The main reasons involve the feathers and the skeleton. Special feathers are required for flight and the "Flightless Birds" have none of these special feathers. There is a unique part of the breastbone called the ridge. An extended part in the center of the breastbone is where the stronger muscles used for the wing movement are anchored. Finally the flightless birds have solid bones to transfer blood and oxygen through the bones themselves. Flight able birds have hollow bones to actually lighten the internal structure and weight of the bird. They also have much heavier blood vessels to transfer blood and oxygen to the limbs.
the weight of an bird
because of the way some birds are built their body structure wont allow them to fly
2 reasons - one is the same as why you can't sit in a vacuum, the other is that to fly anything needs support from air.
cats like to chase and eat birds, and birds like to fly to get away from cats.
Birds do not understand reflections. Often they fly into glass to attack the other bird they see there.
Except for a few kinds of flightless varieties (e.g. ostrich, emu, penguin), all birds are hollow-boned (semi-hollow, to be exact). Birds eat all sorts of different things, from nectar to rabbits -- it depends on the species.
in three weeks
The birds feathers are used for, insulation , this is for when they fly and when thier on the ground, it also helps pretect the skin, from getting damaged.
penguins cant fly, and chickens cant propperly fly!
some birds are to big for their wings to make them fly
Penguin
Fly backwards
well, a bird that cant fly has a larger body mass than one that can
no they cant fly because it weighs down their wings
To say that birds use wings and feathers to fly, so all birds can fly, would be false. Not all birds can fly. An ostrich is an example of a bird that cannot fly.
Most birds can fly. Not all.
Yes they do. Nearly all birds can walk. (Some birds that spend a lot of time on water find it difficult. Some, like Swifts, stay in the air.)
Birds do not fly all the way to the southern hemisphere, they fly to the equator.
all birds fly xept penguins
well there are all types of birds that can not fly for example the penguin well we all know that