Owner Comments:
As has already been established in this collection with the absolutely nightmarish Haast’s Eagle, New Zealand has been home to some incredible modern dinosaurs. While many of them have gone extinct as part of the ongoing Holocene Extinction Event, others are still extant and are as unique and amazing as their extinct cousins. This next coin features one that is still around but far less horrifying than the Hasst’s Eagle: The North Island Brown Kiwi, species name Apteryx mantelli.
The North Island Brown Kiwi is the most widespread and most common of the existing five species of kiwi, ranging widely across the North Island of New Zealand. Ancestrally, the North Island Brown Kiwi preferred the dense sub-tropical and temperate forests of the North Island for habitat. But this little bird has shown remarkable resilience and adaptability compared to its relatives. North Island Brown Kiwis have adapted to live in scrub land, farm land and in pine plantations as well. This adaptability is probably why the North Island Brown Kiwi is now the most common kiwi, though it is still classed as Vulnerable by The International Union for Conservation of Nature (IUCN), the world's main authority on the conservation status of species.
In appearance, North Island Brown Kiwis are flightless ratites with streaky red-brown plumage that is spiky and very different from the feathers seen on flighted birds. As with many species of theropod dinosaurs, sexual dimorphism exists in size with the females being larger than the males. Female Northern Island Brown Kiwis stand about 16 inches high and weigh about 6.2 pounds. Males can reach similar heights, but they are of a much lighter build and average 4.9 pounds. Males and females also produce different vocalizations. Males produce a high-pitched whistle while females produce a lower, throatier call. North Island Brown Kiwis also have no tail and tiny, vestigial wings with a claw on them, a small trait that they share with their earlier theropod kin.
Foodwise, North Island Brown Kiwis are insectivores. Almost their entire diet is made up of insects, arachnids and the larvae and eggs of these two groups. They will also sometimes eat fruit and seeds if they find them, but this is relatively rare behavior for them.
Like many other theropods, North Island Brown Kiwis can mate for life but unlike others like parrots and birds of prey, “divorces” among North Island Brown Kiwis are fairly common. Mating and egg laying can take place at any time of the year, but is most common from June to November. The North Island Brown Kiwi holds the world record for laying the largest eggs in relation to its size of any known animal, not just among birds or dinosaurs as a whole. One or two white colored eggs are produced in a burrow and are incubated entirely by the male for 75 to 90 days. Once the eggs are laid, the female takes off and dad is on his own until the young go out on their own. North Island Brown Kiwis are never going to win any mother of the year awards. The young of the North Island Brown Kiwi are precocial and are up and walking around within a week of hatching and they leave to establish their own territories at between 4 and 6 weeks of age.
The main threat to the survival of the North Island Brown Kiwi is habitat loss. While they are more adaptable than other kiwi species, they still have very specific habitat needs for feeding and nesting. Invasive mammal species such as dogs, feral cats and stoats are a further threat to the eggs and young of this species. With the extinction of the Haast’s Eagle and the Eyles’ Harrier, New Zealand lost its only two large bodied, diurnal raptors. There are also no other large native predators. Because of this, New Zealand doesn’t have natural predators for these invasive mammals like Australia does in the form of the Wedge-Tailed Eagle, the Saltwater Crocodile and the Freshwater Crocodile. However, there are many programs in place to try to reduce the numbers of these invasive mammalian threats.
Kiwis, as a family, are also vitally important to paleontology. Studies have found that kiwis are actually the living bird family that are the most physiologically similar to extinct non-avian theropods. In particular, kiwis have plumage, respiratory systems and metabolisms that are very similar to those of extinct Paravians, the clade including Avialans and Deinonychosaurs. Kiwis often serve as stand-ins in studies on these groups of extinct dinosaurs, allowing us insights into these extinct species that we would never have otherwise.