Old McDonald's container against white backdrop
In one nest, researchers found a McDonald's McChicken container from 1996.
Eurasian coots are round, black waterbirds with distinctive, chicken-like feet. Each year, these birds typically build new, bowl-shaped nests using leaves, rushes and reeds. But, while nesting in cities, they often supplement these natural, biodegradable materials with man-made garbage.
Now, scientists are studying Eurasian coot (Fulica atra) nests to learn more about how humans are affecting the natural world. They’re also using the nests to investigate Eurasian coot behavior in urban environments, they report in a new paper published last month in the journal Ecology.
The inspiration for the study came from Eurasian coot nesting sites on the canals in Amsterdam’s city center. Auke-Florian Hiemstra, a biologist at the Naturalis Biodiversity Center, noticed that the birds were incorporating litter and plastic debris into their nests. He wondered if he could use the layers of trash to unravel each nest’s history—similar to how dendrochronologists use the rings of a tree.
In September 2021, after the breeding season had ended, Hiemstra and his colleagues ventured out into the city looking for nests. After first checking each one for hibernating smooth newts, they placed the nests in plastic bags and hauled them off to the lab for analysis. In total, they gathered 15 nests.
Back in the lab, they carefully dismantled each nest, working layer by layer to separate natural and man-made materials. Then, they studied each piece of trash to search for clues about its age—relying on things like expiration dates or promotions for specific events.
Based on this data, they gleaned that most of the nests were less than three years old. But they found one, nicknamed the “Rokin nest,” that appeared to be more than 30 years old. Since coots have only been nesting in the city since 1989, the nest tells nearly the entire story of the species’ time in Amsterdam.
Pile of trash on a concrete pylon
The "Rokin nest" is 30 years old and has likely been used by at least three generations of Eurasian coots.
The Rokin nest contained 635 pieces of plastic, which functioned “like a time capsule of human waste,” writes Science’s Gennaro Tomma. Inside, they found a candy bar wrapper that referenced the 1994 FIFA World Cup and a McDonald’s McChicken container from 1996. Eurasian coots typically live to be between 5 and 10 years old, so they suspect that at least three different generations may have used the Rokin nest.
“How we interact with our environment is … quite literally woven into the nests of the birds," says Hiemstra in a statement. “History is not only written by humans; nature is keeping track as well.”
Is the abundance of plastic in Eurasian coot nests necessarily bad? Yes and no, says Hiemstra. Since plastic doesn’t break down, using it means the birds don't have to spend as much time building new nests each year. That gives them more time and energy to complete other important tasks, like defending their turf or searching for food. Plastic may also help Eurasian coots thrive and proliferate in urban settings.
“They are one of the only birds that truly adopted plastic as a nesting material,” Hiemstra tells NewScientist’s Madeleine Cuff. “While some say it is a very sad development, I also think it is a very creative development.”
Black bird with white beak swimming atop water
Eurasian coots are round, black waterbirds with "chunky, dinosaur-like feet,” says Hiemstra. Pexels
But plastic can also be hazardous. Animals can easily become entangled in man-made debris, and eating plastic can cause intestinal blockages, starvation and death. Many of the nests contained a layer of disposable face masks—a remnant from the Covid-19 pandemic—and these masks, in particular, are a “dangerous trap for coots, with their chunky, dinosaur-like feet,” Hiemstra writes on social media.
In addition, old nests can also harbor parasites and pathogens that might be harmful to the birds. Reusing the same nests over and over again might also be an indication that the birds can’t find any new nesting sites, which could affect their ability to successfully reproduce. The International Union for Conservation of Nature lists Eurasian coots as “near threatened” in Europe, but as a species of “least concern” globally.
More than likely, the birds are using plastic simply because it’s abundant and available. But, moving forward, researchers hope to conduct additional studies to investigate these and other questions.
“There may be way more data in a bird nest than you may realize,” Hiemstra tells Science.
In the meantime, the trash the researchers pulled out of the nests is being recycled yet again—for an exhibition at the Museon-Omniversum in The Hague, Netherlands, on the Anthropocene, the name for the current era in which human behavior is substantially affecting the environment. Hiemstra hopes the display will inspire “thousands of kids to make our future (nest layers) a bit greener,” he writes on social media.
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Sarah Kuta | READ MORE
Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.