Hi and Nicker,
Ok you have a very nice horse, remember that! Try earplugs, Pomms are great, they do a wonderful job of dampening the sounds and are suppose to stimulate a calming acupressure point just be careful not to pull on his ear hairs taking them out! Your horse is now hearing many sounds emanating from the trees that are triggering his flight response, don’t forget they hear from longer distances and those branches(especially with breeze and wind) along with all the critters scurrying around is like Times Square Manhattan to him, he needs time to adjust, the year you have been there means nothing yet, smells are different(are there deer in the woods? Hunters).
I love circles over rails for the shoulder dropping. Remember inside leg to outside rein to set the perimeters and inside opening rein to invite him to “step thru the door your opening” Do not use inside indirect rein it throws off the balance of his hindquarters, regular direct rein comes later when you start to feel the shoulder is no longer dropping.
As horsepeople there is an art to our discipline, we all want to be respected for what we know and bring to the sandbox, we open ourselves to a lot of scrutiny, its hard on us to move to a new barn. Just remember your relationship with your horse is number one, regain your bond with him, understand your Both under a lot of pressure, sing a silly song while you ride, tell him a joke, relax and have some fun