A drop in immigration results in the extinction of a local woodchat shrike population,Animal Conservation

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A drop in immigration results in the extinction of a local woodchat shrike population
Animal Conservation ( IF 2.8 ) Pub Date : 2020-09-18 , DOI: 10.1111/acv.12639
M. Schaub ₁ , B. Ullrich ₂

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The demographic reasons of local population extinctions are rarely known which hampers learning for preventing extinction of other populations. Here we study the demography of a population of the endangered woodchat shrike Lanius senator at the edge of its distribution range from 1966 to 1992. We recorded the number of breeding pairs and collected reproduction and capture-recapture data which were analysed with an integrated population model. Population size and most demographic rates fluctuated, but did not show long-term trends. The most important demographic driver for the variation in the annual population growth rate was immigration. Despite its dependence on immigration, the local population was not necessarily a sink but may have been part of a balanced dispersal system. A population viability analysis showed that the risk was zero for the population to go extinct due to stochastic events during the 10 years after 1992. Yet, the population went extinct 6 years after the end of the study. The only demographic mechanism that can explain the fast extinction is a stop of immigration. The population was always dependent on immigration due to the strong dispersal of the shrikes and became more isolated due to the overall decline of the species. Our results suggest that the reservoir of potential immigrants may have become insufficient to maintain the local population and highlights that local populations can go extinct without the need of local changes in demography. Successful conservation of bird populations with similar demography as woodchat shrikes need to focus on spatial scales that extend significantly beyond the local one.

中文翻译：

移民减少导致当地木头伯劳种群灭绝

当地人口灭绝的人口原因鲜为人知，这阻碍了防止其他人口灭绝的学习。在这里，我们研究了濒临灭绝的木头伯劳伯劳拉尼厄斯参议员的人口统计数据在 1966 年至 1992 年其分布范围的边缘。我们记录了繁殖对的数量并收集了繁殖和捕获-再捕获数据，这些数据用综合种群模型进行了分析。人口规模和大多数人口比率波动，但没有显示出长期趋势。人口年增长率变化的最重要的人口驱动因素是移民。尽管依赖移民，当地人口不一定是一个汇，但可能是平衡分散系统的一部分。种群生存力分析表明，在 1992 年之后的 10 年中，种群因随机事件而灭绝的风险为零。然而，该种群在研究结束后的 6 年就灭绝了。唯一可以解释快速灭绝的人口机制是停止移民。由于伯劳的强烈分散，种群总是依赖于移民，并且由于物种的整体衰退而变得更加孤立。我们的结果表明，潜在移民的蓄水池可能已经不足以维持当地人口，并强调当地人口可以在不需要当地人口变化的情况下灭绝。成功保护与木头伯劳具有相似人口特征的鸟类种群需要关注显着超出当地尺度的空间尺度。我们的结果表明，潜在移民的蓄水池可能已经不足以维持当地人口，并强调当地人口可以在不需要当地人口变化的情况下灭绝。成功保护与木头伯劳具有相似人口特征的鸟类种群需要关注显着超出当地尺度的空间尺度。我们的结果表明，潜在移民的蓄水池可能已经不足以维持当地人口，并强调当地人口可以在不需要当地人口变化的情况下灭绝。成功保护与木头伯劳具有相似人口特征的鸟类种群需要关注显着超出当地尺度的空间尺度。

更新日期：2020-09-18

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