Question

some birds cannot fly because

Answer 1

Some birds cannot flt bcoz ...they hav short wings and a tall or heavy body..For example.. a ostrich.. it cannot fly high up.. but it can run very fast

Answer 2

Hey! :)

Some birds cannot fly. For eg: ostriches, cassowaries, emus and rheas. These birds can't fly because they have puny wings i.e. their wings are lethal and small, which is unable to lift their heavy body weight. Also, these birds mentioned above, have their breastbones lacking the kneel that anchors the strong pectoral muscles required for flying.

...hope this helps :)