Welcome to Permies!
That's interesting about them nipping at your heels. I can't
answer your question, but I added your post to the Ducks and Geese forum so maybe some knowledgeable permies will notice and answer.
I kind of want to try
gardening with ducks too... but I hear they're really noisy and now you tell me they bite?! Yikes. I hope we can find a solution.