In a fascinating – and somewhat unsettling – discovery, urban birds in Amsterdam have been turning human cast-offs into cozy homes for decades. Biologist Auke-Florian Hiemstra and his colleagues at the Naturalis Biodiversity Center have unearthed compelling evidence that common coots in the Dutch capital have been incorporating plastic waste into their nests for at least 30 years.
The research, published in the journal Ecology this February, reveals a long-term trend of these city birds utilizing discarded food wrappers, face masks, and other plastic debris in their nest construction. Hiemstra explains that analyzing these plastic nests provides a unique window into both avian adaptation and the enduring impact of human waste on the environment.
“It’s truly ironic,” Hiemstra notes, excavating a coot nest collected from Amsterdam’s canals. “Many of these single-use plastic items are used by people for mere minutes, yet these coots have repurposed them for decades.”
Hiemstra, who has dedicated years to studying nesting materials of urban birds, has previously documented coots using face masks during the pandemic and even observed magpies and crows ingeniously building nests with anti-bird spikes. He emphasizes that the use of human trash as nesting material is becoming increasingly common among city birds.
In 2021, the team focused on a specific common coot nest located on a wooden beam in Amsterdam’s Rokin canal. Upon excavation, they found layers upon layers of plastic waste, particularly food packaging. Employing a novel approach, Hiemstra and his team began to analyze the expiration dates printed on these plastic wrappers. This allowed them to effectively “date” the different layers of the nest, much like an archaeologist uses fossils to understand historical strata.
“We used the plastic like fossils,” Hiemstra explains, showcasing a collage of expiration dates from the nest. “By examining the layers of plastic, we could reconstruct a timeline of when different parts of the nest were built.”
Their analysis revealed a significant finding: common coots have been using plastic in their nests for a considerable period. Unlike traditional nests built from plant materials that decompose quickly and require annual reconstruction, the incorporation of plastic creates more durable and stable structures. This allows coots to return to and build upon older nests year after year.
The team identified at least 15 nests containing plastic dating back multiple years, suggesting a pattern of nest reuse. While acknowledging that some older plastic could potentially infiltrate newer nest layers, the researchers found clusters of wrappers with similar expiration dates at specific depths within the nests. This bolstered their confidence in the chronological accuracy of their dating method.
In the lowest layers of the Rokin canal nest, Hiemstra’s team unearthed wrappers dating back to the early 1990s, including a Mars Bar wrapper advertising the 1994 FIFA World Cup. “Remarkably,” Hiemstra points out, holding up the brightly colored wrapper, “it’s in almost perfect condition, as if it was just thrown away yesterday. But we know it’s 30 years old. It powerfully illustrates how long plastic persists in our environment and how deeply it is now woven into the natural world, even shaping the homes of our urban wildlife.”
This study serves as a stark reminder of the pervasive nature of plastic pollution and its unintended consequences, even as it highlights the remarkable adaptability of wildlife in the face of human impact. It also underscores the unexpected potential of everyday waste to provide unique insights into the natural world around us.
