“Just the fact they’re using these anti-bird spikes to protect their nests … is like the perfect comeback,” Auke-Florian Hiemstra, lead author of a study on the nests published this week, said in an interview. “These rebellious birds [are] outsmarting us.”

The birds — mostly of the Corvidae type, which includes magpies and crows — have been spotted making such nests that incorporate the “hostile” architecture in Scotland, Holland and Belgium, according to Hiemstra.

The metal spikes are believed to give “structural support” to the nests, in some instances creating dome-like roofs, he said. They also come in handy for “nest defense,” Hiemstra added, to ward off predators and protect eggs, such that “the nest is like a fortress.” His study was published in Deinsea, an online journal of the Natural History Museum of Rotterdam.

The researcher of artificial materials in animal structures at the Naturalis Biodiversity Center and Leiden University in the Netherlands said he first came across such a nest in a hospital courtyard in Antwerp, Belgium, after it was spotted by a patient. Hiemstra said that massive structure contained about 1,500 metal spikes, or around 50 meters of anti-bird pins, probably stripped from the hospital roof.

The unusual actions may show some “evolutionary advantage,” Hiemstra hypothesized, with birds seeking alternatives to natural thorny plant material for their nests, in favor of sharper, human-made objects like spikes or barbed wire. “Animals always look at materials for their own gains,” he added.

Jim Reynolds, an assistant professor in ornithology and animal Conservation at the University of Birmingham who was not involved in the study, agrees that the materials being “repurposed” is an adaptation technique for birds “living and breeding in a city.”

There could be another advantage: Shiny, spiky nest fodder could be viewed as a “quality indicator” to potential feathery mates that this bird has a nice home and would make a good partner, he said.

Reynolds said he was “not surprised at all” by the birds’ wily behavior, noting that clever Corvidae have long intrigued birdwatchers “because of their toolmaking and cognitive abilities.”

Anti-bird spikes are often laid out at railway stations, car parks or on roofs of buildings to prevent the animals from perching. Similarly hostile architecture is sometimes found in doorways and benches to stop humans from dwelling or sleeping on streets in cities around the world.

“It seems that birds might be taking revenge here somewhat on our anti-bird strategies,” he added.

Although the practice is innovative, there may be some cause for concern, warned Mark Mainwaring, an ornithologist and lecturer at Bangor University in Wales who published a separate study this week on bird species incorporating “anthropogenic materials” such as candy wrappers and plastic strings into their nests.

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For instance, metal spikes may get cold at night and harm chicks. Or certain types of trash collected may be toxic or harmful to the animals, he said, although others such as cigarette butts may have some benefits in killing parasites. Colorful debris could also have the adverse consequence of attracting predators, Mainwaring said.

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He encouraged more people to look in their backyards, outside the active breeding season, and share images of such mixed-material nesting. Mainwaring’s study was published in Britain’s Royal Society Journal.

For U.S. architect Joyce Hwang, the birds’ adaptive behavior is “beautiful and pretty ironic,” she said.

Modern urban buildings often have a raft of “bird deterrents,” including electric-shock wires, netting and spikes — often to prevent “bird poop” in the vicinity — but “birds are still finding a way” to perch and make homes, she noted.

Other methods may offer better solutions, such as slopes and slanted windows to prevent birds from wanting to nest, said Hwang, an associate professor of architecture at the University at Buffalo.

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Fundamentally, anti-bird spikes or deterrents can signal an almost controlling human behavior over nature, she said.

“I think there is a kind of poetic justice,” Hwang said of the birds subverting the materials meant to keep them at bay. “It’s pretty remarkable.”