Okay, but can birds smell?

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And I got back to the lab and
I started to open the bag to take

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the bird out, and I got this
overwhelming fresh bakery scent.

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And I was like, who? Who
brought cookies to the lab? And then

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I realized it was the bird.

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In 2013, I found myself on a
small cruise ship in the middle of

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the Atlantic Ocean, traveling
from Sierra Leone, Africa, to Brazil,

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and ultimately to the tip of
South America. Ushuaia, Argentina.

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If you've never been on the
open ocean, let me paint you a picture.

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Ocean, wind, sky, sun. Nothing
else, save for the occasional seabird.

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But in the equatorial ocean,
that was a rare occurrence. It's

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disorienting, to say the
least. As visual organisms, humans

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often use landmarks. And this
is perhaps stating the obvious. There

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are none of those in the open
ocean. Despite what one well intentioned

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cruise guests thought and
asked me, the equator is not a visible

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line on the Earth. When after
several days, I finally spotted Ascension

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Island, I land. And soon after
spotting the island, I spotted Ascension

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Island. Frigate birds wheeling
in the air around it. This endemic

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species can only be found on
this island, one of the most isolated

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on the planet. Seabirds are
fascinating. Most have delayed reproduction,

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meaning they do not start
breeding until they are more than

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5 and sometimes even 10 years
old. During the time between fledging

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and breeding, they wander the
world's oceans. Sometimes, in the

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case of various albatross
species in the Southern Ocean, they

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circumnavigate the globe many
times. Eventually, they return to

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the islands where they hatch
to find mates and start the next

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generation doing this. Getting
back to their natal island requires

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them to navigate these vast,
featureless oceans. But to seabirds,

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the oceans are full of
landmarks that are invisible to the

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eyes. In this case, the nose
knows seabird navigation, though

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it can rely on visual
landmarks, like islands relies heavily

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on their sense of smell. They
can detect upwellings, food, and,

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yes, even the island that they
grew up on. And birds can use their

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noses for much, much more than
that. Way more. But here's the thing.

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If you say birds can smell at
a dinner party, someone will probably

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correct you. That's because
there's a deeply rooted myth that

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birds have virtually no sense
of smell. And it's been repeated

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so confidently and for so
long, most people accept it as fact.

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Which brings us to the topic
of today's episode. Okay, but can

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birds smell? To get to the
bottom of this, we'll talk with Dr.

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Danielle Whitaker, a scientist
at Oregon State University and author

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of the Secret Perfume of
Uncovering the Science of Avian Scent.

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Danielle has spent her Career
studying chemical communication in

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birds, among other things. And
her work on a little gray bird most

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of us have seen at our feeders
has helped overturn two centuries

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of scientific substance. We'll
trace the surprisingly recent history

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of a myth that refused to die,
Explore what birds are actually broadcasting

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through their scent, and ask
what happens when you start paying

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attention to a communication
channel that science ignored for

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200 years? Because as it turns
out, every bird you've ever watched

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was also wearing perfume. You
just couldn't tell. Stay tuned. Welcome

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back, everyone. I'm really
excited to have Danielle with us

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today to dive into the myth
about birds not being able to smell

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and what they actually use
their sense of smell for. So thanks

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for joining us, Danielle.

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Sure. Thank you so much for
inviting me.

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Of course, most people assume
birds do not have a sense of smell.

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Why is that such a pervasive thing.

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That people think this myth
goes back a long way? This is actually

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the 200 year anniversary of
this myth.

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Oh, man.

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It's been quoted over and over
for decades without any attribution.

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A while back, I tracked it
down to its source. It's actually

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John James Audubon. Oh,
really? He published a paper in 1826.

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And I'm going to read you the title.

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Okay.

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Account of the Habits of the
Turkey Buzzard, Particularly with

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the view of exploding. The
opinion generally entertained of

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its extraordinary power of smelling.

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Exploding. All right. How did
he explode it? Such a weird title.

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So you can tell from the title
he had a little bit of a bias going

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in.

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Yeah.

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And you can also probably
infer that the idea that turkey vultures

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use their sense of smell to
find food was pretty widely accepted

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at the time. They could. They
would be seen attracted to the scent

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of dead animals, for example.
But it was also known at the time

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that a lot of birds,
particularly birds of prey, had excellent

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eyesight. And there was this
pervasive belief that these different

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kinds of traits had to involve
a trade off. So you couldn't be really

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good at one thing without
losing some kind of ability in another

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thing. You can think of it
kind of like when you have a certain

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number that you can assign to
different traits in Dungeons and

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Dragons. Right. You have to
balance them out among the different.

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And so he said, well, birds
have a great sense of eyesight. They

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can't possibly also have a
great sense of smell. And so he did

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a series of, I think we can
all agree, very poorly designed experiments

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to prove this. My favorite one
was when he took a dead pig carcass

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and put it underneath a bush
and waited for the vultures to show

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up. And when they didn't come
down and feed on the carcass, he

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took that as proof that they
couldn't smell it.

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Okay.

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He also notes in the paper,
though, that the vultures were circling

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overhead all day and that his
dogs kept attacking the carcass.

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So I think there's a pretty
obvious reason why they weren't coming

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down to feed on it.

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Yeah, I rarely see vultures
and dogs sharing a carcass, so I'm

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sure it's so funny that they
were circling around. But he didn't

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take that as evidence that
they knew there was a dead thing

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there. He thought they needed
to come to it. That's pretty dumb.

