For decades, the notion that birds possess a poor or nonexistent sense of smell was widely accepted, often traced back to 19th-century experiments suggesting vultures located carrion solely by sight. Modern science has overturned this assumption, confirming that all birds have the anatomical structures necessary for olfaction. While visual acuity is the primary sense for many species, a significant number of birds use their sense of smell for survival, especially when finding food across great distances. The ability to detect scents varies dramatically across the avian world.
The Avian Olfactory System
The avian olfactory system shares the basic anatomical features found in other vertebrates, consisting of paired external nostrils, or nares, that lead into a series of nasal chambers. Air passes through these chambers to reach the olfactory epithelium, which contains the receptor cells that bind to odor molecules. These receptors connect to the olfactory bulb, the part of the forebrain responsible for processing smell information.
Historically, the relative size of the olfactory bulb compared to the rest of the brain was used as a measure of smelling ability, leading to the misconception that birds with small bulbs were anosmic. Research has shown that even birds with proportionally small olfactory bulbs, such as pigeons, exhibit physiological responses when exposed to scents. Genetic studies further support the role of smell, as the number of functional olfactory receptor genes varies widely across species, correlating with the size of the olfactory bulb and the bird’s ecological niche. This indicates that the importance of smell is specialized to a bird’s lifestyle.
Specialized Foragers That Use Scent
The answer to whether birds can smell food from far away is a definitive “yes” for several specialized groups that rely on long-distance chemoreception for foraging. Vultures, particularly the Turkey Vulture, are adept at tracking down carrion using smell. They are highly sensitive to ethyl mercaptan, a gas produced during decay, which they can detect from potentially eight miles away. This ability is demonstrated by their tendency to circle over natural gas pipeline leaks, as utility companies add the same sulfurous chemical to the gas to make leaks detectable.
Seabirds belonging to the order Procellariiformes, which includes petrels and albatrosses, use olfaction to locate food over the vast ocean. These “tubenoses,” named for the distinctive tubes on their bills, are drawn to dimethyl sulfide (DMS). DMS is a compound released when krill graze on phytoplankton, signaling a rich feeding area even when the prey is invisible below the surface. Some albatross and petrel species can detect this odor plume from up to 12 to 20 miles away, allowing them to efficiently navigate to food patches over thousands of miles of open water.
Another notable example is the flightless kiwi of New Zealand, which relies on a highly developed sense of smell for its nocturnal foraging. Unlike most birds, the kiwi’s nostrils are uniquely positioned at the tip of its long beak. This allows it to probe the ground and sniff out insects, earthworms, and other invertebrates buried beneath the forest floor. The kiwi’s olfactory bulb is proportionally larger than that of any other bird studied, underscoring its reliance on scent rather than its underdeveloped eyesight to find food.
Sight Dominance and Non-Foraging Uses
While specialized foragers prove the power of avian olfaction, the majority of bird species, such as songbirds and raptors, primarily rely on their superb vision for hunting and navigating. Their lateral eye placement and high visual acuity allow them to quickly spot prey and predators. For these visually dominant birds, olfaction is often a subtle, secondary sense.
Even in species where sight is paramount for foraging, smell is used for non-food related tasks. Many birds use scent for social communication, such as recognizing mates or individuals based on the odor profile of compounds in their preen oil. Smell helps some species select appropriate nesting materials, with European starlings choosing aromatic, parasite-resisting plants to line their nests. Olfaction can be involved in detecting predators or recognizing their own nest site, particularly for burrow-nesting seabirds that return to their colonies at night.