Flight Number 9 Print

In 2011, Felix Liechti and his colleagues at the Swiss Ornithological Institute attached electronic tags that log movement to six alpine swifts. The small birds—each weighs less than a quarter of a pound—spend the summer breeding in Europe, then migrate to Africa for the winter, thousands of miles away. “We wanted to learn about energy demands during migration. We expected to see how often they fly, how often they stop, that sort of thing,” he said. But a year later, when three of the birds returned to the same breeding site and the scientists removed their tags to collect the data, the electronic tags revealed something unexpected. “When we looked at the data, we were totally blown away,” Liechti said. “During their non-breeding period in Africa, they were always in the air.” For more than 200 straight days straight, as revealed by his team’s study published today in Nature Communications, the birds stayed aloft over West Africa. The tags only collect data every four minutes, so it’s impossible to rule out the chance that they touched down occasionally in between these intervals—but every single one of the data points collected for more than six months in a row indicated that, at the time, they were either actively flying or at least gliding in the air.