As someone who's hunted the Grand River Marsh for every opener going back to the mid 90's when I was a teen..I remember the days when me and my buds would be so irritated cause all we harvested seemed to be Widgeon. There were years where that made up a majority of our 6 bird limit. I remember that lasting until the mid aughts or so and for the latter part of the aughts we were practically despondent because we would hardly ever see them and we whooped for joy whenever someone smacked one of those striped face suckers. Then enter the 2013 and 2014 season and it was just like old times. Circle of life? Less marsh? I don't flippin understand waterfowl one bit I think lol.
Bad example. We were talking HARVEST totals. I was strictly talking harvest numbers of Wood ducks did not go anywhere near off the charts after increasing from 2-3 in the entire MS flyway. According to the Fed harvest numbers in 2012 when the limit Can limit was 1 the MS flyway shot 52K Cans, in 2013 it was increased to limit of 2 and 76K were harvested. Not off the charts by any means.
And just to be clear, the flight count breeding pair numbers for Can's that sets those bag limits is not set up to accurately count Canvasback do to a large number of factors. Unfortunately those were the parrameters that were set so we must work within them.
To respond to your wood duck example I respond with the can example. Every time we go to 2 the following year is 1 or 0. Water levels have been consistent in recent years. With birds that have smaller numbers, limits that are set play more of a role.
Notice I placed widgeon last as they haven't taken as hard of a hit but certainly Wisconsin does not have the numbers they once did. The limit on bluebill and widgeon was 7 and 10 for a while (10 and 15 points). bluebill have never recovered.
of course everything I say is my 2 cents so ono need to be critical of anything I post.