Year-round behavioural and ecological influences on the function and evolution of ornamental plumage in migratory birds

几个世纪以来，鸟类迁徙一直吸引着研究人员和自然历史学家，因为其规模之大和飞行距离之远令人难以置信。以北极燕鸥的跨大陆之旅为例，它们每年从北极北部的繁殖地飞到南极海域，往返行程近3万公里。然而，同样引人注目的是，24小时飞越墨西哥湾的小型红宝石喉蜂鸟。这些迁徙旅程在数量和持续时间上都是惊人的，每年有数十亿的个体旅行数千公里。对于研究候鸟的研究人员来说，一个主要的挑战是了解这些鸟类的进化和生态，尽管这种现象无处不在，但我们仍然对影响它们的生活史和繁殖期以外行为的因素知之甚少。事实上，我们对候鸟的认识绝大多数来自于对欧亚大陆和北美温带繁殖地的研究，很少有研究涉及候鸟的越冬和迁徙生态。然而，全年跟踪个体的新技术为未来研究候鸟的行为和生态提供了有希望的途径。例如，鸟类羽毛和爪子中的稳定同位素（C、N和H等元素的稳定形式，它们在环境中可预测地变化，并沿着食物链向上传播，最终被鸟类组织所吸收）可以帮助确定换羽的位置或鸟类过冬栖息地的质量。此外，背包式的设备，如光照定位器（附着在鸟类身上的记录环境光照水平的数据记录器），使研究人员能够估计每年旅程中单个的纬度和经度。在这项研究中，我的目的是研究在整个一年和跨大洲的候鸟彩色装饰羽毛的功能和演变。这项工作将首次将稳定同位素分析与光级地理定位器结合起来，研究整个年循环中发生的事件如何影响自由生活候鸟观赏羽毛颜色的演变。

Bird migration has captivated researchers and natural historians for centuries, both because of its sheer magnitude and the incredible distances travelled. Take, for instance, the trans-continental journey of the Arctic tern, who travels yearly from its breeding grounds in the Arctic north to the Antarctic seas - a round-trip journey of nearly 30,000 kilometers. No less remarkable, however, is 24-hour trans-Gulf of Mexico flight of the diminutive ruby-throated hummingbird. These migratory journeys are staggering in both number and duration, with billions of individuals traveling thousands of kilometers every year. For researchers studying migratory birds, a major challenge is understanding the evolution and ecology of these birds when, despite the vastness and ubiquity of the phenomenon, we still know little about the factors that influence their life history and behaviour outside of the breeding period. Indeed, the vast majority of our knowledge of migratory birds comes from studies conducted on the temperate breeding grounds in Eurasia and North America, with very few studies addressing the over-wintering and migratory ecology of migratory birds. Yet, new technologies for tracking individuals throughout the year offer promising avenues for future research on the behaviour and ecology of migratory birds. For example, stable-isotopes (stable forms of elements such as C, N, and H that vary predictably in the environment and travel up the food chain to be incorporated in bird tissues) in bird feathers and claws can help determine the location of moult or the quality of habitat a bird spent the winter in. Additionally, backpack-style devices, such as light-level geolocators (data loggers attached to the birds that record ambient light levels) are allowing researchers estimate individual latitude and longitude over the yearly journey. In this study, I aim to examine the function and evolution of colourful ornamental plumage in migratory birds throughout the year and across continents. This work will be the first to combine stable isotope analysis with light-level geolocators to study how events occurring throughout the annual cycle influence the evolution of ornamental plumage colouration in free-living migratory birds.