Payo-Payo Ana, Oro Daniel, Igual José Manuel, Jover Lluis, Sanpera Carolina, Tavecchia Giacomo
Ecol Appl. 2015 Dec;25(8):2228-39. doi: 10.1890/14-2090.1.
The control of overabundant vertebrates is often problematic. Much work has focused on population-level responses and overabundance due to anthropogenic subsidies. However, far less work has been directed at investigating responses following the removal of subsidies. We investigate the consequences of two consecutive perturbations, the closure of a landfill and an inadvertent poisoning event, on the trophic ecology (δ13C, δ15N, and δ34S), survival, and population size of an overabundant generalist seabird species, the Yellow-legged Gull (Larus michahellis). We expected that the landfill closure would cause a strong dietary shift and the inadvertent poisoning a decrease in gull population size. As a long-lived species, we also anticipated adult survival to be buffered against the decrease in food availability but not against the inadvertent poisoning event. Stable isotope analysis confirmed the dietary shift towards marine resources after the disappearance of the landfill. Although the survival model was inconclusive, it did suggest that the perturbations had a negative effect on survival, which was followed by a recovery back to average values. Food limitation likely triggered dispersal to other populations, while poisoning may have increased mortality; these two processes were likely responsible for the large fall in population size that occurred after the two consecutive perturbations. Life-history theory suggests that perturbations may encourage species to halt existing breeding investment in order to ensure future survival. However, under strong perturbation pulses the resilience threshold might be surpassed and changes in population density can arise. Consecutive perturbations may effectively manage overabundant species.
对数量过多的脊椎动物进行控制往往存在问题。许多研究工作聚焦于种群水平的反应以及由于人为补贴导致的数量过多问题。然而，针对补贴取消后的反应进行调查的工作要少得多。我们研究了连续两次扰动——垃圾填埋场关闭和一次意外中毒事件——对一种数量过多的广食性海鸟物种黄腿鸥（Larus michahellis）的营养生态学（δ13C、δ15N和δ34S）、生存及种群数量的影响。我们预计垃圾填埋场关闭会导致强烈的饮食转变，而意外中毒会使鸥类种群数量减少。作为一种长寿物种，我们还预计成年个体的生存会在食物供应减少的情况下得到缓冲，但不会在意外中毒事件中得到缓冲。稳定同位素分析证实，垃圾填埋场消失后，其饮食转向了海洋资源。尽管生存模型确实表明这些扰动对生存有负面影响，随后又恢复到平均值，但它确实暗示了这些扰动对生存有负面影响。食物限制可能引发了向其他种群的扩散，而中毒可能增加了死亡率；这两个过程可能是导致连续两次扰动后种群数量大幅下降的原因。生活史理论表明，扰动可能会促使物种停止现有的繁殖投资，以确保未来的生存。然而，在强烈的扰动脉冲下，恢复力阈值可能会被突破，种群密度可能会发生变化。连续的扰动可能有效地管理数量过多的物种。
