Seabirds track energy in tidal currents

  • A recent study used location data from GPS-tagged seabirds called razorbills to track currents in the Irish Sea.
  • When a team of biologists compared the movements of resting birds on the surface of the water with a mathematical model that lays out the currents, they found that the birds provided solid information on the speed and direction of the flow of water.
  • The researchers suggest that similar research using data from resting seabirds could help identify areas for the harvest of renewable tidal energy.

Data from GPS-tagged seabirds, as they were swept along in the strong currents of the Irish Sea, could help researchers move a step closer to harnessing the energy in those shifting tides.

Four years of tracking razorbills (Alca torda) helped Matt Cooper and his colleagues from Bangor University and the Royal Society for the Protection of Birds in the U.K. understand more about the squawking black-and-white bird’s behavior. They learned, for example, that razorbills sit for long stretches at night on the water’s surface, when they’re pretty much tossed around by the energy of the sea. That gave the team an idea, Cooper said.

A razorbill in Scotland. Image by theleastweasel via Flickr (CC BY-SA 2.0).

“We saw this as an opportunity to re-use the data and test if the birds might be drifting with the tidal current,” Cooper, an oceanographer and former graduate student at Wales’s Bangor University, said in a statement. “We took data that was discarded from the original study and applied it to test a hypothesis in a different area of research.”

Typically, researchers use a combination of high-tech buoys and radar systems to better their understanding of moving currents. But these can also be pricey. Seabirds like razorbills, on the other hand, already spend much of their time on the water, and the ones that provided these insights were the subject of the team’s behavioral study between 2011 and 2014 off the coast of northern Wales. The biologists had attached GPS tracking tags that noted each bird’s location every 100 seconds for up to five days at a time. This research used recordings from 49 tagged razorbills from a colony on Puffin Island.

Razorbills are colony-forming seabirds from the auk family. Image by Ben Andrew/Royal Society for the Protection of Birds.

Once they’d come up with this hypothesis that seabirds could provide this information, the team sifted through the data, stripping out times when the birds were flying. The current in this part of the Irish Sea can move at 1 meter or more per second (3.3 feet per second) — faster than razorbills can swim — so the researchers could determine when the current was carrying the birds along.

“[Their] changing position would reflect the movement of water at the ocean’s surface,” Cooper said in the statement.

When Cooper and his colleagues compared the collected data and compared it with a mathematical model of currents in this part of the Irish Sea, they discovered that rafts of these birds provided solid information on the direction and speed of the flow of water on the surface. The study, published Nov. 29 in the journal Ocean Science, is the first the authors know of that uses birds to track currents, they wrote.

A map shows the drifting of razorbills on currents in the Irish Sea. Image courtesy of Cooper et al., 2018.

It’s not a perfect solution, the authors caution, because the birds won’t stay put the way human-made buoys might.

“We must remember that these birds are behaving naturally and we cannot determine where they go,” Cooper said.

Still, he and his colleagues hope that “drifters of opportunity” — that is, razorbills and other seabirds that biologists study, sometimes in far-flung corners of the world — might pinpoint viable places where we could harvest renewable, tidal energy in the future.

Banner image of two razorbills by Ben Andrew/Royal Society for the Protection of Birds

Citation 

Cooper, M., Bishop, C., Lewis, M., Bowers, D., Bolton, M., Owen, E., & Dodd, S. (2018). What can seabirds tell us about the tide? Ocean Science, 14(6), 1483–1490. https://doi.org/10.5194/os-14-1483-2018

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