What is so special about a kiwi and its egg?

One of the things which makes a kiwi and its egg so special is the sheer size of the egg compared to the bird itself.

The kiwi is about the size of a chicken, depending on the species, averaging about 45 cm (18 in) high, and ranging in weight from 1.3 kg to 4.5 kg (between 3 and 10 pounds).

Its egg, on the other hand, is almost as big as that of the emu (150mm long and about the same diameter) and is one of the largest in proportion to its body size compared to other birds. Just before the egg is laid, it makes up 15-20% of the kiwi's body weight, and takes up so much room that the female is unable to eat because there is no room in her stomach.