Rebellious birds are making nests out of anti-bird spikes. Researchers from two Dutch natural history museums have collected the unusual nests for the first time - some which feature 1,500 pins.
The team from the Naturalis Biodiversity Center and the Natural History Museum Rotterdam have described the "remarkable behaviour" in scientific publication Deinsea as "an ultimate adaptation to life in the city". It started with the discovery of a huge nest in Antwerp in the courtyard of a hospital, which was spotted by one of the patients.
High up in a tree, magpies made a huge nest of up to 1,500 metal spikes. For this particular nest, birds had pulled as many as 50 metres (150ft) of anti-bird pins from the eaves.
Biologist Auke-Florian Hiemstra of Naturalis describes the nest as "an impregnable fortress, because the magpies appear to be using the pins exactly the same way we do: to keep other birds away from their nest". Researchers collected nests of a carrion crow and a Eurasian magpie that were largely built with anti-bird spikes material that should have deterred birds.
Auke-Florian Hiemstra added: "It's like a joke, really. Even for me as a nest researcher, these are the craziest bird nests I've ever seen."
Kees Moeliker, director of the Natural History Museum Rotterdam and co-author of the scientific publication, said: "Just when you think you've seen it all after half a century of studying natural history, these inventive crows and magpies really surprise me again."
Magpies make a roof on their nest to prevent the robbery of eggs and young and they usually specifically look for thorny plants in nature for this purpose. However, in the city there is another option - the anti-bird spikes.
The research says it is not just one pair of magpies that have utilised 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 are currently only known from the Netherlands, the study explains.
