the tactics of the scarecrow of certain birds – Liberation

A bottle of bottle, a piece of plastic, a teaspoon … So many objects that some birds slide in their nest, attracted by everything that shines. Far from being the fruit of chance, this behavior could, in reality, a defense strategy. This is what reveals, this Wednesday, April 16, A published study by two Norwegian researchers in the review Royal Society Open Science : these anthropogenic decorations would reduce the risk of predation by pies and the crows. Therefore, some volatiles would use them to scare their predators with feathers, playing on their fear of the unknown.

The hypothesis is as follows: « We suggest that birds decorate their nest with new objects to trigger a reaction of fear in their enemies, thus reducing the risk of predation of the nest », Summing, in the introduction, scientists. To do this, they carried out hundreds of trials with the same provision. Three identical artificial nests, placed next to each other, with eggs within them. A nest was not decorated, one was adorned with white feathers and the last of a shiny metal teaspoon. Result: the two species studied, the pies and The crows – Large followers of nest looting – were much less seized with eggs protected by decorations. « The study supports the idea that birds could be less exposed to the predation of corvids if they decorated their nests with this type of material », advance the authors.

The explanation is behavioral: the corvids, a kind of bird of which the magpie and the crow is part, would be among the most neophobic, that is to say suspicious, at first glance, of any new or unusual element in their environment. This neophobia would therefore be diverted by nesting birds to scare these predators. « Why not ? comments Jérémy Dupuy, ornithologist at the Bird Protection League (LPO). That birds are able to put in place protective strategies, we already knew it. But the potential use of objects to exploit a behavioral weakness of their predators is quite new. ” And to add that this first experiment, although serious, deserves to be repeated and in -depth.

Do they do it intentionally? In reality, many volatiles insert non -natural elements to adorn their nest, without defensive aim. « Sometimes it has a link with sexual selection: males will decorate the nest of objects, often in colorful plastic, to prove to women their ability to find things in the environment, and therefore that they are able to find food for the little ones », Develops Jérémy Dupuy. Or simply to build a more cozy nest. The researchers also remain cautious: « The decoration can also send a high social and social rank signal to intruders of the same species. » Clearly, the reasons may be many. Especially since the incorporation of such objects in the nests could harm the volatiles: mammals are not very subject to neophobia. “The decoration could increase the attention of other predators. During our study, red foxes did not avoid decorated nests ”, report scientists.

A defensive strategy sometimes counterproductive, therefore. In the long term, it could also experience limits. « Corvids are particularly intelligent species with a large capacity for adaptation, Recalls Jérémy Dupuy. From the moment they understood that they had nothing to fear … It’s like the scarecrow in the field, it lasts two days. Once the crows have understood that it was just straw and a hat, it no longer works. ” The fact remains that the choice of anthropogenic objects by birds is more easily explained: waste is easy to find, especially in urban areas, while France produces millions of tonnes Each year. As this study proves, birds are far from nozzles.