The lake I usually hunt seems to have become a roost with this last cold front. All the ducks pick up and leave about 10 minutes before shooting light. There isn't much agriculture to speak of in this area but all of the birds head off in the same direction so they must be finding it somewhere. In your scouting how far have you tracked birds from roost to feeding?

A lake I hunt on will from time to time become a roost hole late season when all the food is gone. It seems that most of the duck travel out to smaller tanks and two other large lakes that are shallower overall.

Very few actually go out into fields but feed on smaller stock tanks with 10 miles or so. I've spoke to a couple of the other hunters in the area that hunt some of the smaller water and they typically do much better when we bust our lake up in the morning. It's big enough that it will have roosting ducks and ducks coming into feed at the same time. The ducks that come into feed seem to be roosting on a larger Lake about 10 miles away.

They usually come from that direction and there isn't any other large body of water within 30 miles.

Largely depends on where you hunt and available food sources. I’ve got wheat within 50 yds. They’ll hit the fields and back to water. Back and forth all day.

Not ducks but I've hunted geese that were flying 40 miles one way to feed.