Snow Geese Migrating South?

First we saw about where Williams is along Interstate 5 heading north in California these white birds that were fairly large and we couldn't tell if they were egrets or what. But, generally speaking Egrets don't congregate by the hundreds or thousands of birds.

Finally, I didn't know what these birds in fields  were or the main flocks of birds all over the sky around Williams and further north either.  So, finally I looked up "What bird is white with black wing tips?" and it said that Ibis or Snow Geese. This is how we knew they were snow geese that appeared to be all (thousands of them) migrating further south right now. Do they know something we don't or is this their normal pattern?