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

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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

times.

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

after hatching.”

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

on scent.

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.”

Hagelin said.

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 ned.rozell@alaska.edu is a science

writer for the Geophysical Institute.

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