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I mean, yeah, we've learned
since then that birds use their sense

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of smell for lots of different
things. I think, like the vultures.

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I mean, is quite widely
accepted now that vultures use their

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sense of smell to find rotting
food. What other examples of birds

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that use their sense of smell
is broadly accepted versus some of

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the newer insights into what
birds can smell and what they use

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that sense of smell for?

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00:06:07,800 --> 00:06:11,200
Yeah, great question. So this
myth persisted for a long time, but

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there also persisted the idea
that there were some exceptions to

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this rule, vultures being a
primary one. The other major group

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that was thought to be an
exception were the seabirds. So I

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think people are familiar with
the idea that seabirds who have to

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navigate over large expanses
of water with no visual landmarks

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can use their sense of smell
to navigate. They also use their

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sense of smell to find food,
since they're attracted to things

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like fish and squid that are
feeding on phytoplankton. And where

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you have large amounts of
phytoplankton in the ocean, they

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actually give off a chemical
called dimethyl sulfide, which the

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seabirds can detect through
their smell. However, the largest

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class of birds in the world,
of course, is passerans, or the songbirds.

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There are more species in that
group than any other group, and they

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have relatively small brains.
I'm sure we're all familiar with

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the term bird brain and the
part of their brain that is dedicated

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to olfaction, the olfactory
lobe, is quite small relative to

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the rest of their brain, and
so it was widely believed that they

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didn't really use smell. Also,
when we look at songbirds, we associate

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them well. They're called
songbirds, for one. So they rely

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on elaborate songs and calls
to communicate. And many of them

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have flashy plumage, very
pretty feathers that they use to

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attract each Other. And so
this reliance on sight and sound

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made it easy for some people
to discount the importance of smell

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in their lives.

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Yeah. And that discounting the
importance of smell, it's so interesting.

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You know, we make inferences
from the structure of a brain about

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what senses might be
important. And in some cases, those

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inferences seem to hold, but
in this case, it really doesn't seem

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to hold. So passerines do have
a sense of smell, and they use it

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for some really interesting
things. Can you tell us a little

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bit about what you've learned
in that realm?

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Yeah. So I initially became
interested in this topic because

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I was interested in how birds
choose mates. And I've really studied

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this in the context of the
odors that birds produce that they.

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That give information about
themselves that are then interpreted

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by other birds. I've looked at
a substance called preen oil, or

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europegial oil. It's secreted
from the europeal gland, which is

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located just above the base of
the tail. It's the only large exocrine

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gland that birds have
typically. And it secretes an oil

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that birds then put on their
feathers to help protect their feathers

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from exposure to the
environment. In some species, it

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helps with waterproofing, like
in ducks. And we also found pretty

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early on that it gives off an
odor. And I was really interested

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in what information is present
in this odor. And so I teamed up

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with a pair of chemists at
Indiana University, Helena Soini

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and Mila Shnavotny. And we
actually collaborated for about a

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decade trying to understand
what combination of these odorants

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were in each bird's chemical
profile and how it correlated with

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their own biological identity,
I guess. Guess you could say. So.

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Among the first things we
found were that different species

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have different chemical
signatures given off by these compounds

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by this oil. That within a
species, particularly in the breeding

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season, males and females are
different. That individuals have

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repeatable and recognizable
signatures present in these odors,

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and that the odor changes
depending on what stage of breeding

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the birds are in.

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Oh, cool. That's all so
fascinating. Okay. There's a lot

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I want to ask. Can we detect
those differences?

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I've spent a lot of time
sniffing birds. I figured I can tell

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the difference between
different species, but those individual

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differences I'm personally not
able to detect.

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Okay, so we can tell humans
can detect some different scent between

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different species of birds.
I'd be really curious to know which

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birds smell the best. But then
the fact that different individuals

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have different scent profiles,
I mean, it makes sense in that different

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people have different smelling
bo. Or whatever. But I don't know

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why it's so interesting to
think about it in the context of

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birds. So let's start with
which birds smell the best that you've

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smelled.

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My personal favorite is the
brown headed cowbird. They smell

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like fresh baked cookies to
me, like sugar cookies.

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Oh, man.

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The first time I discovered
this, I was actually interested in

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whether or not they gave off
any kind of odor at all. Brown headed

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cowbirds, of course, are brood
parasites. They lay their eggs in

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other species nests and I've
always wondered how they get away

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with that because birds will
notice if something does smell different

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in their nest. I did an
experiment by putting preen oil from

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other species on their nest
and it did affect their behavior.

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Cool. And so I thought, well,
maybe brown headed cowbirds don't

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give off an odor. And so I
captured some. And the way that we

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process birds in the field is
you put them in a little brown paper

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bag, like a lunch bag. It
helps keep them safe, it lets light

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and air in. And then take them
back to the lab for like all the

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measurements and things before
returning them to the site where

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you release them. And I got
back to the lab and I started to

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open the bag to take the bird
out and I got the overwhelming fresh

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bakery scent. And I was like,
who brought cookies to the lab? And

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then I realized it was the
bird. And so I've since found that

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most birds that I've
interacted with that are from the

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blackbird family that cowbirds
are in actually do have kind of a

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sweet, very pleasant scent.

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Oh, that's so cool. Yeah. We
did an episode on brood parasitism

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a few weeks ago and we took
down the idea that brown headed cowbirds

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should be disliked or
maligned. And so here's another reason

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to think they're very cool
birds. They smell like fresh baked

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sugar cookies. So if you ever
get the chance with the correct permits,

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smell one that's so
interesting to these, these individual

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differences, then what is the
evidence that mates.

