Birds turn their nests into grisly crime scenes to deter squatters

Some species use a few strategic white feathers to fake their own death and protect real estate

BIRDS have been found to fake their own death to protect their nests, researchers have discovered.

A study carried out on the outskirts of Oslo uncovered a degree of cunning worthy of the most sophisticated author of Nordic noir detective mysteries.

“The key word is deception,” Prof Tore Slagsvold from the University of Oslo told The Atlantic magazine.

Underpinning the birds’ strategy is the desire to protect their homes from squatters. Nests, it appears, are valuable real estate.

The avian invaders can be other birds or members of a returning migrating flock looking for a home – but seemingly too idle to build a nest of their own. Fights have erupted over the right to occupy a nest, whether it is in a tree, stump or even a wall cavity. Another motivation is to protect eggs.

A nest is most vulnerable when the adults leave to forage for food for their offspring and developing a home security system is clearly essential.

Prof Slagsvold worked with Karen Wiebe of the University of Saskatchewan in developing their “fear of feathers” hypothesis.

They were able to piece together and replicate their ruse by setting up several nest boxes with feathers strewn haphazardly to create the impression that there had been a visit from a hostile intruder – or even that a predator was present.

The site appeared sufficiently gruesome to deter other birds – in this case, blue tits and pied flycatchers – from entering the nest.

They noticed that birds had no hesitation in entering feather-free nests.

But they appeared to freeze when they caught a glimpse of white feathers as it signalled a potential murder scene.

Several studies have shown that birds are spooked by the appearance of a dishevelled nest and will fly on rather than risk an unfortunate – or even fatal – encounter.

“All these birds have to do is make one mistake, to go into a nest box with a predator, and they’re dead,” explained Mark Mainwaring of the University of Montana.

White feathers, which can be easily seen from a distance, appeared to be a more effective deterrent than black ones.

At the very least, the sight of the white feathers would buy the legitimate owner of the nest some time.

“Even 20 minutes can give them enough time to circle back and check in,” and perhaps fight off their competitors,” Ms Wiebe said.

Another motive for creating a messy nest, observed by Sophie Edwards, an ornithologist at the University of St Andrews, was to discourage birds from dumping their unwanted eggs in a neighbour’s nest.

Birds, it appears, are not the only animals who engage in psychological warfare to deter invaders.

Titmice often grab fur from raccoons and dogs to embellish their homes and make them appear less than welcoming.

Feigning death is not uncommon among animals: sharks can go belly up to fool foes but the Japanese pygmy grasshoppers are arguably the most theatrical. Their “death” entails splaying out their legs making them impossible for a predator to swallow.