Flightless bird that require a significant amount of overall metabolic energy, ratites decrease their basal metabolic rate and conserve energy. A study looking at the basal rates of birds found a significant correlation between low basal rate and pectoral muscle mass in kiwis. On the contrary, flightless penguins exude an intermediate basal rate. This is likely because penguins have well-developed pectoral muscles for hunting and diving in the water. For ground feeding birds, a cursorial lifestyle is more economical and allows for easier access to dietary requirements. Flying birds have different wing and feather structures that make flying easier, while flightless birds'
Cuban flightless crane Cuban flightless crane The Cuban flightless crane ("Grus cubensis") is a large, extinct species of crane that was endemic to the island of Cuba in the Caribbean. The remains were found in Pleistocene deposits in Pinar del Rio. Probably derived from an early invasion of sandhill cranes from North America, it differed from that species by, as well as larger size, having a proportionately broader bill, stockier legs, and with reduced wings and pectoral girdle indicating that it may have been flightless. Currently, the only extant Caribbean crane is the Cuban sandhill crane, "Antigone canadensis nesiotes", an endangered subspecies of