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Can detect that people,
including myself, have done a number

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of what we call mate choice
experiments where you give birds

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a choice between, say if it's
a male bird, you give them a choice

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between two females or vice
versa, trying to understand what

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characteristics they're
looking for in a mate. The problem

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with these experiments is
you're not necessarily testing what

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you think you're testing
there. This is not a natural situation.

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They're not actually looking
to mate. They're being watched in

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a little cage,.

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Not the most natural setting
for copulation. And Dating and all

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of that.

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Yeah, exactly. So it's a
little bit tough. Instead of trying

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to come at this a different
angle, one study I did looked at

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which birds had the most
reproductive success in that season

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and whether that correlated
with. With the odor that they gave

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off. Now, that doesn't
necessarily tell you if that was

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important in attracting them
to each other, but it could tell

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you something about the
biology of the birds that were successful

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there. And so I did find a
correlation with certain types of

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compounds and their prenoil,
showing that birds who had the most

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surviving offspring in that
year had the highest amount of certain

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kinds of compounds.

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Oh, cool.

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What I think is probably going
on is that when birds are choosing

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a mate, they're, look, taking
in all the information and trying

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to find indicators. Maybe not.
Well, probably not consciously, but

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there's indicators of health
or some kind of other, like immune

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function or something like
that. We have found that a lot of

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these odors are correlated
with testosterone levels and are

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likely correlated with other
steroid hormones like estradiol and

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progesterone, because
especially in females, they correlate

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very tightly with ovulation
when the female lays an egg. So that

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might be one aspect of the
information they're looking for.

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Okay. Which would maybe help
with coordination or when a male

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really knows it's important to
mate, guard, and all of those things.

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Oh, that's so interesting. And
I guess your work has also connected

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smell to the microbiome,
right? I don't think that's a connection

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people would necessarily make.
I mean, people probably didn't know

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that birds have just really
one major external gland which is

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very different than humans,
which have them all over our bodies.

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We sweat all over the place.
Can you talk a little bit more about

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this potential link between
the microbiome and smell and what

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that might mean for how we
think about bird communication?

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Yeah. So interestingly, most
of the smells that we produce ourselves,

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that we consider our own body
odor, is not produced by our own

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biology. So you mentioned
sweat. What we know of as armpit

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odor is not produced by our
sweat. If you take human sweat that

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is sterile, it has no odor.
That odor is produced by all the

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microbiome that. All the. All
the microbes that live in your armpit,

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that live in your sweat
glands. And so this is common to

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all animals. And I hadn't
really thought about that when I

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first started. I was trying.
People would ask me, what is the

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biochemical pathway to
producing these odors? I didn't have

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even a hypothesis at that
point. And Then I met someone who

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would become my collaborator,
Kevin Tice, who had studied hyena

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scent pouches for his
dissertation and I think his postdoc

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00:15:27,290 --> 00:15:34,690
as well. And so hyenas, they
scent mark very prolifically and

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they have this scent pouch
that's located near the anus and

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it contains this yellowish
green paste that is just full of

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microbes. And the microbes are
actually what is producing the odors

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that the hyena are smelling
from each other when they sniff those

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scent marks. And so Kevin
asked me, do you know anything about

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the microbiome of the
urapygeal gland? And that just kind

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of blew my mind right there. I
said, no, let's collaborate.

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Yeah.

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And so we started. I would
take swabs from the preying glands

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of a lot of different birds,
and then he would do microbiome sequencing

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where you sequence a
particular gene in your whole sample.

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And then you can
computationally assign those sequences

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to different species of
microbes. And of course, they have

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a very rich and diverse
microbiome. There's a lot of microscopic

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things living in those glands
feeding off of that pren oil. And

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so we narrowed it down to look
for known odor producing microbes.

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We found quite a few of those.
And then we did one more set of experiments

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00:16:43,410 --> 00:16:46,890
where we actually. Well,
actually two more sets of experiments.

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One, we injected antibiotics
directly into preen glands and looked

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at the effect on the odor. It
did knock down the microbiome and

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it did affect the bird's odor.
And secondly, we took preen oil and

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then just cultured it on petri
dishes and grew microbes on there

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00:17:05,510 --> 00:17:08,910
and then tested whether those
microbes gave off the same odors

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00:17:08,910 --> 00:17:12,310
as Junco Preen oil. Junco's
being the species we were studying.

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And there was a very clear
match. People have often asked me,

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00:17:19,950 --> 00:17:26,289
like, why would you study such
a boring bird? I know it's offensive.

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00:17:26,529 --> 00:17:27,369
It hurts my heart.

291
00:17:27,369 --> 00:17:28,449
That is so offensive.

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00:17:29,889 --> 00:17:33,729
They are very elegant little
birds wearing tuxedos. I love Juncos.

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00:17:34,849 --> 00:17:37,809
But also I thought they were a
really interesting place to start

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00:17:37,809 --> 00:17:40,849
looking at the information
contained in odor because there's

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00:17:40,849 --> 00:17:44,049
not a lot of sexual dimorphism
between these birds, males and females.

