Effects of migratory bird species on functional diversity in Mato Grosso do Sul, center-western Brazil

The ecological effect on the functional diversity of migrant birds in Neotropical habitats is poorly understood. So, the aim of this study is to investigate functional diversity differences of resident and migratory bird species. Hence, we assess trait space occupancy differences in resident and migrant bird species across three Mato Grosso do Sul (MS) state habitats. Using the MS bird checklist and literature data, we categorized migratory species into three groups based on their habitat associations: aquatic, forest, and non-forest. We utilized 26 functional traits, grouped into three categories (morphological traits, diet composition, and foraging forest stratum preference), to assess the functional diversity in habitat dependency groups. Calculating functional richness and functional dispersion for each habitat dependency group, along with the functional beta diversity between resident and migratory species, we found that migratory birds add new traits to aquatic groups, showing high functional turnover. Conversely, the forest and non-forest groups showed greater nestedness, indicating greater functional redundancy between migratory and resident species in these habitats. Migratory and resident groups exhibited higher overlap in functional volume in forest and non-forest habitats but show minimal overlap in aquatic habitats. This suggests that the effect of migratory species should be higher in aquatic habitats of MS because they add considerable variation in functional traits, which do not exist in the resident species. In conclusion, our study underscores the importance of preserving MS wetlands, particularly the Pantanal and the upper Paraná River floodplains, for the conservation of aquatic migratory species and their ecological role.