Data and Code for "Drought Influences Habitat Associations and Abundances of Birds in California's Central Valley"

As climate change increases the frequency and severity of droughts in many regions, conservation during drought is becoming a major challenge for ecologists. Droughts are multidimensional climate events whose impacts may be moderated by changes in temperature, water availability, or food availability, or some combination of these. Simultaneously, other stressors such as extensive anthropogenic landscape modification may synergize with drought. Useful observational models for guiding conservation decision-making during drought require multidimensional, dynamic representations to disentangle possible drought impacts, and consequently they will require large, highly resolved data sets. In this paper, we develop a multi-model predictive framework for assessing how drought impacts vary with species, habitats, and climate pathways. We found that while fewer than a quarter (16/66) of species experienced abundance declines during drought, nearly half of all species (27/66) changed their habitat associations during drought. Among species that shifted their habitat associations, use of natural habitats declined during drought while use of developed habitat and perennial agricultural habitat increased. Our findings suggest that birds take advantage of agricultural and developed land with artificial irrigation and heat-buffering microhabitat structure, such as in orchards or parks, to buffer drought impacts. A working lands approach that promotes biodiversity and mitigates stressors across a human-induced water gradient will be critical for conserving birds during drought.

Methods
We used a multi-model counterfactual analysis combining predictive linear mixed models and N-mixture models to characterize the multidimensional impacts of drought on 66 bird species. We analyzed counts from the eBird participatory science dataset between 2010 and 2019 and produced species, as well as habitat-specific estimates of the impact of drought on relative abundance.