Influences of spatial variation in vegetation on avian richness and abundance vary by season in the Chihuahuan Desert

Changes in the structure, composition, and distribution of desert vegetation have resulted in altered desert bird communities. One of the most well-known influences on bird diversity and abundance in these ecosystems is the degree of woody shrub dominance. While the influence of vegetation structure and composition gradients on Chihuahuan Desert bird communities of North America has received valuable attention, seasonal variation in these influences is poorly understood. Our goal was to understand how vegetation gradients across space influence bird communities over four seasonal periods. We employed three years of avian survey data and static, spatial vegetation data in generalized linear mixed-effects models, identifying effects of (1) shrub cover in predicting shrubland bird species richness and abundance, (2) grass cover in predicting grassland bird abundance, and (3) grass height in predicting grassland and shrubland species richness and abundance. Effect sizes varied by season, with grass heights exhibiting (1) greatest positive effects on grassland species in the breeding season and (2) greatest negative effects on shrubland species in the winter. In targeting management for birds of the Chihuahuan Desert and other arid regions, managers should consider both bird-habitat associations and the variation in these relationships between seasons.