Spikes placed on buildings to deter birds are being used by birds to build nests in several locations around Europe.
“It sounds like a joke,” says Auke-Florian Hiemstra at the Naturalis Biodiversity Center in the Netherlands. “But it’s kind of heart-warming that these birds are actually outsmarting us and using anti-bird material for their own benefits.”
Birds often use thorny branches as nest material, sometimes placing them as a roof to ward off predators and protect their young. In cities, however, there is a lack of prickly branches around, so a few birds have turned to anti-bird spikes.
So far, Hiemstra and his colleagues have observed this behaviour in carrion crows (Corvus corone) at one site in the Netherlands and in Eurasian magpies (Pica pica) at sites in Belgium, the Netherlands and Scotland.
In a tree near a hospital in Antwerp, Belgium, a magpie made a nest containing around 1500 metal spikes. The spikes on the side of the building closest to the tree were gone, while those on the other side were still intact. This suggests that the birds have been ripping the spikes out, as opposed to collecting loose spikes.
The researchers have also seen magpie nests with defensive domes containing barbed wire and knitting needles.
They hope to find out whether the spike-laden nests are better at defending chicks than regular ones. “Is there more breeding success when birds build nests with the anti-bird spikes? It could be possible, but for that now we have just too low of a number of observations,” says Hiemstra.
“We really hope that people start looking at nests more closely, so we can find more of these examples,” he says.
Journal reference: Deinsea