A candy bar wrapper advertising the 1994 FIFA World Cup is among the items in a nest that is situated beneath a dock on Amsterdam’s Rokin Canal. Above that, about fifteen COVID-19 face masks, plastic condom packaging, and McDonald’s sandwich wrappers are layered in like sediment. The most recent addition is a protein bar wrapper at the top, most likely from the previous year.
This was constructed by a bird. Actually, a number of birds. Common coots unintentionally created what biologists now refer to as a stratigraphic record of human waste over the course of three decades by piling plastic debris on top of older plastic debris. It’s both amazing and subtly devastating.
It has long been known that urban birds use plastic and synthetic waste in their nests. For years, ornithologists have observed it in dozens of species. What is novel is how methodically birds are doing it, and what that means for both their survival and our comprehension of them, as revealed by a 2025 study published in Ecology. After the breeding season ended, Auke-Florian Hiemstra, an urban ecologist at the Naturalis Biodiversity Center in the Netherlands, spent time dissecting coot nests that were gathered from the city center of Amsterdam. He was stopped when he discovered 635 pieces of plastic, some of which had expiration dates as far back as 1991, inside a specific nest that was constructed on top of an old foundation pile beneath a docking station. “We found pieces of nest material which were just as old as I was,” Hiemstra said. It’s the kind of statement that, the longer you sit with it, takes on a different meaning.
In their natural habitat, common coots construct new nests each year. There is little incentive to return because the plant materials they use deteriorate quickly. Plastic, however, does not deteriorate. Plastic is seated. It builds up. Additionally, coots have adapted in the same way that opportunistic urban animals typically do in places like Amsterdam, where there is a dearth of vegetation and an abundance of litter. Nests that endure several breeding seasons, are repurposed and enlarged year after year, and become heavier with synthetic history are the end result.
This story about adaptability and resilience is appealing. A portion of it is genuine. Building a sturdy nest requires less time, which should free up energy for hunting or protecting the area. However, the image is not clear. Midway through 2025, research from the University of East Anglia revealed that fishing line and plastic strings woven into the nest structure caused chicks to perish. Red mites and other parasites that flourish in the accumulated debris can also be found in old nests that are reused throughout the year. In certain situations, the same substance that extends the nest’s lifespan also makes it deadly.
In the words of State University of New York Oswego ornithologist Daniel Baldassarre, “it seems more likely that birds are using plastic because it’s simply everywhere and easy to find, rather than because they’ve somehow identified it as superior building material.” That distinction is important. Accommodation and adaptation are two different things; an animal that thrives is not the same as one that makes due.
The mirror this moment holds up is what makes it unusual and worthwhile to observe. There is more to those nest layers than just a log of bird activity. They serve as a record of the things we discarded. A Mars bar wrapper from the 1994 World Cup. A face mask for the pandemic. packaging for fast food from a chain that has locations in almost every nation on the planet. The birds did not decide to record the Anthropocene. They were just building somewhere to lay their eggs, using the only materials their environment offered.
It’s hard not to notice that the thing scientists are now using to study urban bird populations — the plastic stratigraphy in their nests — is the same waste stream that’s been quietly woven into nearly every ecosystem on the planet. Whether the coots are thriving because of it, or simply surviving in spite of it, is still genuinely unclear. For as long as birds return and trash continues to wash in, the nest on the Rokin Canal will continue to grow, layer by layer.
