Do Birds Have a Sense of Smell? What Prairie Birdwatchers Can Notice

Yes, birds have a sense of smell. For a long time people believed birds relied almost entirely on sight and hearing. Research on anatomy, genetics and behaviour now shows that the avian sense of smell is real and useful. Its strength varies a great deal from species to species. Turkey vultures, kiwis and many seabirds depend heavily on scent. Most songbirds and hummingbirds use it in quieter, more specific ways. On a prairie walk, you can watch for clues that a bird is following its nose as well as its eyes.

Do birds have a sense of smell, and why was it doubted?

Birds have a working sense of smell, called avian olfaction. It was doubted for so long because most birds show no obvious sniffing behaviour, and their nostrils are small and easy to overlook. Early naturalists also ran experiments that seemed to show vultures found food by sight alone. Those tests were later judged flawed. Some of them involved vultures that rely on vision, and some used decayed bait that gave off little useful scent.

Later studies changed the picture. Researchers found well-developed smell centres in many bird brains, identified genes for smell receptors across bird groups, and recorded behaviour that only makes sense if the birds can detect odours. Today the useful question is less "Do birds have a sense of smell?" and more "Which birds use smell, and for what?"

How does the avian sense of smell work?

A bird smells much the way other vertebrates do. Air carrying odour molecules enters through the nostrils. The molecules reach a sensory lining inside the nasal cavity, and signals travel to the brain for interpretation.

Key terms in bird scent detection

• Nares: the nostrils, usually found near the base of the upper bill. In many species you can see them as small openings with binoculars or in a sharp photograph.
• Olfactory receptors: specialised proteins on nerve cells in the nasal lining. Each type responds to particular kinds of odour molecules. Birds carry varying numbers of the genes that build these receptors, which hints at how much a species relies on smell.
• Olfactory bulbs: the parts of the brain that first process smell signals. Scientists often compare bulb size with overall brain size across species. Larger relative bulbs tend to belong to birds that depend more on scent, such as turkey vultures and kiwis. Bulb size is only a rough guide, though, and not a precise measure of smelling ability.
• Odour plume: the drifting, uneven trail of scent carried downwind from a source. Birds that hunt by smell often move back and forth across a plume to track it.

In everyday terms, birds use smell for foraging (finding food), for avoiding danger, for recognising places or other birds, for choosing nest materials, and in some species for navigation.

Which birds have the strongest sense of smell?

The birds best known for a strong sense of smell are turkey vultures, kiwis, and tube-nosed seabirds such as albatrosses, shearwaters and petrels. Hummingbirds and songbirds sit at the other end of the scale. They rely more on vision, but they are not scent-blind.

Vulture bird sense of smell: the turkey vulture

The turkey vulture is the clearest example of a bird that finds food by smell. It can locate carrion hidden under trees or brush, where it could not see the carcass from the air. Turkey vultures have unusually large olfactory bulbs for a bird. Experiments have shown that they respond to gases released early in decay, such as ethyl mercaptan. That is the same strong-smelling compound added to natural gas so people can detect leaks. Pipeline workers once noticed turkey vultures gathering above gas leaks, which shows how strongly the birds react to that odour.

Not every vulture shares this ability. Old World vultures in Africa, Europe and Asia mostly find food by sight. In the Americas, black vultures have a weaker sense of smell than turkey vultures. Where the two species overlap, mostly in the southern part of the continent, black vultures often follow turkey vultures to a meal. On the northern prairies, the turkey vulture is the vulture you are most likely to see, mainly as a warm-season visitor.

What to notice: A turkey vulture hunting by scent often flies low over grassland, shelterbelts and coulees. It holds its wings in a shallow V and rocks gently from side to side, rarely flapping. It may circle back over the same patch of ground, as if checking for something. Often it is.

Kiwi bird sense of smell: nostrils at the tip of the bill

The kiwi of New Zealand is the only bird known to have its nostrils at the very tip of its long bill. Kiwis are flightless and feed mostly at night. They probe the forest floor and soil for worms, insect larvae and other small animals, and they sniff out prey underground. Kiwis also have large olfactory bulbs relative to their brain size. You will not meet a kiwi on the prairie, but it is a striking illustration of how far a bird's body can be shaped around scent detection.

Humming bird sense of smell: subtle but real

Hummingbirds find flowers and feeders mainly by sight, especially by colour, and many flowers they pollinate have little or no scent. Researchers long assumed hummingbirds had almost no use for smell. More recent studies suggest they can detect certain odours. In feeder experiments, for example, hummingbirds avoided sugar water carrying the scent of chemicals linked to ants and other insects. That may help them avoid a feeder or flower that is crowded with insects or contaminated.

What to notice: If hummingbirds suddenly ignore a feeder they usually visit, check for ants, wasps, mould or soured nectar before assuming the birds have moved on.

Other birds that use smell

• Seabirds with tube-shaped nostrils, such as albatrosses and petrels, track odours over open ocean to find feeding areas.
• Homing pigeons appear to use smells carried on the wind as one of several cues for navigation.
• European starlings, common around prairie farmyards and towns, are known for adding fresh aromatic plants such as yarrow to their nests. Studies suggest they choose these plants by smell, and the plants may help limit parasites or bacteria in the nest.

