Research in motion: patterns of large-scale migration in dragonflies and birds
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The work I present here can be broadly described as focusing on the spatial, temporal, and ecological basis to patterns of movement by highly vagile organisms. From this perspective, the differences between chapters are matters of scale: community versus population ecology, and movement by thousands of birds through two localities versus a study of a single invertebrate species crossing North America. Animal movement over large scales has proven difficult to study throughout the history of biology. Proximal challenges have largely reflected practical problems with observing spatial displacement in individual organisms. Population-level evolutionary and ecological analyses -- ultimate explanations for movement -- depend on solutions to those proximal challenges. Here, I have tried to interweave both proximal and ultimate approaches. Large-scale movement also presents challenges from a conservation perspective. The conservation implications of the final chapter are immediately applicable to avian researchers and resource managers. In contrast, understanding why and how Anax junius Drury (Odonata: Aeshnidae) is moving across North America does not have such direct conservation implications. The species is not endangered, nor have threats to its range or behavior been suggested. My interest instead grew from the need for a model system to explore aquatic invertebrate conservation as well as the practical difficulties of studying long-distance migrants of all kinds, invertebrate and vertebrate. These chapters thus form a whole through their focus on determining how and why organisms move over large spatial scales and the connection of that behavior to habitat. Many species move great distances during individual lifetimes. Threats from land-use change, habitat fragmentation, and climate shifts will all have -- are already having -- impacts on many species. We need accurate, inexpensive, and effective tools to be able to count, compare, detect, define, delineate, and explain patterns of movement. I have endeavored to improve a few of these tools and, if possible, provide a few new examples and explanations grounding that movement.