Evidence of the effects of climate change on landbirds in western North America: A review and recommendations for future research

Abstract

To evaluate the effects of climate change on landbirds in western North America, we reviewed the published literature on changes in avian phenology, geographic distribution, morphology, physiology, and population size that have been linked to climate change in the region. Despite a large literature on the projected effects of climate change, we found surprisingly few published papers that evaluated effects already observed on western North American landbirds. The topic that has received the most attention is the phenology of migration and reproduction. However, researchers have demonstrated consistent patterns of phenological change in fewer than 10 of the region's species. Similarly, shifts in the elevational distribution of birds have not been consistent with the expectation that climate change will cause species to shift upward in elevation. Demonstrable effects of climate change, or in some cases lack thereof, will improve future projections of its effects and efforts toward conservation. Some data from which changes can be evaluated are already available. Our review demonstrates that there is still a very real need to understand how climate change is already affecting landbirds in western North America.