This is Scientific Americans' 62nd Science, I'm Emily Schring.

Have you ever looked up to see a hawk sore overhead or a small chickadee flit by and wondered

how do they do that?

Believe it or not, scientists never really knew either, until now.

I looked at the relationship between form and function in the most basic sense.

Talia Lowie-Marie is a PhD student at the University of Toronto in Canada.

She says bird flight has everything to do with the shape and size of a bird's sternum

or breastbone.

Bird's sternums have a projection from the middle called the keel, and this is where

the flight muscles are attached.

It's plausible to think that this element is important for flight, but why does it vary

so much in shape and size relative to the body?

Are there all these questions about it that haven't been answered in the past?

So Mary set out to find some answers, using a database of CT scan sternums from 105 different

bird species, like the red capped lark, leeches storm petrol and the southern cassowary.

She also included two extinct birds, the dodo and the great ock.

The scans combine a series of x-rays to create three dimensional images.

So because the sternum is a complex element in three dimensions, it's not just a 2D bone,

it's got projections of the middle and up the sides.

Looking at it in three dimensions is the best way to quantify the shape and analyze it

in a statistical framework.

So more recently, those methods have become more accessible.

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