Fauna of Australia in Australia, feeding on sea grass in coastal areas. The destruction of sea grass beds is a threat to the survival of this species. Eleven species of seal—family Pinnipedia—live off the southern coast. Australia and its territories are home to around 800 species of bird; 45% of these are endemic to Australia. The fossil record of birds in Australia is patchy; however, there are records of the ancestors of contemporary species as early as the Late Oligocene. Birds with a Gondwanan history include the flightless ratites (the emu and southern cassowary), megapodes (the malleefowl and Australian brush-turkey), and a huge
Flightless bird free to increase in abundance until the population was limited by food and territory. A study looking at energy conservation and the evolution of flightlessness hypothesized intraspecific competition selected for a reduced individual energy expenditure, which is achieved by the loss of flight. Some flightless varieties of island birds are closely related to flying varieties, implying flight is a significant biological cost. Flight is the most costly type of locomotion exemplified in the natural world. The energy expenditure required for flight increases proportionally with body size, which is often why flightlessness coincides with body mass. By reducing large pectoral muscles