But you will only find DUKW in Chambers under the 4th entry for "duck", presumably because that is how it was pronounced (in my youth, at least).
Have now found the first extra jumble in 11ac - "deer I", fairly obvious. I suspect the others are better hidden.
I suppose the birds themselves are a bit "amphibious" - not really! They certainly brighten up the streams round here. Found the next "extra jumble" in 31ac, last three words.