I know your area very well as I lived near Bridge of cally for quite a long time, working on the local farms and sustaining myself with wild foods and anything the dogs caught.
There are lots of hazel nuts and sloe berries to be got too.
I still visit occasionally with my wife and young family, although our last picnic by the river was marred by the attentions of a local landowner, seemingly nervous about our proximity to her new fisherman's hut (out of season)..........I had to politely point out that we were merely having a morning out as a family and, as a country dweller all my life, I was well aware of how to behave and that we were merely exercising our right of responsible access.
Little did this particular person know that, had it not been for my hard work and sense of loyalty to her late father-in-law, and my looking after the place and stock while a relative of hers drank himself stupid in the local hotel every weekend, she may not have still had a viable farm to "protect from outsiders coming in", as she put it.
She only knew we were there because another landowner from the other side of the river had seen us as she walked her dog, and had phoned our would-be harrasser.
Needless to say we left the place as we found it.
I love that part of the country with the steep drops to the river and the pockets of old woodland interspersed with the species trees of more recent times.
Good luck with your foraging.