Unseasonal rain throws winged migration out of gear

Heavy rain that lashed areas around Mysuru late till October and November may have left farmers happy, but it has led to a decline in the number of migratory birds, which tend to roost in southern parts of Karnataka during winter.

“A majority of the migratory wetland birds are waders and prefer marshy ecosystem, but the heavy rain during October/November has altered the habitat, which may have forced these birds to scout for more suitable places further south or in the coastal region,” said K. Manu, an ornithologist focussing on environmental education in schools near M.M. Hills.

Not all birds are fish-eating and those dependent on insects can sustain only if there was a good flowering of hydrophytes or vegetation in water that draw insects. These are found in shallow lakes. But heavy rain affects their growth and this in turn reduces the concentration of insects.

D. Rajkumar of Wildlife Conservation Foundation pointed out that dredging along the lake shores has also caused havoc to the bird habitat. “Incessant dredging destroys the naturally occurring shallow areas in a lake paving way for a sudden depth near the shores. Wading birds that cannot swim or dive abandon the habitat and only those that can swim and eat fish survive,” he said.

The waders constitute more than 75% of the migratory birds and forage for insects and small fish in the shallower portions of the lake, Mr. Rajkumar added. This apart, lakes flushed with water owing to unseasonal rain also heralds fishing activity, which drives away the birds.

The onset of December heralds the arrival of migratory birds from distant lands flying across the Eurasian regions for their winter sojourn but the above factors have reduced their numbers this year.

However, there is a general perception that concentration of birds in wetlands have been declining over the years. “We have a good concentration of birds at Yelladur, Kestur and Kallurkere in Chamarajanagar district, but not much in other habitats where they used to be found in larger numbers,” according to Mr. Manu.

Final stop

The winter migratory birds normally fly in from Iran, Iraq and Russia, with a long flight over Afghanistan and Pakistan before entering the Deccan region which has warmer climate. The Bar-headed Goose flies in from Mongolia after their mountainous flight across the Himalayas and have a stopover in the wetlands in northern and central Karnataka, before their final hop to south interior Karnataka.

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Printable version | Apr 12, 2021 10:13:21 AM | https://www.thehindu.com/news/national/karnataka/unseasonal-rain-throws-winged-migration-out-of-gear/article22277476.ece

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