In a groundbreaking study published in Science on May 1, researchers from Cornell Lab of Ornithology confirmed the results of the 2025 State of the Birds Report. https://www.stateofthebirds.org/2025/
The Cornell team analyzed 36 million bird observations that birdwatchers shared to the Cornell Lab’s eBird program, along with multiple environmental variables derived from high-resolution satellite imagery for 495 bird species across North America from 2007–2021.
The current research featured recent bird population trends at 27 km by 27 km scales, the smallest parcels of land ever attempted for an analysis across such a large geographic area. Previously national and continental monitoring programs could only estimate population trends only across entire ranges, regions or states and provinces.
The results were shocking. Although 97% of species showed separate areas of significantly increasing and decreasing populations, populations tended to decline most steeply in strongholds where species were most abundant – the very places where they should be thriving, yet they fared better where species were least abundant. Of the species they examined, 83% are losing a larger percentage of their population where they are most plentiful. Grassland and Arctic tundra birds show particularly troubling trends.
According to lead author Alison Johnston: “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.”
Some species appear to be doing well across their range or within a region, but are faring very poorly in specific locations within those regions.
“The super interesting thing is, for almost all species, we found areas of population increases and decreases,” said Johnston. “This spatial variation in population trends has been previously invisible when looking at broader regional summaries.”
Areas where populations are increasing are the bright spots, Johnston said. “Areas where species are increasing where they’re at low abundance may be places where conservation has been successful and populations are recovering, or they may point to locations where there may be potential for recovery.”
The study’s detailed mapping of population changes will help conservation organizations and policymakers better target their efforts to protect declining bird species.
Without the massive amount of data from eBird, the researchers would not have been able to complete this study. This proves the power and value of participatory data in platforms like eBird.
Sources: https://news.cornell.edu/stories/2025/05/north-american-bird-populations-suffering-severe-decline
