Apterygidae Kiwis
Version: 1.0 — Published March 4, 2020
Introduction
Kiwis are perhaps the birds that most resemble mammals. They have a mammal-like body temperature, poor vision, almost no wings, and non-feathery, hair-like plumage. Their excellent sense of smell is tied to nostrils and numerous nerve-endings at the end of a long flexible bill, which they use to probe for prey in the undergrowth and duff of New Zealand forests. Kiwis are also quite adept at catching aquatic prey, and the fleshy valves on these nostrils appear to serve the birds well when they forage in forest streams. Kiwis are nocturnal and nest in self-excavated underground tunnels, and the females lay proportionally the largest egg of any bird. In most species, only males incubate, and helpers sometimes assist.
Habitat
Kiwis inhabit primarily wet forests, typically temperate rainforests, but will venture into subtropical rainforest, scrubland, and grassland where soils are light enough for digging burrows and foraging.
Diet and Foraging
Kiwis feed primarily on worms and other invertebrates such as beetles, crickets, spiders, and moths. They sometimes take small amounts of plant material, including fruit and leaves, which may be ingested unintentionally. Kiwis mostly rely on their keen senses of smell and touch to probe for food with their bills.
Breeding
Unlike other ratites, kiwis are monogamous with long-lasting pair bonds. They nest in self-excavated burrows in steep banks, which are often left unoccupied for several months after excavation, which allows covering vegetation to grow around the entrance. Females typically lay 1 or 2 very large eggs, probably investing as much as other ratites in eggs laid, but in a much smaller clutch. Although the incubation behavior of kiwis varies depending on the species, males of all four species exert more effort in the process than females. Some males incubate unassisted, whereas others are assisted by up to five other adult male helpers, which develop brood patches to help incubate eggs they did not father. The chicks hatch after two to three months of incubation, and they are generally brooded by the male but feed themselves. Chicks are independent after about three weeks of age, although they remain in their parents’ territory for several months.
Conservation Status
All apterygid species (100%) face some level of conservation risk (1 NT, 2 VU, 2 EN). Kiwis are currently declining rapidly from habitat destruction and the introduction of mammalian predators. Once widespread, the Little Spotted Kiwi Apteryx owenii was nearly eradicated, and is now found only in predator-free locations where birds have been released. Although it has the smallest population of the five kiwi species, A. owenii was recently downlisted to near-threatened status because of the success of these intensively managed populations.
Systematics History
Apterygids fall within the ancient ratite radiation that is sister to all other living birds. The most recent morphological studies suggest that apterygids are sister to ostriches (Livezey & Zusi 2007). In contrast, a series of molecular phylogenetic studies have consistently placed kiwis sister to Casuariidae (Sibley & Ahlquist 1990, van Tuinen et al. 1998, Hackett et al. 2008, Harshman et al. 2008, Phillips et al. 2010).
Conservation Status
Least Concern |
0%
|
---|---|
Near Threatened |
20%
|
Vulnerable |
80%
|
Endangered |
0%
|
Critically Endangered |
0%
|
Extinct in the Wild |
0%
|
Extinct |
0%
|
Not Evaluated |
0%
|
Data Deficient |
0%
|
Unknown |
0%
|
Data provided by IUCN (2023) Red List. More information