Question

which bird run faster and why

Answer 1

birds like ostrich runs fast because of their strong and powerful legs. 

Answer 2

The Bird Ostrich is the most fastest RUNNER from the category of birds 
The ostriches use half of their energy as much of humans that why they can run so fast in long distances and they have springy legs which help them run faster. Elastic joints help them to run a bit fast. They are born as FAST-RUNNERS