The long-standing belief that birds have a poor or non-existent sense of smell (olfaction) has been decisively overturned by modern biological science. For decades, it was assumed that birds relied almost entirely on their superior vision and hearing, a misconception fueled by early, flawed experiments. A functional sense of smell is widespread across the avian class, and for many species, it is a highly developed tool for survival. This sensory ability allows birds to locate food, navigate vast distances, and communicate.
The Avian Sensory Apparatus
The capacity for smell in birds begins with the olfactory bulbs, which are paired structures in the forebrain that receive and process information from the nasal cavity. The size of these bulbs, relative to the rest of the brain, serves as a strong neuroanatomical indicator of a species’ reliance on olfaction. Researchers can use this ratio as a proxy to gauge how important scent is to a bird’s daily life and ecology.
A typical songbird generally possesses a relatively small olfactory bulb, which historically contributed to the incorrect generalization that all birds have a poor sense of smell. In contrast, species that hunt in low-light conditions or over featureless environments, such as nocturnal birds, often exhibit proportionally larger olfactory bulbs. This variation confirms that olfaction is not a diminished sense across the board, but rather a specialized one that has evolved differently depending on a bird’s needs. The reliance on smell is particularly evident in species where visual cues are limited, such as those that forage at night or beneath a dense forest canopy.
Smelling for Survival: Food and Foraging
The ability to smell food is a primary driver for a highly developed olfactory system in several distinct groups of birds. New World Vultures, particularly the Turkey Vulture, possess an exceptional sense of smell, which they use to locate carrion hidden from sight. These scavengers can detect extremely low concentrations of ethyl mercaptan, a gas released by the decaying tissues of recently deceased animals. This acute sensitivity allows the Turkey Vulture to find a fresh carcass below a forest canopy, a foraging strategy that Black Vultures, which rely more on sight, often exploit by following the Turkey Vulture’s descent.
In the vast, open ocean, Procellariiformes (a group that includes petrels, shearwaters, and albatrosses) use smell to locate patchy food resources over thousands of miles. They are highly attuned to dimethyl sulfide (DMS), a volatile sulfur compound released by phytoplankton as they are grazed upon by zooplankton. By following the plume of DMS, these seabirds efficiently track down areas of rich feeding activity. The small, flightless Kiwi, a bird with poor eyesight, relies on its unique anatomy to find food. It is the only bird with nostrils located at the tip of its long beak, an adaptation that allows it to probe the soil and sniff out subterranean prey like earthworms, grubs, and insects.
Smell in Social and Navigational Contexts
Beyond finding food, olfaction serves functions in navigation, social recognition, and communication. The homing pigeon uses scent cues to create an “olfactory map” of its surrounding environment. By associating windborne odors with specific directions and locations, these birds can orient themselves and navigate back to their home loft, even when released in unfamiliar territory. This suggests that the chemical landscape of the atmosphere plays a role in the long-distance movements of migratory species.
Scent also plays an important role in avian social interactions, often originating from the uropygial gland, which produces preen oil. This oil, spread over the feathers, contains volatile compounds that convey information about an individual’s sex, reproductive status, or genetic makeup. Some songbirds use these chemical signals to assess potential mates or to identify their own offspring within a crowded nest. In some ground-nesting species, the preen oil’s scent profile may be altered seasonally to help camouflage the nest from predators.