re: What do you attribute the migration change to?

I think weather, evidenced by new species like tree ducks and white-wing doves, etc., and as far as the east side of the state is concerned, the raising of the river levels in the 60's and 70's absolutely had an overall negative effect on habitat there. My old man and his friends cashed in on the recently flooded green timber in the 70's and 80's, I got in on the 90's, but it's gone to hell since. Stagnant water in previously seasonally flooded woods has led to dead snags and permanent invasive aquatics. Sucks.

As stated, the ducks rarely have anywhere else to go besides a duck hole, and those holes, although numerous, are a drop in the bucket compared to what used to be.