The annual tradition of flying kites over the Indian capital on Independence Day takes a painful toll on birds that fall victim to their razor-sharp strings.

Workers at the Charity Birds Hospital see it happen every year — mostly to pigeons but also to crows, eagles and parrots. The wounded populate cages lining the halls of the clinic's emergency ward.

The hospital, set up in the courtyard of the Digamber Jain Temple in the old quarters of New Delhi, relies on donations. It treats birds year-round for injuries they might have sustained in animal attacks or from flying into ceiling fans. But every August, its halls fill with hundreds of fluttering, squawking birds that have been sliced up by kite strings.

"This year there have been about 700 birds in just three days" since Monday, the day before Independence Day, said manager Sunil Kumar Jain. About 15 percent of those have died, he added.

Across the Indian subcontinent, kite flying is popular and competitive. Enthusiasts often line the strings of their kites with shards of glass or metal, with the aim of crossing opponents' kite strings and cutting them down. The last kite flying wins.

The competitions can be dangerous. Last year, three people were killed when kite strings cut their throats, prompting New Delhi to ban the coating of kite strings with glass.

The new rules have not helped the birds at the clinic, some of which arrived with razor-sharp strings still embedded in their flesh.

The deaths weigh on veterinarian Rameshwar Yadav, 51: "It's very painful to see your hard work in trying to save a life end in vain."

He adds, however, that he takes solace in helping the survivors take to the sky again. "There's no better feeling than giving them their freedom back."