Answer:
A reaction to being spooked that takes its name from waterfowl
I fly through the air on small feathered wings, seeking out life and destroying all things.
I turn around once. What is out will not get in. I turn around again. What is in will not get out.
Thousands lay up gold within this house, But no man made it. Spears past counting guard this house, But no man wards it.
You'll see savory dishes in Hong Kong sizzling in these.
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?