Migrating from one end of the planet to the other, flapping your wings, is expensive in energy terms. For a 30-gram bird, traveling a distance of 4,800 kilometers from Panama to Canada to spend the winter involves 3.2 million wingbeats and 1,300 kilojoules of extra energy expenditure . And since many stops are not allowed, the flight must be as efficient as possible.
Now, climate change has made it even more difficult for migratory birds, as it causes stronger winds and atmospheric instability that increase the energy needed to move, according to the journal PLoS ONE . The study authors have analyzed for the first time how birds respond in the wild. "Until now, research has been limited to individuals flying inside artificial wind tunnels," explains Melissa Bowlin, a researcher at the University of Montana. Bowlin, however, has attached to the back of the birds a radio transmitter , weighing less than one gram, which records the heart rate and sends the data to an antenna at ground level.
The first results indicate that certain atmospheric conditions increase the physical effort required to fly. In addition, Bowlin and his team have found that birds tend to arrange the tips of their wings so that the weight is distributed evenly, thus saving energy on their long movements.
