I promised another dive into bird biology this month. How about a quick debunking of the old myth that birds have poor senses of smell? This is adapted from a section of a talk I’ve given a couple of times called “Surprising Secrets of Bird Biology.”

Birds tend to have small olfactory bulbs (a brain structure that’s key to processing smells) compared to mammals, and for a long time, scientists assumed this meant they couldn’t smell well.

This goes all the way back to John James Audubon, who did a series of experiments in the 1820s to determine whether Turkey Vultures located meals of carrion by sight or by smell. When Audubon hid a stinky rotting hog carcass under some grass, vultures ignored it, but they quickly began to feed on a freshly killed rabbit that he left out in plain view. So, Audubon concluded that it was sight, not scent, that was key.

Not until the 1960s did an ornithologist named Ken Stager debunk this and show that Turkey Vultures use a specific chemical compound emitted by decaying corpses, ethyl mercaptan, to find meals.(Apparently the vultures didn’t go for Audubon’s disgusting hog because they actually don’t like animals that have been dead for more than a few days.) Stager was tipped off by oil company employees who’d noticed that vultures were attracted to leaks in gas pipelines—ethyl mercaptan is also the substance that gives natural gas its rotten egg smell!

Experiments in the 1990s added certain seabirds, including petrels and albatrosses, to the list of birds for which smell is important. A biologist named Gabrielle Nevitt noticed that these specific seabird species were quickly attracted to crushed krill spread on the ocean’s surface, while others were not. How were they locating the potential food in the big, wide ocean? She eventually figured out they were honing in on dimethylsulfide (DMS), a chemical with a strong odor that’s released when zooplankton like krill digest phytoplankton. This lets these seabirds locate potentially food-rich locations over long distances.

More recently, an ornithologist named Danielle Whittaker has looked at the sense of smell in juncos. Her research focused on oil produced in a gland at the base of birds’ tails, which they use for preening and feather maintenance (they use their bills to spread oil from the gland on their feathers). In juncos, odors in this oil vary between sexes, between seasons, and between birds with different levels of aggression. Whittaker’s experiments show that juncos can detect these smells and seem to get information about each other from them.

There are many more studies I could summarize here, but basically, it’s become clear that the sense of smell is actually very important for a wide range of bird species. So if anyone you know ever repeats the old chestnut about how birds can’t smell, you have my blessing to confidently tell them they’re wrong!

Words About Birds

No new writing from me this month, but I should have more to share soon! Some stories that have caught my eye…

Something fun related to the smell rant above: Audubon did a neat little piece of the sensory worlds of birds, including how robins detect worms under the soil and how shorebirds and kiwis hunt via vibrations. It’s a great reminder that animals often experience the world in vastly different ways than we do.

Why were birds (and only some birds) the only dinosaurs to survive the end-Cretaceous extinction? A paleontoligist takes up this question for Scientific American. Birds were small compared to many nonavian dinosaurs and, therefore, needed less food; they could also fly away from danger. The birds that made it, in particular, were fast-maturing species, lived near water (buffering them from some of the worst effects of habitat destruction), and had beaks that made it possible for them to eat seeds after most other food was gone.

Another one from Scientific American: This is wild, but apparently experiments in five European countries consistently showed that birds more afraid of women than of men. Across 36 different species, birds tended to take flight sooner when approached by a woman than by a man. The data is compelling but the researchers behind the study admit they have no idea why this would be the case, or how the birds even tell male and female humans apart. Weird stuff!

Finally, sorry to end on a downer, but it’s worth noting that last month Emperor Penguins were officially upgraded from “threatened” to “endangered” by the IUCN Red List. The culprit, of course, is climate change, specifically the ongoing loss of the Antarctic sea ice that these iconic birds depend on.

Book Recommendation of the Month

The Breath of the Gods (last month’s recommendation) is a long book that took me a long time to finish, and when I finished it I picked up an equally long novel, but next in my to-be-read pile is Louise Blight’s Where the Earth Meets the Sky. I’m looking forward to this field work memoir about Blight’s experiences studying penguins at a remote research camp in Antarctica.

I hope you’re able to get out there and enjoy spring migration! Thanks as always for being a reader.