When it comes to some senses, birds are so exceptional that it’s an honour to be compared to them.
If you have eyes like a hawk, you’ve got the best sight around. If someone calls you a myna bird, you’re probably an excellent mimic, with the perfect clarity of hearing needed to match pitch and tone exactly.
Yet, if someone has a great sense of smell, we say they’re like a bloodhound, or a shark catching a whiff of blood in the ocean. In fact, many people assume that birds can’t smell at all. But is it true and can birds smell?
The answer is yes, birds can smell.
The erroneous belief that they can’t is based on the fact that the majority of birds we see have a relatively poor sense of smell. Other birds quite clearly demonstrate that those nostrils in their beaks aren’t just for show.
How Do We Know That Birds Can Smell?
If you consult old ornithological sources, you will find that many authorities on avian physiology claim that birds can’t smell.
Claims to the contrary represent a relatively recent change in understanding that began to take root in the latter half of the 20th century. They are supported by behavioural, biological, and genetic studies.
Numerous observational studies began to be undertaken around the world after the 1960s.
Ornithologist, physiologists, and avid enthusiasts watched birds in their natural habitats and posited which behaviours might depend upon a sense of smell.
They followed this up with studies testing their hypotheses, gathering invaluable proof of avian olfactory functionality.
For instance, sea birds with their sense of smell impaired struggle to navigate inland.
Vultures are drawn to the scents of dead animals, even when the scent is being generated by a source that does not visibly resemble a carcass or remains.
Biologist dissected the brains of different bird breeds and gained further evidence. Just like humans and other animals, birds possess an olfactory bulb.
This part of the brain is responsible for identifying and making sense of scents. It is less developed in some birds than others, but its small size does not mean it isn’t functional.
Professor Bernice Wenzel of UCLA showed direct proof of this in 1965. She affixed electrodes directly to bird olfactory bulbs and introduced scented air into their enclosure.
The activity in the bulbs spiked reliably when new odours reached those beaks.
All creatures that smell have olfactory receptor genes in their DNA, and birds are no exception.
Our rapidly expanding understanding of the information encoded in each creature’s genome has to lead to breakthroughs in the understanding of how well birds smell.
Notably, a 2008 study measured the olfactory receptor genes in multiple bird genomes. They found that birds not only have several of these genes but that they possess one variant not present in any other creature.
As number and variety of these genes correspond to the array of scents a creature can recognize, this could mean that birds register scents in ways that no other creature can.
Which Birds Have the Best Sense of Smell?
So, the science confirms birds can smell. That doesn’t change the fact that some of them exhibit far more developed olfactory senses than their brethren.
These carrion birds rule the roost when it comes to following their nose. The iconic scene of the vulture circling above a dead body has just as much to do with scent as sight.
The turkey vulture is proof of this. Studies have shown these birds can zero in on the scent of carrion from hundreds of feet in the air.
In fact, that characteristic circling is their way of zeroing in the source of that enticing (to them) odour.
As amazing as this is, it should come as no surprise. Turkey vultures have the largest olfactory bulb relative to the size of any bird.
Not only that, but these scavengers have an abundance of mitral cells, which are responsible for transmitting scent data from the olfactory glands to the brain.
The island nation of New Zealand is home to a peculiar, flightless bird known as the kiwi. With its long beak, the kiwi hunts for worms on the forest floor, audibly sniffing out the scent of its prey.
That’s right, you can actually hear these birds snorting up the air, hunting by smell. Kiwis have nostrils positioned externally, at the tip of their beak. This unique among birds, and underscores the importance of their olfactory senses.
Like the vulture, kiwi brains sport large olfactory bulbs. In fact, their sense of smell is better than their sight!
Seabirds travel far from shore on long hunting expeditions. They glide over a featureless ocean, with no horizon in sight, yet they are able to unerringly find their way home when the hunt is done.
Their sense of direction plays a part in this enviable ability, but these flying fishers also rely on a map – a scent map.
Multiple studies have begun to shed light on just how scent helps seabirds navigate.
Notably, a study involving 32 Scopoli’s shearwaters (a type of seabird) demonstrated that without their sense of smell, these birds struggle to find their way home. They also rely on smell to hunt.
Experiments involving cloth soaked with the scent of fish consistently garner the attention of birds searching for a meal, even though there’s no way the bits of material could be mistaken for actual fish.
The Bottom Line
The study of olfactory senses in birds is still in its early stages. Several birds that deserve to be lauded for their incredible feats of scent sensing prowess will surely be identified in the years to come.
Do pigeons, the best navigators of all birds, rely on the scent in ways similar to seabirds? Is anecdotal evidence claiming that parrots can smell human pheromones and sniff out illnesses true?
What does the olfactory receptor gene unique to birds allow them to smell that nothing else can?
These questions are still being answered, but the long-held scepticism about birds having a sense of smell can safely be put to rest.