Magpies use 'anti-nesting' spikes to keep other birds away

Impregnable fortress

Scientists from Naturalis Biodiversity Center and the Natural History Museum Rotterdam further studied the nest materials of Eurasian magpie and carrion crow that were mainly built with bird-repellent material.

Auke-Florian Hiemstra, a biologist says, "It's like a joke, really, even for me as a nest researcher, these are the craziest bird nests I've ever seen."

The study also notes that the adaptability and creativity of these birds seem to know no bounds. 

Hiemstra highlights that the birds have created an impregnable fortress, having pulled as many as 150 feet (50 meters) of anti-bird pins from the eaves.

He said, “the magpies appear to be using the pins exactly the same way we do: to keep other birds away from their nest.”

Scientists believe the motive behind building the spiky structures, is because magpies think similarly to humans, and have safety and security concerns about their eggs. 

Past research has already established that birds are not easily deterred by pins and other unique nests have been seen by watchers too. Similar magpie nests have been observed in the Netherlands, Belgium and Scotland, where birds have built roofs for nests using sharp materials like barbed wire and knitting needles. 

Adaptation to modern life

The research highlights examples of more rebellious birds unafraid of anti-bird pegs such as the ‘Parkdale Pigeon’.

Videos of the pigeons show them tearing the spikes from roofs.

Referring to his past research, Hiemstra reports that he regularly encounters birds nests built with plastics including products like condoms, fireworks, cocaine wraps, sunglasses and windshield wipers

“If even bird-repellent sharp spikes are used as nesting material, apparently anything can end up in a bird's nest these days. It doesn’t get any crazier than this, does it?" he said. 

Kees Moeliker, director of the Natural History Museum Rotterdam and study’s co-author said, "Just when you think you've seen it all after half a century of studying natural history, these inventive crows and magpies really surprise me again.”

People can now visit the LiveScience room of Naturalis to view the large magpie nest made of anti-bird pins from Antwerp, free of charge in the Leiden, while the spiky crow’s nest can be viewed at The Natural History Museum, Rotterdam.

The study about the spiky nest structures was published in the scientific journal Deinsea on 11 July. 

Abstract

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, over-arching 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.