The ostrich is clearly ruled out. It weighs about 140 kilograms, but the 1.4 kilogram egg is not exceptional in relation to the size of the bird. The egg is just 1% of bird’s own body weight. The chicken-sized kiwi of New Zealand holds the record in the bird world for laying the largest egg in proportion to the female’s size.
A 1.8 kilogram kiwi produced an egg that weighed nearly 0.450 kilogram — 25% of her own weight. The male incubated the egg in a moss-lined nest in a burrow. Considering the egg’s size, the incubation period lasted 75 to 80 days.