To quote the Forestry Commission:

Glen Affric is a very special place. It contains one of the largest ancient Caledonian pinewoods in Scotland as well as lochs, moorland and mountains.
This wide range of habitats make Glen Affric a haven for wildlife. There are many rare and special birds, animals and plants found here. Amongst many others look out for deer, Scottish crossbills, crested tits and if you’re very lucky, pine marten.
Glen Affric has many designations – it is a Caledonian Forest Reserve, a National Scenic Area and has recently been chosen as a National Nature Reserve.