Coastal raptors make power towers their home

Authors of a study published in the conservation-themed monthly, Journal of Threatened Taxa, say this poses risk to the species, and also points to the lack of suitable nesting sites near the sea

August 20, 2023 12:27 am | Updated 10:26 am IST

Alternative home: A white-bellied sea eagle nests on a powerline tower at Ramanathapuram in Tamil Nadu. Photo: Special Arrangement

Alternative home: A white-bellied sea eagle nests on a powerline tower at Ramanathapuram in Tamil Nadu. Photo: Special Arrangement

White-bellied sea eagles in India are beginning to emulate their counterparts in Australia and Thailand by making their homes on power towers holding high-tension wires.

The use of man-made structures as nesting sites can be both risky and beneficial to these coastal raptors and humans in the vicinity, but the development points to a lack of trees and other natural nesting alternatives, a study published in the latest issue of the conservation-themed monthly, Journal of Threatened Taxa said.

The nests of the white-bellied sea eagles were found on powerline towers about 2 km away from the sea in Ramanathapuram of Tamil Nadu. The nesting sites were strategic for the birds to conveniently scan the marine area for food, the study said.

The white-bellied sea eagle (Haliaeetus leucogaster) is a resident raptor belonging to the family Accipitridae. It has a wide distribution range on the sea coast of India from Mumbai to the eastern coast of Bangladesh, and Sri Lanka in southern Asia, through all coastal south-eastern Asia, southern China to Australia.

The raptor, a diurnal monogamous bird of prey, is categorised as being of ‘least concern’ on the Red List of the International Union for Conservation of Nature.

Feeding mainly on sea snakes and fish, the bird is occasionally seen in inland waters along tidal rivers and in freshwater lakes. It occupies the same localities for years and generally builds nests in tall trees near the seacoast, tidal creeks, and estuaries.

Team behind the study

The authors of the study are H. Byju of Annamalai University’s Centre of Advanced Study in Marine Biology, N. Raveendran of the Madurai-based Iragukal Amritha Nature Trust, and citizen scientist A.J. Mathiyazhagan.

“During one of our routine shorebird monitoring studies in Ramanathapuram on November 24, 2022, we observed a large nest on a powerline pylon near the rainwater storage area of Pudumadam,” Mr. Byju told The Hindu. The team scanned the adjacent pylons and found three nests about 100 metres from each other. These were on the paddy fields adjacent to the rainwater storage area.

Each nest, about 1.4 metres, was at a height of about 18 metres from the ground. The nests were large deep bowls constructed of thick sticks, twigs, and branches and lined with grass, seaweed, or green leaves.

The team observed an incubating adult on the nest of the first pylon on its next visit a month later, and also found a fourth nest on another pylon.

“White-bellied sea eagles have been reported to nest on power poles and transmission towers in Australia and Thailand by birdwatchers. In India, the bird’s nesting was earlier reported on a telecommunication tower from Andhra Pradesh,” Mr. Byju said.

Careful management and monitoring of such unnatural nesting sites are critical to the safety of both eagles and humans, the authors said.

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