Magpies and crows in Scotland, Holland and Belgium are using metal spikes—originally intended to deter bird perching—to build their nests. The spikes appear to provide several nesting benefits, such as structural support, protection against predators and even as a signal of mate quality.

According to researcher Auke-Florian Hiemstra from the Naturalis Biodiversity Center and Leiden University, in the Netherlands, the metal spikes seem to provide a similar function to more natural materials, such as thorns. However, manmade materials in nests can be dangerous. For example, metal may get cold at night and harm chicks, or the spikes can collect materials that can be harmful to the birds.

This is not the first documentation of birds using harsh, manmade materials for nesting. The first account of a crow’s nest made of barbed wire dates back to 1933, and more modern examples include the use of nails, screws and syringes.