In the 1820s, painter and naturalist John James Audubon designed an
experiment to test if birds had a sense of smell. He dragged a rotten
hog carcass into a field, then piled brush on top of it. After none of
the local turkey vultures appeared, Audubon concluded that vultures
hunted using their eyes alone.
Gabrielle Nevitt has for years pondered the smelling abilities of
animals. She has studied salmon finding their way back to their birth
streams and “tube-nosed” ocean birds, like albatrosses and
shearwaters. The researcher from the University of California, Davis
started a recent lecture in Fairbanks by pointing out how Audubon
erred in his pig-and-vulture experiment.
Turkey vultures are most sensitive to a gas called ethanethiol, the
rotten-egg scent that wafts from a carcass in the first 24 hours after
something dies. Audubon, it seems, employed a dead pig that was quite
far along in the decomposition process, emitting compounds even turkey
vultures found offensive.
Nevitt said she still notices some textbook references to birds’
inability to smell, though scientists have proven the opposite many
In Nevitt’s study of the “odor landscape” of the great southern ocean
surrounding Antarctica, she and her colleagues examined how
albatrosses could find one of their favorite meals, dead squid
floating on the surface.
“How do they find prey in a featureless ocean?” she said.
Nevitt discovered that the large seabirds could smell a few molecules
of squid from more than 15 miles away. The birds zig-zag up a scent
trail to reach their target, much like a Labrador retriever zeroes in
on a grouse.
A student who worked with Nevitt also discovered a few years ago that
seabirds’ attraction to the sulfurous smell of phytoplankton may be a
reason people find dead birds with bellies full of plastic.
Matthew Savoca, now a postdoctoral researcher at Stanford, found that
plastic discarded in the ocean becomes stinky within a few weeks as
algae coats it. Birds may gulp plastic chips down based on this scent
alone, which they associate with food. He also tested birds with
plastic not soaked in ocean water. Birds did not eat the raw plastic.
While different birds have varying senses of smell, Nevitt has studied
species with noses more sensitive than some dogs’. Even the smallest
land birds use their noses, scientists have found.
Biologist Julie Hagelin of UAF’s Institute of Arctic Biology recently
worked on a study of zebra finches, tiny birds often for sale in pet
stores. After a mother finch laid eggs, Hagelin’s colleagues in
Germany moved the eggs to the nests of a “foster” mother. When they
hatched, chicks begged for food more actively when an experimenter
puffed the real mother’s scent in the face of a chick.
“They can smell their genetic mom, even though they have never met
her,” Hagelin said of the day-old chicks. “It’s possible that Mom may
provide some chemical information in the egg that chicks recognize
Hagelin pointed out how important scent is for zebra finches and other
species like dark-eyed juncos, soon to be visitors to many Alaska
backyards. Other scientists have shown juncos select their mates based
Finches and juncos don’t possess the snorkel-like nose of an
albatross, nor the large olfactory bulb (devoted to smell) in the
brains of albatrosses and turkey vultures.
“The olfactory bulb of a zebra finch or junco is a tiny dot compared
to the rest of the brain, proving we have a lot left to learn.”
A correction: Last week, I wrote about the Innoko River. A few savvy
readers pointed out that while the Innoko may be the fifth-longest
river in Alaska depending on what branches you count, it is not
Alaska’s fifth-largest in volume of water. Among others, the Koyukuk
and Teedriinjik (Chandalar) move more water.
photos: The sense of smell is important for birds, like these robin
chicks and this spruce grouse. Photos by Ned Rozell.
Since the late 1970s, the University of Alaska Fairbanks' Geophysical
Institute has provided this column free in cooperation with the UAF
research community. Ned Rozell firstname.lastname@example.org is a science
writer for the Geophysical Institute.