Unraveling a century of global change impacts on winter bird distributions in the eastern United States

• Published in: Global change biology Vol. 28; no. 7; pp. 2221 - 2235
• Main Authors: Saunders, Sarah P., Meehan, Timothy D., Michel, Nicole L., Bateman, Brooke L., DeLuca, William, Deppe, Jill L., Grand, Joanna, LeBaron, Geoffrey S., Taylor, Lotem, Westerkam, Henrik, Wu, Joanna X., Wilsey, Chad B.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.04.2022
• Subjects: Anthropogenic factors; Aquatic birds; Audubon Christmas Bird Count; Avifauna; Biodiversity; Bird impact; Birds; Climate Change; community science; Conservation; Ecosystem; Environmental changes; Grasslands; Habitat availability; Habitats; habitat‐constrained; Human influences; Land management; land‐use change; occurrence probability; Population Dynamics; Probability; Probability theory; Resilience; Seasons; Spatial variations; Species; Temporal variations; United States; Waterfowl; Winter; United States; United States > US; Audubon Christmas Bird Count; land-use change; habitat-constrained; occurrence probability; community science; climate change
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.16063

One of the most pressing questions in ecology and conservation centers on disentangling the relative impacts of concurrent global change drivers, climate and land‐use/land‐cover (LULC), on biodiversity. Yet studies that evaluate the effects of both drivers on species’ winter distributions remain scarce, hampering our ability to develop full‐annual‐cycle conservation strategies. Additionally, understanding how groups of species differentially respond to climate versus LULC change is vital for efforts to enhance bird community resilience to future environmental change. We analyzed long‐term changes in winter occurrence of 89 species across nine bird groups over a 90‐year period within the eastern United States using Audubon Christmas Bird Count (CBC) data. We estimated variation in occurrence probability of each group as a function of spatial and temporal variation in winter climate (minimum temperature, cumulative precipitation) and LULC (proportion of group‐specific and anthropogenic habitats within CBC circle). We reveal that spatial variation in bird occurrence probability was consistently explained by climate across all nine species groups. Conversely, LULC change explained more than twice the temporal variation (i.e., decadal changes) in bird occurrence probability than climate change on average across groups. This pattern was largely driven by habitat‐constrained species (e.g., grassland birds, waterbirds), whereas decadal changes in occurrence probabilities of habitat‐unconstrained species (e.g., forest passerines, mixed habitat birds) were equally explained by both climate and LULC changes over the last century. We conclude that climate has generally governed the winter occurrence of avifauna in space and time, while LULC change has played a pivotal role in driving distributional dynamics of species with limited and declining habitat availability. Effective land management will be critical for improving species’ resilience to climate change, especially during a season of relative resource scarcity and critical energetic trade‐offs. Using a 90‐year community science dataset comprising 89 species within nine habitat groups, we reveal that spatial changes in winter bird occurrence probabilities were consistently explained by climate, whereas temporal changes in bird occurrence over the last century were primarily associated with land‐use change, most prominently for habitat‐constrained species. We provide new evidence for the importance of land‐use change in shaping avian distributions, especially for grassland birds and waterbirds. Our findings advance our understanding of how concurrent global change drivers differentially affect avian groups, informing climate adaptation and habitat‐based conservation strategies during winter.