By attaching ultralight tracking devices to pied flycatchers (Ficedula hypoleuca), researchers have discovered that these little songbirds can fly 40 to 60 hours across the Sahara desert without stopping. The findings, published in Biology Letters this month, challenge the idea that these long-distance migrants rest during the day when it’s the hottest. Rather, it seems flying nonstop saves both time and energy.
Every year, over 2 billion songbirds cross the Sahara – the world’s largest desert – between their temperate breeding grounds and their African wintering grounds. How they accomplish this daunting task is still mostly a mystery since their small size and large numbers make them difficult to track. Pied flycatchers, for instance, weigh just 12 grams (0.03 lbs). Recent studies suggest that nocturnally migrating species make their trek intermittently, even though this strategy might take longer.
To investigate, a team led by Janne Ouwehand from the University of Groningen attached geolocator loggers to 52 male and 28 female pied flycatchers using leg-loop harnesses in 2013. These presumed nocturnal, long-distance migrants come from a population in Drenthe in the Netherlands, and they’re known to winter in the western Ivory Coast and eastern Guinea in sub-Saharan Africa. The loggers recorded light levels, temperature, and longitude data.
The team managed to recapture 27 of the birds in 2014 and 2015. They discovered that most of the tracked flycatchers made flights in the daytime during the autumn and spring. In the springtime, the birds embarked on a nonstop flight directly from their wintering grounds, 500 kilometers (310 miles) south of the desert. In the fall, the birds likely avoided part of the desert by flying over the ocean instead.
The flycatchers’ maximum flight duration ranged from 40 to 60 hours, and with an average ground speed of 15.3 meters (50 feet) per second, the little birds could cover as much as 3,350 kilometers (2,080 miles).
Image in the text: J. Ouwehand & C. Both, Biol. Lett. 2016