The kiwi, a unique and flightless bird, stands as an iconic symbol of New Zealand. This nocturnal creature, roughly the size of a domestic chicken, possesses a distinctive appearance with its long beak and hair-like feathers. Unlike most birds, the kiwi occupies a specialized ecological niche on the forest floor, where it navigates its environment primarily by senses other than sight. Its unusual characteristics have long fascinated researchers and enthusiasts alike, prompting a closer look into its feeding habits and specific dietary components.
The Staple Diet
Kiwi birds are omnivores, consuming both plant and animal matter, but their diet largely consists of invertebrates. Earthworms are a favorite food source and can constitute a significant portion of their intake, sometimes reaching lengths of over half a meter. New Zealand’s diverse worm population, with over 178 native species, provides an abundant supply for these birds.
Beyond earthworms, kiwis also feed on various insects and their larvae, including:
- Beetles
- Grubs
- Crickets
- Cicada nymphs
- Woodlice
- Millipedes
- Centipedes
- Slugs
- Snails
- Spiders
These invertebrates are readily available in the moist, rich soil and leaf litter of their habitats. Kiwis supplement their diet with plant material, such as fallen fruit, berries, and seeds from native plants like totara, hinau, and miro. They have also been observed consuming bracket fungi, small crustaceans like freshwater crayfish, and occasionally amphibians such as frogs.
Ingenious Foraging Strategies
Kiwi birds are primarily nocturnal, emerging from their burrows after dusk to forage for food. Their keen sense of smell is their primary tool for locating prey, a trait unusual among birds. The kiwi is the only bird with nostrils located at the very tip of its long beak, allowing it to sniff out insects and worms buried underground without relying on sight. Their olfactory bulb, the part of the brain processing smell, is proportionally large, similar to that of mammals.
As they move, kiwis constantly probe the soil and leaf litter with their sensitive beaks, which can be inserted up to 12 centimeters deep. Their beaks are equipped with sensory pits that can detect subtle vibrations caused by moving prey underground. This “remote touch” ability, combined with their sense of smell, enables them to pinpoint the exact location of their next meal. Kiwis also use their strong legs to stamp the ground, which can bring earthworms closer to the surface, making them easier to detect and capture. Loud snuffling and snorting noises are often heard as kiwis clear their nostrils of dirt while probing.
Habitat’s Role in Food Choices
The kiwi’s diet is directly influenced by its preferred habitat, which typically consists of dense forests, woodlands, and scrub. These environments often feature damp, rich soil and thick leaf litter, providing ideal conditions for the abundance of ground-dwelling invertebrates that make up the bulk of their diet. Moist soil supports a thriving population of earthworms and allows for easier probing with their beaks.
While kiwis primarily inhabit native forests, some populations have adapted to other areas, including sub-alpine scrub, tussock grassland, and even commercial pine plantations. This adaptability suggests they can utilize various food sources found in different environments. Seasonal changes can also affect food availability, with droughts, for example, making it harder for kiwis to access earthworms when the ground becomes too hard. The water content of their food, particularly juicy earthworms, often provides enough hydration, allowing kiwis to thrive even in drier locations.