Why is kiwi most different to the other birds?

The kiwi is most different from the other birds because it is a ratite, which means that it lacks a keel, or breastbone, and therefore cannot fly. Ratites are also characterized by their long necks and legs, and their feathers are typically soft and hair-like. In addition, the kiwi is unusual among birds in that it has no tail, only vestigial wings that are barely visible, and three digits on each foot. It also has a long beak with nostrils located at the tip, which is unusual among birds. Finally, the kiwi is nocturnal, which is also unusual among birds.