Why does a アヒル, 鴨 quack?

Because it doesn't know how to moo. Duh.

I once had a little pet duck
Who had a habit of liking to cluck
I was taken aback
When he finally 発言しました quack
And I started to run amock.

It doesn't quack.
















It makes アヒル, 鴨 sounds.

BECAUSE ELMO TOLD HIM TOO!!!! :3

*Goku arrives on namek* "Ah...now it's so peaceful!"
*Krillin in distance* "HELP! WE'RE GONNA DIE! HEEELLLP!"
Goku: "That sounds like a duck! That's silly!"
Krillin: "Quack....quack..."
Goku: *gasp* "That sounds like Krillin! Hold on!!"


So to answer your question, ducks don't quack, Krillin does.

because they want crack.