YOU SAID:

if it quacks like a duck then it's a duck

INTO JAPANESE

アヒルのように鳴くならば、それはアヒルだ

BACK INTO ENGLISH

If it crows like a duck, it's a duck.

INTO JAPANESE

アヒルのように鳴くならアヒルだ

BACK INTO ENGLISH

If it crows like a duck, it's a duck.