oh, ain't duck huntin' fun. I've never timber hunted so I can't give you any specifics on timber. I mainly hunt open water and usually smaller bodies of water anywhere 2 to 5 acres. I have plenty of birds circle and never commit. A lot of the times it might be weather related. Those blue bird calm days are hard to decoy pressured birds. First there is very little movement on the decoys and the birds can really get a good look at the decoys. Some days the birds want a lot of calling--other days they want no calling. Some days a big spread works while other days a smaller spread works.
what I have found that helps me is I made a jerk decoy. Took a magnum hen and tied a 2.5# weight as the anchor. I attached a bungie cord to the weight then decoy line from the bunbie to the decoy. Then a long piece of green trot-line from the decoy to my blind. The jerking created quite a bit of movement and the birds seem to decoy better for me.
When I get birds (several groups) that don't commit then I know something is wrong so I change things up such as moving the decoys--taking some it or putting more out. Change my calling or don't call at all. You usually just have to experiement and change things up to see what they want.