One night makes a big difference

So I have a friend with a wheat field. I hunted it last night and it wasn't bad. Saw a good numbers of birds. Also a couple of larger flocks headed to the trees being me to roost at sunset. Tonight I went out again and scratched one bird. Saw no birds (except for the one)! No flocks coming into roost either.

I woke up this morning with allergies and sneezing and it seemed a little cooler but not much. I know something happened with the weather and that slight difference meant moving all the birds out. Its like they woke up and said time to move on. My question is what was it so I know next time? Is it a cool front? Barometric pressure? ??

Cool fronts and cooler weather can and do move birds further south, especially when rain is involved.
The birds are migratory.

However, don't be discouraged. Northern dove from other states will be moving in at some point.