Greg,
Can't say I agree with everything you wrote although parts I do agree with. Ethics are a set of personal beliefs so everyone's are different based on their experience. I personally don't hold hybrids as any less desirable than a "pure" breed. In fact I personally don't believe there is such a thing as a pure bred because I believe in evolution and that they came from common ancestors who have probably cross bred randomly over the last few hundred thousand generations. If it looks like a black and I shot it as a black, my ethics tell me its a black, and I shouldn't shoot another. If it looked like a hen mallard in flight when I shot it, I'm happy to count it as a hen. If it has substantial green on it's head, I call it an immature drake mallard. If it falls midway between a hen black and mallard, I choose not to take a chance, and I consider it as both a black and as my second hen as it isn't worth the hassle to defend myself in court. Conservation Officers come from different backgrounds and my experience is that most are not serious waterfowlers and few, if any are waterfowl biologists. In our area they are stretched very thin due to the poor economy and if they find you in what they believe to be a violation they will cite you. Talking your way out is tough because day in & day out they are lied to making them very jaded.
With respect to getting experts and taking it to court, go for it, it's only money and time. Of course you won't have the duck in hand for your experts and if you followed Mark W.'s story the judge may not even be interested in tying up his court. He'll simply follow the concept that if the CO says it looked enough like the duck he wrote the citation for, it must have been one. In that case here in CT you won't hunt or fish for a year. But it is your right to try, personally I'm not going to intentionally put myself in this position.
One additional comment, while pushing the limits can preserve your rights, it can also result in the rewriting of rules to legally clarify the situations the cause everyone to loose out. For instance, while not likely, it is possible that if enough stink was made over the definition of black to mallard hen divide, a state could simply say your allowed a single hen mallard, mallard cross or black duck in the bag. There by guaranteeing that no one will take more than one black duck and they won't have to go into court and waste their valuable time. Don't think it happens? How about all the areas around the northeast coast closed to hunting because guys pushed the limits and pissed off the home owners. While the hunters were legal, maybe by not pushing the limits we all would have been better off.
So follow your personal ethics and push the limits, but be aware of any consequences and be willing to pay the cost.
Respectfully,
Scott