Kiwis are unique, flightless birds that are found only in New Zealand. They are about the size of a chicken and have a long, narrow beak which they use to probe the ground in search of food. Kiwis are omnivores, meaning they eat both plant and animal material. Their diet consists mainly of invertebrates, fruits, seeds, and small amphibians and reptiles.
Invertebrates
Invertebrates make up the bulk of the kiwi’s diet. They use their long beak to probe deep into the soil and rotting logs to find worms, insects, grubs, spiders, centipedes, millipedes, snails, and beetle larvae. Some of the common invertebrates eaten by kiwis include:
- Worms – Such as earthworms, flatworms, and nematodes.
- Insects – Such as beetles, grasshoppers, crickets, cicadas, and weta (a large flightless cricket).
- Spiders
- Centipedes and millipedes
- Snails and slugs
- Grubs – Such as huhu grubs, an important source of protein.
Kiwis will also eat freshwater invertebrates such as crayfish and water insects when they come across streams and pools while foraging.
Fruits
Kiwis supplement their diet with a variety of seasonal fruits. Some native fruits commonly eaten include:
- Tawa berries
- Miro berries
- Hinau berries
- Karaka berries
- Bush lawyer berries
They also consume fallen fleshy fruits from introduced plants such as figs, feijoas, apples, plums, tomatoes, and grapes when available.
Seeds
Kiwis eat a variety of small seeds they come across while probing the forest floor. Seeds from native plants like nikau, tawa, and karaka are eaten. They also consume seeds from introduced plants like gorse, apples, plums, and blackberry.
Small vertebrates
Though not a main component of their diet, kiwis will occasionally prey upon small vertebrates like amphibians and reptiles they encounter while foraging at night. Some examples include:
- Frogs
- Lizards – Such as skinks and geckos
- Worms – Such as earthworms, flatworms, and nematodes.
They swallow their prey whole and their digestive system is able to dissolve the bones and scales.
Foraging behavior
Kiwis are nocturnal birds and do most of their foraging at night. They use their highly developed sense of smell along with touch to find food. Their nostrils are located at the tip of their beak, allowing them to sniff out prey along the forest floor. They probe the ground in a slow, deliberate motion using their flexible beak. The beak has receptors that can detect movement from potential prey.
Kiwis forage solitarily and have large home ranges from 20-50 hectares. Their territories may overlap with other kiwis. They often return to productive feeding areas night after night. Excellent hearing allows them to locate subterranean invertebrates.
Adaptations for foraging
Kiwis have several unique adaptations that aid their ground foraging lifestyle:
- Long, narrow, flexible beak – Allows them to probe deep into soil, rotting logs, and underground burrows.
- Nostrils at beak tip – Gives them an excellent sense of smell to sniff out prey.
- Vibrissae around base of beak – Sensitive whiskers to detect prey movements.
- Robust legs and strong claws – Built for scratching and digging in leaf litter and dirt.
- Excellent hearing – Can locate insects and worms under the ground.
- Small eyes – Vision less important than other senses at night.
Diet by species
There are five living species of kiwi birds. They inhabit various habitat types across New Zealand. Though they are all omnivores, their specific diets can vary slightly by species:
North Island Brown Kiwi
- Beetles, huhu grubs, and earthworms are key prey.
- Also eat cicadas, spiders, snails, slugs, and millipedes.
- Occasionally prey on frogs and skinks.
- Favor berries from native plants like hinau and miro.
Little Spotted Kiwi
- Mainly eat earthworms, huhu grubs, millipedes, snails, and weta.
- Also consume fruits and seeds.
- Forage in forest litter and fallen logs.
Great Spotted Kiwi
- Diverse diet includes beetles, weta, snails, spiders, and centipedes.
- Eat fruits like tawa, nikau, and wild figs.
- Probe forest floor and excavate burrows for prey.
Rowi
- Skinks and geckos make up over 50% of diet.
- Also prey on beetles, spiders, millipedes, snails, and earthworms.
- Occasionally eat seabird chicks and eggs.
- Consume native fruits and seeds.
Tokoeka
- Invertebrates like weta, huhu grubs, and beetle larvae are key food.
- Also eat frogs, skinks, berries, and seeds.
- Probe tussock grassland vegetation for insects.
Threats to kiwi prey
Several introduced mammalian predators like stoats, rats, possums, ferrets, and feral cats prey on many of the same invertebrates, small vertebrates, fruits, and seeds that kiwi rely on for food. Competition and loss of food sources from these invasive predators may impact kiwi populations. Conservation efforts focus on controlling pest species in areas where kiwis live to ensure abundant prey availability.
Conclusion
Kiwis have an omnivorous diet consisting mainly of invertebrates like insects, worms, and grubs which they probe for underground using their long, narrow beaks. They also consume a variety of fruits and seeds from native plants and will occasionally eat small vertebrates like lizards and frogs. Different kiwi species tend to favor slightly different key prey items based on the habitats they live in. Introduced predators can compete with kiwis for food sources, posing a threat to their survival. Protecting kiwi habitat and controlling invasive mammals helps provide abundant prey availability for these unique, iconic birds.
