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

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

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.