What Am I Riddles

Question: I'm the part of a bird that's not in the sky,
I can swim in the ocean and remain dry?

What am I?

Question: Crawls over pages and fells wild beasts.
Helps guide you along in your home and on streets.

What is it?

Question: You bury me when I'm alive,
and dig me up only when I die.

What am I?

Question: You use me from your head to your toes,
the more I work the thinner I grow.

What am I?

Question: Walk on the living, they don't even mumble.
But walk on the dead, they mutter and grumble.

What are they?