A merlin preened on a branch of a skeletal tree, contorting its body into all sorts of interesting positions as it tidied and fluffed its feathers with its beak and talons. Far away, in the distant overcast sky, the chatter of two crows sounded. Two black spots flew into view. And they saw the merlin.

A large shape was on top of the otherwise thin and angular branch and looked slightly out of place. But it was not out of place at all. It was an owl.

A spectacular avian migration occurs with concentration in the American Midwest at the end of each year. The sound of loud bugling calls signals one to search the sky for flocks of sandhill cranes.