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00:17:44,449 --> 00:17:49,169
To most humans, they look
pretty much the same. We would often

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00:17:49,249 --> 00:17:52,610
have to measure the amount of
tail weight in their tails to be

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sure whether we had a male or
female if they weren't fully in breeding

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condition. So for your
listeners who might not know, males

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00:17:59,250 --> 00:18:03,650
have a bit more tail white and
those outer tail feathers, and they

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00:18:03,650 --> 00:18:07,929
also sometimes have longer
wings than females. But other than

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00:18:07,929 --> 00:18:13,010
that, they're very similar. So
if the birds are not necessarily

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00:18:13,010 --> 00:18:17,010
using plumage ornaments as an
attractant, I was thinking along

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00:18:17,010 --> 00:18:19,970
the lines of maybe odor would
be more important in the species

305
00:18:20,370 --> 00:18:25,070
than in a species that has,
you know, flashier visual signals.

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00:18:25,230 --> 00:18:28,750
Does a bird's sense of smell
work any differently than mammals?

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00:18:29,070 --> 00:18:32,830
I think I would assume that
sense of smell has been studied most

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00:18:32,830 --> 00:18:39,430
in depth in mammals and mice
and model systems. Do we know if

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00:18:39,430 --> 00:18:42,550
it compare if, like, the sense
of smell in birds is comparable in

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00:18:42,550 --> 00:18:45,430
terms of just the way it works
to what's going on in mammals, or

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00:18:45,430 --> 00:18:46,590
is there still more to do there?

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00:18:47,390 --> 00:18:52,830
Overall, it is basically the
same system. Okay, so we have a mucous

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00:18:52,830 --> 00:18:56,850
lining in our nasal passages.
That's the olfactory epithelium.

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00:18:56,850 --> 00:19:00,290
Birds have the same thing
lining the inside of their nasal

315
00:19:00,290 --> 00:19:05,370
passages, inside their beaks.
That epithelium contains hundreds

316
00:19:05,370 --> 00:19:09,250
of different olfactory
receptors. So these are proteins

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00:19:09,250 --> 00:19:14,970
that get activated when they
encounter an airborne odorant that

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00:19:14,970 --> 00:19:20,570
matches up with it in some
way. What's different here? There's

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00:19:20,570 --> 00:19:23,180
a couple of things that are
different between birds and mammals.

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00:19:23,820 --> 00:19:26,900
One, looking at these
receptors, if you look at the DNA

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00:19:26,900 --> 00:19:29,940
sequences of these receptors
and the evolutionary history of them

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00:19:29,940 --> 00:19:33,300
that we can infer from these
sequences, birds have actually evolved

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00:19:33,300 --> 00:19:36,740
a whole different class of
olfactory receptors. They don't match

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00:19:36,740 --> 00:19:42,180
up very well with the same
ones that mammals have. They're separated

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00:19:42,180 --> 00:19:45,660
into alpha, beta, et cetera.
It's actually, I think the gamma

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00:19:45,900 --> 00:19:51,060
group in birds has really
exploded. It's hard to draw parallels

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00:19:51,060 --> 00:19:58,980
between what exactly those
receptors are doing. It's also just

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00:19:58,980 --> 00:20:03,100
notoriously difficult in any
species, including humans, to understand

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00:20:03,500 --> 00:20:07,740
how those receptors actually
map to odorants. That's been a long

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00:20:08,220 --> 00:20:11,420
field of study that I think is
finally starting to make some progress.

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00:20:11,420 --> 00:20:14,220
I saw some pretty interesting
papers in the last couple of years.

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00:20:15,660 --> 00:20:18,340
The other major difference
between birds and mammals is birds

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00:20:18,340 --> 00:20:24,320
completely lack something
called a vomeronasal organ. Interestingly,

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00:20:24,320 --> 00:20:29,480
so do humans. But almost all
other mammals have this. So if you've

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00:20:29,480 --> 00:20:32,600
ever seen a dog or a cat sniff
each other's butts.

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00:20:32,840 --> 00:20:36,600
Yeah, my dog, you know,
they're not, first thing every dog.

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00:20:37,160 --> 00:20:40,800
Exactly. And they're not,
like, leaning in delicately from

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00:20:40,800 --> 00:20:43,680
a respectful distance to get a
sniff. They're actually getting their

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00:20:43,680 --> 00:20:47,280
nose up in there. And the
reason for that and the reason why

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00:20:47,280 --> 00:20:50,800
they have these wet noses is
that they're actually detecting compounds

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00:20:50,800 --> 00:20:53,720
that are not airborne, but
that are actually suspended in liquid.

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00:20:53,720 --> 00:20:57,260
And they're not using their
nasal olfactory receptors for this,

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00:20:57,260 --> 00:21:01,140
they're using something called
a vomeronasal organ, and it's located

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00:21:01,140 --> 00:21:06,500
in the palate of the mouth. A
lot of things that we think of as

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00:21:06,500 --> 00:21:11,539
pheromones in mammals anyway
are these kinds of compounds. They're

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00:21:11,539 --> 00:21:17,140
not being detected through
inhaling air. Humans and our very

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00:21:17,140 --> 00:21:20,780
close primate relatives don't
have a functioning bomb or nasal

348
00:21:20,780 --> 00:21:25,050
organ. We're kind of unique in
the mammalian world that way. And

349
00:21:25,050 --> 00:21:28,090
birds lack it entirely. Which
might be another reason why it was

350
00:21:28,090 --> 00:21:30,250
thought that odor wasn't very
important to them.

351
00:21:30,490 --> 00:21:34,290
Yeah, that's so fascinating. I
guess I knew about the vomeronasal

352
00:21:34,290 --> 00:21:37,290
organ. I didn't really fully
understand how it works. So now thank

353
00:21:37,290 --> 00:21:40,649
you for shedding light on my
dog's very aggressive butt sniffing

354
00:21:40,649 --> 00:21:42,490
that he does every walk.

