Hummingbirds are known for their incredible vision and ability to hover in midair, but do they also have a strong sense of smell? Here we will explore what science tells us about hummingbird olfaction and how their sense of smell may aid them in essential tasks like finding food and avoiding predators.
Quick Summary
Hummingbirds do possess a sense of smell, but it is not as well developed as their vision or even their hearing. Their small size limits the size of olfactory structures in their brain. However, smell likely plays a supporting role in feeding, reproduction, predator avoidance, and migration.
Anatomy of the Hummingbird Nose and Brain
To understand hummingbird smell, we first need to examine the structures that allow them to detect odors. Like other birds, hummingbirds do not have a nose per se. Instead, they have two small nostril openings on their bill called nares. These lead to an internal nasal cavity and olfactory epithelium – specialized tissues containing olfactory receptor cells that detect smells.
The olfactory bulbs in the hummingbird brain that receive and process smell information are quite small relative to the size of their brain. One study found that the olfactory bulbs of three hummingbird species made up just 2-5% of total brain volume, compared to over 10% in pigeons. Their tiny size suggests smell is not a hummingbird’s most vital sense.
Size of Olfactory Structures Relative to Body Size
Looking at the size of olfactory structures relative to overall body size can also give clues to the importance of smell. By this measure, hummingbirds have olfactory bulbs that are proportionally much smaller than songbirds of similar body size. However, they are still larger relative to body size compared to birds that rely less on smell, like parrots.
Hummingbird Responses to Smells
Several behavioral studies demonstrate that hummingbirds do perceive and respond to odors, confirming they do have a functional sense of smell.
Reactions to Floral Scents
Multiple experiments have shown hummingbirds are drawn to the scent of flowers, even when no visual cues are present. When smelled the scent of certain flowers alone, without being able to see them, hummingbirds will readily attempt to feed.
They also learn to associate floral scents with food rewards. Hummingbirds that smell a fragrance while feeding will later respond to that smell by searching for food.
Avoidance of Predator Odors
Hummingbirds exhibit behavioral and physiological responses indicating fear when exposed to odors from predatory hawks and cats. Just the scent puts them on alert, similar to hearing a predator’s call.
Use of Smell in Reproduction
There are indications hummingbirds may use scent in courtship displays and assessing potential mates. Males will perform display dives in front of perfumed females. Females also spend more time investigating scented versus unscented males.
Importance of Smell to Hummingbirds
While hummingbirds clearly can and do detect smells, their sense of smell appears weaker overall compared to other birds like pigeons, parrots and vultures. But it likely still serves several important functions:
Finding Food Sources
The strong link between floral scents and nectar rewards means smell helps hummingbirds locate preferred flowers, even through dense vegetation or at night.
Assessing Predation Risk
Detecting predators by smell allows hummingbirds to anticipate threats that may be out of sight. This gives them more time to flee or hide.
Choosing Mates
Smell may help hummingbirds identify appropriate mates and assess reproductive compatibility through chemical signals invisible to humans.
Navigation
Some scientists speculate hummingbirds may use smells in navigation, particularly during migration. Smells wafting from land may guide them towards stopover sites.
| Sense | Importance for Hummingbirds |
|---|---|
| Vision | Extremely high |
| Hearing | High |
| Smell | Moderate |
| Touch | Low |
| Taste | Low |
Differences Between Hummingbird Species
Most research has focused on a few common hummingbird species. But there are over 300 different hummingbirds, and there are some indications smell may be more important for certain species.
One comparative study found hermit hummingbirds had significantly larger olfactory bulbs compared to other species. These differences likely relate to adaptations in their specific feeding behaviors and food sources.
More research is needed comparing anatomical, behavioral and genetic differences across hummingbird lineages to fully understand variation in avian smell capabilities.
Conclusions
While vision is their dominant sense, scientific evidence confirms hummingbirds do use smell to locate food, detect threats, interact with mates, and possibly navigate over long distances. Their limited olfactory anatomy probably rules out a sophisticated sense of smell on par with dogs or even pigeons. But their unique evolutionary pressures have clearly resulted in a sense of smell adapted to the needs of being a hummingbird.
Understanding all the senses and abilities of hummingbirds allows us to better provide for their needs in gardens, conservation, and captivity. Appreciating the subtleties of hummingbird smell can help us support their behaviors in nature and their remarkable ecological adaptations.
