The Most Metal Bird Nests You’ll Ever See
Magpies are using anti-bird spikes for their own purposes.
Two summers ago, a patient looking out his Belgian-hospital window spied in a tree an odd, abandoned magpie nest of plastic and wire. He had, by coincidence, just read a newspaper article about a Dutch biologist who studies bird nests built of trash. So he dashed off an email, and that Dutch biologist, Auke-Florian Hiemstra, was soon in the hospital courtyard, climbing aboard a cherry picker to see the nest up close.
From this aerial vantage point, Hiemstra noted that the plastic-mounted wires were actually anti-bird spikes—at least 1,500 of them, he later counted—knit together into a “fortress.” The hospital had installed such spikes to deter landings on its roof, but in areas closest to the nest, they had gone missing. There were only remnants of the glue that once held the spikes in place, as if someone—some bird—had wrested them free. Hiemstra has found some surprising stuff in bird nests before: condoms, face masks, paper packages for cocaine, pieces of windshield wipers. But this was truly the weirdest. A bird nest made of anti-bird spikes? “It sounds like basically a joke,” he told me.
What’s more, the magpie nest’s spikes were arrayed outward, as if to scare off other birds. Had the owners of this nest actually repurposed our anti-bird defenses for themselves? Magpies do often gather thorny branches—even breaking them from trees—to defend their large nests from predators. “In urban environments, there are not that many thorny branches. Or at least there’s a good alternative—namely, anti-bird spikes,” speculated Hiemstra, a Ph.D. candidate at the Naturalis Biodiversity Center, in Leiden, the Netherlands. In our bid to keep pesky birds away, we may have handed one species a novel defense.
Hiemstra, whose big halo of curly hair can resemble a bird’s nest, began eagerly sharing this discovery with biologist friends. Not long thereafter, one of them was contacted by a tree-maintenance worker who found another nest made of anti-bird spikes, this time built by crows in a tree just a short drive away from Leiden, in Rotterdam. (This nest, in contrast, had spikes facing inward, so it’s unlikely the crows were also using them defensively.) Then another magpie nest with spikes on top turned up in Glasgow, Scotland. And a third one in Enschede, the Netherlands. “More and more kept popping up,” Hiemstra told me. Wherever there are anti-bird spikes and wherever there are crows and magpies, he said, more anti-spike nests are likely waiting to be found. The discovery that seemed so unusual at first was perhaps not so unusual after all; scientists just started paying attention.
Plenty of other artificial material ends up in the nests of birds. Hiemstra had started studying this phenomenon after following a coot carrying a piece of plastic to its nest. Tim Birkhead, an ornithologist who wrote a book about magpies, told me via email that he’s seen magpie nests in Sheffield, England, made of metal wire. A recent review of why some birds use “anthropogenic materials” noted that trash has been found in the nests of 176 different species, on every continent other than Antarctica. “We were surprised at just how many species use man-made materials,” says Mark Mainwaring, an ornithologist at Bangor University, in Wales, who co-authored the review. Birds are adaptable, added his co-author Jim Reynolds, an ornithologist at the University of Birmingham, in England. “Why would birds travel miles and miles and miles to find nesting materials if there’s material closer by?” These nests full of artificial materials are reminders of how thoroughly humans have changed birds’ habitats: We’ve cleared them of native plants, littered them with plastic, and even blanketed them with hostile spikes.
Until now, though, scientists were only dimly aware of how much birds have been interacting with the very objects meant to shoo them away. Hiemstra couldn’t find much about it in the published literature. But when he took to the greater internet, he found a trove of viral videos and articles celebrating the triumph of birds: Cockatoos have been known to rip spikes off of buildings too; peregrine falcons skewer their prey leftovers on the spikes to save for later; a bird dubbed the “Parkdale Pigeon” achieved folk-hero status for stubbornly building a nest atop anti-bird spikes in Australia. Far from being simply deterred by our spikes, birds have repurposed, reused, and resisted. Maybe using stronger glue to keep the spikes in place is possible, Hiemstra mused, but he doesn’t want to give humanity any ideas: “I’m definitely cheering for the birds.”