Bird sense of smell compared to human

Comparing a bird's sense of smell with a human's has no single answer, because it depends on the species and the odour. Some birds, such as turkey vultures, kiwis and petrels, are likely far more sensitive than people to the specific scents that matter to their survival. Many songbirds probably rely on smell less than we do in daily life, yet they still respond to odours in experiments and in nature.

Bird or group	Main use of smell	Compared with humans	What a birder might notice
Turkey vulture	Finding carrion, including hidden carcasses	Likely much more sensitive to scents of early decay	Low, rocking flight; repeated passes over one area
Kiwi	Locating prey in soil and leaf litter at night	Highly specialised for detecting buried food	Not a prairie bird; an example of extreme adaptation
Hummingbirds	Possibly avoiding insect-infested food sources	Smell plays a smaller role than vision	Feeder avoidance when ants or spoilage are present
Songbirds such as starlings	Nest material choice, food, possibly predator cues	Varies; generally a supporting sense	Green aromatic plants carried to nest cavities
Tube-nosed seabirds	Finding food over open water	Likely more sensitive to certain ocean odours	Seen mainly on coasts or at sea, not on the prairie

One helpful way to think about it is that humans are generalists who notice a wide range of smells, while many birds are tuned to a narrower set of odours that matter in their own lives.

What can you notice about bird scent use on the prairie through the seasons?

Signs of smell-based behaviour on the prairie change with the seasons, because temperature, wind and food supply all affect how scent travels and which birds are present.

Spring

Turkey vultures return to the prairies as the weather warms. Melting snow uncovers carcasses left over from winter, and warming air helps odours rise and spread. This is a good time to watch vultures quartering low over pastures and road edges.

Summer

Warm days carry scent strongly and help vultures find thermals for soaring. Hummingbirds visit gardens and feeders, so clean nectar and an ant-free feeder matter more. Starlings and other cavity nesters are busy with nests, and you may see green plant material carried in.

Fall

Turkey vultures often gather at communal roosts in tall trees or on structures before migrating south. Watching a roost at dusk or early morning is a calm, rewarding outing. Hummingbirds pass through on migration, so keep feeders fresh until they have gone.

Winter

Cold air holds and carries less scent, and turkey vultures have left the northern prairies. Winter scavengers such as magpies and ravens are generally thought to find food mostly by sight and by watching other animals. That contrast is useful to note in your field journal.

How can you observe smell-related behaviour on your next outing?

You can watch for scent use in birds with patience, a notebook and attention to the wind. These steps help you turn a general walk into a focused observation.

1. Check the wind before you leave. Note its direction and rough strength. Scent drifts downwind, so birds tracking an odour often work into the wind or cross back and forth across it.
2. Choose a good vantage point. A hilltop, coulee edge or roadside pullout with a wide view of grassland and shelterbelts suits watching vultures in flight.
3. Bring the right gear. Pack binoculars, a field notebook or phone notes, water, sun protection and layers for changing prairie weather.
4. Watch flight patterns, not just birds. Low, searching flight, repeated circling over one spot, or several birds converging on a place can all suggest a bird has picked up a scent.
5. Record conditions alongside behaviour. Write down the time, temperature, wind, sky conditions, habitat and what the birds did. Over many outings, patterns emerge.
6. Look closely at bills when you can. With good optics or a clear photo, try to spot the nostrils. Compare the large, open nostrils of a turkey vulture with the small nares of a songbird.
7. Keep your distance. If vultures are feeding, stay back so they are not driven off a meal they may have searched for over a long time.

A simple field note format

• Date, time and location
• Weather: temperature, wind direction and strength, cloud cover
• Species and number of birds
• Behaviour: flight style, circling, landing, feeding, nest building
• Possible scent source, if seen: carcass, flowers, feeder, nest material
• Questions to follow up on next time

Respectful care: scent, birds and their habitat

Knowing that birds have a sense of smell can shape how gently we behave around them.

• The nestling myth: Most birds will not abandon a chick just because a human touched it. Even so, handling nestlings causes stress and can draw attention to the nest, so leave young birds alone unless they are in clear danger.
• Keep feeders clean and unscented. Change hummingbird nectar often, especially in summer heat. Wash feeders with hot water and avoid perfumed soaps. Use ant moats rather than sprays or sticky substances near feeding ports.
• Avoid chemicals around bird areas. Pesticides and strong-smelling products near feeders, gardens and nest sites can harm birds and the insects many of them feed on.
• Value scavengers. Turkey vultures clean up carrion across the prairie landscape. Give them space on roadsides and in pastures, and avoid disturbing roost sites.
• Protect native habitat. Native grasses, wildflowers and shrubs support the insects, small animals and plant material that birds find by sight and by scent.

The next time a turkey vulture tilts low over the grass, or a hummingbird passes up a feeder it usually favours, you may be watching a bird read the air in ways we cannot. Quiet attention, a few honest notes and steady care for the land are all it takes to start noticing.