Each summer, like clockwork, thousands of whimbrels, an elegant shorebird with a long, thin beak, hatch along the Arctic tundra. Their parents soon depart, and when the hatchlings are old enough, they make their way, too — guided by intuition to stop on Cape Cod to feed and rest before continuing on to Brazil.
It’s a migration as steady as the tide. No one tells them where to go, they just go. Which is why it’s so disturbing that, like dozens of other shorebird species, the whimbrels are not showing up like they used to.
In a new study, researchers from the United States and Canada analyzed nearly four decades of observations of shorebirds along the Atlantic coast, finding that almost every species is in decline — some experiencing more than 50 percent losses since 1980. Whimbrels are among the most affected, with a nearly 80 percent population decline.
“When we start to lose birds, it should be a really big warning sign — a really big red flag for us that something is wrong,” said Lyra Brennan, director of Mass Audubon’s coastal waterbird program, who was not part of the study. The findings are sobering, even for those who aren’t necessarily bird people, she said. “If you could take or leave the birds, that’s fine. But when we think about how everything is connected, that’s when we start to worry.”
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Shorebirds — with their long migration paths, specific nesting needs, and reliance on coastlines — are in many ways a health indicator for the planet. And the dramatic declines observed in the study, published this month in the journal Ornithological Applications, tell the story of a planet in peril that is experiencing both a climate crisis and extreme losses of biodiversity.
The study’s findings are based on observations of 69.6 million shorebirds between 1980 and 2019 at sites spanning the North American Atlantic coast, which allowed the authors to extrapolate to make conclusions about the health of each species. It builds on a 2007 study based on the same body of observations. The authors found that since the earlier publication, both the pace and scale of the declines have increased.
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“What we’re seeing is sort of the worst case scenario,” said Stephen Brown, vice president of science at the nonprofit environmental research group Manomet and an author of the study. “Not only have they declined dramatically, the rate at which they are declining is faster.”
Of the 28 species the study focused on, all but two experienced declines since 1980. Sixteen lost more than 50 percent of their populations during the study period. These kinds of observational studies can be vulnerable to sources of bias, the authors note, including changes in how long birds stop-over at a location and changes in migration paths that takes the birds outside of the area being observed. “However, the ubiquity and magnitude of the declines reported here provide strong evidence for widespread declines among North America’s migratory shorebird species,” they wrote.
For 19 of the species, the losses are so significant that they pass the threshold for being listed as either vulnerable or endangered species, according to the International Union for Conservation of Nature, which ranks species according to their risk of extinction.
The losses were most pronounced north of North Carolina, including in Massachusetts, where 87 volunteers conducted nearly 800 surveys of 88 sites. Several factors are probably causing the declines, the authors wrote, including coastal development that disturbs habitat, competition from such species as geese that have gained in abundance, and climate-related threats.
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Sea level rise and stronger storms can drive water further up beaches, destroying the birds’ habitat. And rapid warming in the Gulf of Maine can cause the birds’ prey to migrate further north in search of cooler waters. Even some climate adaptation efforts — such as building seawalls along coasts — can cause a problem, by converting beaches or estuaries to hardened surfaces.
“Climate change, water temperature change, water chemistry change — all of that goes into the health of our coastal systems,” said Stephen Kirk, coastal program director for The Nature Conservancy in Massachusetts, who was not part of the study.
The study’s findings in some ways tell a story that is otherwise invisible, he said. “You stare out at the ocean and it looks vast and wide and blue, and the intricacies of the food web and the things that make an ecosystem healthy are sometimes challenging to see,” Kirk said.
For researchers working in the field, the results can feel personal. Brown, of Manomet, said the report’s findings broke his heart. “I’ve spent my career trying to give these birds a chance,” he said.
But, he said, there is some reason for hope. Earlier research showed that the American oystercatcher, a species that can be found in Massachusetts, was facing a 10 percent decline. But thanks to a conservation effort by Atlantic coastal states and the Gulf of Mexico, with support from the National Fish and Wildlife Foundation, their prognosis has changed. After taking steps like installing fencing to preserve and protect nesting areas, the American oystercatcher has increased by 23 percent.
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“This is not a problem that we can’t solve,” Brown said. “There are a lot of thorny problems that we don’t really know what to do about. But the oystercatcher program was sort of proof that the approach we’ve developed works — we just need to do it.”
Sabrina Shankman can be reached at sabrina.shankman@globe.com. Follow her @shankman.