Which Bird Lays the Largest Eggs for Its Size?

The kiwi is the bird that lays the largest eggs for its size. On average, the kiwi lays eggs that about 20% of the mother’s size. Although the kiwi is about the same size as a chicken, it lays eggs that are roughly six times larger. Although it is not known why the kiwi lays such large eggs in proportion to its body size, a generally accepted theory is that the species used to be larger. It is thought that the kiwi gradually became smaller over time, while its eggs remained the previous size, but it is not known why.

More about kiwi eggs:

• Kiwi eggs are 65% yolk, in comparison with 35-40% for other bird eggs, on average.


• The female kiwi can lay as many as 100 eggs in her lifetime, or about two per year.


• In the days before she lays an egg, the female kiwi generally fasts simply because there is no more room in her midsection for any food.

Frequently Asked Questions

Which bird lays the largest eggs relative to its body size?

The Kiwi, a flightless bird native to New Zealand, lays the largest eggs relative to its body size. A kiwi egg can weigh up to one-quarter of the female's body weight. This is akin to a human giving birth to a 4-year-old child, showcasing an extraordinary feat in the avian world.

How big is a kiwi egg compared to the bird itself?

A kiwi egg is disproportionately large compared to the bird itself, measuring up to 20% of the female's body size. The egg's volume is about six times that of a chicken's egg, despite the kiwi being only about the size of a domestic chicken.

Why do kiwi birds lay such large eggs?

Kiwi birds lay large eggs to give their chicks a head start. The substantial yolk provides ample nutrients, allowing the chick to hatch fully feathered and independent. This evolutionary adaptation is crucial for survival, as kiwi parents do not feed their young, who must fend for themselves immediately after hatching.

Are there any other birds known for laying large eggs for their size?

While kiwis hold the record, other birds also lay notably large eggs for their size. The Wandering Albatross, for example, lays an egg that is around 10% of its body weight. Hummingbirds also lay eggs that are large in proportion to their tiny bodies, although the eggs themselves are small.

How does the size of the kiwi's egg affect its reproduction process?

The size of the kiwi's egg imposes a significant burden on the female during the incubation period. It affects her mobility and requires a lengthy incubation period of around 70-80 days. The large egg size also limits the number of eggs a kiwi can lay at one time, typically resulting in a single egg per clutch.

What adaptations do kiwi birds have to lay such large eggs?

Kiwi birds have evolved several adaptations to manage their large eggs. Their bodies are designed with a more flexible and spacious pelvis. Additionally, they have a unique reproductive system with disproportionately large ovaries and oviducts. These adaptations facilitate the development and laying of the egg, which is critical for the continuation of their species.