Hey it's me Destin welcome back to Smarter Every Day.

So some of my favorite things to learn are those things that I've seen for several years

and I've made a lot of observations and I kind of think I get it, you know.

I mean, like really get it. And then I find out, I don't.

So when I first saw what I'm about to show you, it blew my mind because it was

so simple I should have seen it my entire life but I didn't. Look at this bird.

The muscle that flaps the wing is here toward the center, and he pushes down on the wing.

But the feathers going out towards the edge of the wing are overlapping in such a way

that they all push together on the down-stroke, but on the back stroke they

delaminate, allowing them to open up like louvers and allowing the wind

to pass through them. This means there's a lot less resistance on the back stroke.

Basically this bird wing is a biomechanical check valve. That's amazing.

I've never thought about that, but I saw it in the high speed video in Peru on the macaws

for the first time. This is why I've never seen it.

Look how fast it happens.

There's no way I could have observed that.

But watch the macaws on high speed and you can see for yourself, clearly the feathers are delaminating

on the back stroke. On the down stroke you can see that all the feathers

overlap in such a way that they provide a firm boundary layer that air can't pass,

but on the up stroke look what happens. You can see that the wing separates and the feathers turn

so that the air is flowing straight in between them. You can even see

straight through the wing. I think that's amazing, so he has a lot less resistance on the back stroke

than he does the down stroke. Another thing he does to decrease this resistance on the

back stroke is he's performing more of an elliptical sweep with his wings instead of

just an up and down flap. So what he's doing is, on the back stroke he's pulling that

wing in, and he's decreasing the length so he decreases the surface area

of the total wing. That's pretty awesome as well. So one of the coolest misconceptions I had

is pretty clear to see on this red macaw. I used to think that birds just flap down

and they create high pressure underneath them and they push themselves up. But if you look

at this macaw something else is happening. Look at the back of his wing here.

You can see that the feathers are being lifted up on the down stroke. What that means is we have

a low pressure situation there. It's like in engineering when we use something called

computational fluid dynamics. Basically what we do is we analyze the flow field and we figure out

what pressure situations we have at each location. Now you know

that on an airplane wing we have a low pressure situation on top. That's exactly what's happening

with this red macaw. So look at his wing and you can see that not only does he have a high pressure

situation on the bottom, but the low pressure is so great that it's pulling those feathers

off of his wing. That's amazing. So not only is he pushing down but he's

being pulled up on the same stroke. That's pretty awesome.

Now this green parrot's doing the last thing that I thought was pretty wild. If you notice he is angling the tips

of his wings on the back stroke and pushing back behind him, so he's providing

thrust, but one thing that's happening that I don't really understand but it looks like it could be

true, he's breaking his wing in half between the secondary and primary feathers,

and he's angling it and it looks like he's diverting that flow down,

almost like a vertical take off Harrier jet. It's pretty cool, and I think it could be

happening, but I've never actually thought about a bird being able to provide downward thrust

on a backward stroke. That's pretty wild. So I thought I knew

how flapping flight works but clearly I didn't. Send this to any of your buddies that like to think critically

cause they'll do what I do now. Every time I see a bird against the sky I watch his wing

and on the down stroke right at that point where he's pausing to transition back to an up stroke

if you watch you can see sunlight pop in between the feathers because he's

opened it up for lower air resistance on the back stroke, and I think that's awesome

because now I know how bird flight works. Anyway I'm Destin, you're getting

Smarter Every Day and I'll leave you with this picture that my daughter made by gluing homing pigeon feathers to a piece of paper

to create her own bird. You're getting Smarter Every Day. Have a good one.

We are in the middle of a cotton field in Alabama. If you've never seen it, it's a really pretty sight.

And what are we gonna do here son? - Let this bird go.

- We

- We're gonna let this bird go, but before we let the bird go, we're gonna talk about his feathers, aren't we.

[ Captions by Andrew Jackson ] captionsbyandrew.wordpress.com Captioning in different languages welcome. Please contact Destin if you can help.