Since it's nearly Easter, we're going to share some slightly cursed egg knowledge. Let's talk about kiwis (the national bird of Aotearoa/New Zealand, not the fruit) and their frighteningly ginormous eggs. 
Ostriches lay the biggest eggs, but kiwi eggs are by far the biggest as a proportion of body size. Kiwi eggs are up to a quarter of their body mass - that's the equivalent of a human giving birth to a four year old.
They can lay up to 100 eggs in their lifetime. Ouch.
As well as being huge, kiwi eggs are very, very yolky. Most bird eggs are about 35% yolk. Kiwi eggs are 65% yolk. This nutrition means baby kiwis hatch with open eyes, full feathers and able to walk quickly. They don't need to eat for up to two weeks after they're hatched.
The relative maturity of baby kiwis is one theory as to why their eggs are so colossal - it may be beneficial to the birds to be able to practically stroll out of their eggs and not need to eat for a while.
However, the OTHER, arguably more cursed, theory about the size of kiwi eggs is in its evolutionary past, the kiwi was a much bigger bird. And when it got smaller, nature just forgot to set the egg size to Normal Size For Smallish Bird, and just kept it on Huge Bird.
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