Influence of habitat structure and spatial configuration on bird abundance in wet grassland patches

Understanding how habitat structure and spatial configuration jointly influence species abundance is critical for conserving grassland birds in fragmented landscapes. We evaluated the effects of within-patch habitat structure and patch- and landscape-scale attributes on bird abundance in wet grassland patches ranging from 3,350 to 160,207 m², embedded within natural rangelands managed under extensive livestock grazing in southern Brazil. Using complete-coverage surveys of 60 patches, we modelled abundance for 46 species across five ecological guilds, relating species-specific counts to fine-scale habitat cover, patch area, shape, isolation, and surrounding habitat amount. Within-patch habitat structure emerged as the strongest and most consistent correlate of abundance, with bog vegetation and tall graminoid cover being the most frequently retained positive predictors. Among patch- and landscape-scale predictors, patch area showed uniformly positive effects across guilds, whereas isolation, patch shape, and habitat amount in the surrounding landscape had weaker and more heterogeneous influences. Responses were guild-dependent: bog- and shrub-associated species showed the strongest relationships with internal habitat structure and patch area, while open-country generalists responded weakly or inconsistently. Landscape-scale habitat amount provided limited explanatory power beyond patch attributes. Our results highlight the importance of patch size and internal structural integrity in shaping wet-grassland bird assemblages, whereas broader landscape configuration played a comparatively minor role. Conservation strategies should therefore prioritize the maintenance of large wet-grassland patches with bog vegetation and tall graminoid structure within predominantly natural grassland mosaics under extensive livestock use.