Tens of millions of landbirds migrate through western North America each spring and fall, where they rely on spatially and temporally restricted resources to fuel their journeys. En route migrants face increasing uncertainty in habitat and resource availability as human-associated landscape changes continue through such activities as urbanization, agriculture, livestock grazing, and water management. In addition, projected changes in global climate will intensify the existing uncertainties faced by migrants as the resources upon which they depend are redistributed in space and time. Protection of migratory birds requires a better understanding of the process of migration itself, and the last decade has witnessed a proliferation in research that has yielded significant progress in understanding migration patterns of North American birds. In a recent article in The Condor, USGS scientists Barbara Kus, Susan Skagen, and Charles van Riper III collaborated with Jay Carlisle of the Idaho Bird Observatory, Kristin Paxton of the University of Southern Mississippi, and Jeff Kelly at the University of Oklahoma to review and briefly synthesize the latest avian migration findings and advances and consider research needs to guide future research on migration in the West.

Recognition is growing that migration is likely the most limiting time of year for migratory birds, and this places increasing importance on continuing to decipher patterns of stopover ecology, identifying critical stopover habitats, and documenting migration routes in the diverse and changing landscapes of the American West. Expanded use of techniques such as radar, plasma metabolites, mist-netting, count surveys, stable isotopes, genetic data, and animal tracking, coupled with an increase in multi-investigator collaborations, have all contributed to a growth of knowledge regarding western migrants. Many questions remain, however, including: What is the impact of environmental change on migratory life histories? In particular, what are the effects of land use and climate change? What are the drivers of population dynamics in migratory animals? What are the determinants of behavioral plasticity in migrants and what are the constraints on behavioral adaptation? The answers to these and other priority questions will be essential for guiding management to effectively prepare for and respond to environmental change.

Management Implications

• Coordinated efforts to protect migrants will rely on an understanding of the roles that specific habitats throughout the western hemisphere play in the annual cycles of migratory species. Targeting species, habitats, or sites for conservation action will be most effective when informed by research allowing prioritization of such actions based on relative need and expected benefits to birds.
• As our understanding of the interconnectedness among different stages of the annual cycle grows, so too will the need for international partnerships to protect migratory birds throughout their ranges.
• How migratory birds will respond to the rapid rate of current and future climate change poses an unprecedented challenge to our ability to protect birds and the habitats upon which they depend. The use of climate models to understand the scope and nature (e.g., negative, positive, or neutral) of effects of climate change on bird populations and to delineate ways to mitigate for and adapt to this far-reaching challenge is a high priority need.

Carlisle, J. D., S. K. Skagen, B. E. Kus, C. van Riper III, K. L. Paxton, and J. F. Kelly. 2009. Landbird migration in the American west: Recent progress and future research directions. Condor 111:211–225.

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