Stan, you need to talk to your local raptor rehabilitator, if you have any in your vicinity. They get plenty of sick and dying patients. Especially eagles. Why especially eagles? Well, because they're big, very visible, and there are a lot more of them now than there used to be. And people like to watch eagles.
Waterfowl fall into somewhat the same category. They're relatively large, and lots of them tend to congregate around lakes, marshes, etc. Many of those lakes and marshes are either federal or state wildlife areas, which means that there are either USFWS or state DNR employees around, keeping a watch on things. Seeing sick and dying birds is part of their job.
Stan, I lived in northern Wisconsin for 4 1/2 years. There was no question we had wolves. I saw evidence of wolves. But in my 4 1/2 years, including a whole lot of time spent in the woods, both before the bird season as well as during the season, I never saw a wolf. Not once. Doesn't mean they weren't there, or that I might not have trapped one or more of them had I desired to do so and known how to go about it.
And when the bird flu hit in Iowa, I don't recall that the DNR had any trouble finding dead birds to examine. And the most common species impacted were crows and bluejays. Not all being cleaned up by scavengers before they could be collected.
So no, sorry, I don't accept your contention (or Keith's if he's still making it) that there could still be a lot of waterfowl getting sick and dying, and no one would notice.
Last edited by L. Brown; 01/25/16 09:28 AM.