Even minor disturbances can harm nesting sites of long-billed vultures

Breeding sites of the critically endangered species in the craggy cliffs towering over the Moyar River in the Nilgiris were monitored from 2018 to 2021. Forest fires pose a huge risk to the sites, as was evident from the fallout of a 2019 forest fire in Kodanad

Updated - March 22, 2024 05:03 am IST

Published - March 22, 2024 01:25 am IST

Fighting for survival: While the loss of a single nest may not seem much, the breeding population itself is very small and each nest counts, says a researcher. A pair of long-billed vultures in the Mudumalai Tiger Reserve.

Fighting for survival: While the loss of a single nest may not seem much, the breeding population itself is very small and each nest counts, says a researcher. A pair of long-billed vultures in the Mudumalai Tiger Reserve. | Photo Credit: SPECIAL ARRANGEMENT

The Nilgiris is home to some nesting sites of the critically endangered long-billed vulture. But they are susceptible to disturbances from human interventions. After multi-year monitoring of the nests, researchers say even minor disturbances from tourism-related activities can cause the nesting sites to fail.

From 2018 to 2021, researchers S. Manigandan, H. Byju, and P. Kannan monitored four nesting sites in the Mudumalai and Sathyamangalam Tiger Reserves. Their findings have been laid out in a paper on ‘Monitoring observations of the southernmost breeding population of Long-billed Vultures, Gyps indicus, in the Nilgiri Biosphere Reserve, India’. The paper has been published in the Journal of Threatened Taxa, a peer-reviewed, scientific journal.

A nest abandoned

The breeding sites of the species, which prefers to make its nests in the craggy cliff faces towering over the Moyar River, were monitored and each site’s successes and failures were recorded. The researchers noted that though the number of vultures remained relatively stable, ranging from 17 to 21 individuals, they witnessed how the functioning of an illegal resort could have contributed to the abandonment of a nest in the area.

“The Ebbanad Nesting Colony had two nests in 2018, but the number came down to one the next year, most likely because of tourism,” said Mr. Manigandan. “This decline was attributed to the frequent disturbance by visitors from a nearby cottage frequented by tourists and may have caused the birds to leave the location. An illegally constructed cottage was located 100–150 metres away from the colony, with a viewpoint for the tourists. We observed people screaming and shouting during the daytime and campfires in the night,” he added. Interestingly, after the closure of this cottage, the number of nests at Ebbanad went up to two again in 2020-21, he said.

Mr. Byju said each of the four nesting sites had only one or two nests. “While the loss of a single nest may not seem much, it needs to be understood that the breeding population itself is very small, and each nest counts.”

Combined with the fact that long-billed vultures prefer nesting in cliff-faces and rocky crevices, safeguarding these limited sites is of crucial importance for the survival of the species in the region, researchers say. Even more of a threat than tourism is the impact of forest fires, as evident from a 2019 forest fire in Kodanad, which led the vultures to abandon their nests in the area.

“The Kallampalayam nesting colony exhibited a positive trend, with 100% breeding success in 2020–21. This success is likely due to the colony’s limited exposure to forest fires and lower human disturbances, as no signs of human presence were detected near the nesting area during the study,” the researchers said in the paper.

“There have also been incidents of poisoning that have led to the death of many vultures; the impact of the use of certain Non-Steroidal Anti-Inflammatory Drugs [NSAIDs] for cattle, which can poison vultures; and deaths due to the birds coming into contact with power infrastructure,” Mr. Manigandan said, calling for a strategy to minimise threats to the species.

Population stabilised

The Forest Department has succeeded in stabilising the population of the species. Apart from awareness campaigns and crackdown on drugs suppliers and pharmacists to discourage the use of NSAIDs, steps have been taken to increase the carrying capacity of the landscape, said P. Arunkumar, Deputy Director of the Mudumalai Tiger Reserve (Buffer Zone).

He told The Hindu that even veterinarians were told not to prescribe NSAIDs banned in vulture habitats. “In addition, the synchronous vulture surveys, conducted over the last two years, have yielded an accurate estimate of the population, which in itself is a step in the right direction,” he said. To ensure availability of food for the scavengers, the Forest Department is assisting the birds in finding the carcasses of large animals dying of natural causes. “As riverine forests account for most of the habitat in the Sigur plateau, vultures find it difficult to see the carcasses of animals like elephants. The department is leading vultures to carcass sites by leaving portions of it in the open where it would be more visible to the birds,” he added.

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