The new study published today in Scientists progress proves that it’s not just albatrosses that perform the aerobatics needed for spirited flight over the windy ocean. Research shows that elegant seabirds called Manx shearwaters perform the same flight feat in the seas around the UK.
The albatross glides in a corkscrew motion to harvest energy from the wind gradient on the ocean surface, where the wind gets faster with height. This method of harvesting wind power to conserve effort is called dynamic flight and explains how the albatross can travel thousands of miles across the oceans with barely flapping its wings.
Using bird-borne video cameras and GPS recorders, researchers from Oxford University’s Department of Biology have shown that the Manx shearwater also uses dynamic flight. The main difference is that by flapping their wings for part of the cycle, shearwaters can perform the same flight feat in lower winds.
The weaving and undulating flight characteristic of dynamic flight was first described scientifically in 1883 and was noticed almost 400 years earlier by Leonardo da Vinci. It has, however, remained a remarkably difficult phenomenon to prove.
“Demonstrating experimentally that a bird harvests energy from the wind shear gradient is very difficult, especially in flying birds like the shearwater,” said study co-lead author James Kempton. “So we developed a new way to calculate energy.” harvest by modeling the shape of their flight paths relative to the wind.
The researchers analyzed video footage recorded from the backs of shearwaters flying at high speed over the Irish Sea. Using this to calculate the birds’ weaving and wave motion relative to the wind, the research team was able to determine when the shearwaters used dynamic flight to harvest energy from the wind rather than expend their own energy.
The GPS loggers provided behavioral data from over 200 birds on their preferred direction of travel under different wind conditions. Analysis of this GPS data revealed that not only could the shearwaters use dynamic flight to harvest energy from the wind like the albatross; they also actively chose terms that offered the opportunity to work smarter, not harder.
“When the winds are stronger, shearwaters actively move in a direction that uses those winds to the greatest energetic advantage,” said co-first author Dr. Joe Wynn of the paper. “However, we only see it when flying to feed and not when the birds need to return to the colony, regardless of the prevailing winds.”
Unlike previous approaches to dynamic flight analysis, the approach developed by the authors could be applied to a variety of species, even birds not traditionally associated with dynamic flight such as gulls and hawks which may use the same flight technique less conspicuously.
“Our results show that it is possible to save energy by sneaking even in fairly light winds, as long as you are willing to put in a little effort to get a big return on investment,” said the lead author, Professor Graham Taylor. “The fact that the Manx Shearwater does this suggests that smaller drones could pull the same trick to extend their range and flight time when patrolling UK coastal waters.”