Why do eggs have so many shapes?

Approximate Reading Time: 3 minutes

A massive new study finds that how much a bird flies influences how their egg rolls


Great webpage, design-wise.

BUT, I have TWO problems with the science.

Yes, yes, I don’t have degrees in ornithology.
OTOH I *DO* have 30 years’ experience keeping and raising poultry (ducks, geese, turkeys, chickens, guineas, and the odd wild rescue).

Problem ONE:


In order to get the most out of (or into) their eggs, strong fliers make them with asymmetrical or elliptical shapes—which have more volume, relative to their girth, than perfectly spherical eggs.

Forgive me, but this is BULLSHIT.

The ones who are better adapted survive better.

NO, the bird did NOT make symmetrical eggs so there’d be more room! Those eggs that had more room tended to hatch better, and maybe even produce stronger babies. THOSE babies survive and then THEIR eggs are more likely to be the same shape as theirs were.

It may seem like a subtle distinction, but it’s really not.

 These days, when so many people have become so far removed from nature that they no longer understand any of it, let alone knowing where their food comes from, keeping this distinction clear is more important than ever.

Too many people now believe that every baby born on the planet should get to live (you know, eating meat is wrong, “culling” is evil, we need to save all the baby polar bears, ….).

Digit & the Turkeys

The TRUTH is that by FAR the VAST majority of life on the planet exists to be food for something else. Take cod for example:

A female cod will lay up to 500 000 eggs per kg of her own weight. Consequently, a 3 year-old female of half a kg can produce 250000 eggs; an 8 year-old female of 5 kg can produce 2.5 million eggs per year. A cod can live to over 25 years of age and weigh over 90 kg. (Source: http://www.ucd.ie/codtrace/codbio.htm)

Just imagine what the oceans would look like if even HALF of those millions and millions of eggs survived to adulthood. They DON’T. They were NEVER designed to. In order to keep the population stable, ONLY TWO of those eggs need to survive long enough to reproduce.

ONLY TWO. Any more and we get an overpopulation. Any less, and the population will eventually die out.


Problem TWO:


The relationship between flying ability and egg shape does have exceptions, though. For example, whereas ostrich eggs tend to be spherical, kiwi eggs are elliptical—even though both species don’t fly. Flightless penguins also lay asymmetrical eggs, which researchers pin on their streamlined body plans, designed for powerful underwater swimming.

These guys really have to spend more time actually WITH birds.

Do turkeys feel? Offer one a dandelion and tell me they don’t look happy…..

Never mind the reiteration of Problem #1 here (again), it’s incredibly naive to imagine that there is ONE deciding factor in something as complex as egg shape. That said, it is not the distance they fly that will have influence on the egg, but rather the shape of the bird. Not just the baby bird either.

Let’s suppose the egg just HAPPENS to be a perfect shape. That means the baby will be able to get out of the shell easily (something affected by the baby’s shape AND the egg’s shape, among other things). It will also mean that THAT baby will grow up into an adult healthy enough to live long enough to have it’s own eggs, at least TWO of which need to survive long enough to have THEIR own eggs,…..

In addition to that, the egg needs to survive its own life as an egg …. meaning it needs to come out without injuring mom, stay in the nest, survive mom (or dad) sitting on it, and do that long enough for the baby to develop and hatch. This easily explains the difference between ostrich and kiwi eggs: ostriches are BIG birds and lay their eggs in a sandy nest – round is fine, and kiwis lay gigantic eggs in relation to their body size – their eggs HAVE to be body shaped or they’ll never make it out without injuring mom.

On the whole, pointier eggs tend to laid by birds who have nests on the ground. Asymmetrical eggs tend to roll back to their starting position.  this was not a design CHOICE. The ones that didn’t roll back didn’t hatch. Eggs laid in well-made nests, for the most part, don’t need to be so asymmetrical. So there is less selective pressure favouring the pointy ones.

Be the first to like.

Leave a Reply