How bird babies can breathe in their eggs
Have you ever thought about how birds can breathe inside their hard eggshells? It’s all because of some really clever egg-ineering.
Bird eggs have tough shells that hold an egg white and a yolk inside. When the egg is fertilized, the baby grows inside the yolk, getting food from it and the egg white around it. When the baby bird has food and a place to stay, you might wonder what else it needs. There is one more important thing that must be present: fresh air.
People and other animals get oxygen through their umbilical cords while they are still inside their moms, but birds don’t have this direct way. Instead, it is the egg itself that makes gas exchange possible.
In this interesting process, there are two special layers inside the eggshell that work like lung tissue and connect the chick’s circulatory system to the outside world. The eggs are warm when the mother bird lays them, but as they cool down, the material inside them shrinks a little. The two membranes make a small pocket or air sac as a result. The bird takes in oxygen from this air sac and lets out carbon dioxide as it grows. Thousands of tiny holes spread out across the egg’s surface let oxygen move through them. The same holes also let carbon dioxide escape.
These holes also do something very important: they let water into the egg, which keeps the bird and its parts from drying out. This is why hard-boiled eggs feel a little heavier than raw eggs: the cooking process closes off the pores, stopping the flow of water.
The clever way that nature made the bird’s egg lets the growing chick get the oxygen it needs while still being protected by the shell. You can see how life finds new ways to stay alive by looking at this amazing example of change and survival.
When you see a bird’s nest full of eggs and are amazed by the sight, think about the amazing processes that allow the baby birds to breathe and grow inside their eggs before they leave for the world.
