Avian communities show distinct responses to forest-to-bog restoration.

Abstract

Since the 1990's, attempted restoration of blanket bogs which have been previously afforested with non-native conifers has taken place in Ireland and Britain, with the aim of reinstating hydrological functioning and hence, peatland biodiversity. Here, we assess the conservation benefit of these restoration measures at sites in the west of Ireland, 16-20 years post works, by comparing avian communities between trios of restored (n = 6), near-natural (n = 6), and afforested (n = 6) lowland blanket bogs. We assessed avian community response in terms of differences in the richness and density of all bird species and of Birds of Conservation Concern in Ireland (BoCCI), as well as community composition. We also investigated which structural habitat variables were responsible for variation in community composition among site types. Restoration resulted in no changes in overall species richness and lower overall bird density but importantly, increased BoCCI richness in comparison to afforested sites. In particular, restoration benefited red-listed species, with richness and density of these species being similar to that of near-natural sites. Avian communities of restored sites were variable but more similar overall to those of near-natural than afforested sites, indicating partial restoration success. Changes in conifer cover, dwarf shrub height, deadwood cover, and broadleaf cover explained the majority of variation occurring across site types. These results indicate that the response of avian communities following forest-to-bog restoration is a prolonged process influenced by the evolving habitat structure, which, in turn, is contingent on the effectiveness of hydrological restoration measures, local conditions and ongoing management.