Ostrich is the world's largest bird which belongs to family Struthionidae, flightless, two-toed terrestrial bird.
They can from 7 to 9 ft (2.1 to 2.7 m) and weigh from 220 up to 350 lbs (100 to 160 kg).
Ostriches are fleet, strong runners which can sprint up to 43 miles (70 kilometers) an hour and run over distance at 31 miles (50 kilometers) an hour.
They may use their wings as "rudders" to help them change direction while running.
Roadrunners on the other hand are members of the Cuckoo family of birds.
They are large slender ground-dwelling birds measuring 18 to 24 inches from tail to beak and weighing 8-24 ounces.
Although capable of flight, the roadrunner prefers to spend most of its time on the ground. Roadrunners can run at speeds of up to 20 miles per hour and generally prefer sprinting to flying because their short wings are only able to keep their large body airborne for a few seconds at a time.
They will usually only fly to escape predators or when traveling down steep slopes.
Identifying a bird can be challenging. Birds are active, energetic animals and you need a quick eye to spot as many details as possible in a short span of time. The obstacles are many—the light may be dim, you could have the sun in your eyes, or the bird may dive into a bush.
So to stand the best chance of landing a name for a bird, you'll want to know what to look for—what matters most and how to spend your precious viewing time. Here are some bird watching tips for beginners shared by About.com.