Making Sense of Senses: How Well Can Birds Smell?

Featured Image Caption: What do we know about how well birds can smell? Image Source: “Head of the yellow billed tropic bird phaeton flavirostis“, Popular Science Monthly Volume 32 via Wikimedia Commons, Public Domain.  

Source Article: Creece, D., Freire, R. and Massaro, M. (2025), Past research and future directions in understanding how birds use their sense of smell. Ibis, 167: 853-881. https://doi.org/10.1111/ibi.13398 

The Basics of Smell and the Olfactory Bulb

Take a deep breath in through your nose. What do you smell? Maybe it’s a steaming cup of coffee perched on your desk, or the familiar scent of your own perfume or cologne. Maybe, if you’ve had the recent misfortune of catching a cold, you woefully smell nothing at all. Regardless of the specifics, our human sense of smell is something that we often take for granted.  

The purpose of olfaction – finding food, navigating, and detecting danger – is very similar across the animal kingdom, but the strength of the sense between taxa (groups of animals) is highly variable. A structure called the olfactory bulb is believed to largely determine just how well many vertebrates can smell. This structure sits near the front of the brain, receives signals from the nasal cavity, and translates these signals into the perception of scent. The relative size of this structure compared to body mass likely drives the degree to which an animal can smell – the larger the olfactory bulb is compared to the rest of the body, the better the sense of smell.  

Until very recently, it was thought that birds were not heavily reliant on their sense of smell.  Given their diversity of plumage and songs, their senses of sight and hearing were assumed to be their most relied upon senses. In turn, other senses like smell were assumed to be much less critical. This assumption was also influenced by how small the olfactory bulb is in some birds, leading scientists to believe that their sense of smell was near obsolete. However, the last two decades or so in avian research have spurred a new interest in a bird’s ability to smell. Continued studies in avian neuroanatomy and genetics have revealed a wide diversity in olfactory bulb sizes and olfactory receptor genes between bird species, suggesting some sort of functional underpinning shaped by ecological needs and environmental conditions. Therefore, we are left with a deceptively complicated question: “can birds smell?”. 

How do Birds Use Their Sense of Smell?

A recent review paper from a research group out of Charles Sturt University has compiled all the known behavioral evidence of birds’ ability to smell. Behavioral studies reviewed in this paper typically employed one of two methods to test whether birds could smell; they either temporarily took away a bird’s sense of smell or introduced new odor stimuli to gauge whether there was any change in behavior. Specific responses or behavioral deficiencies implied that the birds in the study could detect certain odors. Three major behaviors were reviewed: foraging, navigation, and social behavior. For each of these categories, several bird species were tested and evaluated on their olfactory abilities.  

Locating food is the most well-researched function of olfaction in birds. Birds that feed on a diet consisting of little to no visual or auditory cues are expected to rely more heavily upon olfactory cues. These include species of vultures, tube-nosed seabirds, and kiwis, which all forage on heavily obscured food.  

Certain birds are more likely to use smell when foraging due to their feeding strategies. Vultures soar over densely forested canopies seeking hidden carrion (left), tube-nosed seabirds search for sea creatures in choppy oceans (middle), and kiwis root around in the soil with their beaks to sniff out buried invertebrate prey (right). Image Sources: “Turkey vulture in flight“, Charles J. Sharp via Wikimedia Commons, CC-BY-SA 4.0; “Wandering Albatross- east of the Tasman Peninsula“, JJ Harrison via Wikimedia Commons, CC-BY-SA 3.0; “Juvenile little-spotted kiwi (Apteryx owenii)“, Kimberley Collins via Wikimedia Commons, CC-BY-SA 4.0.  

Finding optimal foraging locations can also be achieved using smell in some birds, especially some species of tube-nosed seabirds. Certain birds in this order can detect a compound called dimethyl sulfate (DMS), which is released by ocean-living zooplankton as they feed on phytoplankton, thus indicating that the area is rich in resources. Chicks can even learn to associate certain smells with food, which will allow them to find food-rich areas after they leave the nest. This is especially important for birds that eat odorous foods with a patchy distribution, like nectar or carrion.  

Navigation also seems to be somewhat reliant on smell in homing pigeons and tube-nosed seabirds. This theory was often tested by capturing these birds, temporarily impairing their sense of smell, releasing them in a new location, and seeing how long it took them to return home. Pigeons and seabirds with impaired senses of smell often failed to return to their colonies, suggesting that odor cues are required to navigate efficiently. Unfortunately, the specific chemical compounds that assist in this navigation are not yet known, so future research is needed to determine the specifics of scent-based navigation. 

Olfaction can also drive several social behaviors in birds, including the differentiation of closely-related species, mate selection, and the recognition of individuals. By using the scent of preen oils – which is an oil naturally secreted by a bird’s preen gland – birds can recognize other birds of their own species, which is crucial when it comes to choosing a mate with which to produce viable offspring. During the breeding season, the volatile, scent-causing, compounds in these oils fluctuate in tandem with a bird’s hormone levels. The more odorous the preen oil, the higher the hormone levels! This suggests that the scent of these oils may play a role in mating, such as signaling the sex of an individual, and influencing mate choice, or indicating the overall readiness of a bird to breed.  

The preen gland, located on the lower back of the bird, secretes preen oil. This oil is typically used to condition the bird’s feathers, but may also release scents that influence social behavior. Image Source: “Pelecanus onocrotalus cleaning its feathers at sunset“, Basile Morin via Wikimedia Commons, CC-BY-SA 4.0.

Other than the recognition on the species- or sex-level, some birds can also discern the identity of individuals using scent alone. This ability is especially valuable in birds that nest in large colonies, allowing them to recognize their own offspring when they return from a foraging trip at night. Tube-nosed seabirds, like some petrels, have indeed demonstrated this capability, as chicks can recognize their own scent and adults can recognize the scent of their offspring.  

What We Know and What is Left to Learn

Clearly, olfaction is a critical sense in many birds, but the degree of its importance depends on the species. In particular, birds that are less reliant on sight for feeding, travel long distances, nest in large colonies, or are more social tend to have higher olfactory acuity. However, there is still a long way to go in terms of research in this field. Since the field’s inception, there have been less than ten studies per year on bird behavior related to olfaction. Moreover, these studies are biased towards tube-nosed seabirds and songbirds, with other taxa heavily underresearched.

It is critical to determine how odors, especially those produced by human activity, affect the livelihood of birds. Sites like landfills that emit odors from decaying food may attract birds, thus drawing them into more urbanized areas. Some seabirds might also mistake plastic debris floating in the ocean as food, as it releases the same volatile chemical (DMS) as the birds’ natural prey. Overall, awareness, understanding, and continued research on the impact of odors on birds, as well as other wildlife, is paramount in preserving the health of our ecosystems. Hopefully, with these efforts, we can “sniff out” just how well birds can smell.

Reviewed by: Cassie Welander