Yesterday (the day after Thankgiving) I heard the wonderful chortling song of migrating sandhill cranes. It took me several moments to see them because they were so high. I would estimate that they were flying at about a thousand feet in altitude. The large flock, about 60 cranes, was catching a thermal to gain altitude before they resumed the southward journey. As the flock wheeled and turned as they spiraled upward, I could see a flash of silverly white from under their wings against a clear blue sky.
I found this description of their exodus from the Baker Sanctuary
In late autumn, Michigan's Sandhills begin an exodus to southeastern Georgia and Florida. Cranes usually take advantage of a northwest tail wind and wait until mid-morning when the sun causes warming thermals to rise, carrying them with the least amount of effort on their southward journey. Flying at speeds up to 50 miles per hour, they can cover nearly 500 miles in one day. Cranes often sail for prolonged periods on set wings, riding the thermals until they are out of view. The bulk of migration takes place nearly a mile above the ground, but there are records of them flying even higher. They usually land before dusk and resume their flight the next day.
This was the first flock of sandhill cranes that I have seen this autumn. I am not outside as often I would like, so I probably have missed the flocks that take hours to pass over that I have seen in the past.
Update: On Sunday, two days later, Ann heard sandhill cranes from inside our home. When we went out, we saw many flocks scattered across the sky. Some flocks were headed south, some were circling on thermals to gain altitude, and several birds were lost (always a few of those in every crowd). The volume of so many sandhill cranes calling at once is incredible (click on this link to hear).
Update (December 3): I heard sandhill cranes today when I went to the mailbox. I finally spotted four flocks (a total of about 200 cranes) flying in V formations high in the flyway. I was only out for a short while so who knows how many flocks have passed by today.
Update (December 17): I was only outside for a short while today, but several hundred sandhill cranes passed over.