Wingless Birds

Not all birds fly. Ostriches and Emus are fast runners that never fly. But all birds carry at least relics of the apparatus of flight.

Ostrich Wing Stubs are only used for balancing and steering while running and when they enter into social and sexual displays.

Kiwi wings are too small to be seen outside the birds fine coat of feathers, but vestiges of wing bones are there.

Moas (which got extinct 1500AD)

Moas have lost their wings entirely. Their home country of New Zealand has more than its fair share of flightless birds, probably because the absence of mammals left wide open niches to be filled by any creature that could get there by flying. But those flying pioneers, having arrived on wings, later lost them as they filled the vacant mammal roles on the ground. This probably doesnt apply to the moas themselves, whose ancestors, as it happened, were already flightless before the great southern continent of Gondwana broke up into fragments, New Zealand among them, each bearing its own cargo of Gondwanan animals. But it sure does apply to kakapos, New Zealand's flightless parrots, whose flying ancestors lived so recently that kakapos still try to fly although they lack the equipment to succeed.

Kakapos, the heavyweight champion of all parrots

Penguins and Galapagos Cormorants are another two birds who use their wings for other purposes than flight. Ostriches, emus and rheas are great runners, but penguins and Galapagos flightless cormorants are great swimmers. But unlike penguins, who use their short wings to fly underwater, Galapagos cormorants propel themselves with their powerful legs and huge webbed feet, using their wings only as stablizers.

Galapagos Cormorants

But all flightless birds, including ostriches and their kind, which lost their wings a very long time ago, are clearly descended from ancestors that used them to fly.