Which bird cannot fly?

The story behind the answer

Ostriches are the world’s largest living birds and are flightless. Unlike flying birds, they have a flat breastbone without a keel, so they can’t anchor the powerful flight muscles needed for takeoff. Their wings are relatively small, and their soft, non-aerodynamic feathers and heavy bodies are adapted for running instead of flying.

Evolution favored speed on open African savannas: ostriches have two-toed, springy legs that propel them up to about 70 km/h (43 mph). They use their wings for balance while sprinting and for courtship displays, not for flight. They also lay the largest eggs of any living animal and have excellent eyesight to spot threats. Memory tip: “Ostrich = outstanding sprinter”—built to outrun, not outfly.