at the time of his death updating his 1980 "revision" of Kortright's book. What happened the planned update after his death I do not know....
Madge and Burn is from 1987 so it too is a bit outdated as far as "common names", the seperation of some "species" and "sub-species" and current status but as far as I know its the most recent comprehensive book that covers only waterfowl and that provides detailed life history information on the birds, including descriptions of all plummages, ranges, habits, etc. etc.....
One of the more recent field guides would be more accurate as to current common name and any changes in scientific classification but you won't get the detailed information that is include in Waterfowl so until it is updated, or something of equal detail comes out to replace it, it remains the most accurate and comprehensive of the field guides, at least that I'm aware of...
That said any book is outdated almost as soon as it goes into print which is why the internet has become such a huge resource....everything you want to know, from the earliest studies to the lateset is right ther at yout fingertips courtesy of that internet wizard, Al Gore.....
Steve