Kakapo the presence of kakapo. As a nocturnal species, the kakapo has adapted its senses to living in darkness. Its optic tectum, nucleus rotundus, and entopallium are smaller in relation to its overall brain size than those of diurnal parrots. Its retina shares some qualities with that of other nocturnal birds but also has some qualities typical of diurnal birds, lending to best function around twilight. These modifications allow the kakapo to have enhanced light sensitivity but with poor visual acuity. The skeleton of the kakapo differs from other parrots in several features associated with flightlessness. Firstly, it has the smallest
Flightless bird 85–92 days while females feed. They can go up to a week without eating and survive only off fat stores. The emu has been documented fasting as long as 56 days. If no continued pressures warrant the energy expenditure to maintain the structures of flight, selection will tend towards these other traits. Many flightless birds are extinct; this list shows species that are either still extant, or became extinct in the Holocene (no more than 11,000 years ago). Extinct species are indicated with a dagger (†). A number of species that are suspected, but not confirmed to be flightless, are