Swedish biologists have studied the migration of the common nightingale using miniature sensors attached to the birds' backs. Their research revealed that when crossing the Sahara and the Arabian Desert, nightingales fly exclusively at night and do not search for food, traversing these challenging stretches without refueling by relying on fat reserves accumulated in advance.

Migration Patterns of Songbirds

Every spring and autumn, millions of songbirds migrate between Europe and Africa, crossing the Mediterranean Sea, the Sahara, and the Arabian Desert. Until recently, it was unclear how these birds survive the extreme conditions of the deserts: whether they make long, non-stop flights or pause to rest and feed along the way.

Research Methodology

To study the behavior of nightingales (Luscinia luscinia), researchers in southern Sweden fitted the birds with microscopic devices weighing about one gram (less than 4% of the bird’s body weight). The devices, attached with elastic loops, included an accelerometer, barometer, thermometer, light sensor, and flash memory. Since the devices did not transmit data via satellite, scientists had to wait for the birds to return over the course of a year. In the spring, 23 returning nightingales were recaptured, and the recorded data was retrieved from their devices.

Observation Results

Analysis showed that during the autumn migration across the Sahara (averaging 4.1 days) and the spring crossing of the Arabian Desert (4.8 days), nightingales traveled only at night. During the day, their physical activity was almost nonexistent, and they did not search for food. The exception was the crossing of the Mediterranean Sea, where the birds flew non-stop for 16 hours, both day and night, as landing on water was impossible.

Energy Expenditure and Behavioral Strategy

Stopping in the desert is not energy-efficient. Calculations showed that a 34-gram bird, resting motionless in the shade for four days, would use about 0.7 grams of fat per day for basic metabolism—about 12% of its energy reserves over the entire stop. Flying non-stop during the day would be more economical, but the birds choose to rest during daylight. This helps them avoid dehydration and overheating under the sun, and also reduces the risk of attacks from daytime predators such as Eleonora’s falcons.

Preparation for Migration

Completely abstaining from food while crossing desert barriers requires thorough preparation. Sensors recorded that before heading into the Sahara, nightingales make a stop in Central and Eastern Europe for about a month, during which they actively feed on insects to build up the fat reserves necessary for the long journey ahead.

Conclusions

The study demonstrated that successful desert crossings depend entirely on the birds’ ability to stop searching for food in time, switch to maximum energy-saving mode, and rely solely on the energy reserves accumulated thousands of kilometers before reaching the desert.