Post-fire successional effects on breeding grassland birds in mesquite savanna habitats of the Texas rolling plains

摘要

North American grasslands and grassland birds have declined drastically due tohabitat degradation by fire suppression (i.e., woody encroachment), fragmentation, andconversion to croplands. A better understanding is needed of the relationships amongdisturbance regimes (e.g., fire), resultant vegetation changes, and grassland birdcommunities to effectively manage remaining grasslands and grassland birds. I assessedthe relationship between post-fire succession, and mean relative abundance and nestingecology of breeding grassland birds (i.e., nest-site selection and nest success) inmesquite-dominated rangeland of the Texas Rolling Plains, where prescribed fire is usedas a tool to manage shrub encroachment. Brush cover, grass cover, and visualobstruction generally increased with post-fire succession, and bare ground decreasedwith post-fire succession. Species richness, grasshopper sparrows (Ammodramussavannarum), Cassin??????s sparrows (Aimophila cassinii), and dickcissels (Spiza americana)responded positively to post-fire succession, and lark sparrows (Chondestes grammacus)responded negatively to post-fire succession.; abundance of these avian groups was lowon the control sites. During 2004??????2005, 90 grassland bird nests were monitored. Ifound conflicting results for vegetation parameters important to nest site selection and probability of nest success. For all species except lark sparrows, nest-site location waspositively associated with visual obstruction and with grass or forb cover. However, theprobability of nest success increased with lower visual obstruction, bare ground cover, orgrass cover. Grassland bird abundance, nest-site location, and nest success had differingassociations with vegetation variables. These results suggest that to effectively manageremaining grasslands for sustainable breeding grassland bird populations, managersshould engage in practices that keep habitat in multiple vegetative successional stages.