Recent changes in global temperatures have spurred significant interest in documenting ecological responses to climate change, with increased reliance on citizen science projects. Large, spatial data sets with long time series are rare, even for birds, but are increasingly critical for studying the role of modern climate change in driving range shifts. Citizen science efforts such as Audubon’s Christmas Bird Count and Breeding Bird Atlases have become invaluable for documenting changing distributions over broad spatial and temporal scales. Many of these broad-scaled surveys have been used to document poleward range shifts for numerous taxa across the world, providing some of the strongest evidence that species are responding to recent climate change. What characteristics of these programs have been most important for documenting range shifts in relation to climate change? What limitations do these programs impose on documenting ecological patterns, and what steps will be necessary to increase their usefulness in future research?

Results/Conclusions

We reviewed several landmark studies that used volunteer-collected data on species occurrences to quantify range shifts in relation to climate change.  We found that volunteer-based surveys, such as atlases, offer a number of advantages including the ability to quantify range boundaries, account for large changes in overall distribution, and track range changes over long time periods. Several challenges remain, however, and few studies account for imperfect detection probabilities, link species distributions with climate data, and incorporate ancillary data (e.g., land-use change). To demonstrate the possibilities of addressing these challenges, we present recent research that combines occupancy modeling and estimation, new daily models of climatic variation, and data from Project FeederWatch (a long-term, national survey of wintering birds that visit feeders). We examined the relationship between climatic variation and bird detectability and distribution for over 3,000 sampling stations across the northeastern United States and Canada. For 18 bird species, we found wintering bird detectability was influenced by daily deviations in minimum temperature and sampling effort by program participants. At regional scales, winter-long gradients of minimum temperature were strong limiting factors for many birds such as Carolina Wren and Song Sparrow. Quantifying the dynamic relationship between species distributions and temperature, while accounting for imperfect detectability, is of critical importance in elucidating the effects of climate change on species ranges.