Kiwis (Apteryx genus) are 5 species and several subspecies of flightless birds native only to New Zealand. They are the smallest of the flightless birds and are considered a symbol and large part of the identity of New Zealanders.
Kiwis are about the size of a domestic chicken, and depending upon species weigh between 2 and 8lbs. They have short, bristly feathers and stubs for wings. Unlike most birds, kiwis do not have hollow bones but rather bones containing marrow like a mammal, and are thus heavier than similarly sized flying birds. Also unique to the kiwi is the fact that it has nostrils at the end of its long, pliable beak and a very powerful sense of smell.
Kiwis feed almost exclusively on ground-dwelling invertebrates such as grubs, earthworms and various insects. They have also been known to eat different types of fruit. Their preferred habitat is scrub forest, but kiwis are capable of adapting to life in a variety of biomes.
Unlike most other continents or islands, there are no predatory mammals native to New Zealand. It is likely that the kiwi developed its flightless characteristics due to the fact that is has no natural predators. However, in the time since humans began to populate the island more and more nonnative predators have been introduced. Pigs, dogs, cats and stoats prey heavily upon the kiwi, as it has never evolved any way to escape or defend itself from large predators. Because of this, kiwis that exist in environments with predators tend to be more nocturnal; where as those in protected environments are more active during the day.
Kiwis mate for life, and often a pair can be together for up to 20 years. Most kiwis only lay only one egg, and this is for good reason; kiwis lay the largest eggs in proportion to the size of their bodies of any bird in the world, with some eggs up to ¼ the weight of the female. After the egg is laid, its incubation period will take 2-3 months; a task that is entirely the responsibility of the male.
Although the kiwi is the size of a chicken, the eggs it lays are six times larger than a chicken egg.