In proportion to the size of their brains, the kiwis olfactory bulbs the cerebral regions that coordinate the sense of smell are the second largest recorded among birds, after petrels. In addition to these bloodhound noses, kiwis ears are well developed. Cocking their heads toward the ground, kiwis can locate the whispering sounds of tiny arthropods deep in the humus. At the base of their bill, long, modified feathers called rictal bristles protrude like whiskers, giving the birds a well-developed sense of touch that helps them navigate around obstacles on moonless nights. With a nocturnal lifestyle and burrowing habits to boot, some scientists jokingly refer to kiwis as honorary mammals.
Kiwi reproduction is stranger still.
A female little spotted kiwi is burdened by an egg that is by far the largest relative to body size among birds, growing to 26 percent of her body weight, while the eggs of other kiwis average 15 to 20 percent of a female s weight. Instead, the bird generates a super-egg six times larger than expected, equal in size to the eggs laid by their giant relatives, the moas. Female kiwis lay one, two, or rarely three of these gargantuan eggs in a breeding season, spacing them about 33 days apart. After each egg is laid in the underground burrow or under the protective cover of a log, male kiwis have the only slightly less onerous task of incubating the egg for 70 to 85 days, nearly twice the duration of most bird species. If a subsequent egg is laid, the male incubates even longer.