355
00:21:46,010 --> 00:21:51,330
Okay. So one of the earlier
studies on seabirds and their use

356
00:21:51,330 --> 00:21:55,610
of smell beyond the context of
navigation and foraging was looking

357
00:21:55,610 --> 00:21:59,510
at how used it in a social
context. Francesco Bonadonna, who's

358
00:21:59,510 --> 00:22:03,270
a French researcher, was
studying blue petrels. And these

359
00:22:03,270 --> 00:22:09,310
are arctic seabird that they
live in big colonies and they spend

360
00:22:09,310 --> 00:22:12,990
the entire day looking for
food over the ocean. And then they

361
00:22:12,990 --> 00:22:16,830
come back at night in the
dark, and they actually build their

362
00:22:16,830 --> 00:22:19,910
nests in burrows. And so
you've got thousands of birds on

363
00:22:19,910 --> 00:22:22,950
an island with all these
identical little burrows. It's actually

364
00:22:22,950 --> 00:22:26,110
their sense of smell that
helps guide them to the correct one.

365
00:22:26,110 --> 00:22:27,870
They know what their nest
smells like, they know what their

366
00:22:27,870 --> 00:22:32,410
mate smells. These researchers
did this really cool experiment where

367
00:22:32,410 --> 00:22:35,410
they would capture a bird and
this would be a known bird, they

368
00:22:35,410 --> 00:22:37,650
would know which one was its
burrow. And they made this little

369
00:22:37,650 --> 00:22:40,890
contraption where they had one
arm going to that bird's own nest

370
00:22:40,890 --> 00:22:44,450
and the other arm going to a
different nest. And then they put

371
00:22:44,450 --> 00:22:47,650
the bird in a little box that
connected these two arms and bird

372
00:22:47,650 --> 00:22:50,530
always knew which one was its
own nest just by the scent alone,

373
00:22:50,530 --> 00:22:54,210
which I'm not sure I could
find my own house by smell.

374
00:22:55,330 --> 00:22:59,620
I know I could not. I think I
would know if I was in my own house

375
00:23:00,010 --> 00:23:03,090
by the sense of smell,
perhaps. But even that, like, it

376
00:23:03,090 --> 00:23:05,490
can change so much. I feel
like my grandma's house for some

377
00:23:05,490 --> 00:23:09,930
reason had a very distinct
smell. She was not a hoarder by any

378
00:23:09,930 --> 00:23:12,770
means, but I don't know, the
house smelled a certain way. She

379
00:23:12,770 --> 00:23:16,890
baked a lot, so maybe it was.
Yeah, brown headed cowbird vibes.

380
00:23:16,890 --> 00:23:21,730
But that's cool. Yeah. One
thing I wanted to talk about, it

381
00:23:21,730 --> 00:23:25,050
came up a little bit earlier,
this dimethyl sulfide scent with

382
00:23:25,290 --> 00:23:29,250
a Lot of seabirds using that
to detect upwellings in food. There's

383
00:23:29,250 --> 00:23:32,370
an interesting conservation
story there, too, I believe, where

384
00:23:32,770 --> 00:23:37,010
plastics get colonized by
microbes that then release the same

385
00:23:37,010 --> 00:23:37,370
smell.

386
00:23:37,370 --> 00:23:37,650
Right.

387
00:23:37,650 --> 00:23:39,730
Is that something you've read about?

388
00:23:40,290 --> 00:23:44,170
I was not aware of that. It
doesn't surprise me, though. Plastics

389
00:23:44,170 --> 00:23:44,610
are terrible.

390
00:23:44,850 --> 00:23:47,770
Yeah. I mean, so, yeah,
plastics are terrible. Microplastics

391
00:23:47,770 --> 00:23:50,930
are awful. But a lot of
albatross feed their chicks plastic

392
00:23:50,930 --> 00:23:54,450
objects, and it doesn't make
any sense because it doesn't look

393
00:23:54,450 --> 00:23:58,680
like food, like a lighter or
a. Literally like a toothbrush or

394
00:23:58,680 --> 00:24:01,800
whatever. You'd expect that a
sea bird wouldn't be like, oh, that's

395
00:24:01,800 --> 00:24:07,200
squid. But apparently when the
plastics get colonized by these microbes,

396
00:24:07,200 --> 00:24:10,200
which we were just talking
about, you know, microbes are releasing

397
00:24:10,200 --> 00:24:14,520
these scents in preen glands
as well. They release the same scent

398
00:24:14,520 --> 00:24:18,160
as actual food. And so the
albatross might actually think they're

399
00:24:18,160 --> 00:24:19,440
feeding their chicks real food.

400
00:24:21,200 --> 00:24:23,360
That's fascinating and horrifying.

401
00:24:23,680 --> 00:24:26,500
Right? I know. I mean, it
explains this insane pattern of.

402
00:24:27,050 --> 00:24:29,850
Of chicks. And for folks
listening, the albatross chicks obviously

403
00:24:29,850 --> 00:24:35,090
can't digest any of this
plastic, but it fills up their gut

404
00:24:35,090 --> 00:24:37,890
and they can't pass it, and
then they end up just starving to

405
00:24:37,890 --> 00:24:41,050
death. And you get these
carcasses with dead baby albatross

406
00:24:41,050 --> 00:24:45,730
that have a gut full of
plastic, which is horrific. But until

407
00:24:45,730 --> 00:24:49,530
I think that dimethyl sulfide
finding. Dimethyl sulfide finding.

