Bird eggs are available in different shapes- ranging from the perfectly round egg of the brown hawk owl to the raindrop shaped egg of Sandpiper. Scientists have always wondered about the reason for the change of egg shapes in the birds. For years, they have tried to unravel the mystery that lies in the different shapes of the eggs of the birds.
A new research study conducted on this subject suggests that flight of the birds is responsible for the change of shape in the eggs of the birds. ‘Grand Unified Hypothesis’ helps in explaining the reason for the plethora of diverse egg shapes for the species of the birds. It said that as the birds have evolved for various different types of flight, the changes that occurred to their body have been instrumental in changing the shape of their eggs.
For example, the birds which are strong fliers have the tendency to lay more stretched out eggs. It has fascinated the scientists that when all eggs, irrespective of their shapes, have just one function- protection of the baby chicks, then why do they come in this wide plethora of different shapes and sizes.
The research work is done on this subject previously had suggested that different shapes tend to help the birds. For example, the cone-shaped eggs help the cliff dwelling birds to be tension free since they are more stable and less likely to roll out of the nests and fall down. Or that the round eggs can resist damage in the nest. But none of the suggestions could hold true for all the wide range of birds.
Mary Caswell Stoddard along with her team of biologists analysed more than 50,000 eggs which represented 1400 species, basically 14% of the overall species of the birds. They used variables like shape and symmetry in their algorithm. They even researched about the traits with respect to the bird family. On conclusion, they found that the strong fliers had more asymmetrical and elliptical eggs.
- Mahadevan, the biologist at Havard University, interlinked the flying strength and the egg shape. He claimed that with the evolution of birds in flying, their bodies even became streamlined, making them reproductive tracts to become narrow too. Since eggs provide nutrition to the babies, shrinking eggs could have harmed the developing birds and hence, long stretched eggs came about to give eggs volume without an increase in width.
This theory links the shape of the eggs of the bird to the flight patterns. It has managed to hold true in various cases.