Experts say ‘road transect’ method is most effective for vulture population estimation in Mudumalai Tiger Reserve
The Hindu
A group of researchers has ascertained that the road transect method is the most effective method to estimate vulture populations in the Mudumalai Tiger Reserve (MTR), home to the southernmost, viable populations of at least three species of endangered vultures in India.
A group of researchers has ascertained that the road transect method, is the most effective method to estimate vulture populations in the Mudumalai Tiger Reserve (MTR), home to the southernmost, viable populations of at least three species of endangered vultures in India.
Road transects are a sampling methodology between two points along which a survey is undertaken to identify the species and number of individual animals seen along the line. If suitably planned, road transects can cover large areas with little chance of individuals being double-counted by volunteers undertaking the count.
A recent paper published in an international peer-reviewed journal— Environmental and Experimental Biology— by the University of Latvia, titled, ‘Assessing the accuracy of population estimation methods for vulture populations: a case study from the Mudumalai Tiger Reserve, Tamil Nadu, India,’ by authors S. Manigandan, H. Byju and P. Kannan, compared estimations of vulture populations in the Mudumalai Tiger Reserve done through different methods: the road transect method, carcass monitoring and nest counting.
A comparative population estimation method was conducted due to the challenges and limitations of each of these methods, including “limited access for assessing breeding populations because they are mostly located in inhospitable and undulating terrain that is difficult to cover by road transect method, nest counts being only viable option for nesting populations and carcass monitoring being dependant on the wildlife kills of cattle.”
Of the three estimation methods evaluated, the researchers found that the road transect method was the most accurate method to estimate the vulture population in MTR. Road transects were successful in identifying all four species of vultures seen in the MTR —the white-rumped vulture, long-billed vulture, Asian king vulture and the Egyptian vulture. This would have been difficult otherwise, as only the nesting sites of white-rumped and long-billed vultures are accessible to researchers in MTR, while the nesting site of the Asian king vulture is yet to be identified and the Egyptian vulture is known to have stopped nesting in the Nilgiris altogether.
“Any accurate population estimation of vultures in the critical habitat (MTR) requires considering various factors such as logistics, cost-effectiveness of the surveys, accessibility to breeding colonies, elephant migrations and tiger habitats,” said Mr. Byju, one of the authors of the paper.
“Apart from resident vultures, migratory vultures can also be found using the road transect method,” said S. Manigandan, the lead author of the paper. “As vultures in general, move in and out of a territory, the road transect method is very effective in determining population change over a time,” he said, pointing out that this was the case with white-rumped vultures in the MTR, with fluctuating populations each year. “Only through continuous monitoring and population estimation exercises can there be a better understanding of the factors causing such fluctuations,” he said.
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