Hi Dave,
There are certainly plenty of interesting sites to visit and species to see, although at this time of year the birds can be thin on the ground and some areas can be very quiet. However, if you enjoy going for a walk and are willing to accept whatever turns up, don't have too high expectations (and have reasonable weather!) then you should have an enjoyable time.
I would second Andrew's comments about Glen Muick- I have seen Golden Eagles from the carpark at the end (although they aren't usually that easy!) and have had Black Grouse perched less than 5 metres frorm the road near the carpark. Early morning is probably best for the grouse. There are some nice walks by Loch Muick too.
As Andrew says, Capercaillie will be difficult to find (and more or less impossible to photograph) and as they have had a poor breeding season there will be fewer about. However, they are easier to see at this time of year. Your best chance near Ballater is probably Pannanich Forest (Forestry Commission), which is just across the river to the south of Ballater. I don't really know this site very well, but any birds will most likely be right at the top of the hill among the older pines.
Glen Tanar, south of Aboyne is another possible site for capercaillie, but as with all caper sites on Deeside,they tend to occur in the highest parts of the wood, furthest away from the public roads. Glen Tanar has fantastic native pinewood, and although the birds are few and far between, you may encounter crossbills here - Common, Scottish and Parrot all occur, so good luck with the ID!
Other sites worth a visit are:
Cairnwell/Glenshee - The A93 south of Braemar up to the ski centre is good for red grouse (often close to the road), while Ptarmigan are present in the hills around the ski centre. If weather conditions permit, a walk to the summit of Cairnwell on the west side of the ski centre could be good for this species. There are sometimes snow buntings around the car park too and the last couple of times I've been over there this year there have been a few Ravens knocking about.
Linn of Dee, west of Braemar. Another scenic site with native pinewoods (and crossbills) nearby. A walk along the Dee to the west of here can sometimes produce a Golden Eagle on the skyline.
Dinnet National Nature Reserve, between Ballater and Aboyne. Loads of footpaths from Dinnet village and Burn o'Vat visitor centre through birchwoods, heath and pinewoods. Good for woodland birds and waterfowl on loch Kinord (although the huge numbers of greylags that used to roost here now winter much further north). Burn o'Vat (a glaciated gorge) is well worth a visit for non-birding reasons too.
