Elevation and landscape change drive the distribution of a montane, endemic grassland bird.

Abhimanyu Lele,V V Robin,Devcharan Jathanna,Viral Joshi,M Arasumani,C K Vishnudas

doi:10.1002/ece3.6500

Abstract

ContextTropical 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.ObjectivesWe 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.MethodsWe 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.ResultsElevation 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.ConclusionsThe 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.

Highlights

Tropical montane habitats are highly biodiverse, and harbour high endemicity (Ricketts et al., 2005; Dimitrov, Nogués-Bravo, & Scharff, 2012)
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 found moderate positive correlations with other variables contributing to local habitat heterogeneity and vegetation structure, a correlation supported by the behavioural observations of Vinod (2007), who found that Nilgiri pipits preferred marshy habitat with tall grass for nesting, and more open habitat for feeding

Summary

Introduction

Tropical montane habitats are highly biodiverse, and harbour high endemicity (Ricketts et al., 2005; Dimitrov, Nogués-Bravo, & Scharff, 2012). They are hotspots of extinction risk, due to the presence of threatened species with restricted distributions (Ricketts et al, 2005; Hoffmann et al, 2010). Montane specialists may be threatened by climate change, which can trigger elevational range shifts (Stuhldreher & Fartmann, 2018) Where such shifts are limited by topography, species may face habitat decline and local extinctions (Parmesan, 2006; Forero-Medina, Joppa, & Pimm, 2011; Freeman, Scholer, Ruiz-Gutierrez, & Fitzpatrick, 2018). The effects of climate change may interact with those of habitat loss and fragmentation (Fahrig, 2003), threatening montane habitats and the unique species assemblages they host

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