The ability of birds to fly is truly a marvel of engineering! Yesterday we learned that feathers are complex structures that are lightweight yet strong. Well, in order to fly, birds need something else to be lightweight—their bones. They achieve this with specially designed hollow bones.

Not only are these bones lightweight, but they form an important part of a bird’s respiratory system. Birds don’t have a diaphragm muscle like we do. Instead, the breastbone operates their breathing system. We’ll learn more about that unique system tomorrow.

Flight, well, it’s highly complex and couldn’t have evolved slowly over millions of years.