Natural allies Chennai

Barn swallows can get rid of mosquitoes

Barn swallow on a power line at Sholinganallur.

Barn swallow on a power line at Sholinganallur.   | Photo Credit: Prince Frederick

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During winter months, barn swallows visit Chennai in thousands, and by the nature of their flight, they are organically inclined to trap mosquitoes

Usually peddled on urban pavements, this doodad is attention-getting — tied to a stable object with a flexible sting, the bird-toy would keep circling. Nothing far-fetched about the design. Birds go around in circles while flying on the thermals. Birds hover and keep encircling a space where they have spotted food. In some rare cases, the circular flight will be characterised by orbital eccentricity, seem ceaseless and lacking in purpose.

That takes us to the barn swallows, which have arrived in Chennai in thousands, as they do every wintering season.

Birder Rama Neelamegam points out that the barn swallows have had an earlier “appointment” with the city. “They are usually expected in September, but this year, they are being reported from August,” she explains.

Barn swallows hover over grassy patches filled with shallow waters, and keep circling in a what is called “swarming” action to gobble the maximum number of insects. The manoeuvre is loosely comparable to how pelicans “raft” in shallow waters to ensure a huge catch of fish.

Barn swallows belong to a category of birds called “airborne insectivores”, which get their insects on the wing. Because of the nature of their flight, barn sparrows are believed to be naturally inclined to trap mosquitoes.

“They fly with their beaks open to trap insects, and what is of considerable significance is that they fly at a low height, often very close to the surface of the water. They regularly would skim the surface of the water, and could be picking up what is found there,” says ornithologist V. Shantaram.

As they skim the water surface, the barn swallows can be picking up mosquito larvae, if any.

Swallows are aerial insectivores, but there could be slight variations in their technique, especially in the height they maintain.

“The red-rumped swallows fly at a higher level than the barn swallows. The barn swallows can fly really low, and when they fly across roads, a birder can be filled with trepidation, fearing these birds can be hit by oncoming vehicular traffic. But all swallows are agile and quick in their flight, and stay safe,” observes Shantaram.

With the arrival of barn swallows, would these birds and the red-rumped swallows together form a combined mosquito eradication force?

“The red-rumped swallows are not very commonly seen in Chennai, but in the outskirts. I have seen red-rumped swallows nesting in the outskirts of the city. But sometimes, in the morning hours of winter months, you may see flocks of barn swallows and red-rumped swallows parked on the same power lines,” explains Shantaram.

He points out that in their breeding habitats — in India, they breed in places that are part of the Himalayan range — the barn sparrows are usually welcome into people’s homes and shops.

Considering they can gobble mosquitoes, they are welcome in Chennai too.

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Printable version | Jan 21, 2020 9:55:12 AM | https://www.thehindu.com/news/cities/chennai/barn-swallows-in-chennai/article30230675.ece

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