Behavioral and Physiological Differences in Migratory Strageties of a Long-distance Migrant, the Blackpoll Warbler, and a Facultative Short-distance Migrant, the Yellow-rumped Warb

候鸟在途中就何时何地休息和补充能量储备做出选择，通常是在它们以前从未去过的地区，而且是在食物和天气可能不可预测的时候。它们在良好条件下及时到达目的地的能力可能会影响它们获得最佳越冬或繁殖区域的机会，从而影响它们的生存或繁殖成功。黑角莺，Dendroica straiata，在准备穿越北大西洋前往南美洲过冬时，几乎将其体重增加了一倍，脂肪储备也增加了一倍。该物种已被发现在迁徙过程中体重减少率最低。这表明它们比许多其他鸟类更有效地利用脂肪，并能腾出骨骼肌作为能量储备。相比之下，黄腹林莺Dendroica coronata在繁殖地上与黑斑林莺重叠，但它是一种短途迁徙(主要是陆路迁徙)，不会拥有如此广泛的脂肪储备。这项研究的重点是调查这两种林莺在行为和生理上的差异，以反映它们不同的迁徙能量需求。在这个项目中，主要强调皮质酮和相关代谢物在控制食物摄入量和脂肪储备方面的作用。一系列的实验室和野外研究将调查这两个物种皮质酮分泌模式的可能差异，这可能反映出它们不同的育肥模式，以及它们在迁徙过程中各自保护骨骼肌的需要。在实验室研究中，PIS将调查皮质酮在调节鸟类能量需求的季节性变化方面具有多种作用的可能性，以及这两个物种对皮质酮对肥育和肌肉蛋白质利用的影响可能具有不同的阈值。通过了解具有不同能量需求的鸟类如何在最佳条件下进化来应对迁徙的挑战。我们将对鸟类在天气和栖息地质量等条件恶化时的行为和生理限制有更多的了解。该项目的结果可能说明迁徙期间遇到的环境因素如何影响整个年度周期中的鸟类数量。

Migrating birds make choices en route about where and when to rest and replenish energy reserves, often in areas they have never visited before and at a time when food and weather may be unpredictable. Their ability to reach their destinations in good condition and in a timely manner can influence their chances of gettting the best wintering or breeding territories and, thus, influence their survivorship or reproductive sucess. The Blackpoll Warbler, Dendroica straiata, almost doubles its body mass with fat reserves as it prepares for a trans-oceanic migration over the North Atlantic to winter in South America. This species has been found to have the lowest rate of weight loss during migration. This suggest that they use fat more efficiently and can spare skeletal muscle for use as energy reserves longer than many other birds. In contrast, while the Yellow-rumped warbler, Dendroica coronata, overlaps with the Blackpoll warbler on its breeding grounds, it is a short-distance migrant (primarily overland) and does not put on such extensive fat reserves. The focus of this study is to investigate differences in the behavior and phsiology of these two species of warblers that reflect their different energetic demands of migration. In this project, the primary emphasis is on the role of corticosterone and related metabolites in controlling food intake and fat reserves. A series of laboratory and field studies will investigate possible differences in patterns of corticosterone secreation in these two species that may reflect their different patterns of fattening and their respective need to protect skeletal muscle during migration. In laboratory studies, the PIs will investigate the possibility that corticosterone has multiple roles in regulating the seasonal changes in energy demand in birds and that these two species may have different threshold for corticosterone's effects on fattening and muscle protein utilization. By understanding how birds with different energetic demands have evolved to meet the challenges of migration under optimal conditions. we will have a greater understanding of the behavioral and physiological constraints of birds when conditions such as weather and habitat quality deteriorate. The results from this project may illustrate how environmental factors encountered during the migratory period may impact bird populations throughout the annual cycle.