I am a bit wet behind my ears from this experience. Migrating swans are common place living in the Mississippi River Valley. I can hear their massive flocks migrating over my house throughout the night. The din of their call is very pronounced.
I have experienced an odd Sandhill Crane in the marsh here and there however never before have I seen over 75 of these birds congregated.
Thanks for watching this short video that I grabbed on my to work at the National Eagle Center in Wabasha, MN.