I learned what seems to be a later variant:

Be kind to your webfooted friends,
For a duck may be somebody's mother.
They live in the mud and the swamp
Where it's always cold and damp.

You may think that this is the end,
But it it isn't because here comes the chorus ---
Da, da-da-da, da-da-da,
Da-da-da-da, da-da-da, da=da=da=da.

Be kind to you webfooted friends,
For a duck may be somebody's mother.
They live in the mud and the swamp
Where it's always cold and damp.

You may think that this is the end
Well it is.

I had always thought it to be an English translation of an oriental poem about reincarnation, but perhaps not!