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Rebellious birds make nests from anti-bird spikes

The latest innovation in nest building: bird nests made from anti-bird spikes. Researchers from Naturalis Biodiversity Center and the Natural History Museum Rotterdam have collected these special nests for the first time and described this remarkable behaviour in a scientific publication as ‘an ultimate adaptation to city.’

The Antwerp magpie nest built from anti-nesting spikes

Many city buildings are equipped with anti-bird spikes: sharp metal spikes to scare away birds and prevent them from building nests there. But it now appears that birds are made of sterner stuff. The researchers collected the nests of a carrion crow and a Eurasian magpie that were largely built with material that was supposed to deter birds: bird nests made of anti-bird spikes. ‘It’s like a joke’, says biologist Auke-Florian Hiemstra from Naturalis, ‘These are the craziest bird nests I’ve ever seen – and I’m a nest researcher.’

The adaptability and creativity of urban birds seem to know no bounds. Researchers from Naturalis Biodiversity Center and the Natural History Museum Rotterdam describe these spiky structures in the Deinsea journal. ‘Just when I thought I’d seen it all after 50 years of studying natural history, these inventive crows and magpies have managed to surprise me again,’ says Kees Moeliker, Director of the Natural History Museum Rotterdam and co-author of the scientific publication.

1,500 metal spikes

It started with the discovery of a huge nest in the courtyard of a hospital in Antwerp, spotted by one of the patients. High up in a tree, magpies had made a huge nest about a square meter in size from around 1,500 metal spikes. For this particular nest, the birds had wrested up to 50 meters of anti-bird spikes from the eaves. ‘An impregnable fortress’, says Hiemstra, ‘because the magpies appear to be using the spikes in exactly the same way as we do: to keep other birds away from their nest.’

Magpies make a roof on their nest to prevent the predation of eggs and young, and they specifically look for thorny plants in nature for this. Spiky branches keep hungry egg predators away. In cities there is another option: anti-bird spikes. ‘They are literally made to keep birds at bay.’ says Hiemstra, ‘And that is how they seem to be used by birds as well.’

Several magpie nests have been found that are made from sharp materials such as anti-bird spikes, barbed wire and knitting needles.

Rebel birds

And it is not just one pair of magpies that have ventured to use the bird-repellent material. The article describes several magpie nests with anti-bird spikes as nesting material. This behaviour has already been seen in the Netherlands, Belgium and Scotland. Other sharp materials, such as barbed wire and knitting needles, are also used by magpies for the roof of their nests. Crow’s nests made of anti-bird spikes have only been found in Rotterdam thus far.

It was already known that birds are not easily deterred by the spikes. The ‘Parkdale Pigeon’ gained fame for not being scared away by anti-bird spikes and several videos show the rebellious behaviour of birds tearing spikes off roofsThe collaboration between the Leiden and Rotterdam museums has now resulted in the first scientific publication showing that birds also use those wretched anti-bird spikes as nesting material.

Biologist Auke-Florian Hiemstra with the bird-spike nest

Condoms and cocaine wraps

Auke-Florian Hiemstra (1992) is doing a PhD at Naturalis and Leiden University on the use of artificial materials in animal structures, and has previously published on the use of face masks and plastic plants in bird nests. He also regularly encounters condoms, fireworks, cocaine wraps, sunglasses and windshield wipers as nesting material for his coots. ‘If even sharp bird-repellent spikes are used as nesting material, apparently anything can end up in a bird’s nest these days. It doesn’t get crazier than this, does it?’

The large magpie’s nest made from anti-bird spikes that was found in Antwerp can be seen from 11 July as a new highlight in the LiveScience room at Naturalis, which can be visited free of charge. The Natural History Museum Rotterdam is exhibiting the crow’s nest of anti-bird spikes in the recently opened exhibition 'National Park Rotterdam', along with a number of other remarkable constructions of urban animals.

Photo of Auke-Florian Hiemstra: Alexander Schippers
Nest photos: Auke-Florian Hiemstra

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