About a week back, in mid-November, researchers at Bengaluru-based ATREE were alerted to data transmitted from a small 9.5 gm transmitter connected to the back of a bird. The Pallid Harrier, geo-tagged by them, has reached its roosting ground in Tirunelveli, all the way from Kazakhstan.
Harriers, winged migrants from Central Asia, have started visiting India, flying about 5,000 km in search of grasslands.
The Harrier Watch Project, a long-term project founded by researchers T. Ganesh and Prashanth M.B., has been monitoring the six harrier species that arrive in India in winter, with the aim of monitoring the raptors and their grassland habitats and assessing the impact of loss of grasslands on the species.
Roosting on the ground
“Did you know Madiwala lake was a roosting site for Western Marsh Harriers?” asks Arjun Kannan, a PhD student who works with the project, citing a study published in 2010 by Ashok Verma.
Among the winter visitors to India are Western Marsh Harriers, Montagu’s Harrier, Pallid Harrier, Hen Harrier, Pied Harrier, and Eastern Marsh Harriers. Unlike many other birds, they roost on the ground among tall grasses and therefore make grasslands their habitats.
“We have mapped their roosting sites spanning Western India to South India. We’ve also tagged a few to understand their migration,” said Mr. Kannan.
Starting in 2016, the ATREE team has so far tagged about 20 harriers- eight Pallid Harriers and 12 Montagu’s Harriers- from roosting sites in Tal Chhapar in Rajasthan, Nannaj in Maharashtra, and Tirunelveli in Tamil Nadu.
Around the Himalayas
The birds, which breed in Central Asia, come to the Indian sub-continent in winter. Owing to physiological reasons, they don’t cross over the Himalayas, but fly around it. This detour migration which takes about 25 days means an additional flight path of 1,500 km approximately, compared to crossing over the Himalayas. By March, they start flying to Central Asia again, crossing Pakistan, Afghanistan, Uzbekistan, and Tajikistan to reach Kazakhstan.
“Interestingly, the birds, en route to India, stop over for a few days at the Thar desert bordering India and Pakistan. They don’t do the same while flying back to Kazakhstan. We think it is because when they fly to India, it is just after the monsoon, and therefore, there’ll be a lot of lush green grass available. It could also be that the birds are fatigued more as they are flying post-breeding,” said Mr. Kannan.
Declining numbers
The project data shows that the number of harriers has been consistently declining in the roosting sites, while some of the roosting sites have simply ceased to exist, thanks to the change in land use patterns.
“Madiwala used to be a roosting site. Hesaraghatta is another important one. In comparison to the 80 to 90 harriers that once used to be spotted there, we saw only eight there the other day. In the place where the roosts were, a lot of trees have been planted in the last few years. Given that there is only a small patch remaining for grazing, there is also the problem of over-grazing. Most of the grass is very short now,” said Mr. Kannan.
According to him, Harriers are significant mobile links for seed dispersal between grassland patches. The IUCN has categorised Pallid Harriers as near threatened, and according to the State of India’s Birds reports, Montagu’s Harriers and Pallid Harriers have declined by around 50% compared to pre-2000s assessments.
Grass land conservation
During the project, the researchers also observed that the loss of grassland cover was affecting the home range sizes of the harriers, forcing them to move around more in search of prey and suitable habitat.
“They spend a lot of energy flying around the mountain ranges. Sight fidelity is another important feature of harriers. It has been observed that they come back to the exact same spot every year. So, when the route or the roosting sites get threatened, it becomes a concern as to how the species is going to fare in the long term,” said Mr. Kannan.
“Harriers are raptors, birds of prey. If they can be considered as flagships to conserve grasslands, then we will also be conserving a lot of other grassland species like the Lesser florican that are critically endangered and are not as charismatic,” he adds.
Published – November 24, 2025 08:50 pm IST
