A third of North American bird species are rapidly declining, study warns
Researchers tracked 495 species using citizen data and found nearly 75 percent are plummeting in the regions they once thrived.
Yellow-rumped Warbler, Image: Mike" Michael L. Baird, Creative Commons Attribution 2.0 license.
Around three-quarters of bird species are in sharp decline across North America in the areas where they are most plentiful, a new study has found.
The analysis, conducted by researchers at the Cornell Lab of Ornithology, tracked 495 bird species between 2007 and 2021 using over 36 million observations submitted to eBird, an online database used by citizen scientists to record bird sightings.
“Birders have been keeping logs in their journals for 100 years or more. It’s just part of birding,” said Ken Rosenberg, a retired conservation scientist at the Cornell Lab of Ornithology who was part of the team that designed and launched eBird in 2002. “So there had been this dream, this vision of, like, what if we could harness all that information?”
The vast scale of the dataset enabled researchers to track changes across 27 square kilometre segments of bird ranges across North America, revealing that nearly 75 percent of bird species in North America are sharply declining across their habitats.
The study comes on the heels of a 2019 research project that revealed North America had lost more than three billion birds between 1970 and 2017. But rather than directly building on this research by only measuring overall species declines, the new study offers a more thorough analysis of population patterns by mapping where bird populations are rising or falling. Researchers hope this approach will guide more effective conservation, helping recovery efforts focus where they’re needed most.
“It is this kind of small-scale information across broad geographies that has been lacking and it’s exactly what we need to make smart conservation decisions,” said Professor Amanda Rodewald of the Cornell Lab of Ornithology and a co-author on the study. “These data products give us a new lens to detect and diagnose population declines and to respond to them in a way that’s strategic, precise and flexible. That’s a gamechanger for conservation.”
Image from eBird North American bird declines story map. View here.
The study also found that 83 percent of bird populations are plummeting in areas where they should be thriving. Interestingly, numbers tend to fare better where species are least abundant.
Habitat destruction and climate change are considered likely causes for the decline, but researchers said further studies were needed to uncover the exact reason.
“We’re not just seeing small shifts happening, we’re documenting populations declining where they were once really abundant,” said Alison Johnston, director of the Centre for Research into Ecological and Environmental Modelling at the University of St Andrews, UK, who led the study published in the journal Science. “Locations that once provided ideal habitat and climate for these species are no longer suitable. I think this is indicative of more major shifts happening for the nature that’s around us.”
While birds that breed in grasslands and drylands are experiencing the steepest declines, the research found that populations in the Appalachians and western mountain ranges remain stable or are even increasing.
Despite widespread population declines, the research suggests there is hope. An estimated 97 percent of bird species have at least some areas where their numbers are increasing, pointing to specific locations with potential for recovery.
“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.”
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