DISSERTATION RESEARCH: Making the transition: Comparing avian biogeographic responses to climate change across biomes

该项目将研究气候变暖对莫哈韦、索诺兰和大盆地沙漠鸟类群落的影响。这些沙漠有不同的气候、植被和动物群落，在过去的50年里，它们都经历了逐渐变暖的气温。这项研究将利用一个独特的资源：在当前变暖开始之前，从1904年到1945年发生的沙漠动物的系统计数。这些调查提供了在人为引起的生态变化之前对沙漠生态系统健康的早期看法。对大盆地30个地点和莫哈韦69个地点的重新调查将提供关于目前100多种鸟类丰度的数据。这项研究将评估持续变暖的索诺兰和莫哈韦沙漠的物种是否正在向变暖较少的大盆地沙漠扩张，或者两种沙漠之间的区域是否成为物种从一种向另一种扩张的障碍。这项研究还将增加关于个别物种的地理分布范围如何应对气候变化的知识，方法是确定物种是否独立地改变其分布范围，从而导致鸟类群落的重新洗牌，或者物种是否作出类似的反应，从而导致整个物种集合一起改变其分布范围。（西南沙漠），利用独特的历史资源（格林内尔时代的调查），允许在大的空间尺度上检查殖民和灭绝过程，这项研究将量化20世纪世纪变暖和干旱对鸟类地理分布的影响。在气候显著变暖之前最初访问的大盆地沙漠30个地点的鸟类重新调查将补充莫哈韦沙漠69个沙漠地点的重新调查，其南部与索诺兰的过渡，以及其北方与大盆地沙漠的过渡。本研究探讨了鸟类群落结构如何随着时间和空间的变化，在温暖的（索诺兰和莫哈韦）和寒冷的（大盆地）沙漠，以及如何沙漠之间的过渡区影响地理对气候变化的反应。了解莫哈韦-大盆地过渡区的分布变化将有助于评估温暖沙漠的物种是否正在向寒冷沙漠扩张，或者过渡区是否是向北扩张的障碍。如果温暖沙漠物种的南部界限也在收缩，鸟类向北扩张的障碍可能导致范围崩溃。

This project will examine the impact of warming climate on bird communities in the Mojave, Sonoran, and Great Basin Deserts. These deserts have different climates, vegetation, and animal communities, and all have experienced gradually warmer temperatures over the last fifty years. This study will make use of a unique resource: systematic counts of desert animals that occurred from 1904 to 1945, before the onset of current warming. These surveys provide an early view of desert ecosystem health prior to human-caused ecological changes. Re-surveys at 30 sites across the Great Basin and 69 sites across the Mojave will provide data on the current abundance of over 100 bird species. This study will evaluate whether species of the Sonoran and Mojave deserts, which continue to warm, are expanding into the Great Basin desert, which as warmed less, or whether the area between the two types of deserts acts as a barrier to expansion of species from one to the other. This study will also increase knowledge of how the geographic ranges of individual species respond to climate change by determining if species shift their ranges independently, resulting in a reshuffling of bird communities, or if species respond similarly, resulting in entire sets of species moving their ranges together.In a climate change hotspot (the desert southwest), using a unique historical resource (Grinnell-era surveys) that allows examination of colonization and extinction processes at a large spatial scale, this study will quantify how rapid 20th century warming and drying influence avian biogeographic distributions. Avian re-surveys at 30 sites in the Great Basin deserts originally visited prior to significant climate warming will complement re-surveys at 69 desert sites in the Mojave Desert, its southern transition with the Sonoran, and its northern transition with the Great Basin desert. This study examines how avian community structure varies over time and space across warm (Sonoran and Mojave) and cold (Great Basin) deserts, and how the transition zone between the deserts impacts the biogeographic response to climate change. Understanding distributional change at the Mojave-Great Basin transition zone will enable the evaluation of whether species of the warm deserts are expanding into the cold desert, or whether the transition zone is a barrier to northward expansion. Barriers to northward expansion for birds could result in range collapse if the southern limits of warm desert species are also contracting.