Post-Gaja, change in pattern of arrival of migratory birds: study

There has been a change in pattern of arrival of migratory birds to sanctuaries, wetlands and waterbodies in delta districts after Gaja cyclone, according to a study.

The three-month duration from November is a standard period for avian visitors to the bird sanctuaries in the State. The migratory birds belonging to distant continents come in large numbers, stay for three to four months and fly back.

The bird sanctuaries at Point Calimere in Nagapattinam district and Karaivetti in Ariyalur district and Vaduvoor lake on the border of Thanjavur and Tiruvarur districts are among the most sought destinations for the winged visitors.

At times, the birds arrive in early November and fly back in February after extended stay by three to four weeks. There are years in which birds return a bit early, says A. Kumaraguru, Conservation Scientist, Biodiversity Foundation, Tiruchi.

November to January is not just a period of rainy and winter season. It is the peak of paddy cultivation period. The abundant availability of food particles, small organisms, insects, fresh water and warm temperature attract the migratory, terrestrial and aquatic birds, Mr. Kumaraguru points out.

His study indicates some deviations in the pattern of arrival of migratory birds, particularly after Gaja cyclone that caused extensive damage to the flora and fauna at the Wildlife and Bird Sanctuary at Point Calimere.

Scientists, who are on a project to compile a detailed data on bird census, have spotted the migratory birds visiting various wetlands in non-seasonal months including May, June and July in 2019 and 2020. They returned after a brief stay of three to four weeks.

“We mainly spot migratory birds from November to January and February. But, we often come across birds in farmlands and water bodies across delta districts in non-seasonal months. It is a new phenomenon after Gaja cyclone. We need to study whether it is a temporary or not,” Mr. Kumaraguru said.

Open billed stork, great egret, black headed ibis are among the birds spotted in significant numbers across paddy fields, water bodies and wetlands in the delta region in non seasonal time.

‘Not just cyclone’

S. Ramasubramanian, Chief Conservator of Forest-In-Charge, Tiruchi, told The Hindu that the pattern in change of arrival of migratory birds could not just be the impact of the Gaja cyclone.

Climate change and disturbances in their habitats could also be the reasons. An in-depth study was required, he said.