What does it mean when my mackerel clouds are shaped like actual fish?
Mackerel clouds over the barn
And seagulls take flight across the sky?
Seagulls seem to like farm fields just as much as the seashore
I live on a farm. I feel like I should know these things.
Home on 129 Acres 
We used to call those “lost gulls”. But I know clouds of gulls follow tractors that are seeding or harvesting, just as if they were fishing boats. Maybe it has to do with the newly-mown hay?
Flocks do congregate in the fields, whether it’s seeding or harvest time or not.