What mechanisms drive avian demographic and population responses to climatic change?

我们目前对气候变化对生物多样性影响的潜在机制的了解是初步的，阻碍了对这些影响的准确预测以及适当的适应和缓解。该项目的目的是确定气候变化对温带鸟类物种的影响的调节机制(S)。人口结构决定了人口趋势，从而最终决定了人们普遍预测的气候变化将导致的范围扩大和收缩。因此，迫切需要了解气候变化、人口结构和人口趋势之间的机械联系。到目前为止，在这一领域进行的研究主要集中在营养错配假说上，这一假说最常应用于鸟类。这表明，产卵日期没有与春季气温同步提前的物种可能会在食物可获得性达到峰值后繁殖，导致繁殖成功率降低，从而导致种群数量下降。相比之下，产卵期显著进步的物种预计繁殖成功率高，种群数量稳定或增加。营养错配假说经常被认为是对气候变化下鸟类种群趋势的有力解释。然而，令人惊讶的是，它只得到了对两种鸟类的研究支持。此外，替代的人口统计机制可以解释气候变化和人口趋势之间的联系。温带鸟类的繁殖季节受到严格的限制，如果繁殖较早，繁殖季节可能会延长，从而增加繁殖尝试的次数和繁殖成功的可能性，例如通过减少鸟巢被捕食事件的影响。在留鸟物种中，冬季死亡率经常调节种群大小，并可能通过气候改善而减少，从而产生种群增长。这一案例学生将对这些将气候变化与人口趋势联系起来的替代人口机制进行第一次严格的测试。它使用长尾山雀Aegithalos caudatus作为模型系统。这一物种是本研究的理想物种，因为它在产卵期表现出英国任何一种居住的小型雀形目动物中最显著的物候进步，它的种群正在迅速增加，它经历了很高的巢穴捕食率，在寒冷的天气里，冬天的死亡率很高。该项目结合了对国家和地方关于繁殖成功、存活和招募的长期数据集的分析，以及密集的局部田野工作，以确定气候诱导的繁殖物候变化、捕食抗性和冬季生存对种群规模的相对影响。对谢菲尔德附近的长尾山雀种群的深入研究将提供20年的种群生态和行为的详细数据(17年的数据将在学生开始时提供，另外3年的数据在学生期间整理)。由英国鸟类学信托(BTO)运营的国家计划，包括其响铃计划和Nest Record计划，将提供英国范围内的数据。BTO CASE合作伙伴在评估鸟类对环境变化的反应方面，无论是在种群趋势方面，还是在潜在的因果人口机制方面，都是全球公认的领导者。因此，BTO在人口参数和人口趋势的统计建模方面提供的培训增加了学生的实际价值。此外，作为一家独立的研究组织，BTO案例合作伙伴与自然保护和政界有着密切的联系，是促进知识转移的理想位置，从而最大限度地发挥此案例学生的结果的影响。

Our current understanding of the mechanisms underlying the impacts of climatic change on biodiversity is rudimentary, hindering the development of accurate predictions of these impacts, and appropriate adaptation and mitigation. The aim of this project is to determine the mechanism(s) through which the effects of climatic change on a temperate bird species are mediated. Demography determines population trends, and thus ultimately the range expansions and contractions that climate change is widely predicted to generate. Therefore, there is an urgent need to understand the mechanistic links between climatic change, demography and population trends. The research that has been conducted to date in this area has focused predominantly on the trophic mismatch hypothesis, which has most frequently been applied to birds. It suggests that species whose lay dates have not advanced at the same rate as spring temperatures are likely to breed after the peak in food availability, resulting in reduced reproductive success, and hence population declines. In contrast, species with marked advances in lay date are predicted to have high reproductive success and stable or increasing populations. The trophic mismatch hypothesis is frequently considered to provide a robust explanation for avian population trends in response to climatic change. Surprisingly, however, it receives support from studies of just two bird species. Moreover, alternative demographic mechanisms may explain associations between climatic change and population trends. Temperate bird species have tightly constrained breeding seasons, which may be lengthened by earlier reproduction, thus increasing the number of breeding attempts and the probability of breeding successfully, e.g. by reducing the impact of nest predation events. In resident bird species, winter mortality frequently regulates population size and is likely to be reduced by climatic amelioration thus generating population growth. This CASE studentship will provide the first rigorous test of these alternative demographic mechanisms linking climatic change with population trends. It uses the long-tailed tit Aegithalos caudatus as a model system. This species is ideal for this study as it exhibits the most marked phenological advance in lay date of any resident small passerine in the UK, its population is rapidly increasing, and it experiences high rates of nest predation and, in cold weather, winter mortality. The studentship combines analysis of national and local long-term datasets on breeding success, survival and recruitment, with intensive localised fieldwork to determine the relative effects of climate-induced changes in breeding phenology, predation resistance and winter survival on population size. Intensive study of a long-tailed tit population near Sheffield will provide 20 years of detailed data on population ecology and behaviour (17 years of data will be available when the studentship starts, with an additional 3 years of data collated during the studentship). The national schemes run by the British Trust for Ornithology (BTO), including its ringing programmes and nest record scheme, will provide data on a UK-wide scale. The BTO CASE partner is globally recognised as a world leader in assessing avian responses to environmental change, with regard to both population trends and the underlying causal demographic mechanisms. The training provided by the BTO in statistical modelling of demographic parameters and population trends thus adds real value to the studentship. Moreover, as an independent research organisation with close links to both the conservation and political communities the BTO CASE partner is ideally placed to facilitate knowledge transfer, thus maximising the impact of the results of this CASE studentship.