Short-term winners, long-term losers: Habitat affinity and successional trajectories shape avian persistence in burned piñon-juniper woodlands

Abstract

Increased fire activity driven by climate change and land use legacies has led to habitat conversion across the American Southwest, with significant implications for forest-dependent birds. Piñon-juniper woodlands on the Mesa Verde cuesta in southwest Colorado have experienced repeat, high-severity fires in recent decades, and current monitoring suggests limited woodland regeneration. We assessed (1) how vegetation structure and composition vary across three burn scenarios (unburned, newly burned, and old burn), (2) which aspects of vegetation and fire history influence avian species densities, and (3) how predicted densities differ between piñon-juniper specialists and the broader breeding community in post-fire habitats. We modeled 2022–2023 breeding season densities for 26 species using Bayesian N-mixture models and habitat covariates derived from aerial LiDAR and Landsat 8 satellite imagery. Canopy cover, vegetation height, and deciduousness differed significantly between unburned and burned sites. Low vegetation cover and height and high deciduousness persisted for decades after fire, suggesting shrub-dominance over woodland recovery. Positive supported responses to vegetation cover and height were concentrated among piñon-juniper specialists and forest-associated generalists, while associations with deciduousness were most common among species reliant on diverse vegetation structure, including shrub-nesters and insectivores. Most (67%) piñon-juniper specialists showed decreased densities in newly burned habitat, likely driven by mature woodland loss, while most (82%) non-specialists either increased or remained stable up to two decades post-fire. However, this flexibility did not always persist; 38% of all species showed significantly lower predicted densities in old burn habitat than in unburned, suggesting that contemporary long-term succession in burned piñon-juniper landscapes supports neither woodland obligates nor the broader breeding bird assemblage at pre-fire densities. In a system constrained by limited post-fire regeneration capacity, these findings underscore the need for proactive management, including conservation of remaining old-growth piñon-juniper, to support bird communities under novel fire regimes.