Drought influences habitat associations and abundances of birds in California's Central Valley

Aim

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 two-stage predictive framework for assessing how drought impacts vary with species, habitats and climate pathways.

Location

Central Valley, California, USA.

Methods

We used a two-stage counterfactual analysis combining predictive linear mixed models and N-mixture models to characterize the multidimensional impacts of drought on 66 bird species. We analysed counts from the eBird participatory science data set between 2010 and 2019 and produced species- and habitat-specific estimates of the impact of drought on relative abundance.

Results

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, the use of natural habitats declined during drought while use of developed habitat and perennial agricultural habitat increased.

Main Conclusions

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.