Why are bird eggs of different shapes?

Bird eggs are like tears, owl eggs are like golf balls, and hummingbird eggs are like jelly bean candies . Why are they so different?

Scientists have for the first time convincingly explained this difference. Accordingly, the shape of the egg depends on the flight ability of the bird.

Over the past century, the Museum of Vertebrate Animals in Berkelry, California, has collected thousands of eggshells of about 1,400 different bird species. Evolutionary biologist Mary Stoddard of Princeton University, USA, based this on conducting research on egg diversity.

Stoddard's team wrote a computer program called Eggxtractor to be able to calculate the length, width and statistics of the eggs in the photos from the museum.

The shape of the egg depends on the flight ability of the bird.

When Stoddard and his colleagues designed the genealogy tree for 1,000 bird species, they found that each group of birds usually had some common properties. However, there is almost no relation between egg shape and factors such as egg type, nesting position or number of chicks in the nest - hypotheses given earlier to explain the diversity of egg.

Later, the team stumbled upon a question that no one had ever noticed before: whether the bird's flight ability - calculated as the ratio of bird's wings to the length of the bird - affected the image. egg form or not? And surprisingly, this vague hypothesis proved reasonable.

Very good flying birds such as birds often produce slender and asymmetrical eggs, while birds fly less or not, like tropical tail-tailed birds that lay eggs almost like spheres.

Stoddard deduced that rounder eggs would be able to hold larger pelvic bones than slender eggs. Birds that spend a lot of time working in the air have evolved their bodies more slender and lighter with smaller skeletons. Since then, its eggs have also developed to match this pelvis.

'I was really surprised but then convinced,' said Martin Sander, a paleontologist at Bonn University in Germany. According to Sander, it is now possible to guess whether a species is good or not, depending on the shape of the egg. At the same time when looking at an egg, you can immediately learn some basic information about this bird.

The only type of eggs that no bird can produce is the same egg-shaped balloon.

Previously, knowing that the shape of the egg was not only determined by its shell, but also by the inner membrane , Stoddard worked with physicist L.Mahadevan of Harvard University and student Ee Hou Yong. to create a mathematical statistic based on the characteristics of this membrane and the bearing capacity from the inside of the egg.

They use a model to create the eggs by changing two indicators: the hardness of the membrane and the internal pressure . 'Changing these traits allows us to create every shape egg we see in nature,' Stoddard said. However, the only type of eggs that no bird can produce is the same egg-shaped balloon.

According to Stoddard, her research and her colleagues created two special things. Firstly, understanding the shape of the egg and the role of the egg membrane are of great value to the egg production industry, thereby enabling more durable eggs. But the most significant thing for Stoddard is simply decoding the question about egg diversity.