Local extinction of a montane, endemic grassland bird driven by landscape change across its global distribution

Abstract

28Context 29 Tropical montane habitats support high biodiversity, and are hotspots of endemism, with 30 grasslands being integral components of many such landscapes. The montane grasslands of the 31 Western Ghats have seen extensive land-use change over anthropogenic timescales. The factors 32 influencing the ability of grassland-dependent species to persist in habitats experiencing loss and 33 fragmentation, particularly in montane grasslands, are poorly known. 34Objectives 35 We studied the relationship between the Nilgiri pipit Anthus nilghiriensis, a threatened endemic 36 bird that typifies these montane grasslands, and its habitat, across most of its global distribution. 37 We examined what habitat features make remnants viable habitat, which is necessary for 38 effective management. 39 Methods 40We conducted 663 surveys in 170 sites and used both single-season occupancy modelling and N-41 mixture modelling to account for processes influencing detection, presence, and abundance. 42 Results 43Elevation had a positive influence on species presence, patch size had a moderate positive 44 influence and patch isolation a moderate negative influence. Species abundance was positively 45 influenced by elevation and characteristics related to habitat structure, and negatively influenced 46 by the presence of invasive woody vegetation. 47 Conclusions 48The strong effect of elevation on the highly range-restricted Nilgiri pipit makes it vulnerable to, 49 and an indicator of, climate change. This highly range-restricted species is locally extinct at 50 several locations and persists at low densities in remnants of recent fragmentation, suggesting an 51 extinction debt. Our findings indicate a need to control and reverse the spread of exotic woody 52 invasives to preserve the grasslands themselves and the specialist species dependent upon them. 53 54