Elevation and landscape change drive the distribution of a montane, endemic grassland bird. Issue 14 (6th July 2020) - Lele, Abhimanyu
Abstract: Context: Tropical montane habitats support high biodiversity and are hotspots of endemism, with grasslands being integral components of many such landscapes. The montane grasslands of the Western Ghats have seen extensive land‐use change over anthropogenic timescales. The factors influencing the ability of grassland‐dependent species to persist in habitats experiencing loss and fragmentation, particularly in montane grasslands, are poorly known. Objectives: We studied the relationship between the Nilgiri pipit Anthus nilghiriensis, a threatened endemic bird that typifies these montane grasslands, and its habitat, across most of its global distribution. We examined what habitat features make remnant grasslands viable, which is necessary for their effective management. Methods: We conducted 663 surveys in 170 sites and used both single‐season occupancy modeling and N ‐mixture modeling to account for processes influencing detection, presence, and abundance. Results: Elevation had a positive influence on species presence, patch size had a moderate positive influence, and patch isolation had a moderate negative influence. Species abundance was positively influenced by elevation and characteristics related to habitat structure, and negatively influenced by the presence of invasive woody vegetation. Conclusions: The strong effect of elevation on the highly range‐restricted Nilgiri pipit is likely to make it vulnerable to climate change. This highly range‐restricted species is locally extinct at several locations, and persists at low densities in remnants of its habitat left by recent fragmentation. Our findings indicate a need to control and reverse the spread of exotic woody invasives to preserve the grasslands themselves and the specialist species dependent upon them. Abstract : The montane grassland ecosystem of the Indian Western Ghats is experiencing severe anthropogenic threats. We examined factors influencing the occupancy and abundance of the Nilgiri pipit, endemic to these grasslands. We found that the presence and abundance of the species are strongly shaped by elevation, making it vulnerable to climate change, and is also shaped by landscape change, including invasive woody invasion, which has driven substantial local extinction.