Here today, gone tommorrow

[anthropisces]

One day last week  a few ducks approached my spread near the very end of the day. After legal hunting hours while packing my blind and other gear, more and more ducks were arriving. By 4:45 there were thousands of ducks in the sky and landing. The place looked like the entrance to a busy bee-hive.
A few days later, I was hunting this same place and the conditions were not that different. I still had a couple of fly-bys, but as I packed up there were pretty much zero ducks in the sky.
The conditions were not exactly the same but they were fairly close. What is responsible for that sort of thing? Did I witness some mass-migration, with those ducks passing through and headed somewhere else?

[Stein]

Could be a bunch of things, conditions change pretty quickly here and the birds will move around.  More or less water in the fields will move them from some areas to others.  Could be a migration too.  Could also be hunting pressure pushing them off somewhere one day but not the next.  Could be they ran out of food wherever they were feeding and moved areas.

I wish I had a buck for every time I thought I had it figured out only to return and the ducks have moved.