They overtake us: birds build nests of anti-bird spikes

Auke-Florian Hiemstra, a biologist who studies how wild animals reuse human materials, thinks he’s seen it all. In his search for the waterfowl, a waterfowl often found in Dutch canals, he discovered nests containing windshield wipers, sunglasses, plastic carnations, condoms, and envelopes used to package cocaine.

“So my definition of what nesting material is was really broad,” said Mr. Heemstra, a PhD student at the Naturalis Center for Biodiversity in the Netherlands. “Almost anything can become part of a bird’s nest.”

However, he wasn’t prepared for what he found when he went looking for a strange nest that was spotted outside a hospital in Antwerp, Belgium, in July 2021. It was a Eurasian magpie-like nest near the top of a sugar maple tree, a cyberpunk porcupine, with thin metal rods protruding all over it. direction.

“I couldn’t believe my eyes,” he recalls. “These are birds making a nest with anti-bird nails.”

Rows of these sharp metal spikes have become a common feature in the urban environment, attached to rooftops and ledges to prevent birds from perching or nesting in buildings. But outside the Antwerp hospital – where many nails on the roofs have disappeared – the magpies have managed to turn hostile architecture into a home.

“They are outpacing us,” said Mr. Heemestra. “We try to get rid of the birds, the birds are collecting our metallic spines and actually making more birds in these nests. I think it’s just a great comeback.”

And the magpies weren’t alone in Antwerp. Over the next two years, Mr. Heemestra and his colleagues discovered several other nests, built by Eurasian magpies and carrion crows, that contained anti-bird spikes. They described it their findings This week in a research paper published in the journal Deinsea.

“It’s very cool,” he said. Mark Mainwaring, an expert on nesting birds at Bangor University in Wales, who was not involved in the new study. “It shows just how easy these birds are, and it shows a certain amount of flexibility to go out and find and use these new materials.”

Magpies and crows are both members of the corvid family, a group of birds known for their intelligence and problem-solving skills. Magpies often build domed nests, clumping thorny branches into roofs designed to protect against predators. In the nests found by Mr. Heemestra and his colleagues, magpies seemed to use anti-bird spikes for the same purpose, turning them into a thorny nest cover.

“The Antwerp nest is really like a lair for birds,” said Mr. Heemstra, who calculated that it contained nearly 50 meters of anti-bird tape and 1,500 visible spikes. “You should feel really safe sitting in the middle knowing there are 1,500 coins or a pin defending you.”

Although the researchers did not catch magpies tearing strips from the roof of the hospital, nails disappeared from the area near the birds’ nest, and other birds have been observed tearing such nails from buildings. Scientists noted that sharp human materials, including barbed wire and knitting needles, were found in magpie domes. (“That happy magpie must be coming home with the big knitting needle in its beak,” says Mr. Heemestra.)

Crows seem to use spikes differently, turning sharp spikes towards the inside of the nest. Although the idea remains unproven, placing the spikes in this way may provide the nests with more structural support, Hiemstra speculated.

It’s not entirely clear whether the birds use nails simply because they are available—in the urban wild, they may be easier to obtain than thorny branches—or if they are more convenient to work with from natural materials.

But the use of synthetic nesting materials is common throughout the avian world, according to her New review From the scientific literature of Dr. Mainwaring and colleagues, which was published in Philosophical Transactions of the Royal Society B on Monday. They found reports of tens of thousands of nests — built by 176 different species of birds, on every continent except Antarctica — containing artificial materials, including plastic bags, cloth tape, fishing line, paper towels, dental floss, and rubber bands. , and cigarette butts. .

“Whenever there is an opportunity to incorporate anthropogenic materials, man-made materials, into your nest, you are likely to do so as a bird,” said Jim Reynolds, an ornithologist at the University of Birmingham in England, and author of Birds of Prey. from the new revision. “Some of them cause furrowed eyebrows among field ornithologists, because you think, really?”

Dr. Reynolds said the results reflect the amount of litter humans leave behind, and research indicates that the use of synthetic nesting materials is becoming more common.

The long-term consequences are unknown. Bright or colorful materials can help a bird attract a mate — or attract the attention of predators. Research suggests that chemicals in cigarette butts can help Protect nests from parasites – But it can also be toxic for birds. There are many reports of chicks getting entangled in plastic or string that made its way into the nest.

As for the use of anti-bird spikes, Dr. Mainwaring was curious to know “if the behavior is spreading, if other magpies see their neighbors using these spikes on nests and think, ‘This is how they build a nest,'” he said. “And the offspring raised in those nests will also grow up thinking they are completely normal and normal.”

Mr. Heemestra suspects that there are more spikelets out there waiting to be found. He certainly hopes to be there.

“I definitely root for the birds,” he said, “I cheer for the birds and actually enjoy the birds fighting back a little bit.” “Because they deserve a place in the city just as much as we do.”