River terns fly back home leaving Vairamani deserted

Giji K. Raman
IDUKKI, 
The Hindu, June 10, 2015 

Vairamani islet, the largest nesting place of Indian river terns (sterna aurantia) inside the Idukki Wildlife Sanctuary wears a deserted look after the migratory season.

While ornithologists hoped for a second window for brooding, the unexpected heavy rains and winds played a spoilsport. During this brooding season (from March to May) large number of chicks was found dead and unhatched eggs dotted the islet. Hundreds of river terns turned up this season to lay eggs on the sand as the waters of the Idukki reservoir waned. But many eggs did not hatch and chicks were found dead. According to ornithologist R. Sugathan, the eggs need a particular duration for brooding and if there is wind, the birds would fly away leaving the eggs unhatched.

“There were heavy rains and winds which resulted in the large mortality rate of the chicks,” said the official.

Ornithologists were expecting a second brooding which is possible if food is readily available. Fresh water fish is the staple of river terns and the islet is undisturbed from human intervention and predators including the snakes. The reservoir provides the feeding ground for the brooding birds that usually fly away after the season. According to Assistant Wildlife Warden G. Jayachandran there is a plan to document the seasonal birds in the sanctuary which has been identified as a major habitat for resident birds. He said that climate changes and human intervention could result in poor availability of local fish varieties in the reservoir making an impact on the arrival of river terns in future.

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River terns at summer rain’s mercy

Giji K. Raman
Kattappana,  
The Hindu, April 26, 2015

This summer is unlikely to add much to the population of Indian river tern ( Stema auratia ), a common bird species on the islet of Vairamani. The islet, a natural habitat of the bird, is strewn with eggs and dead chicks. Heavy summer rain is believed to have caused the damage.

Vairamani is accessible only by boat and is situated deep inside a sanctuary. It is considered the largest breeding place of the bird, which lays eggs on sand and hatches them if undisturbed by human or other intervention.

The breeding season of river tern is from March to May. By March, the birds would arrive there and the islet would soon have hundreds of eggs, each pit having one to four. Ornithologist R. Sugathan says the eggs need a particular temperature for a particular duration to hatch. If there are winds, the brooding birds could fly away, and the eggs would not hatch. Mr. Sugathan says that many factors, including climate change, result in advancing of the breeding season. There are chances of a second brooding by a bird, depending on the availability of food in the area. Forest Department officials are keen on protecting the habitat from outside intervention. Assistant Wildlife Warden G. Jayachandran says the breeding is being monitored.

The death toll of chicks this year is the highest, he says. It could also see a drop in the number of arrivals. Heavy rain could be a reason for the chicks’ death as they lie in the open without any natural protection.

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