Soaring is better than flapping for big and small birds

Washington, Dec 9 (ANI): The flight patterns of large birds have been well studied. They save energy on the flight to their wintering grounds by soaring through the air on thermal currents. Now, scientists have discovered that small migrating songbirds also do the same thing.

Until now, nothing was clear about the flight patterns of small birds, such as whether they flap their wings or soar and whether these styles of flight allow them to save energy.

Now, a team of scientists at the Max Planck Institute for Ornithology in Radolfzell, Ben-Gurion-University of the Negev, and Hebrew University of Jerusalem have tracked the movement of European bee-eaters (Merops apiaster) along the Africa-Eurasia migration flyway with the help of tiny radio transmitters.

Analysing measurements of heart rate, flight speed and flying style, they found out that these small birds also soar. Further, they found that the birds fly just as quickly when soaring as when flapping their wings, while using as little energy as it takes to sit in its nest.

When we think of birds gliding majestically through the sky without beating their wings, we imagine large species like storks or hawks searching silently for prey.

The flight patterns of large birds have been well studied. Ornithologists know how quickly and how far they fly, and how often they flap or soar while in flight.

However, much less is known about these patterns in smaller birds. Until recently, it was thought that small birds were not able to glide and save energy in the same way, due to their smaller musculature and wings. Gliding would reduce the flight speed, so it was assumed.

In a recently published study, scientists at the Ben-Gurion University of the Negev and the Hebrew University of Jerusalem, along with Martin Wikelski, director of the Max Planck Institute for Ornithology in Radolfzell, determined for the first time the energy use of small songbirds in the wild.

The researchers attached tiny radio transmitters onto the backs of European bee-eaters (Merops apiaster) caught in Israel to record their wing beat frequency, heart rate and flight speed. In order to estimate the birds' energy use, they determined in the laboratory that the birds' heart rate increased with oxygen consumption, and therefore the heart rate measurements indicate the birds' energy use while flying.

"Analysing the data, we were surprised to see that bee-eaters often switch between soaring and flapping, and also that the frequency of heart beats while gliding was only as half what it was while flapping. The birds needed the same amount of energy while soaring or gliding as they did when they were resting on a branch or in a nest," says Martin Wikelski.

The study has been published in PloSOne 11, November 2010. (ANI)

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