408
00:24:50,330 --> 00:24:55,260
It's a mouthful. It didn't
make sense that they would be doing

409
00:24:55,260 --> 00:24:57,780
that. But, yeah, if they're
relying so much on their sense of

410
00:24:57,780 --> 00:24:59,980
smell, like we've been talking
about, it makes a lot more sense

411
00:24:59,980 --> 00:25:07,700
and is disturbing. Yeah, yeah,
that's a dark one, but important

412
00:25:08,420 --> 00:25:12,300
to put out there. But can you.
I guess, like, it'd be fun to talk

413
00:25:12,300 --> 00:25:15,780
more about your work. Like,
when you were. When you started,

414
00:25:15,940 --> 00:25:18,980
what was something you ended
up finding that you didn't anticipate

415
00:25:18,980 --> 00:25:22,860
or. Or was there a moment that
you were like, oh, man, this really

416
00:25:22,860 --> 00:25:26,140
is a really exciting direction
of research to be pursuing.

417
00:25:27,900 --> 00:25:31,980
So when I first got the idea
that scent might be important in

418
00:25:31,980 --> 00:25:37,380
mate choice, this was when. So
my chemistry collaborators and another

419
00:25:37,380 --> 00:25:41,020
member of the lab had looked
at whether there was a difference

420
00:25:41,100 --> 00:25:45,020
in the amount of odorants that
Junco prenoil produced when they

421
00:25:45,020 --> 00:25:47,380
were in breeding condition
versus when they were not in breeding

422
00:25:47,380 --> 00:25:50,020
condition. The reason they
were studying that this is because

423
00:25:50,020 --> 00:25:55,420
there's this species of bird
called the red knot. It's a shorebird.

424
00:25:55,660 --> 00:26:01,620
And a different researcher had
found that they changed the components

425
00:26:01,620 --> 00:26:05,899
of their preen oil when they
were nesting. And this chemical change

426
00:26:05,980 --> 00:26:08,580
made their nest harder to
detect. And they did some really

427
00:26:08,580 --> 00:26:11,340
cool studies using a dog that
was trained to go look for their

428
00:26:11,340 --> 00:26:14,140
nests and he couldn't detect
them when they were in this breeding

429
00:26:14,140 --> 00:26:18,100
condition. Juncos nest on the
ground. They don't have very well

430
00:26:18,100 --> 00:26:22,360
hidden nests. They're. And
they were very, very susceptible

431
00:26:22,360 --> 00:26:25,840
to predators, Especially
things like chipmunks and snakes.

432
00:26:26,160 --> 00:26:29,120
And so they were interested in
seeing, well, maybe they're trying

433
00:26:29,120 --> 00:26:31,720
to do the same thing as the
shorebirds. Maybe they're trying

434
00:26:31,720 --> 00:26:34,959
to camouflage the scent of
their nests. And what they found

435
00:26:34,959 --> 00:26:37,840
was the exact opposite. Birds
in non breeding condition produced

436
00:26:37,840 --> 00:26:41,120
almost nothing in terms of
odor. And birds in breeding condition

437
00:26:41,120 --> 00:26:45,320
produced a ton of odor. And so
I immediately said, wow, this must

438
00:26:45,320 --> 00:26:49,670
be some kind of matrize
signal. And, and like many bird researchers,

439
00:26:49,670 --> 00:26:53,590
my first thought was males
must be using this to attract females.

440
00:26:55,670 --> 00:26:59,430
And we tried a lot of
different things. We did find a difference

441
00:26:59,430 --> 00:27:05,230
in males and females, but
males weren't. Females really weren't

442
00:27:05,230 --> 00:27:08,790
that interested in male odors
in experimental behavior experiments.

443
00:27:09,910 --> 00:27:12,990
And males were actually more
interested in male odor than female

444
00:27:12,990 --> 00:27:17,070
odor, which turned out to be
because it is actually correlated

445
00:27:17,070 --> 00:27:18,390
with aggressive responses.

446
00:27:18,550 --> 00:27:19,510
Ah, cool.

447
00:27:20,450 --> 00:27:24,890
But over time, I started to
notice that females produced larger

448
00:27:24,890 --> 00:27:27,730
amounts of these compounds
than males in the breeding season.

449
00:27:28,290 --> 00:27:32,890
I started to take this insight
and look at other species that other

450
00:27:32,890 --> 00:27:38,930
people had studied and started
to see a consistent pattern. I teamed

451
00:27:38,930 --> 00:27:41,890
up with a friend and
collaborator of mine, Julie Hagelin,

452
00:27:42,690 --> 00:27:46,210
who studied this before me.
She actually looked at crested aucklets.

