Bird assemblage changes on peatland affected by large-scale non-native afforestation in the Flow Country (Scotland)

The Flow Country blanket bogs in the counties of Caithness and Sutherland (northern Scotland, UK) harbour internationally important populations of specialist open-bog breeding bird species. However, commercial afforestation carried out in the 1980s, involving the non-native tree species lodgepole pine (Pinus contorta) and sitka spruce (Picea sitchensis) covering over 67,000 hectares (ca. 17 %) of the peatland, has significantly affected bird assemblages within and around the plantations. We conducted a literature review to identify the avian winners and losers resulting from this transformation. Our synthesis of existing findings confirms that afforestation has led to changes in the availability of breeding and foraging habitat, alterations in inter- and intra-specific competition dynamics, and the creation of forest edge effects. Crucially, the open-bog bird assemblages have been largely replaced by woodland specialists and generalists. While 33 species (including five Red-listed Birds of Conservation Concern) are observed to benefit from afforestation, these gains are arguably of lower conservation value than the original open-bog assemblages (27 species including 11 Red-listed species). As a mean proportion of the British population range, the Flow Country has a significantly higher proportion of Amber and Green-listed loser species than winners. Understanding the changes in assemblages is crucial for informing future decisions regarding forest planting and re-planting, particularly in the context of the ongoing dual challenges of climate change and biodiversity loss. Further research is necessary to comprehend the effects of afforestation on populations of waterfowl associated with open water features present in the blanket bog landscape. Given the need for woodland creation, bird conservation would benefit from leaving naturally open habitats intact and siting new woodland in areas that were formerly naturally forested.