Kiwi: Endangered national symbol
Even though many people may think of as a brown fruit with a furry skin, the term ‘kiwi’ is originally due to a rather inconspicuous New Zealand bird species whose resemblance to the fruit of the same name is obvious.
The flightless, night-active kiwi (type Apteryx) lives endemically in the forests of New Zealand. The genus is the only one of the family Apterygidae and consists of three or five species depending on the doctrine. The kiwi is the national symbol of New Zealand – colloquially the term is also used for its inhabitants.
Kiwis are 35 to 65 centimetres long, up to 35 centimetres tall and weigh one to five kilogrammes, making them one of the smallest representatives of the group of ratites. Females are on average slightly larger than males and 10 to 20 percent heavier.
Although kiwis are omnivores that feed on all animal and plant materials (fruit and seeds), they mainly poke for invertebrates in the soil, especially earthworms, millipedes and insect larvae. The movements of the animals in the ground can be perceived by kiwis, so that they sink their beaks purposefully into the ground and feel the prey. Through this, Kiwis leave characteristic holes in the ground that are up to 15 cm deep and are a sign for the bird’s presence (attentive track readers will surely spot them).
The strictly monogamous way of life of the small birds is particularly striking. Kiwi couples who spent more than ten years together have already been observed. Only if one of the partners dies, a new one is looked for, so that a constant reproduction can be guaranteed. Every year between August and October, the breeding season begins for the kiwi pairs. During mating season, they hunt each other then, execute jumps and are extremely ‘loud’. Only one of the many breeding caves in the area is used for breeding, preferably one of those that are already several years old, as their entrances are usually overgrown with protective vegetation. The male prepares the nest there, by collecting moss and grasses and padding out the nesting hole with it. The female then usually lays one, but rarely also two or three eggs.
It is remarkable that the egg has an enormous size in relation to the size of the mother. The egg of a brown kiwi is 13 cm long and has a diameter of 8 cm. The weight is about 500 grams. These are the largest bird eggs in the world in relation to the body size of their producers – they reach up to 30 percent of the body weight of the female! In lots of kiwi species, males are responsible for incubation. The female then usually sleeps in another place that is in close proximity. At 63 to 92 days, the incubation period lasts unusually long. The brooding male leaves the den every night in order to eat; for this time, the female then takes over the brood-business.
The freshly hatched kiwis already look like small adults. As a precocial species, they are independent usually directly after the hatch and are able to find food independently. They are only partially guarded by their parents.
The population situation of the kiwi is dramatic, since they fall more and more victim to the cats, dogs and weasels that were introduced into New Zealand. Within the framework of various conservation projects, it has been possible to free smaller coastal islands from imported predators and to establish stable kiwi populations there.
By the way: Kiwis can reach a proud age of up to 20 years!