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'
The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals is an encyclopedia of prehistoric and extinct animals which had a vertebrate. The "Encyclopedia" is published by Chartwell Books. Early Tetrapods Lepospondyls Early Reptiles Turtles, Tortoises, and Terrapins Semi-Aquatic and Marine Reptiles Marine Reptiles Early Diapsids Snakes and Lizards Early Ruling Reptiles Crocodiles Flying Reptiles Carnivorous Dinosaurs Early Herbivorous Dinosaurs Long-necked Browsing Dinosaurs Fabrosaurs, Heterodontosaurs, and Pachycephalosaurs Hypsilophodonts Iguanodonts Duckbilled Dinosaurs Armored Dinosaurs Horned Dinosaurs Early and Flightless Birds Water and Land Birds Pelycosaurs Theraspids Primitive Mammals Marsupials Glyptodonts, Sloths, Armadillos, and