间尺度（环半径为0-5，5-10，10-15，15-20，20-25和25-30公里）和Kittiwake人口密度。这些解释变量并不能解释大量的年人口增长率（λ）的变化，但我们对人口变化的估计是高度保守的，我们不能排除第二类错误的可能性。Kittiwake繁殖成功率与Sandeel可用性呈正相关，与焦点殖民地的Kittiwake数量呈负相关。在控制了这些影响后，大贼鸥的数量也对繁殖成功产生影响，在5-10和20-25 km尺度上呈负相关，但在10-15 km尺度上呈正相关。此外，对被细分为暴露或受保护悬崖的Kittiwake种群的分析表明，暴露的亚群比受保护的亚群下降得更快--这可能是由于对贼鸥捕食的敏感性不同。我们建议，比较人口率的差异可能是有用的，在解开海鸟捕食者-猎物动态，但只有在有一个全面的人口数据集，在那里有可能纠正混淆因素，如食物供应，和栖息地捕食相互作用的信息。
Large skuas and gulls are top predators in marine ecosystems, feeding on shoaling fish, fishery discards and facultatively on smaller seabirds. As generalist predators they may have deleterious impacts on prey populations of seabirds, particularly when alternative foods are scarce. Declines in discards and lipid-rich shoaling fish may result in these large scavenging birds turning to prey on seabirds to meet their nutritional needs, yet we know relatively little about seabird predator–prey dynamics. Declines in Black-legged Kittiwakes Rissa tridactyla in the UK are attributed to reductions in Sandeel Ammodytes marinus availability, but may also be due to predation by Great Skuas Stercorarius skua in some parts of their range. We investigate whether variation in two demographic parameters (breeding success and population growth rate) of Kittiwake colonies across Shetland are explained by skua population density at increasing spatial scales (rings with radii of 0–5, 5–10, 10–15, 15–20, 20–25 and 25–30 km) and Kittiwake population density. These explanatory variables do not explain a significant amount of the variation in annual population growth rate (lambda), but our estimate of population change is highly conservative and we cannot exclude the possibility of type II errors. Kittiwake breeding success is positively correlated with Sandeel availability and negatively correlated with the number of Kittiwakes at the focal colony. Having controlled for these effects the number of Great Skuas also has an influence on breeding success, being negatively correlated at the scale of 5–10 and 20–25 km, but positively correlated at the scale of 10–15 km. In addition, analysis of Kittiwake populations subdivided into exposed or protected cliffs reveals that exposed sub-colonies declined more steeply than protected ones – presumably as a function of differences in susceptibility to Skua predation. We propose that comparing differences in demographic rates may be useful in unravelling seabird predator–prey dynamics, but only where there is a comprehensive demographic dataset, where it is possible to correct for confounding factors such as food availability, and information on habitat–predation interactions.