Wildlife in the scrub
Many birds stand to benefit from the restoration of montane scrub. A range of thrushes and finches would be at home in the scrub. It would also be valuable for migrants, especially in autumn when fruits and seeds would provide a refuelling stop for them on their journeys south. The scrub might encourage more breeding in Scotland by redwings (Turdus iliacus), fieldfares (T. pilaris) and bramblings (Fringilla montifringilla), which at present nest here scarcely or sporadically. It may even encourage colonisation by other Scandinavian woodland and scrub species, such as bluethroats (Luscinia svecica) and Lapland buntings (Calcarius lapponicus). The scrub would not hinder golden eagles, buzzards or other birds of prey, which still could hunt amongst the sparse shrubs and might benefit from an increase in small mammal and bird prey.
Black grouse (Tetrao tetrix) are birds of the forest edge. They shelter in the forest, but move into open areas for their spectacular breeding displays, called leks. They feed on plant material both in the forest and outside it.
They are currently in serious decline across Scotland, but should benefit from an increase in montane scrub. However, any essential fences would need to be carefully sited and well marked, because collisions with deer fences are one of the main causes of death in adult black grouse.
A spread of montane scrub would increase numbers of voles, mice and shrews, which would, in turn, help the foxes, stoats and pine martens that hunt them. Mountain hares (Lepus timidus) are more problematic. Large winter gatherings of hares could cause localised damage to scrub regeneration, and hares might need to be discouraged or excluded while the scrub is establishing. Deer and sheep would also need to be kept away from regenerating scrub. However, in time, the natural re-establishment of montane scrub would be a potent indicator that deer had been brought into sustainable balance with their range - one of the main objectives of current deer management policies.
A number of specialised invertebrates are associated with montane scrub species. At least six species of sawflies in the genus Potania make 'cherry-galls' on the leaves of montane willows, including two species that are only known from Scotland. An attractive 'micro-moth', called Callisto coffeella, is found in Scotland only on isolated bushes of dark-leaved willow on north-facing slopes in the Angus and Aberdeenshire glens. Several aphids and moths are associated particularly with dwarf birch, and about thirty species of insects and mites are exclusive to juniper.
The value of montane scrub for biodiversity is recognised by the Royal Society for the Protection of Birds. Its Abernethy Reserve in Strathspey extends almost to the summit of Cairn Gorm, and one of the longterm management objectives of the reserve is the expansion of Caledonian forest up to the treeline, with a natural scrub zone beyond.
The Creag Meagaidh Experiment
Since its purchase by the former Nature Conservancy Council (now SNH) in 1985, and its establishment as a National Nature Reserve, a great experiment in woodland restoration has been underway at Creag Meagaidh, on the north shore of Loch Laggan in Inverness-shire.
The reserve includes high elevation woods of downy birch, goat willow (Salix caprea) and rowan, but at the time of purchase most of these were moribund as a result of intensive grazing. The regeneration and extension of native woodland and montane scrub was one of the key objectives for the reserve.
This has been achieved with minimal use of fencing. Instead, management has aimed to exclude sheep as far as practicable, and large numbers of red deer have been culled or removed from the reserve (without impact on neighbouring deer-stalking estates). The results have been spectacular, with a sevenfold increase in downy birch regeneration, and healthy rowan and willow growth. Although recovery has been best on the lower slopes, there are encouraging signs of scrub development above the timberline, providing a pointer to what could be achieved elsewhere.