If I have several hours on my hands, I like to slip out to the field edges, or lay on a open ridge top around 5 to 5:30pm or so. Watching the birds those last few hours on the ground gives you vital information. Most of the time, the way a big bird flys up is the same way he will fly down. Those big guys like to fly down the way they know is "safe"........that is until you see him do it and get there early in the dark of the morning!
I have had a lot of luck using an owl hooter......and if you know all the birds are in the tree (it is dark and they are all up)...I love to use a coyote howler......gets them gobbling.