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减缓。该项目的目的是确定气候变化对温带鸟类影响的机制。人口统计学决定了人口趋势，并最终决定了人们普遍预测的气候变化将产生的范围扩张和收缩。因此，迫切需要了解气候变化、人口和人口趋势之间的机械联系。迄今为止，在这一领域进行的研究主要集中在营养失配假说上，该假说最常应用于鸟类。这表明，那些产卵日期没有以与春季温度相同的速度提前的物种很可能在食物供应高峰之后繁殖，导致繁殖成功率降低，因此人口下降。相比之下，在奠定日期的显着进步的物种预测有很高的繁殖成功率和稳定或不断增加的人口。营养不匹配假说经常被认为是鸟类种群趋势对气候变化的反应提供了一个强有力的解释。然而，令人惊讶的是，它只得到了两种鸟类研究的支持。此外，其他人口机制可以解释气候变化与人口趋势之间的联系。温带鸟类有严格限制的繁殖季节，这可能会延长较早的繁殖，从而增加繁殖尝试的数量和繁殖成功的概率，例如通过减少巢捕食事件的影响。在留鸟种，冬季死亡率经常调节人口规模，并可能减少气候改善，从而产生人口增长。这个案例奖学金将为这些将气候变化与人口趋势联系起来的替代人口机制提供第一次严格的测试。它使用长尾山雀Aegithalos caudatus作为模型系统。这个物种是理想的这项研究，因为它表现出最显着的物候提前奠定日期的任何居民小雀形目在英国，它的人口正在迅速增加，它经历了高利率的巢捕食，在寒冷的天气，冬季死亡率。该奖学金结合了对国家和地方长期数据集的分析，包括育种成功，生存和招募，以及密集的本地化实地考察，以确定气候引起的育种物候，捕食抗性和冬季生存变化对种群规模的相对影响。对谢菲尔德附近长尾山雀种群的深入研究将提供20年关于种群生态学和行为的详细数据（17年的数据将在学生开始时提供，另外3年的数据将在学生期间整理）。由英国鸟类学信托基金会（BTO）管理的国家计划，包括其振铃计划和鸟巢记录计划，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，无论是在人口趋势还是在潜在的因果人口机制方面，都是全球公认的世界领导者。因此，毛里求斯统计局提供的关于人口参数和人口趋势统计模型的培训增加了奖学金的真实的价值。此外，作为一个独立的研究组织，与保护和政治社区的BTO CASE合作伙伴有着密切的联系，非常适合促进知识转移，从而最大限度地发挥CASE学生奖学金结果的影响。

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.