Birds use nests for breeding, very few use one for more than a very few weeks in any year. They find them just as humans find home - landmarks and memory.
yes
Powered flight.
Birds fly every day. If you have seen a unusually large amount of birds flying, they could be migrating birds passing your area.
they use it to steer their body in the sky
The birds are flown high in the sky under their own power.
Speed.
If I understand you correctly, you are saying that a bird flying in the sky does not have a shadow. If this is the case, it is not true. Birds do have shadows. I have noticed shadows of birds flying overhead, like a hawk, for example. I believe, that for small birds, the shadows are probably so small we just don't notice them.
The birds flying in the sky do not cast their shadow on the earth because the umbra is absent and the penumbra is too large and too faint that it is not visible as the distance of the earth is very large from the bird.
yes, there is fesies(poop) flying above us because most birds drop fesis from the sky when they are flying
Birds are the only dinosaurs that could fly. However, there were flying reptiles that were not dinosaurs. They were called pterosaurs.
Chuck Norris
Yes, ducks geese and swans, possibly more.