It’s the North Island brown kiwi that lays the largest egg in relation to its body size. This bird nests in deep burrows, which makes for an environment where flying predators can’t easily attack them. But this is not always true because what matters most is how much nutrition females get before they lay eggs.
For example, seabirds like petrels and gulls produce large eggs even though they don’t eat very much because their chicks receive food from milky substances provided by special glands in their parents’ mouths before they ever leave the nest. All other organisms are restricted by basic metabolic constraints imposed by their own life cycle development during ontogeny – including ecology, predator-prey relations, parental care strategies.
There are many birds that lay larger eggs than the North Island brown kiwi. Ostriches, emus, cassowaries, and certain species of ducks can produce some enormously large eggs. Even ostriches have eggs that are four times more voluminous than North Island brown kiwi eggs! Emu eggs are five times larger in volume. The largest of all is thought to be ostrich egg at 5-7 pounds (2.3kg) with an equivalent by volume size of about 30 hen’s or chicken’s eggs!