A newly published study has found that nearly 75% of bird species in North America are sharply declining across their ranges, and eight in 10 plummeting in the very areas where they’re thought to be thriving and plentiful. Nearly every species, 97%, had gains and losses in their populations depending on the location, the study found.
The researchers used birdwatcher citizen science data from eBird, an online database where birders can record checklists of all the birds they see at a particular place and time. The researchers analyzed observations from 36 million checklists from 2007 to 2021 that included nearly 500 bird species in North America, Central America and the Caribbean.
Rather than just look at population declines for each species, the study identifies specific areas where populations are either declining or increasing, which paints a more comprehensive picture of population trends and highlights areas where conservation actions could be focused.
While three-quarters of all species declined across their ranges, the study found that 83% of bird species experienced significant population decreases in areas where they were most abundant and where habitat is considered most suitable for them — a counterintuitive finding that surprised the researchers. This pattern of decline was pronounced for birds breeding in grasslands and arid lands.
Birds that breed in the Arctic and northern latitudes showed the highest declines. The researchers posit that the warming climate, especially in the tundra, could be impacting breeding habitats there for many of the species, driving the declines.
“That is a worrying signal,” study author Alison Johnston from the U.K.’s University of St. Andrews told Mongabay. “That’s a wake-up call for us in terms of understanding the extent of damage that we’re having on the natural world.”
A 2019 study sounded the alarm on declining North American bird numbers, finding the region lost nearly 3 billion birds since 1970. “This new analysis helps us turn that alarm into action by pinpointing where declines are happening within species’ ranges,” James J. Giocomo from the American Bird Conservancy (ABC), who wasn’t involved with the study, told Mongabay by email.
Despite the troubling overall decline, the study suggests that most bird species still have small areas in their range where populations are growing, which can potentially serve as refuges to help their populations recover.
“We can learn what is working for those species in those places, and that can help our conservation planning,” Johnston said. “We have so much more knowledge about what’s happening ecologically, and that knowledge is power.”
“For American Bird Conservancy, this kind of spatially explicit trend data is invaluable,” Giocomo said, adding it helps prioritize conservation efforts. “We can use this information to fine-tune our collaborative work with ranchers, farmers, and land managers — targeting resources where they’ll matter most and adapting where needed.”
Banner image: Williamson’s sapsucker (Sphyrapicus thyroideus), one of the birds declining in areas where they’re abundant. Image courtesy of Blair Dudeck/Macaulay Library/Cornell Lab of Ornithology.
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