it sounds like a local problem to me. it would be happening in other places if it were a threat. I agree that they probably ate something with the grain. I know in my hometown i knew farmers that would either expect you to kill every bird in their fields or they would bait them into a spot that they poisoned. NO JOKE. I wonder if any Geese were affected? To me it sounds like poison Because it is fishy that the eagles and other birds werent affected.
thats my Two cents (not that it counts)
Ill keep hunting until The Feds put it to a stop ( and then again ill still probably hunt) you guys have a great weekend
and MERRY CHRISTMAS