1) Why do birds fly in a 'V' ?

Some aerodynamic least resistance business.
'W's are too complicated.
They don't, they fly in a '>'.
For victory.
I don't know, man.
Because V's are open ended and the birds can fly out (Birds never fly in a 'D').
I suppose the scientific explanation has something to do with wind dynamics - personally the V shape is pleasantly aesthetic and brings to mind a greater question - the absolute insanity of migration.
Because it's too hard to fly in a 'Q'. (Queue?)
To take advantage of the updraft caused by the vortex shed by the bird ahead; it's kind of like surfing on air.
It's the only letter they know how to spell. Plus if they tried flying in a 'Z', they wouldn't know which way to go... It's also short for "vich vay to ve go?"
Because the logistical difficulties would be insurmountable if they tried to fly in an ampersand.
Because they couldn't get out of a 'Q'.
They don't see straight.
So that people can look up at them and ask, "Why do birds fly in a V?"
When they flew in straight lines, hunters would just lead them with a 50. caliber machine gun and get the bonus round like on Galaga.
Because it's easier than flying in a 
So they know what direction they are going.
Drafting. (Lowers air resistance for the followers.)
To signal UFOs as to where nuclear missile silos are located.
There can only be one leader. It is a lot easier to fly when someone's not flying right in front of you.