Crows and magpies using anti-bird spikes to build nests, researchers find

Nests recovered from trees in Rotterdam in the Netherlands and Antwerp in Belgium were found to be constructed almost entirely from strips of long metal spikes that are often attached to buildings to deter birds from setting up home on the structures.
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While the Rotterdam nest was made by crows, the other three were built by magpies, which construct large dome-like nests. The crows used the anti-bird spikes as a sturdy construction material, but the magpies may have appreciated their intended use: they placed most of the spikes on the nest’s roof where they could deter predators, including other birds and weasels.
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It is not the first time birds have been found to incorporate urban materials into their nests. In 1933, a South African museum reported a crow’s nest fashioned from hard-drawn copper, galvanised iron and barbed wire. Nails, screws and even drug users’ syringes have all found their way into birds’ nests.
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Rather than finding old strips of anti-bird spikes at rubbish dumps, Moeliker, who previously won an Ig Nobel prize for documenting the first known case of homosexual necrophilia among ducks, says crows and magpies appear to be finding and removing the metal strips from buildings. “They are ripping the stuff off. It’s been observed in several kinds of birds,” he said.