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Scientists in Europe have discovered that magpies (喜鹊) and crows (乌鸦) are using an unusual material to build their nests (巢) — spikes (防鸟钉) designed to keep birds away from buildings. The birds appear to be taking away the spikes from buildings and adding them to their own nests.

Auke-Florian Hiemstra is a Dutch scientist who studies how wild animals use materials made by humans. He has seen nests that include some pretty unusual materials — things like plastic flowers, sunglasses and even fishing lines. Mr Hiemstra thinks that in large cities, it’s hard to find suitable materials to make nests, so birds build nests with whatever materials they can find.

Someone at a hospital in Antwerp, Belgium sent Mr Hiemstra a picture of a magpie nest. He never expected spikes could be used by magpies to build their nests. The top of the nest had thin spikes sticking out all over. The spikes were “anti-bird spikes”. They are usually placed on buildings to prevent birds from landing. But this time, the birds had used the spikes to make a nest.

Magpies and crows are known for being clever. The two kinds of birds are related, and are famous for being able to solve challenging problems. But the birds didn’t use the spikes in exactly the same ways. The crows used the spikes on the inside of their nests to help make the nests stronger. Magpies have to worry about other birds, including crows, stealing their eggs. They appeared to use the spikes like humans do-putting them on top of their nests to keep other birds from landing.

Mr Hiemstra said, “We learned about several other nests in Europe that also used anti-bird spikes. What’s more, there are probably more nests out there that are built with anti-bird spikes. They just haven’t been found yet.”