Have you ever heard a bird singing? [birdsong]
Or just making noise? [gull screaming]
How do they make those sounds? It's surprisingly different from the way we sing.
Let's hear a little bit about birdsong.
Let's start by seeing how we make sounds. At the top of our trachea is the larynx, and inside are
two folds of tissue. These are the vocal cords. We have vocal cords that vibrate as we breathe out.
Technically vocal chords can work on an inhale but it's really rare [deep beatboxing bass]
where literal babies can teach themselves how to vibrate their vocal chords on an exhale [baby cry]
The sound produced by vocal chords does not sound like a voice. It's a buzzing,
as if we were blowing through a rubber band [buzzing rubber band sound]
which is then shaped in the resonant chamber of the mouth, throat, and sinuses.
So human songs have to be written with only one "note" at a time, and they have to leave
some pauses for the singer to breathe. Still, we can make some nice sounds [acapella singing]
Birds are totally different. There is some diversity, but let's focus on
songbirds, which are the most famous singers.
At the bottom of the trachea is a split that sends air out to the two lungs,
and each tube is called a bronchus. There is a stretchy air sac with membranes on both sides.
There are bumps of tissue on the inner and outer sides of both bronchi,
and the inner ones are connected to the membranes. There are up to six or seven pairs of muscles
that can stretch and shape different parts of this system. When the bird sings it expands
the air sac, which pushes the bumps closer together to constrict air. The inner bump is
also connected to a membrane, so it can wobble and create pressure waves, also known as sound.
You have probably done this before and it's a really good model of how birds sing.
Blow up a balloon and then stretch the neck of it while letting
air out. [high-pitched squeaks and buzzing]
When we stretch the balloon, we're making tiny bumps and ridges in the constriction that block
air. Also they're connected to a stretchy membrane that pushes them back into place.
It makes a high-pitched sound, and you can change the rate of vibration by changing the tension.
Notice how high-pitched the sounds are? This is why birds can sing so high.
The muscles of the syrinx are made of superfast muscle tissue that can change quickly,
and songbirds have sub-millisecond control of what sound they are making.
They can adjust volume by changing how much air passes through. And this vibration is
further changed into a unique sound by the shape of the mouth, tongue, and sinuses.
And there are two sides, remember? So songbirds can make different sounds
with both at the same time. The Canary trill is just switching sides really fast [Canary trill].
The Northern Cardinal switches sides partway through each rising whistle [Cardinal whistle].
The Thrush just sings two songs at the same time [Thrush songs]
Different birds have different ways to produce sound. Just as an example,
pigeons and doves make sounds with membranes higher up in the trachea.
New World Vultures have no syrinx and sound like this. [hiss]
Then some birds a different location for their syrinx.
Either way up in the trachea [Ovenbird singing]
Or way down in the bronchi. [Eagle owl hoot]
If we were to write music for a songbird singer, we could have two notes at the same
time. And no need to stop singing for a breath. Because they can sing on an inhale or exhale.
A Skylark has been recorded singing for 18 minutes straight. [Skylark's fast and nonstop singing]
Another thing that's interesting about birdsong is that it does not take much energy.
A singing bird only uses 15% more calories than a bird that's at rest. So birds are able to fill
our world with beautiful birdsong. [birdsong] Or the other noises they make. [weird echoing squawk]
Thanks for learning about birdsong! If this struck a chord with you, you can subscribe to continue
learning about birds. Or you can play it by ear and watch another video to watch on this channel.
Thanks for stopping by this week to learn what makes Life awesome!