Study offers a bird’s eye view of a bird’s smell

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Male junco. Image: Nicole Gerlach

By: Kaylie Connors

A birds-eye view is a good one, but researchers are finding that a bird’s ability to use smells and odors may be another of their senses worthy of praise.

They may use odor to communicate and help them mate, according to a Michigan State University study.

“Until a few decades ago it was widely believed that birds didn’t even have a sense of smell,”  said Danielle Whittaker, a biologist who led the study published recently in the Journal of Experimental Biology. “We are way behind in birds compared to other animals on understanding how they use odors.”

In the 1970s, researchers began hypothesizing if animal scents were a result of their microbiome, said  Kevin Theis, another biologist and co-author of the study. A microbiome is a collection of bacteria and microbes that live in and on an organism.

“Their phenotype that they are presenting to the world is a product of their microbiome.”

Phenotype refers to common  traits that an organism obtains through their DNA and the environment.

In 2013, Whittaker and Theis injected antibiotics into some birds’ preen glands to see if their odors and microbiomes would change. This experiment resulted in the changing of both.

Then in 2017, they captured wild birds and cultured their preen oil in petri dishes to test whether the bacteria made the same odors without the birds.

They did.

Preen oil comes from a bird’s preen gland and is important for mating and flight.  Whittaker had previously found that odor may be important to bird behavior such as communication and mating. They wanted to find out if antibiotics injected into the preen gland changed the birds’ microbiome, Theis said. The results were that the antibiotics changed the microbiomes and odors as well.

“We wanted to know if we actually hit the preen glands of these birds with antibiotics and change the microbiome, would the odor profiles of those secretions from those glands also change,” he said. “So that’s what set this study apart; we actually experimentally manipulated the microbiome to see if indeed the odor of the bird would change.”

The study could also apply to people, Whittaker said. In fact, it was her interest in microbiomes in humans that helped her research on bird behavior.

“Everyone has their own unique bacteria communities which changes their smell,” she said. ”We affect armpit bacteria with things like deoderant so that was a good analog for understanding these odors in the birds.”

Francie Cuthbert, an ornithologist and professor at the University of Minnesota, said that studies like the one led by Whittaker and Theis are crucial to future research.

“For a really long time researchers thought that few birds relied on odor,” said Cuthbert, who was not involved in this study. “And to uncover this is really important because it’s going to get people to think about their research and how they ask questions in different ways.”

Early in her career, Cuthbert said she  was skeptical about a birds’ sense of smell.  Once she buried her garbage in the soil of an uninhabited island during her doctoral research.

“I would dig a hole and bury my food garbage and I discovered that herring gulls were digging it up,” she said. “I kind of superficially put it there, it wasn’t at all that deep, but I saw with their beaks they were like probing, so they had to have smelled something,” she said.

“At the time I thought ‘Wow, this is interesting’ because of what people have to say about birds ability to smell, but I never pursued it.”

Discoveries like these are changing bird research, Cuthbert said.

“It’s going to be a variable that people put into their studies.”

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