The Birds That Fly Into Cyclones
Streaked shearwaters have adapted to survive in one of the stormiest places on Earth
Every time a typhoon barrels through the Sea of Japan, streaked shearwaters are faced with a choice. These seabirds could take the obvious path and fly around the storm, avoiding the swirling vortex of wind and water altogether. This seems like the safest option, but it can be risky: behind every cyclone are strong south winds which could blow these seabirds directly on to land. There, they face predators, struggle to fly, and risk colliding with buildings and trees. So, if a storm is too big to fly around, these birds will take more drastic action: they will fly directly towards the center of the typhoon, riding it north through the Sea of Japan.
“Birds consistently fly into the eye of the storm,” said Emmanouil Lempidakis, a postdoctoral student at Swansea University, “and that appears to be an active strategy, not something like moths being attracted to light.” Lempidakis and his team, publishing in Proceedings of the National Academy of Sciences, found that streaked shearwaters will purposefully fly into these large storms and travel inside them. This research is the first time that this behaviour has ever been recorded in birds.
For this study, Lempidakis teamed up with a group of researchers including Ken Yoda from Nagoya University. Yoda tracks the shearwaters’ movements using GPS transmitters attached to the birds’ backs and has collected years of data from these devices. When the team looked at data from the largest cyclones, the researchers realized that the shearwaters were drawn toward the storm’s center: “60% of birds reached within 60 kilometers of the eye”, Lempidakis said.
However, the researchers “don’t think they’re within the calm section of the storm,” said Swansea University professor Emily Shepard; instead, the birds are likely within the extremely windy eye wall, braving some of the strongest winds in the entire cyclone. They are only able to survive in these conditions thanks to their incredible flight technique.
Shearwater wings are designed to fly over the open ocean. They can harness the wind currents generated by waves, allowing these birds to glide above the water’s surface. This technique is called dynamic soaring. When using this flight style, shearwaters travel up and down in dramatic arcs. Their wings look like they are slicing the waves — in other words, shearing the water.
In conditions like these, dynamic soaring keeps these birds alive. Shearwaters “can use dynamic soaring more in windy conditions….as the wind speed increases, the amount they flap actually decreases,” Shepard explained. This flight strategy is perfectly built for high winds.
Even for shearwaters, though, flying into windy environments is risky. Todd Hass, a researcher with the Puget Sound Partnership, studied how relatives of streaked shearwaters called black-capped petrels respond to hurricanes. According to Hass, the deadliest storms for petrels are the ones where the eye of the hurricane collides directly with the land. Here, “the flight strategies that served them well during most storms can backfire and sweep the seabirds hundreds of miles inland,” he said. These events, known as “wrecks,” can kill huge numbers of seabirds. Nearly 400 shearwaters and petrels died this way in South Africa in the summer of 1984. Fortunately, this type of storm is rare: most of the time, “only a small percentage of birds get wrecked,” said Lempidakis.
Climate change, however, is making these events more common. In the Sea of Japan, “the most intense storms are becoming more intense and more frequent,” Lempidakis said. Each extreme weather event brings with it a chance for disaster. In addition to the risk of wrecks, Lempidakis explained that traveling within these storms prevents the birds from feeding; by the time the cyclone ends, they are “starving and exhausted,” he said.
As shearwaters are forced to fly into bigger and bigger storms, scientists are unsure how they will fare. “It’s so hard to know how animals respond to these rare events,” explains Chapman. It is impossible to say how much these birds will be affected by cyclones, especially in the long-term. “What will happen if they have to respond to many more every year?” Lempidakis asked.
Nonetheless, it is impossible not to feel in awe of these birds that choose to fly in the harshest storms on earth.
