Earlier in the week I only saw a handful in formation. It has been several cold months since I heave heard their voices. Made me happy. They are all basically headed Northwest towards the Missouri river it seems. Yesterday the numbers have increased with flocks of several hundreds moving at a rapid pace.  Several flocks in the air at once. The Northern plains and it’s great openness allows you to be a visual witness. Then last night they were heard but not seen passing overhead. Many calling in the darkness as they passed overhead. You could almost feel the movement.