Wind beneath their wings

April 03, 2022 12:00 am | Updated 05:31 am IST

The large migratory black-eared kites are different from their country cousins — they are selective about what they feast on and where

Black kites are the ecosystem’s clean-up squad, living off the detritus of human civilisation. As an undergraduate student in 2009, Nishant Kumar wondered about the impacts of the collapse of vulture populations. Were the kites picking up the slack in disposing off organic matter? Although they replaced vultures on garbage piles, the density of their nests remained the same in Delhi. Why didn’t the abundance of food translate to an increase in reproduction? These intriguing questions led Kumar to set up the Black Kite Project with Urvi Gupta from the Wildlife Institute of India.

Delhi has no dearth of meals for scavenging birds. Landfills offer a gargantuan buffet of zoological waste.

In the old parts of the city, pious Muslims have a special affection for the kites, throwing pieces of meat in the air in a centuries-old custom. The raptors know the routine and materialise in numbers, flapping above people’s heads while vying for these morsels. They keep an eye on the chunk in the human’s hand and another on their neighbours as they snatch a scrap before it touches the ground without colliding with each other. The believers feel feeding them eases one’s worries in life, that they transfer their problems to the flesh by touching it, which is then carried away by the birds.

To their surprise, the researchers discovered most of the raptors congregating in the garbage hills were not the common resident small Indian kites but the larger migratory black-eared kites. Despite their different names, both belong to the same species, sporting forked tails and voicing whinnying shrieks. But their habits vary.

Flight in autumn

The filth-eating birds, which have a smudge of black behind their eyes and are thus called black-eared kites, migrate from the steppes of Central Asia in autumn. Until then, many bird specialists thought these raptors flew as far as the Himalaya and not farther south into the Indian peninsular.

When the black-eared kites leave Delhi on their annual return migration, the small Indian kites don’t flock to the mountain-high piles of stinking offal. Instead, these acrobatic meat-catchers grab chunks in mid-air and stay within the city limits. No wonder the absence of vultures didn’t boost the number of nests of the urban area. Although black kites are synonymous with filth, they are selective about what they feast on and where.

Kumar and Gupta started a GPS tracking programme to understand these raptors: where they roost, nest, and find food, and how far they travel. They outfitted a young subadult black-eared kite caught at a landfill with a transmitter. It took off for Chandigarh, thence to Ladakh, and all the way to southern Siberia. The researchers were downcast as that bird wouldn’t give them any insights into its city life. But soon, they recognised the value of the data. They had discovered the migratory route and the raptors’ feat of crossing the mountains at 6,500 m.

No to transmitter

Kumar and Gupta tagged the wing of a small Indian kite fledgling from a nest in Delhi Zoo. It was next seen in Bikaner, Rajasthan. Even these birds were not year-round city dwellers. A third, also a small Indian kite, detested the transmitter so much, it shredded the Teflon harness straps with its sharp beak. The field assistant couldn’t believe it was the work of the bird and exclaimed that it appeared as if a rat had hitched a ride with the predator. The research team salvaged the device that was dangling like a necklace from the kite’s throat.

By monitoring nests and weighing nestlings, Gupta became an unpopular figure among the raptors of Inderlok, Delhi, which perhaps feared for the safety of their young. Weeks later, when she visited the site with a different group of people, none of whom had participated in the nest checking effort, a kite recognised her and showed its displeasure towards the entire party, swooping down on them with its talons drawn.

The birds, which lighten the burden of human worries, have concerns of their own.

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