Migrants under threat: Conservation challenges for open habitat birds in the Indian wintering region

Twice every year, birds undertake journeys often thousands of kilometres long between their breeding and non-breeding (wintering) sites, termed as migration. These voyages are demanding both in terms of energy requirement and various threats they encounter en route such as unforeseen weather conditions, predation risk and lack of food availability. A recent review on the status of the world’s birds has estimated that approximately 48% of the extant species are undergoing population declines. In regions where long term bird surveys have been conducted, the results suggest that migratory birds are undergoing steep declines compared to resident species. Among these birds, losses were severe in species associated with open habitats (OH’s) such as savannahs, grasslands and scrublands. For the first time ever, the review also includes long term population trends of birds from India, owing to the state of India’s birds report. Out of the 146 species used in this citizen science assessment, nearly 80% were found to be declining. Even in India, 59% of declining species were those which specialise in OHs. Although the drivers behind bird declines vary across different regions, habitat degradation and conversion is thought to be one of the major causes.

The Indian subcontinent is an important wintering region for about 140 species of birds that breed in central Asia. These species travel via what is termed as the Central Asian Flyway (CAF) during their migration. A Flyway is defined as the entire range used by bird species which includes their breeding and wintering regions, migratory pathways and stopover sites (resting and refuelling places during migration). The CAF is one of the most understudied flyway compared to the remaining 9 flyways across the world. Detailed studies on migration and movements of bird species in the CAF has been done only for 8 species. Even population assessments for most species remains unknown and patchy.

Our long term monitoring work has focussed on harriers in OHs across India. Harriers are migratory birds of prey (raptors) that winter in the Indian subcontinent during the months of September to March. Six species of harriers winter in India out of which the Montagu’s and Pallid harrier specialise in arid and semi-arid grasslands. They are communal roosters, meaning they roost on the ground in large flocks in the evenings. One of the largest roosts of harriers in India was recorded in Velavadar, Gujarat comprising of about 3000 birds in the year 1997. Monitoring of harriers in the past 6 years paints a grim picture of their populations. Harrier roost surveys in north-west India, Deccan and south India has shown that harriers have been on the decline in grasslands that are located within and outside protected areas.

Loss of roosting sites as a result of land conversion has been one of the major reasons of harrier declines outside protected areas. Many roosting sites have undergone conversions to quarries, farmlands, plantations and energy projects during the study period especially in south India. Within protected areas which have largely remained intact, the reasons are currently unknown although reduced prey availability, intensive agriculture in the fringes and pesticide poisoning are thought to be few of the causes. Energy infrastructure, mainly solar and wind farms is an emerging threat for OHs across India. The country has set an ambitious goal of generating at least 500GW of power from green energy projects by the year 2030. This can mean a death for OHs from north-west India to south India. OHs are also primary targets for compensatory afforestation projects. Unfortunately, the rich biodiversity harboured by these habitats are often overlooked and thus, these ecosystems are under serious threats from various anthropogenic activities.

As part of our research to understand why harriers are declining and how they might respond to such unfavourable changes in OHs, we are equipping individuals of Montagu’s and Pallid harriers with GPS trackers. These devices enable us to track their movements throughout their life journeys. Data from these tags have already given us valuable information on where these birds exactly breed in central Asia and what routes they take during migration. We have also been able to map previously unknown roosting sites of harriers from these trackers. In coming months, we will be analysing where harriers prefer to forage and how they move around dynamic OH landscapes. Our observations in field has shown that they can forage along certain crops but require grass cover for roosting in the evenings. Information from the GPS trackers can help formulate effective management plans for conservation of harriers. Since we have now almost lost the bustards, harriers are the flagship species in OHs their protection can also aid in the conservation of other grassland specialist species.