Shrinking shola grasslands threaten bird connectivity in the Western Ghats

In the Nilgiri hills of Tamil Nadu, the gradual loss of shola grasslands is reshaping how resident birds travel across the landscape. Researchers examined a 2,900 sq km area that includes the two largest sky-island blocks - the Nilgiris and the Palani-Anamalais - at elevations above 1,400 metres. By modelling movement patterns for seven endemic species, they highlighted how habitat fragmentation is affecting both forest- and grassland-adapted birds, with the sole grassland specialist, the Nilgiri pipit, facing the greatest obstacles. ## Habitat changes and bird behaviour The shola sky islands consist of a patchwork of montane forest and open grassland. Over recent decades, large-scale planting of non-native trees such as acacia, eucalyptus and pine has replaced native vegetation. Between 1973 and 2017, the region lost more than 500 sq km of grassland and over 60 sq km of forest. Using 126 predictive models, the team found that all studied birds tend to steer clear of human-dominated areas like farms, tea estates and settlements. However, their responses diverged in zones where woody plantations had encroached on grasslands. Forest specialists - including the white-bellied sholakili, Palani laughingthrush and several Nilgiri flycatchers - encountered fewer barriers in these wood-invaded patches, whereas the Nilgiri pipit’s movements were consistently impeded regardless of location. ## Consequences for the Nilgiri pipit The Nilgiri pipit is the only grassland-adapted bird included in the study, and its range is confined to the high-elevation grasslands of the shola islands. The researchers noted that the species’ ability to move across the landscape has been reduced by both woody invasions and human activities, echoing earlier findings of steep population declines. Prolonged isolation could diminish genetic diversity, raising the risk of inbreeding. Co-author Chiti Arvind emphasized the need for future work on genetic connectivity to determine whether reduced movement has already impacted gene flow. ## Wider implications and restoration priorities The pattern observed in the Nilgiris mirrors findings from other Indian regions, such as Maharashtra, where afforestation of grasslands has altered understorey conditions and led to declines in grassland-dependent birds while favoring forest dwellers. Birds serve as bioindicators, and the mosaic of forest and grassland in the shola islands supports water-recharging soils and stream health. Loss of grasslands compromises soil quality and water retention, potentially affecting downstream ecosystems. V.V. Robin, an associate professor involved in the research, called for targeted restoration of native grasslands to maintain connectivity for specialist species. The study’s results, combined with similar work across the Western Ghats, can help identify priority areas for conservation interventions aimed at preserving the unique biodiversity of these sky islands. *The study underscores how land-use change can reshape movement corridors for endemic birds, with the Nilgiri pipit exemplifying the vulnerability of grassland specialists in a landscape increasingly dominated by exotic woodlands.*