hello sir
my question is that when i see birds i wonder what if these birds could fly without wings and i know for lift and balance to fly they need wings. But are there any bird who can fly without wings.

even tell me how birds are able to stretch their wings and then compress it.
i am studying aerospace engineering and want to know so that it could help in designing .

thank you

As you say, wings provide lift, without which birds could not fly.  The wing size and shape determines the amount of lift and consequently the weight that can be carried - essentially the birds' body.  Many birds cannot fly because their wings are too small, such as ostriches, penguins and some rails.  Wing-derived lift does not confer powered flight though, and to get beyond gliding birds need to flap their wings.  The wing is equivalent to our arm and extended fingers, so the musculature of the wing together with the arrangement of feathers and the type of power stroke determine flight characteristics, ranging from soaring and gliding albatross and eagles to highly manoueverable flycatchers and humming birds.  The wing is simply folded against the bird as you would close your hand and bring your elbow in to your side.