Precipitation and winter temperature predict long‐term range‐scale abundance changes in Western North American birds

Abstract

Predicting biodiversity responses to climate change remains a difficult challenge, especially in climatically complex regions where precipitation is a limiting factor. Though statistical climatic envelope models are frequently used to project future scenarios for species distributions under climate change, these models are rarely tested using empirical data. We used long-term data on bird distributions and abundance covering five states in the western US and in the Canadian province of British Columbia to test the capacity of statistical models to predict temporal changes in bird populations over a 32-year period. Using boosted regression trees, we built presence-absence and abundance models that related the presence and abundance of 132 bird species to spatial variation in climatic conditions. Presence/ absence models built using 1970-1974 data forecast the distributions of the majority of species in the later time period, 1998-2002 (mean AUC = 0.79 AE 0.01). Hindcast models performed equivalently (mean AUC = 0.82 AE 0.01). Correlations between observed and predicted abundances were also statistically significant for most species (forecast mean Spearman 0 s q = 0.34 AE 0.02, hindcast = 0.39 AE 0.02). The most stringent test is to test predicted changes in geographic patterns through time. Observed changes in abundance patterns were significantly positively correlated with those predicted for 59% of species (mean Spearman 0 s q = 0.28 AE 0.02, across all species). Three precipitation variables (for the wettest month, breeding season, and driest month) and minimum temperature of the coldest month were the most important predictors of bird distributions and abundances in this region, and hence of abundance changes through time. Our results suggest that models describing associations between climatic variables and abundance patterns can predict changes through time for some species, and that changes in precipitation and winter temperature appear to have already driven shifts in the geographic patterns of abundance of bird populations in western North America.

Species‐specific and temporal scale‐dependent responses of birds to drought

“…We found strong spatial autocorrelation for each drought index but minimal spatial autocorrelation of model residuals, both of which are consistent with other studies that have investigated weather or climate impacts on wildlife (e.g., Albright, Pidgeon, Rittenhouse, Clayton, Wardlow, et al, 2010;Illán et al, 2014). We found strong spatial autocorrelation for each drought index but minimal spatial autocorrelation of model residuals, both of which are consistent with other studies that have investigated weather or climate impacts on wildlife (e.g., Albright, Pidgeon, Rittenhouse, Clayton, Wardlow, et al, 2010;Illán et al, 2014).…”

“…Previous studies have also tended to focus on raw climatic variables to assess bird responses to precipitation variability (e.g., Bateman et al, 2016;Illán et al, 2014). However, using metrics that more comprehensively capture deviations from average moisture conditions, such as the Standardized Precipitation Evapotranspiration Index ("SPEI"), may also reveal important patterns.…”

Consistent response of bird populations to climate change on two continents

“…A growing body of evidence also suggests that morphological changes are a common response to altered climates (7,8). However, despite some clear cases of climate-caused alterations of local population dynamics (9,10), multi-species, large-scale analyses of population responses to global climate change are rare (11,12).…”

The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs)

“…Therefore, precipitation can affect bird populations directly through the survival of offspring [77,78], indirectly changing the abundance or availability of invertebrates [28], flowering and fruiting of plant species, and through their impact on the vegetation structure [79]. Illán [80] studied birds of western North America, and highlighted that precipitation was one of the main determinants in the distribution patterns of land birds. Sousa et al [81] studied birds in the Catimbau National park (Caatinga area) and found strong difference between the richness of birds between the dry and the rainy seasons.…”