The North Island brown kiwi (Apteryx mantelli) is a nocturnal flightless bird and species of kiwi that is widespread in the northern two-thirds of the North Island of New Zealand and, with about 35,000 remaining, it is the most common kiwi species. The eggs laid by the North Island brown kiwi are among the largest eggs relative to its body size.
Genetics The genome of Apteryx mantelli was sequenced in 2015.
Description It is a large brown kiwi, possessing spiky, streaked feathers. North Island brown kiwi display size-based sexual dimorphism, where the females are observably larger than the males. The males weigh between 1.44–3.06 kg (3.2–6.7 lb) and females weigh between 2.06–3.85 kg (4.5–8.5 lb). The long bill measures 13–20.5 cm (5.1–8.1 in) in length.
Taxonomy
The North Island brown kiwi, or brown kiwi at the time, was first described as Apteryx australis by Abraham Dee Bartlett, in 1813, based on a specimen from Dusky Sound, South Island, New Zealand. This is a monotypic species. The brown kiwi (then Apteryx australis) was originally thought to additionally include the rowi (Okarito kiwi) and the tokoeka species. However, through genetic testing in 1994, it was determined that the tokoeka was a separate, distinct taxon. Once the tokoeka was separated into its own species, it was given the name Apteryx australis, eventually leading to the official binomial name of Apteryx mantelli to describe the North Island brown kiwi. Soon after, in 2003, more comprehensive genetic tests were performed and it was definitively determined that rowi was also a separate species and was later given the binomial name Apteryx rowi. In 2004 an injured bird was found with streaked white around the head and identified by Massey University. The white feathering is likely due to a rarely seen genetic variation sometimes described as a partial albino. Few documented cases exist with only a painting of one found in Ōtorohanga in the 18th century and a specimen in the Canterbury Museum. The injured bird recovered and was introduced into a breeding programme.
Range and habitat
North Island brown kiwi (Apteryx mantelli) inhabit four primary regions within New Zealand's North Island, outside of sanctuaries and zoos. They are Northland and its associated islands, the Coromandel, eastern North Island and western North Island. Historically, prior to human colonisation, New Zealand's indigenous forests covered terrestrial land and provided the assumed primary habitat for all kiwi species, which thrived in this ecosystem. In modern day New Zealand, North Island brown kiwi appear to generally prefer densely vegetated lowland and coastal New Zealand indigenous forest as their population densities are highest in these habitats. However, due to widespread deforestation and destruction of these native forests post colonisation, the availability and abundance of these preferred habitats has significantly decreased. Although the characteristics of North Island brown kiwi, such as a low reproductive rate and their longevity, suggest this species is accustomed to a stable environment, the North Island brown kiwi has been shown to be adaptive to an array of habitat types outside of their historical, ideal habitats. Brown kiwi can also be found utilising exotic pine forests, overgrown pasture, sand dunes, regenerating forests and forest remnants etc. This variety in potential habitat usage has been suggested to be possible by the North Island brown kiwi selectively utilising small patches of favourable or ideal habitats amongst other habitat type patches. North Island brown kiwi appear to thrive in exotic forests similarly to indigenous forests. Anecdotal evidence suggests that the population densities, body weights and productivity of North Island brown kiwi in exotic forests is comparable to those within New Zealand indigenous forests. However, as this evidence does not originate from published data, further research needs to be conducted to confirm this claim. Although there is an acknowledged favourable habitat, the current primary driver of habitat usage in the North Island brown kiwi appears to be food and shelter site availability with purpose/need such as reproduction also being a factor. Not in relation to favourable habitat availability within a given territory. For example, nesting sites of the North Island brown kiwi in a territory (purpose – reproduction) containing patches of different habitat types typically were found within or 25m near secondary succession vegetation and/or native vegetation. Kiwi chicks shortly after hatching can only walk short distances and therefore require adequate nearby habitats, which are selected for by nesting parental North Island brown kiwi.
Behaviour
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