Halfway between Scotland and Bermuda, a wild expanse of ocean draws millions of seabirds from vast distances every year. A new study published in Conservation Letters uses decades of tracking data to document that at least five million migratory birds, representing about two dozen species from both hemispheres, rely on a North Atlantic hotspot of almost 600,000 square kilometers for food.
Ecologists have long suspected that the North Atlantic served as a critical foraging zone for migrating seabird species, but they lacked data on birds’ travel patterns to justify protecting these international waters. Migratory seabirds are “one of the most threatened taxa today,” says Tammy Davies, a conservation scientist at BirdLife International and lead author of the study. Seventeen of the 21 species studied, including Atlantic puffins, Arctic terns and Bermuda petrels, face declining populations. The birds are harmed by pollution, overfishing and industrial fishing operations that net the animals along with their catches. Although seabirds’ breeding zones on land tend to be protected, their foraging sites are typically in the high seas, beyond any country’s jurisdiction.
Analyzing individual birds’ satellite-tracked migration patterns, the researchers were stunned by their sheer numbers and diversity, as well as how steadily this part of the ocean is used year-round. “What’s surprising is the amount of species congregating in this area and the distances that some seabirds are traveling to the site,” Davies says. “You have birds in the remote South Atlantic traveling 13,000 kilometers to forage in this site. Clearly, something fantastic is there which is making these birds take these journeys.”
The “something fantastic” is likely a buffet delivered by converging ocean currents, suggests a complementary study in Progress in Oceanography. It paired satellite data and computer modeling with old-fashioned birdwatching from a ship that crossed the North Atlantic in 2017. “I think there’s still a lot to be learned by going and actually looking,” says University of Glasgow ecologist Ewan Wakefield, lead author of the Oceanography study.
Within the hotspot, seabirds stuck to these food-rich currents, Wakefield says. The researchers even noticed different species hanging out in different currents, most likely driven by dietary preferences and variations in foraging behaviors such as diving.
“It’s really incredible to see one place that is so singularly important ... for some of the smallest seabirds on up to some of the really big wanderers,” says Smithsonian ecologist Autumn-Lynn Harrison, who was not involved in either study. “It’s a really unifying place.”
The researchers hope these new data will lead the international Convention for the Protection of the Marine Environment of the North-East Atlantic to designate the seabird hotspot a Marine Protected Area—and maybe set a precedent for shielding other areas in the high seas.