The term 'Big Australian Birds' can be summarized by the crossword solution of 'Emus'. Emus are the largest bird native to Australia and the second-largest bird in the world by height, after the ostrich. They are flightless birds with long necks and legs, and can reach up to 2 meters in height. Emus are omnivorous, eating a variety of plants and insects. They are also known for their fast running ability, reaching speeds of up to 50 km/h.