Welcome to this in-depth look at one of New Zealand’s most iconic yet misunderstood birds – the kiwi. Over the following post, we’ll discuss all you need to know about these nocturnal feathered friends, from their lifespan and size to fascinating behaviors and conservation status.Â

Kiwi bird

The kiwi is a flightless native bird endemic to New Zealand. They are particularly notable for having a largely nocturnal lifestyle as well as soft, thick brown feathers instead of flight or tail feathers. The scientific name for the common brown kiwi, which is the most populous species, is Apteryx mantelli.

Kiwi are easily identifiable by their long, thin, downward curved bill and stout legs with strong claws. Their bodies are compact with short flexible necks, which allow them to forage for food on the ground in dense undergrowth. With poor vision, kiwis rely heavily on their keen sense of smell and touch to hunt for worms, beetles, slugs, and other invertebrates at night.

Kiwi bird lifespan

Most kiwi species have lifespans of 20-30 years in the wild. However, longevity varies depending on threats and environmental conditions. In ideal circumstances, some kiwi individuals have been documented living up to 50 years old. In comparison to body size, this lifespan places kiwi among the longest-living bird species.

Though long-lived, kiwi sexual maturity is not reached until 3-7 years old depending on sex and species. Females can lay one very large egg weighing around 15% of their body mass annually thereafter. This low reproductive potential and lengthy time to breeding age makes kiwi populations vulnerable to predation and threats. More on kiwi reproduction later!

Kiwi bird size

Kiwi comes in a range of sizes depending on species, from the tiny little spotted kiwi, the world’s smallest, to the nearly turkey-sized great spotted kiwi, the largest. On average, however:

• Adult brown kiwi stand 40-50cm tall
• Weigh 1.5-2.5kg
• Have bills around 12-18cm long

This makes for a bowling ball-sized bird. Females tend to be slightly larger than males. Despite their small stature, kiwi are well-muscled under their feathers which allows them to power through dense bush and fend off predators like rats, stoats, and even dogs with their sharp claws if needed.

Kiwi bird egg

The egg a female kiwi lays each year is nothing short of incredible both in size and natural defenses. Weighing around 15% of the mother’s body weight, kiwi eggs are truly enormous – often measuring over 5cm tall and over 4cm wide at their fullest point.

In comparison to body size, the kiwi egg is one of the largest of any bird species. To support this massive egg, the female kiwi possesses special calcium-rich medullary bones, which break down during egg formation to provide the necessary minerals for shell development.

The semi-glossy green eggshell is around 2-3mm thick with a leathery texture. It contains natural antimicrobial compounds on its surface to deter bacteria build-up during the long 55-75 day incubation period. Not only does this giant egg have to incubate, but hatchling kiwi also need to chip their way out – a process that can take multiple days! Truly amazing adaptations, all while keeping vulnerability low.

Ten facts about kiwi birds

To give you a snapshot of some of the fascinating traits of these unique birds, here are ten quick facts about kiwi:

1. They have no tail feathers and only soft, thin brown outer feathers for camouflage instead of flight feathers.
2. Kiwi have poor vision but an excellent sense of small concentrated near the end of their long bills.
3. Nocturnal hunters kiwi are most active from dusk till dawn foraging on the forest floor.
4. They have disproportionately large feet and clawed toes for climbing and powerful legs for running up to 32km/h.
5. Some kiwi species live solitary lives, while others form breeding pairs or family groups.
6. Both sexes incubate and care for eggs and chicks though females contribute more time.
7. Their eggs are truly enormous relative to adult body size, up to 15% of the mother’s mass.
8. Chicks develop quickly and fledge at 12-16 weeks though still dependent on parents for 6+ months.
9. Kiwi are resilient but vulnerable to introduced predators like stoats and have undergone major population declines.
10. Today kiwi conservation efforts focus on predator control, translocations, and population monitoring to ensure species survival.

Now that you have a primer on kiwi, let’s take a deeper dive into some common searches and questions readers may have!

FAQs

Where do kiwi birds live?

As the national emblem and only flightless bird of New Zealand, kiwi is uniquely endemic to this island country. Five species of kiwi are found across New Zealand’s North and South Islands, and populations are on offshore islands as well.

Species ranges vary but common brown kiwi inhabit both main islands as well as subspecies present in some outlying regions. Great-spotted kiwi are limited to North Island forests, while little-spotted kiwi are called South Island forests’ home. Rowi kiwi survives only in fenced predator-free enclosures on offshore islands. Understanding kiwi habitat needs is key to their continued conservation.

Why did the kiwi bird go extinct?

Sadly, one kiwi species – the North Island kokako or “little grey kiwi” went extinct in the late 19th century due to overhunting and introduced predators like rats, cats, and mustelids, significantly impacting populations. Other kiwi species were driven to the brink of extinction in the early 1900s for similar reasons.

Predator pressures remained immense until the 1970s, when concerted pest control and conservation efforts began turning the tide. Translocations to offshore predator-free islands also bolstered declining numbers. Today intensive management keeps introduced predator populations low, allowing kiwi numbers to slowly rebound on the mainland in designated sanctuaries. While no longer facing imminent extinction, introduced predators continue to severely threaten kiwi survival.

How many kiwi birds are left?

The last major census in 2015 estimated 58,000 kiwi remained in New Zealand – a figure that has increased significantly from a low of 10,000 birds in the 1970s. However, numbers are still a small fraction of pre-human settlement populations estimated in the millions. Breaking it down by species:

• Brown kiwi (5 subspecies) – 45,000
• Great spotted kiwi – 7,000
• Little spotted kiwi – 3,000
• Okarito kiwi – 2,500
• Rowi kiwi – Only 300-350 on offshore islands

While figures indicate conservation efforts are having an impact, ongoing predator control and ecosystem protection is still needed long-term to ensure thriving, self-sustaining kiwi populations. The rowi, down to just a few small groups, remains one of the world’s rarest and most endangered birds.

Can kiwi birds fly?

Unlike many other ratite birds, all kiwi species are completely flightless with tiny nub-like wings covered in feathers. This adaptation has evolved over millions of years as kiwi adapted to living as terrestrial browsers and foragers in New Zealand’s dense forests and shrublands.

Wings became functionless as they no longer needed to fly for survival or migration, and flight muscles atrophied. Instead, kiwi invest their resources into strong legs for running up to 32km/h, keen senses of smell and touch, and powerful claws for defense and climbing. While flightless, their camouflage feather coat and low profile body shape allow them to move unseen through leaf litter and bush.

How fast can kiwis run?

For a bowling ball-sized ground-dweller, kiwi certainly knows how to get up and go when needed! On their sturdy legs and clawed feet, brown kiwi have been clocked running at top speeds of up to 32km/h, which is very fast for an animal of their size.

This burst of speed is an important survival trait, allowing kiwis to escape threats like stoats, dogs, and more. Their powerful legs also aid climbing abilities through dense bush habitats. Generally, kiwis move at a more modest pace while foraging at 3-5km/h to conserve energy. But that explosive acceleration when fleeing danger shows why kiwis are still surviving predators today despite their vulnerability. Truly impressive speed for a flightless bird!