Humans to blame for steep decline in common birds
Kenda Leon Barrionuevo
(CN) — Geography, habitat and species composition didn’t matter — researchers said common North American birds are declining while rarer species are increasing their numbers.
For their study published Wednesday in Science Advances, Gates Dupont and his Princeton University colleagues uncovered this troubling trend when trying to figure out how a species’ rarity or commonness factored in to nearly a third of all North American birds vanishing over the past 50 years.
That meant doing a lot of research. The team said it analyzed 38,800 surveys spanning 50 years, six regions, and 10 million square kilometers of the United States and Canada, which included information on 1,500 bird species’ routes and the annual dynamics for 648 populations of 244 bird species.
After reviewing that crowdsourced data, the team broke down its findings.
We were surprised by the pattern
The researchers said they needed to meaningfully compare and analyze bird species across North America, balance broad ecological representations and deal with the practical constraints of their study to make their findings as accurate as possible. To that end, they analyzed six large bird conservation regions because they possessed clear east-west counterparts, so the researchers could signal potential environmental differences in their results, and they represented dominant habitats like forests, mountains and prairies.
To their surprise, they found a consistent pattern of formerly common bird species in the six regions facing decline, while formerly rare species thrived in defiance of narratives dictating that less abundant species die out first.
In fact, the researchers found that only 5% of the species across communities on average made up for 80% of the total number of declines. Among those species were the formerly most common North American birds.
“We were surprised by how consistent the pattern is across regions of common species declining rapidly and less common species increasing,” said Dupont via email. He works at Princeton University’s Department of Ecology and Evolutionary Biology. “We think there's some effect of exposure to land use change. We found that species with certain habitat preferences were previously more abundant and that those habitat preferences were related to known land use changes at the regional scale. In essence, there's some numerical exposure effect where being more common means more overlap with human impacts that are detrimental.”
Every little action helps
Although the findings are unfortunate, Dupont said they reflected a reality some people already noticed.
“People who have been bird watchers for a long time often share stories about how many more birds there used to be just a few decades ago,” said Dupont via email. “We can't continue to accept biodiversity declines and let those stories of more plentiful landscapes get lost across generations.”
Instead of sinking into the feeling of inevitability, Dupont said the public can still take action to protect the North American birds that stubbornly remain.
“Stay on top of environmental issues locally, call your representatives and donate to conservation organizations that are doing great work to protect birds and other aspects of the environment,” said Dupont via email. "Also, get to know what plant species are invasive and remove them from your yard, and replace them with native plants that can better support birds and other animals. Every little action helps.”