When we think about birds, we often picture their colourful plumage: the iridescence of a peacock’s tail or the electric blue flash of a kingfisher. Or we might consider how they use voices, from the song of the nightingale to the coo of a dove or the shriek of a jay. So it’s easy to imagine that vision and hearing must be the senses these birds use to explore their environment and interact with each other. However, smell is also vital to birds for navigating, foraging and even communicating. Yet this sense is often underestimated or ignored entirely. Some of the blame for this long-standing underestimation can be assigned to influential 19th century naturalists like John James Audobon, whose early experiments on turkey vultures led him to conclude that they could not smell and must use sight to locate their carcass suppers. He presented vultures with paintings of dead sheep, which they pecked away at. But when he shrouded putrid carrion with plant material the vultures ignored it. However, later work revealed flaws in Audobon’s …