NO!! If they did, they wouldn't fly!
If your talking about crows then yes, they caw while flying.
they sit
They usually do it to call in birds to mate.
59%
through their nose
The skylark.
if something hits them
They do cast shadows.
No, birds cannot stay completely still in the air while flying. They need to constantly flap their wings to maintain lift and stay airborne.
Gravity
no more than when flying over anywhere else.
No- In Fact Canadian Geese Never Collide When Flying In Formation