Bird eggs come in different shapes, sizes, and colors. Bird eggs have a range of shapes from round to oval shaped. Some eggs are larger on one end than the other. The scientists wondered how bird eggs get their different shapes.
First, they tested the membrane (a flexible layer that separates one side from the other) on the inside of the shell. They used a model (a way to explain how something works in the real world) and found that the thickness and stiffness of the membrane both affect the shape of an egg.
Next, they looked at how much a bird flies. They found that birds that spend more time flying have eggs that are more oval-shaped or that are larger on one end than the other. These shapes allow a bird to have a body that is streamlined (shaped to decrease air resistance when moving through air) for flying.
Let’s look at an example. An albatross is a large bird. Hummingbirds are much smaller. Even though they differ in size, both of these birds are great flyers.
Every year albatrosses fly thousands of kilometers across oceans. Hummingbirds don’t fly such long distances. But they spend a lot of time hovering to drink nectar (sugary liquid produced by plants) from flowers. And they can fly backwards and upside down!
Both of these great flyers also have eggs that are oval-shaped. When eggs are shaped like this, birds can develop and lay the egg and still have the streamlined body needed for lots of flying. Birds that do not fly as much have eggs that are round, like a golf ball.
What Do You Think? Some owls fly short distances to hunt for food. They live in one place all year. Do you think the shape of their eggs are round or oval?
Photo Credit: (t)Oldrich/Shutterstock, (bl)John Giustina/The Image Bank/Getty Images, (br)Jiri Hrebicek/Shutterstock
