RSPB Centre for Conservation Science, The Royal Society for the Protection of Birds, Perth, UK.
British Antarctic Survey, Cambridge, UK.
J Anim Ecol. 2019 Jan;88(1):138-153. doi: 10.1111/1365-2656.12904. Epub 2018 Oct 23.
Habitat management to restore or create breeding sites may allow metapopulations to increase in size and reduce the risk of demographic stochasticity or disasters causing metapopulation extinction. However, if newly restored or created sites are of low quality, they may act as sinks that draw individuals away from better quality sites to the detriment of metapopulation size. Following intensive conservation effort, the metapopulation of roseate tern (Sterna dougallii) in NW Europe is recovering from a large crash in numbers, but most former colonies remain unoccupied and hence are potential targets for restoration. To inform conservation efforts, we studied the dynamics of this metapopulation with a multistate integrated population model to assess each of the three main colonies for important demographic contributors to population growth rate, source/sink status and possible density dependence. All three study colonies are managed for roseate terns (and other tern species) in similar ways, but the demographic processes vary considerably between colonies. The largest colony is a source involved in almost all dispersal, and its growth is determined by survival rates and productivity. Productivity and juvenile apparent survival at the largest colony appear to be density-dependent. Although the mechanisms are unclear, this may provide an increasing impetus for emigration of recruits to other colonies in future. The smallest of the three colonies is a sink, relying on immigration for its growth. Simulation models suggest the metapopulation would be c. 10% larger in the absence of dispersal to the sink colony. This work indicates that, due to variable site quality, aims to enhance both distribution and size of metapopulations may be mutually exclusive. In this case, before future attempts to encourage recolonisation of former sites, assessments of site suitability should be undertaken, focusing on food availability and isolation from predators to maximise the likelihood of attaining levels of productivity and survival that avoid creation of a sink population to the detriment of the overall metapopulation size.
栖息地管理可以恢复或创造繁殖地，从而使复合种群的规模得以扩大，并降低因种群随机性或灾害而灭绝的风险。然而，如果新恢复或创造的繁殖地质量较差，它们可能成为吸引个体离开优质繁殖地的汇，从而对复合种群的规模产生不利影响。经过密集的保护努力，西北欧的粉红斑嘴鸥（Sterna dougallii）复合种群数量已从大幅下降中恢复，但大多数以前的繁殖地仍然无人居住，因此是恢复的潜在目标。为了指导保护工作，我们使用多状态综合种群模型研究了这个复合种群的动态，以评估三个主要繁殖地对种群增长率、源/汇状态和可能的密度依赖性有重要贡献的重要种群动态。所有三个研究繁殖地都以类似的方式管理粉红斑嘴鸥（和其他燕鸥物种），但繁殖地之间的种群动态过程差异很大。最大的繁殖地是一个源地，几乎参与了所有的扩散过程，其增长取决于存活率和生产力。最大繁殖地的生产力和幼鸟的出现存活率似乎与密度有关。尽管机制尚不清楚，但这可能为未来的繁殖地提供越来越多的移民激励。三个繁殖地中最小的一个是一个汇，其增长依赖于移民。模拟模型表明，如果没有向汇繁殖地扩散，复合种群的规模将增加约 10%。这项工作表明，由于栖息地质量的变化，扩大复合种群的分布和规模的目标可能是相互排斥的。在这种情况下，在未来尝试鼓励以前的繁殖地重新定居之前，应该对繁殖地的适宜性进行评估，重点关注食物供应和与捕食者的隔离，以最大限度地提高实现生产力和存活率水平的可能性，避免因创建汇种群而对整个复合种群的规模产生不利影响。
