Go to CuriosityStream.com/SciShow to learn more.

[♪ INTRO]

On the remote, rocky islands of the North Pacific,

you might find a happy-looking little bird.

Called the crested auklet, it looks

kind of like a cross between

a penguin and a quail.

They live in big, dense, noisy colonies

and go out to the ocean to feed.

They also, apparently, smell like tangerines.

The smell, which has been described as

“distinctive” and “pungent”, emerges

at the beginning of the breeding season.

As for what's actually causing it,

the smell seems to come from a mix of

compounds secreted by a patch of special,

hair-like, possibly hollow feathers called

wick feathers found on a particular area

of skin on their back.

They just got a little tangerine patch back there.

The mix of compounds is dominated by aldehydes,

a kind of chemical that contains a

carbon bonded to a hydrogen and

double-bonded to an oxygen.

As for why, there are two hypotheses.

One is that the smelly aldehydes might be

a way for the birds to repel parasites like lice

— kind of like a built-in can of bug spray.

Experiments have shown that some of

the compounds in the smell can repel

or paralyze ticks or lice.

The other idea is that it might be

some kind of sexual display or some

other sort of social signal.

During courtship, crested auklets approach

potential mates and bury their bill in

that patch in what's known as a “ruff-sniff”.

And they can definitely smell it.

Studies have shown the birds can tell

the scent apart from other smells and even

appeared to be attracted to it when

presented with a smelly fake bird.

Which is kind of neat, because for a

long time many experts thought birds

couldn't really smell things.

That idea was debunked by scientists

in the 1960's, and that research doesn't

have much of anything to do with crested auklets,

but as a myth it's had surprising staying power.

It might seem kind of funny,

but choosing the smelliest mate

might have some benefits.

If the scent is a parasite repellent,

for example, a smelly mate is less likely

to pass infestations to their mate or offspring.

The smell might also be an indicator

of how healthy the animal is in general.

Its body has to produce those smelly chemicals,

which requires energy.

And because all smells eventually fade over time,

an animal that depends on cologne to win a mate

has to keep making new compounds all the time.

Which means it has the energy to burn

to make smelly molecules, even though

those resources could be used for other,

more survival-oriented things.

This means for crested auklets, a strong scent

might be a way to show that you're not only healthy,

but you have the resources to burn.

Citrus-scented birds are pretty neat,

but they're far from the only

fascinating animals out there.

If you want to learn about more of them,

you might enjoy the documentaries on CuriosityStream.

CuriosityStream is a subscription streaming service

that offers over 2,400 documentaries and

non­fiction titles from some of the world's

best filmmakers, including exclusive originals.

Like Animal Builders, which is all about

the incredible engineers of the animal kingdom.

Do you know beaver homes are self-ventilating?

Because I do now…

And right now you can get unlimited access

to that and more starting at just $2.99 a month.

For SciShow viewers, the first 31 days are

completely free if you sign up at

curiositystream.com/SciShow and use the

promo code 'SciShow' when you sign up.

And checking them out also helps us

continue doing what we love, so thanks.

[♪ OUTRO]