Small birds who migrate from Scandinavia to Africa during autumn fly as high as 4,000 meters above the sea level sometimes, according to a new research done by researchers from Lund University in Sweden. Scientists suspect that small birds do this to adjust their flight to make good of winds that are favorable for them and various wind layers.
This research is a first of its kind to track how high small birds can fly when they travel from Sweden to Africa. While previous studies about the maximum heights of migratory birds do exist, they are mostly focused on larger birds.
“We only followed two individuals and two species. But the fact that both of them flew so high does surprise me. It’s fascinating and it raises new questions about the physiology of birds. How do they cope with the air pressure, thin air and low temperatures at these heights?”, explained Sissel Sjöberg, who is a biologist at Lund University and the Zoological Museum in Copenhagen.
The research team wanted to find out whether or not the measuring method was applicable on small birds. The acceleration, barometric pressure and temperature during the flight were measured by a small data logger, which was attached to the bird.
The small transmitter was made by technicians from the Centre for Animal Movement Research, CanMove, at Lund University. The study was published recently in the Journal of Avian Biology- which is a collaboration between Lund University, the Nature Research Centre in Vilnius and the University of Copenhagen.
The data logger was then attached to two birds belonging to different species: the great reed warbler and the red-backed shrike. The results showed that the time that each bird took to reach their destination. The barometric pressure that was measured by the logger demonstrated that the great reed warbler occasionally flies as high as 3,950 meters, and the red-backed shrike occasionally flies at 3,650 meters.
Both the birds attained the highest peak above ground across the Mediterranean Sea and the Sahara Desert, but the shrike species flied at higher altitudes when it was closer to its winter grounds in southern Africa.
Sjöberg believes that there is a strong chance that there exist other small birds that can fly as high or even higher, but no data about them exists as of yet. “In this study, we only worked with data collected during the autumn, when the small birds migrate to Africa. There are other studies that indicate that the birds fly even higher when they migrate back in the spring, but we cannot say for sure”, he added.