Carry-over effects and the dynamics of migratory bird populations

候鸟数量的长期下降重新引起了人们的兴趣，即候鸟种群受其繁殖地、越冬区或迁徙事件的影响最大。一些研究表明，繁殖地发生的事件可能足以解释长期的下降，但另一些研究表明，越冬地区的事件对候鸟数量的影响更大。最近的研究还表明，越冬地发生的事件可以延续到繁殖季节，并影响个体繁殖成功和繁殖地种群的动态。由于我们无法在整个年度周期中跟踪个体，以及缺乏关于越冬和繁殖地之间联系的信息，对结转影响的重要性的调查一直受到阻碍。然而，最近的技术进步使得能够检查迁徙的连通性，并更详细地调查繁殖地和越冬地的事件如何影响种群。我们将使用无线电遥测和羽毛的稳定同位素分析来研究冬季和繁殖地是如何联系在一起的，并评估留存效应对短途高度候鸟(美洲北斗星)和长途新热带候鸟(黄莺)种群动态的重要性。具体地说，我们将，1)询问天气、食物供应和越冬地的密度如何影响迁徙的时间和持续时间、开始繁殖和迁徙的年生产力；2)评估气候条件和冬季栖息地的使用变化如何影响加拿大西部(不列颠哥伦比亚省的雷弗斯托克和西北部的因努维克)繁殖的黄莺的到达时间、条件和繁殖成功；以及3)使用种群模型来评估留存效应对候鸟种群的重要性。这项研究将评估结转效应的重要性，并有助于我们了解气候变化和越冬地栖息地的丧失将如何影响候鸟数量。

Long-term declines in the abundance of migratory birds have led to renewed interest in whether migratory bird populations are most affected by events on their breeding grounds, on wintering areas or on migration. Some studies suggest that events on breeding grounds may be sufficient to explain long term declines but others show that events in wintering areas have greater impacts on migratory bird populations. Recent studies have also demonstrated that events on wintering grounds can carry over into the breeding season and influence individual reproductive success and the dynamics of populations on breeding grounds. Investigation of the importance of carry-over effects has been hampered by our inability to follow individuals throughout the annual cycle and the lack of information on the links between wintering and breeding grounds. However, recent technological advances allow examination of migratory connectivity and more detailed investigation of how events on both breeding and wintering grounds influence populations. We will use radiotelemetry and stable isotope analyses of feathers to investigate how winter and breeding grounds are linked, and evaluate the importance of carry-over effects for the population dynamics of a short-distance altitudinal migrant (the American Dipper) and a long-distance neotropical migrant (the Yellow Warbler). Specifically, we will, 1) ask how weather, food availability and density on wintering grounds influence the timing and duration of migration, the onset of breeding and annual productivity of migratory dippers, 2) evaluate how variation in climatic conditions and winter habitat use influence the arrival times, condition and reproductive success of yellow warblers breeding in western Canada (Revelstoke, BC and Inuvik, NWT), and 3) use population models to assess the importance of carry over effects for migratory bird populations. This research will evaluate the importance of carry-over effects and contribute to our understanding of how climate change and habitat loss on wintering grounds will influence populations of migratory birds.