ArtikelBird nests made from anti-bird spikes

The use of man-made, even sharp materials for nest building in birds is well known. The first report of a crow’s nest made of barbed wire dates back to 1933, and recent (news) reports document the use of e.g. nails, screws, and drug users’ syringes in avian architecture. Here we report the first well-documented study on nests of carrion crow Corvus corone and Eurasian magpie Pica pica that almost entirely consist of material that is meant to deter birds: anti-bird spikes. Carrion crows in Rotterdam (The Netherlands) and Eurasian magpies in Enschede (The Netherlands), Antwerp (Belgium), and Glasgow (Scotland) tear entire strips with sharp metal pins off buildings and use them as nesting material. Two anti-bird spike nests, now in the collections of Natural History Museum Rotterdam (crow) and Naturalis Biodiversity Center (magpie), were analyzed for composition and structure. Magpies may use the anti-bird spikes not just as ordinary nest material, but specific placement in the dome, overarching the nest, hints at functional use. The anti-bird spikes may be used by birds in the same way as they were intended to be used by humans: to ward off (other) birds. Crows, for example, are known to prey on magpie eggs and offspring and the specific choice of this sharp material could benefit nest defense, for which magpies may normally rely on thorny branches. Other magpie domes observed were constructed with barbed wire and knitting needles. In the Anthropocene, now that living biomass is outweighed by anthropogenic mass, alternative nesting materials are increasingly being adopted by urban birds. With birds even using bird deterring materials like anti-bird spikes as nesting material, anything may become part of a bird’s nest.