Flightless Birds

 Flightless Galapagos Cormorant

The few flightless birds (called Ratites) of the world are probably local adaptations to peculiar habitats and they themselves probably evolved from flighted ancestors. They have the same bones in their wings and bodies as do birds that fly. Intermediates between flying birds and ratites are known. Ratites are mostly known from islands--why? Penguins are flightless birds who "fly" through the water. Interestingly, the major ratites (ostriches, emus, and rheas) share the same ectoparasites. Does this mean they rubbed shoulders back before continental drift?