No Bird Wants to Live in a Murder Nest

In the spring of 2019, the biologist Tore Slagsvold headed into the forests outside Oslo to stage a series of tiny crime scenes. He didn’t need bullets, or bootprints, or even bodies or blood; only a handful of plush, white feathers.

Slagsvold’s audience was avian—the region’s blue tits and pied flycatchers. And with any luck, his faux, fluffy evidence was going to scare the bejesus out of them. He set up several nest boxes and scattered the feathers inside, and just as he hoped, the birds balked. They were, Slagsvold told me, afraid of the feathers, or at least what they seemed to represent: fresh violence, a predator on the loose, the possible remnants of a sharp-toothed weasel’s afternoon snack. The likely fate that awaited , should they dare enter