They have started using the spikes in their nests to keep other birds away. For this particular nest, magpies pulled up 150 feet of the spiky metal strip from the rooftop of a nearby hospital, creating "an impregnable fortress," said Hiemsa. Hiemstra told the BBC that more research is needed to confirm the intent of the corvids using the spikes in the nest. Magpies build roofed nests and favor spiky materials. Other spiky materials had previously been spotted in nests in the area, such as barbed wire and knitting needles.

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Persons: Auke, Florian Hiemstra, Hiemstra, —, sandra standbridge, isn't, Jim Reynolds, wasn't, Reynolds, it's, Peregrine falcons Organizations: Service, Naturalis Biodiversity Center, BBC, Magpies, University of Birmingham, Guardian Locations: Europe, Wall, Silicon, Rotterdam, Netherlands, Antwerp, Belgium, Scotland, Amsterdam