flying bird enemines?

hi, I was wondering on how to a flying projectile (bird in this case) it would work the same as any enemy, you touch it and a message pops up saying that you died! I am having trouble on making it
1- Defy the games gravity
2- Making it so when the game restarts when you die, it still works
3- basically when it hits a wall, it will turn around it the other wall, and hit the other wall, etc.

sorry if my grammar is bad in this post, im kinda tired lol