453
00:27:46,450 --> 00:27:52,310
It's one of the first studies
of, of seabird olfaction. And we

454
00:27:52,310 --> 00:27:55,350
did this review of everything
we could possibly find. And we found

455
00:27:55,350 --> 00:27:59,870
that in most species in the
breeding season, females either produce

456
00:28:00,430 --> 00:28:05,430
more diverse compounds in
their odor or greater amounts of

457
00:28:05,430 --> 00:28:10,510
compounds, like more intense
smells than males. So it really kind

458
00:28:10,510 --> 00:28:16,070
of makes you stop and think
about your own bias. Like, oh, females

459
00:28:16,070 --> 00:28:20,340
are just the choosers. Males
are the ones that are out there showing,

460
00:28:20,410 --> 00:28:23,330
showing off. And females are
just these, just selecting. But they're

461
00:28:23,330 --> 00:28:27,170
actually quite involved in
communicating as well. And it could

462
00:28:27,170 --> 00:28:29,850
be communicating that they're
in breeding condition. It could be

463
00:28:29,850 --> 00:28:33,490
communicating that they have,
you know, good health, a good immune

464
00:28:33,490 --> 00:28:36,010
system, therefore I would be a
good mother to your offspring. I

465
00:28:36,010 --> 00:28:39,130
don't know, there's all kinds
of things that could be there, you

466
00:28:39,130 --> 00:28:42,290
know, And I'd always thought
of myself as someone who didn't have

467
00:28:42,290 --> 00:28:45,810
that kind of bias in my
behavioral research. But it's a little

468
00:28:45,810 --> 00:28:49,510
bit of a shock to see that.
That I had immediately fallen into

469
00:28:49,510 --> 00:28:50,070
that trap.

470
00:28:50,390 --> 00:28:54,030
It's amazing how easy it is. I
mean, based on, like, what we learn

471
00:28:54,030 --> 00:28:58,630
going through university and
as graduate students. Even if you

472
00:28:58,710 --> 00:29:02,030
are trying. Yeah. To come at
things in an unbiased way, there's

473
00:29:02,030 --> 00:29:06,990
just this whole world of
training that we've had that kind

474
00:29:06,990 --> 00:29:10,670
of reinforces some of those
biases, and it's hard to get yourself

475
00:29:10,670 --> 00:29:12,910
out of them, but it's amazing
when you do. And you can be like,

476
00:29:12,910 --> 00:29:16,460
oh, man. One, recognize that
the bias exists, but two, you can

477
00:29:16,460 --> 00:29:19,300
push past it and then provide
all this really cool new information,

478
00:29:19,780 --> 00:29:22,660
which is similar with respect
to the importance of female bird

479
00:29:22,660 --> 00:29:26,620
song. One of our earliest
episodes, the bs, was that female

480
00:29:26,620 --> 00:29:30,460
birds don't sing. They do, and
it matters. And here we have female

481
00:29:30,460 --> 00:29:35,220
birds producing a lot of scent
that probably matters a lot for mate

482
00:29:35,220 --> 00:29:39,060
choice and all of these
things. Back to the crested auklets.

483
00:29:39,220 --> 00:29:40,110
Have you ever smelt one?

484
00:29:41,540 --> 00:29:44,260
I've never had the pleasure of
interacting with a Crestedocolate.

485
00:29:44,260 --> 00:29:46,100
Oh, man, me neither. But I
want to.

486
00:29:46,420 --> 00:29:47,300
I really want to.

487
00:29:47,380 --> 00:29:50,820
For our listeners. They smell.
And you can correct me if I'm wrong,

488
00:29:50,820 --> 00:29:52,740
but I've been told they smell
like tangerines.

489
00:29:53,300 --> 00:29:54,020
That's correct.

490
00:29:54,020 --> 00:29:57,260
Oh, my gosh. And they're so
cool looking. Can you imagine being

491
00:29:57,260 --> 00:30:01,260
in a colony of seabirds that
just smell like tangerines? That

492
00:30:01,260 --> 00:30:01,700
would be.

493
00:30:02,100 --> 00:30:02,980
That would be great.

494
00:30:03,060 --> 00:30:05,660
That would be great. The booby
colonies I used to work in definitely

495
00:30:05,660 --> 00:30:10,350
did not smell like tangerines.
Neither did any individual booby.

496
00:30:10,430 --> 00:30:13,030
Oh, man. All right, we've
reached the part of the show that

497
00:30:13,030 --> 00:30:15,590
we call that's BS or that's
Bird Stuff, where we give our guests

498
00:30:15,590 --> 00:30:18,270
an opportunity to debunk a
myth that ruffles their feathers.

499
00:30:18,510 --> 00:30:20,750
So, Danielle, what do you want
to call BS on?

500
00:30:20,910 --> 00:30:23,910
Well, as I was researching,
you know, this myth that birds had

501
00:30:23,910 --> 00:30:26,750
no sense of smell, and it was
dating back to the 19th century,

502
00:30:26,750 --> 00:30:29,990
there was another parallel
myth that was coming up at the same

503
00:30:29,990 --> 00:30:33,070
time, and it's closely
related, and it really bugs me. It's

504
00:30:33,070 --> 00:30:35,070
not about birds, though. It's
about humans.

505
00:30:35,070 --> 00:30:36,350
Yeah, go for it.

506
00:30:37,540 --> 00:30:41,460
So we also tend to think that
humans don't have a very good sense

507
00:30:41,460 --> 00:30:45,700
of smell, and this dates back
to the same time period when Audubon

508
00:30:45,700 --> 00:30:49,420
was claiming that birds didn't
have a sense of smell. And it comes

509
00:30:49,420 --> 00:30:54,740
down to the same belief in
this trade off. So, Paul Broca, for

510
00:30:54,740 --> 00:30:58,620
whom an area of the brain is
named Broca's, area, which is involved

511
00:30:58,620 --> 00:31:03,020
in language processing. That's
not relevant here. But he was studying

512
00:31:03,020 --> 00:31:06,780
the human brain, and he
noticed that the olfactory lobe was

513
00:31:06,780 --> 00:31:10,560
much smaller in humans than it
is in other mammals. But the forebrain,

514
00:31:11,840 --> 00:31:15,840
where all of our thinking is
done, is much larger. And he basically

515
00:31:15,840 --> 00:31:22,080
concluded that. He also noted
that humans aren't led by their smell.

