2023-07-11 18:16:41
Anti-bird spikes are very effective in deterring unwanted birds from landing on balconies, railings or window sills. The humans have understood this well… and the sparrows too. Not frightened for a penny, some corvids do not hesitate to steal these metal pins from the cornices of buildings to reuse them for their own purposes. To cover a nest and protect it from predatory birds, for example. By dint of seeing testimonies of this astonishing phenomenon, four Dutch biologists concluded that it was not so anecdotal, and listed the cases – including four very recent ones – in a scientific study published this Tuesday, July 11 by Deinsi, the review of the Rotterdam Natural History Museum.
Traces of white glue
“To our knowledge, the oldest documented discovery of a partially constructed nest with anti-bird spikes dates from March 2009 in Rotterdam, the Netherlands, write the researchers. There, carrion crows were observed at a height of about 12 meters in a poplar tree, on a nest containing at least 16 anti-bird spikes. According to the author, the woodpeckers were probably taken from a nearby construction site.
This method of collecting peaks from the nearest building seems to be widespread among corvids. More recently, in July 2021, a patient at the University Hospital of Antwerp, Belgium discovered a nest of magpies in a maple tree from his fourth-floor bedroom window. This impressive nest, 30 cm in diameter, had two very distinct layers: at its heart, a classic assembly of twigs and earth to accommodate the eggs. And on the periphery, “a visible total of 148 bands of anti-bird peaks”, or “up to 1,500 individual peaks facing outwards”. Biologist Auke-Florian Hiemstra, lead author of the study, sent a drone to take pictures of the hospital roof to figure out where the magpies had stolen their weapons. Bingo. The roof edges that were closest to the tree were devoid of spikes, but you could still see traces of the white glue that had originally been used to attach them to the stone – “it is likely that the spikes were forcibly removed by the magpies themselves,” the researchers note. The edges of the roof a little further from the nest were intact.
defensive function
“Being able to build a nest with anti-bird spikes is already remarkable, the study reads, but it is even more interesting that birds use these spikes according to their original function. [à savoir, de repousser les oiseaux, ndlr].” We are beyond the simple observation that birds use artificial materials to provide their nests – the oldest examples cited by the study are telephone cables found in a nest in 1938. There, there is also a “functional use”. Magpies like to protect the top of their nest from attack, covering it with at least a dome of impenetrable twigs, or even a roof of more aggressive branches with thorns: blackthorn, sea buckthorn, hawthorn … Biologists have been convinced for nearly a century that the use of thorny branches has a defensive function in magpies: according to a 1928 study“the piling of these prickly twigs above the nest is a protective habit, acquired by this weaker member of the crow family against its enemies, there is no doubt”.
And if they have understood the interest of thorns, why not that of stainless steel picks? We know today that the mass of manufactured products on Earth exceeds biomass of all living beings. Corvids live with their time.
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