We speak with filmmaker Shaunak Sen about his Oscar-nominated documentary, “All That Breathes,” which follows two self-taught brothers who rescue black kite birds suffering from air pollution in New Delhi. The brothers, Nadeem and Saud, have saved about 25,000 black kites from the dirty air in India’s capital over the last 15 years. “When you live in the city of Delhi, you’re almost always preoccupied with the air,” says Sen, who explains why he centered the film on the brothers and purposely stayed away from obvious environmental and political messages. “The idea is to open the conversation and not close it,” he says. “All That Breathes” became the only film ever to win the best documentary prize at both the Sundance and Cannes film festivals last year.