For thousands of years, humans have bred rock doves (a.k.a. pigeons) to travel home over massive distances. These domesticated pigeons have helped us fight wars, find shipwrecks, and deliver blood samples. But despite our long partnership, we have yet to understand exactly how they navigate hundreds of miles back to their roost. New research shows that they may, in part, be sniffing their way home.
To navigate, scientists believe that birds use both a map and a compass. The compass—the sun or the Earth’s magnetic field—tells pigeons where, say, south is. The map, which tells them home is south, could come from odors carried on winds around a pigeon’s home perch, reports German ornithologist Hans Wallraff, of the Max Planck Institute for Ornithology, in the journal Biogeosciences.
Earlier research revealed that impairing a pigeon’s sense of smell disorients the bird so that they cannot return to their home site. Wallraff’s meticulous study of air samples surrounding a pigeons’ roost suggests that odors offer consistent location cues. He believes that this can allow birds to learn to associate a given direction with a scent. So when they’re traveling and detect a certain odor—whether the sharp scent of seawater, ripe reek of the local dump, or mouth-watering aroma of a bakery—they build a mental map of the area using their olfactory memories.
In fact, the scent trail may be so strong that pigeons can navigate by it alone, Wallraff’s new model shows. Wallraff input data from his previous air sampling work, which included 46 odorous chemical compounds from 96 sites surrounding the pigeons’ home. He then modeled whether virtual birds could learn to navigate using these odoriferous signals. He found that over evolutionary time, birds become more sensitive to scents and can in fact use these pungent clues to travel home.
Although he has yet to determine which odorous chemical clues are most important, Wallraff’s findings reveal how avian olfaction may enable a bird to successfully traverse more than 1,000 miles, which is nothing to sniff at.