516
00:31:22,080 --> 00:31:24,880
They're not. I can't remember
the phrase he used, like odor directed.

517
00:31:25,360 --> 00:31:27,680
Like if a dog smells
something, he'll go after. Right.

518
00:31:27,680 --> 00:31:31,880
But we are not compelled by
the odors that we detect. And so

519
00:31:31,880 --> 00:31:35,040
he said, no, we gave up our
sense of smell in exchange for free

520
00:31:35,040 --> 00:31:38,690
will. What? What? Yes.

521
00:31:38,770 --> 00:31:39,650
That's insane.

522
00:31:39,890 --> 00:31:43,490
It is. But this myth has
continued to persist. You'll still

523
00:31:43,490 --> 00:31:46,490
find people referencing the
idea that humans don't really have

524
00:31:46,490 --> 00:31:49,930
a very good sense of smell
compared to other mammals. But there's

525
00:31:49,930 --> 00:31:53,130
been some really fun studies
where they've compared, like in a

526
00:31:53,130 --> 00:31:57,450
competition between humans and
dogs. My favorite was when they blindfolded

527
00:31:57,450 --> 00:32:02,250
volunteers and had them track
the scent of chocolate that they

528
00:32:02,250 --> 00:32:06,170
had dragged through the grass.
And then they compared. They blindfolded

529
00:32:06,170 --> 00:32:08,110
them, they covered up their
hand, they covered up all their other

530
00:32:08,110 --> 00:32:10,950
senses. Basically, they could
really only use their smell. And

531
00:32:10,950 --> 00:32:13,590
then they compared, like,
their scent finding behaviors and

532
00:32:13,590 --> 00:32:17,590
the path they took and their
accuracy to a dog that was doing

533
00:32:17,590 --> 00:32:20,390
the same test with a pheasant
they had dragged through the grass.

534
00:32:20,390 --> 00:32:21,950
And it was remarkably similar.

535
00:32:22,270 --> 00:32:26,510
Really. I mean, I do sometimes
feel compelled by my sense of smell.

536
00:32:26,910 --> 00:32:31,310
Like, if I'm in a grocery
store and I smell a bouquet of freesia,

537
00:32:31,310 --> 00:32:34,240
which are my favorite smelling
flower, I will buy that. I don't

538
00:32:34,240 --> 00:32:37,040
care how much money it is.
That's not even in a food context.

539
00:32:37,040 --> 00:32:40,520
That's just a scent memory
context for me. But that's a great

540
00:32:40,520 --> 00:32:43,120
one. So funny that. Sorry.

541
00:32:43,120 --> 00:32:45,880
If I'm at the Safeway at 4pm,
that's when they put out the fresh

542
00:32:45,880 --> 00:32:48,760
baked loaves of French bread.
I'm guaranteed to go home with a

543
00:32:48,760 --> 00:32:49,799
loaf of bread that day.

544
00:32:49,800 --> 00:32:54,240
Yeah. Yeah. That's awesome. We
gave it up for free will. Absolutely

545
00:32:54,240 --> 00:32:58,440
not. Well, thanks so much for
joining us today. I've really appreciated

546
00:32:58,840 --> 00:33:01,360
all of your insights, and this
has been an awesome conversation.

547
00:33:01,360 --> 00:33:02,450
So thanks for coming to the podcast.

548
00:33:03,160 --> 00:33:04,520
Thanks so much. I really
enjoyed it.

549
00:33:04,680 --> 00:33:11,480
Awesome. Birds are dinosaurs.
And around here, we like our snacks.

550
00:33:11,480 --> 00:33:14,600
So we end each episode with a
dinosaur nugget. Today's Nugget.

551
00:33:14,600 --> 00:33:18,200
For 200 years, we told
ourselves birds couldn't smell. One

552
00:33:18,200 --> 00:33:21,360
famous ornithologist, one
terrible experiment and everyone

553
00:33:21,360 --> 00:33:24,800
just went with it. Turns out
every species of bird that's ever

554
00:33:24,800 --> 00:33:28,800
been properly tested can smell
every single one. But they're not

555
00:33:28,800 --> 00:33:32,010
just smelling the world around
them. They're broadcasting that oil

556
00:33:32,010 --> 00:33:34,690
birds spread on their feathers
carries chemical signatures that

557
00:33:34,690 --> 00:33:37,810
say, here's who I am, here's
whether I'm ready to mate, and maybe

558
00:33:37,810 --> 00:33:40,970
even here's how healthy I am.
It's a dating profile written in

559
00:33:40,970 --> 00:33:44,370
chemistry. And the kicker?
Those scents are produced by bacteria

560
00:33:44,370 --> 00:33:47,250
living in a gland above the
tail. So the next time you watch

561
00:33:47,250 --> 00:33:50,050
a bird preen its feathers,
just know it's not just grooming,

562
00:33:50,050 --> 00:33:53,330
it's low key. Putting on
perfume. That's a wrap on this week's

563
00:33:53,330 --> 00:33:56,530
episode. Okay, but can birds
smell? We're gaining more listeners

564
00:33:56,530 --> 00:33:59,010
every week, so help us keep
that going by sharing our show with

565
00:33:59,010 --> 00:34:07,850
a friend. End. We'll catch you
next time. Byeee. Okay, But... Birds

566
00:34:07,850 --> 00:34:12,250
is hosted by Scott Taylor with
production and creative by Zach Karl.