Not only monkeys and mammals are capable of curing and preventing the diseases that afflict them, but also birds and even insects. Foolish people prevent them from doing so, but wise people observe them.

I tread through the forest with high, heron-like steps. I try to brush as gently as possible against the wet hazel catkins and dripping branches. The forest smells of water and moss. I’m holding a map with mysterious little crosses marked on it—I feel as if I were playing some kind of outdoor game. Each cross is a miniature world of one bird couple, a rectangular box made of pinewood hiding a nest woven of grass, moss and feathers, always as unique and one-of-a-kind as the female that builds it. This is the setting for a mini-epic that quietly unfolds over the course of about one month—from the initial weaving of the delicate structure and the appearance of the impossibly small and fragile eggs to the feathered fledglings leaving their wooden home in mid-June.

The cool Swedish month of May has just begun—so most of the birdhouses will be empty, and I won’t find parents perched on the edges of their little nests. At this stage of the season, I could be basking in the sun on the porch of my Swedish home and eating a sweet semla from a nearby patisserie, waiting for the real action: the hatching of baby birds and the ensuing flurry of field research. But—somewhat uncharacteristically—I venture into the oak forests in the month of May to look inside the birds’ freshly set-up households. I’m on the trail of tit witches, shamanesses and crazy herbalists well versed in remedies for diseases and infections plaguing their feathery micro-worlds.

I catch a whiff of the