Wetzlar (dpa/lhe) – Despite the current heat, the first swifts are already making their way to their African winter quarters. “Among other things, the starting impulse for the departure is given by the decreasing length of the day and the dwindling food supply,” said ornithologist Maik Sommerhage from the Nature Conservation Union (Nabu) Hessen in Wetzlar on Thursday. Swifts are master fliers who spend most of their lives in the air and even sleep there. They now leave a few days later than before and return from their winter quarters up to two weeks earlier in the spring. During a count by Nabu this year, an unusually large number of swifts were registered – compared to the previous year, the increase was 73 percent.