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When the Royal Society for the Protection of Birds of the United Kingdom (RSPB) decided to label the razorbills, their goal was to track their behavior and their movements along the coast of North Wales. The tag data revealed that at night, these seabirds spent a lot of inactive time on the sea surface. "We saw this as an opportunity to reuse the data and test if the birds are drifting with the current. tide, "says Matt Cooper, a graduate in oceanography from the University of Bangor in Wales. According to a new study conducted by Cooper, it turned out to be the potential to use seabirds to measure ocean currents. The results are published today in the Journal of the European Union of Geosciences Ocean Sciences.
Using seabirds to tell us about the tide could be particularly useful for the marine renewable energy sector. Tidal power generation requires detailed knowledge of current speeds. Scientists and engineers traditionally measure tides using radar or deploying anchors and buoys with scientific instruments. However, these screening methods are difficult and expensive. If tagged seabirds could provide tidal data over a large area, they could help identify sites that would be good sources of tidal power.
Cooper's supervisors at Bangor University were aware of his interest in tidal energy and data collection. They therefore suggested that the RSPB collect seabird data to determine if tidal information could be extracted. A few years earlier, from 2011 to 2014, aRSPBteam had installed GPS tags on razorbills from Puffin Island, in North Wales, to study their distribution, reproduction, and feeding behavior. . These black and white seabirds, similar to puffins and guillemots, do not breed on land. They spend most of their time at sea, looking for food or resting on the surface of the ocean.
Data collected when birds sat on the sea surface for hours was interesting in terms of bird behavior, but researchers at Bangor University discovered another potential use. "We took data that had been discarded from the baseline study and used it to test a hypothesis in a different area of research," says Cooper. "To our knowledge, this document is the first to describe the use of tagged seabirds to measure currents of all kinds," write the researchers in their Ocean Sciences study.
Non-invasive GPS tags on razorbs recorded their position every 100 seconds. Scientists could calculate the speed and direction of bird movements with a set of positions and a known time between each of them. After sunset, the birds spent long periods resting on the surface of the sea, drifting pbadively with the current. "[At these times] their changing position would reflect the movement of water on the surface of the ocean, "says Cooper.
With velocities greater than 1 meter per second, the average tidal currents in the Irish Sea area on which researchers focused are very fast, faster than a razorbill can paddle, but much slower than speeds reached by birds. This means that the team could filter the flying hours of the birds. In addition, the filtered data showed that when the birds were drifting, the direction of movement changed at low tide and high tide, while currents in the region had to go from down to normal and vice versa. As a result, the team could be sure to track the speed and direction of the ocean currents rather than the independent movements of the birds.
The use of seabirds to measure tidal currents has limitations. "We have to remember that these birds behave naturally and we can not determine where they are going," says Cooper. But the Ocean Sciences A study shows that this inexpensive method is likely to provide crucial tidal information over a large area. By studying other tagged seabirds, we could learn more about our oceans, especially in more remote areas where it is difficult to collect oceanographic data.
Cooper also hopes that this method will reduce the costs of producing tidal renewable energy, "which has been an obstacle to the development of this industry if necessary".
Source:
European Union of Geosciences. .
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