Can Ducks Smell?

I can still remember that 1950s Sports Afield magazine. The cover illustration depicted two weathered hunters clutching their Winchester pump shotguns, peering over the gunnels of a wooden boat that was tucked into the cattails. Their faces showed disbelief as a flock of greenheads flared away from their decoys. The headline read: “Do Ducks Have the Power of Scent?” Inside the issue, the article that accompanied the cover illustration was filled with anecdotes told by seasoned hunters telling how they had been duped when ducks “caught wind of them.”

That Sports Afield headline kept running through my head but when I asked my dad about it, he fired back at me, “Ducks can’t smell. It’s just a gimmick article to get hunters to spend a quarter and buy the magazine.” My dad had hunted more ducks than anyone I knew and I took his opinion as fact.

Just like Dad, some of the earliest ornithologists were certain that birds couldn’t smell. They dissected bird brains which revealed few, if any, olfactory bulbs – the nerve structures that send signals to the brain in order to complete the sense of smell. Their conclusions were supported by John James Audubon, often referred to as the Father of Ornithology in North America. He tested the ability of turkey vultures to follow their sense of smell by hiding a rotten carcass in some brush. When the vultures didn’t circle the dead carcass, he concluded that they could not smell.

Fast forward to the 1960s when ornithologist Kenneth Stager discovered that turkey vultures do locate their food by smell. As a carcass begins to deteriorate it emits ethyl mercaptan, a colourless liquid with a distinct sulphurous odour. This smell rings the dinner bell for turkey vultures. It’s the same chemical added to natural gas so we can detect it if it’s leaking in our homes. Since the time pipelines were first constructed, repair crews and engineers would look for circling vultures to find the exact location of leaks from a ruptured natural gas line.

At the end of the 20th century, ornithologists began to conduct many different studies that involved exposing various groups of birds – from waterfowl to scavengers, raptors and songbirds – to smells and scents. They connected electronic neuron receptors to their tiny brains. Every bird responded to some degree to different odours, shattering the age-old belief that they were nose blind. These studies also revealed that some birds use their sense of smell to locate food, others use it during mating season (male birds often emit an odour much like cologne that’s appealing to females) while others use it to identify their mates in large flocks.

These facts helped explain an incident I witnessed a few years back on a still, frigid January morning. Tuckered out from cutting firewood, I sat down with my thermos on the log pile and was enjoying a hot coffee. In the swamp below me, I heard a ruffed grouse flush. Sure enough it flew up the hogback and sailed past me, twisting and turning until it finally settled in a cedar thicket about 200 yards away. A minute later, a goshawk flew up from the swamp and in the still air, perfectly traced the flight path the grouse had taken to the cedar thicket, not missing a single twist or turn. I was amazed and could only think at the time that the hawk was indeed following the scent left in the air by the grouse.

The old Sports Afield headline, “Do Ducks Have the Power of Scent?” came back to haunt Dad and me decades later. Although Dad was on the far side of his 80s, he never missed a chance to take a potshot at a fat mallard in October. We were hunkered down in a duck blind on a mist-covered farm pond ringed with smartweed. In the predawn light, well before legal shooting time, the air was filled with swooshing ducks braking in the air, then splashing down mere yards from us. Small flock after small flock lit until we were right beside more than a hundred mallards. We didn’t move a muscle. but neither did the ducks. Instead of feeding on the luscious smartweed, they all sat bolt upright. It was eerie. Not a sound, not a breath of air, just darkness, and as if time were standing still, a hundred wild birds at attention right beside us for more than five minutes. A hen mallard moved first and quacked a warning. Simultaneously all the ducks lifted and thundered away. Nary a duck returned that morning. As we trudged back to the pickup, Dad muttered, “Those ducks knew we were there. They couldn’t see us; maybe they smelled us!”

I reminded him of the Sports Afield headline and suggested that it was possibly true. He chuckled, “I remember that article.”