Good question! No idea. I hope this is not a hijack, but I would like to know what the whites and the yolks are for in the eggs, and this seems the right place to ask. I guess that the yolk has more fat and cholesterol (and water) while the whites have more protein (and water), but why are they separated like this, evolutionary speaking? How does a developing chick use what part of the egg and why? And I hope it is not a hijack because if there is a reason for that we might get an idea of what the ratio boundaries between yolks and whites are. Just like the form of an egg is quite optimal (try holding an egg between your index and thumb on the pointy and the round sides and squeeze hard, let’s see if you can break it) I guess the interior is quite optimized too. I would not be surprised if the ratio boundaries where relatively narrow, but the reason could be interesting.
ETA: I recently learned that threads can be spun off from other topics, so this is what I just did in a lazy way (copy & paste).
I’m not sure if this is exactly what you’re asking, but as I understand it, the yolk provides most of the nutrients for the growing embryo. The white is mainly protection for the yolk. The white is 90% water without much in the way of nutrients.
The yolk is more concentrated nutrition (the white is much more water and virtually no fat) and is surrounded by the yolk sac (humans have yolk sac in early embryologic development too BTW). The yolk sac actively absorbs and processes the nutrition for the developing chick embryo/fetus for most of its development.
My assumption is that in the final days the chick actually eats the white and digests it itself. Not positive of that though. If some of it is left behind less of a waste than leaving any yolk behind.
I think the yolk sack is equivalent to the placenta, and the yolk is, um, analogous to the nutrients transported by the blood in a mammal. I agree that the white is like amniotic fluid and the shell is kinda the uterus.
So why this seems so interesting to me I don’t know but …
The egg white, aka the albumen, is full of a bunch of stuff to protect from infection. Much of the protein in it gets transferred to the yolk in early development and is then absorbed from there. Apparently most of the protein of the hatched chick comes from there.
So confirmed that the chick just eats most of the last bits of the white, but, of course! it is more complicated than that.
Unfortunately your link is not open in continental Europe, it looks very interesting indeed. I’ll have a look, perhaps I can get it via another channel.
Thanks a lot, @DSeid, your pdf is great*. And goes to show how very complex and fine tuned an egg is, which leads me to infer that concerning the original question from which this thread was spun the balance between so many and complex interactions implies that the ratio between yolk and whites and all the rest must be pretty constant for each bird species, and probably still quite constant too between species.
*And what a lot of fancy new words for me!