Vegetation structure shapes occupancy patterns of specialist and non-specialist birds in xerophytic woodlands

Dry forests and woodlands are valuable yet fragile ecosystems prone to rapid degradation and structural simplification by overuse, including livestock grazing, fire, and logging. In these systems, forest birds depend on vegetation structural complexity to meet key foraging and breeding needs, making them sensitive indicators of habitat condition. We assessed bird occupancy in the Espinal woodlands of east-central Argentina, testing whether assemblage- and species level occupancy patterns of woodland specialists’ and non-woodland birds were related to vegetation structure and mediated by habitat affinity. Using a hierarchical occupancy model under Bayesian framework, we found that woodland specialists were associated with sites featuring closed canopies and larger trees, whereas non- woodland (disturbance-tolerant) species were more frequent open and structurally simplified woodlands. Increasing degradation—characterized by smaller trees, reduced canopy cover, and increased shrub encroachment— drove shifts from specialist-dominated assemblages toward those dominated by non-woodland (open-areas and shrubland) species. Several common woodland species showed consistent associations with well-preserved dense woodlands or with mature but more open stands, supporting their potential use as indicators of woodland condition. Although maintaining high canopy cover and large trees is essential for conserving disturbance-sensitive woodland bird assemblages, some insectivorous species restricted to xerophytic woodlands preferred mature stands with open understories, underscoring the importance of structural heterogeneity. Our results highlight the value of detectability-corrected occupancy modeling for identifying assemblage- and species-level responses to woodland degradation and for guiding conservation-oriented management in livestock-grazed dry woodlands.