Birds’ bones are hollow, which makes them lightweight and able to fly easily. This is one of the things that most birds have in common.
It seems like anytime that I go for a walk I see a bird flying around. Sometimes I see the tiny ones quickly flying amongst trees. Or at times I look high up in the sky and see a large bird of prey soaring effortlessly. They all seem to weigh nothing as they go against gravity and fly. Most birds are able to do that because their bones are very lightweight yet strong.
What Are Our Bones Made Of?
Most bones, at least bones in people are made up of different layers. An outer layer is very thin and contains nerves and blood that nourish the bone. Inside that is the strong compact bone that is made up of a mixture of calcium and a protein called collagen. Then inside of that is a spongy substance, and finally most bones have a core of bone marrow.
What Are Birds’ Bones Made Of?
The bones of birds also have layers. However, the majority of the bone is simply hollow.
There is a layer of hard bone on the outside. Then inside of that the bone is filled with air spaces. However, there are lots of struts, thin strong structures, that go from one side of the inside of the bone to the other. These struts are super important as they make the bones very strong. Without the struts the bones would easily break due to their hollowness.
In Fact – Birds’ bones are so lightweight that some birds feathers weigh more than their skeleton! For example, the feathers of a frigate bird weigh more than its skeleton.
Why Are Birds’ Bones Hollow?
Their bones are hollow because they have evolved the ability to fly. If their bones were thick they would be heavier. Heavier bones would make it harder for birds to fly. They would still be able to do it, but it would cause them to use a lot of energy. Using more energy means the bird would need to eat more food to replace the lost energy or simply eat less and fly less.
So, the short reason birds’ bones are hollow is so that they can fly efficiently and easily.