How do birds migrate in unfavourable winds?
Bird migration has always fascinated scientists, and the behaviour of billions of migratory birds has been studied for decades. One important question was how these migratory birds coped with adverse wind conditions when flying over deserts, large lakes, seas and oceans. Recent studies have shown that migrants can choose when to fly in order to avoid adverse conditions and also increase their travel speeds. Birds can also avoid drifting off-course by migrating in favourable tailwind conditions; however, it costs extra time and energy when these tailwinds are infrequent.
Researchers from the University of Oklahoma, Norman, Oklahoma, U.S. examined the flight strategies of nocturnally migrating birds (February 2016, Scientific Reports). During the autumn of 2013 and 2014, they used radars to collect data about bird behaviour every five to ten minutes for 55 nights.
They found that migratory birds in flight often drifted sideways when facing cross-winds or wind blowing across their direction of travel. These birds also actively assessed the degree to which they need to compensate for wind.
They noted that when facing cross-winds, birds at inland sides preferred drifting, while those flying near the Atlantic coast oriented and tracked away from the coast. These behaviours suggest that birds migrate in an adaptive way to conserve energy.
