The best time to do this is either in the fall after the young have learned to fly or in winter after bats have migrated south.
(bats; have migrated south; ) (The best time to do this; is; either in the fall after the young have learned to fly or in winter after bats have migrated south)
bats The best time to do this
have migrated south is
either in the fall after the young have learned to fly or in winter after bats have migrated south