A new study shows how tiny seabirds master the art of working smarter instead of harder when flying out to sea.
The new study published today in scientific progress proves that it’s not just albatrosses that perform the aerial acrobatics necessary for dynamic hovering on the windswept open ocean. The research shows that slender seabirds, called Manx shearwaters, deliver the same flight performance in the seas around the UK.
Albatross slide in a corkscrew motion to harvest energy from the wind gradient across the ocean’s surface, where the wind speeds up with height. This way of harvesting wind energy to save effort is called dynamic hovering and explains how albatross can travel thousands of miles across the oceans while barely flapping their wings.
carried by birds video cameras and GPS loggers, researchers at the Department of Biology at the University of Oxford have shown that Manx shearwaters also use dynamic ascent. The main difference is that, by flapping their wings for part of the cycle, shearwaters can perform the same feat in weaker winds.
The weaving and undulating flight characteristic of dynamic hovering was first scientifically described in 1883 and was noticed by Leonardo da Vinci nearly 400 years earlier. However, it has remained a remarkably difficult phenomenon to prove.
“Experimentally demonstrating that a bird harvests energy from the wind shear gradient is very difficult, especially in flap gliding birds like the shearwater,” said James Kempton, co-lead author of the study, “so we developed a new way to calculate energy harvest by modeling the shape of their flight trajectories in relation to the wind.”
The researchers analyzed video footage recorded from the backs of shearwaters skimming the Irish Sea at high speed. Using this to calculate the weaving and undulating motion of the birds relative to the wind, the research team was able to determine when the shearwaters were using dynamic uplift to get energy from the wind rather than expending their own energy.
GPS loggers provided behavioral data from more than 200 birds about their preferred direction of travel in a variety of wind conditions. Analysis of this GPS data revealed that not only shearwaters could use dynamic ascent to harvest energy out of the wind like the albatross† they also actively chose conditions that allowed them to work smarter, not harder.
“When the wind is stronger, shearwaters actively travel in a direction that uses those winds the greatest energetic advantage,” says Dr. Joe Wynn, co-first author of the article. “However, we only see this on the outbound flight to feed and not when the birds have to return to the colony, regardless of prevailing winds.”
Unlike previous approaches to analyzing dynamic hovering, the approach developed by the authors can be applied to a variety of species, even birds not traditionally associated with dynamic hovering, such as gulls and falcons that could use the same flight technique less conspicuously. .
“Our results show that energy savings can be made by weaving even in fairly light winds, as long as you’re willing to put in a little effort to get a big payback,” said senior author Professor Graham Taylor. “The fact that Manx shearwaters do this suggests that small drones can do the same trick to keep their flight range and duration when patrolling British coastal waters.”
James A. Kempton et al, Optimization of dynamic hovering in a flap-gliding seabird affects its large-scale distribution at sea, scientific progress (2022). DOI: 10.1126/sciaadv.abo0200
University of Oxford
Quote: Researchers show dynamic uplift isn’t just for albatrosses (June 2022, June 1) Retrieved June 1, 2022 from https://phys.org/news/2022-06-dynamic-soaring-isnt-albatrosses.html
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