Explain why some seabirds have pear shapes

According to Auk: Ornithological Advances magazine, British scientists explain why the eggs of some seabirds are pear-shaped.

The half-century study has shown that this form makes seabird eggs difficult to break and does not allow eggs to accidentally roll off the cliff into the sea.

Pear-shaped eggs of some species of seabirds appear during evolution that lasted for centuries - (Photo: Flickr).

The eggs of some Alcidae have irregular pear shapes, one is slightly pointed, and the other, on the contrary, is larger than other birds' eggs. Alcidae live on a rocky shore and lay eggs directly on the rocky outcrops.

Previously, ornithologists assumed that the egg form would not allow them to fall off the cliff and if the bird accidentally pushed the egg, when it fell, the egg would not roll in a straight line, but in a circle. But now scientists from Sheffield University (UK) think that this is not entirely true.

According to the results of the study, the problem is not the trajectory of motion, but in mechanical stability : the irregular shape of the egg does not even allow it to roll down. Because of the enlargement below the eggs, the eggs are completely difficult to roll off the hollows.

According to the authors, this form appeared during evolution for centuries, because pear-shaped eggs have no chance of falling into the sea and are more likely to survive until they hatch.

To test the hypothesis, the authors examined eggs with different shapes when stabilized on a slanted surface. The scientists compared the eggs of the sharp-billed uranium (uranium aalge) and the recessive albatross (Alca torda). At different angles of the surface from 20 ° to 40 °, pear-shaped eggs have been shown to be more stable. Moreover, the pear-shaped fruits are harder to push down.