No mammal predators
One reason New Zealand has so many flightless birds is that before humans arrived about 1000 years ago, there were no land mammals that preyed on birds. Predators were other birds, such as the laughing owl, eagle, goshawk, and falcon. With no mammalian predators sniffing them out, kiwi and other flightless birds could safely forage on the forest floor, living and nesting on the ground.
Since people arrived in the kiwi’s land, the forest floor has become a place of threat and peril for all New Zealand’s flightless birds.
Saving energy
Flying takes a lot of energy. With the ground being so safe, birds could save energy by walking. There is debate about whether kiwi evolved from a flightless ancestor or lost its ability to fly. Regardless, the kiwi does have a very small vestigial wing with a tiny cat-like claw on the end. This stumpy wing gave rise to the species’ name: ‘Apteryx’ meaning ‘wingless’.
