A Prickly Nest.

Birds in Belgium have been observed using anti-bird spikes, typically used to deter birds from perching on buildings, to build their nests. This behavior has been seen in Eurasian magpies and crows, who use the spikes both to keep out egg-stealing birds and to provide structural support for their nests. Scientists believe that the birds are attracted to the spikes for the same reasons that people are—they serve a practical purpose. [Extracted from the article]