Avian recolonization of unrestored and restored bogs in Eastern Canada

Abstract

Over the last several decades, peat has been extracted from bogs of temperate, populated regions of Eastern Canada, leaving large areas devoid of vegetation if unrestored. For the last 25 years, projects have been conducted in these regions to re-establish vegetation and facilitate recolonization by wildlife. We tested whether vegetation structure and bird species assemblages 10 to 20 years post extraction differ among natural, unrestored and restored bogs at the scales of individual sites and entire bogs. We conducted bird counts and vegetation surveys between 1993 and 2019, using both point counts (309 sites) and Autonomous Recording Units (80 sites). According to our vegetation surveys, restoration of sites that were previously used for peat harvesting accelerated the establishment of Sphagnum and herbaceous strata, but ericaceous and tree strata were unaffected over a 17-year period. None of the bird species with large home ranges were associated specifically to natural, unrestored, or restored areas at the bog level. Bird species diversity was similar in restored and natural sites, but lower in unrestored sites. Alder Flycatcher and American Goldfinch occupied restored and unrestored sites more frequently than natural sites, independent of the number of years post extraction. Occupancy of restored sites by Palm and Yellow-rumped Warblers increased over the years, reaching levels similar to those in natural sites 20 years after restoration was implemented. Occupancy of restored sites by Song and Savannah sparrows increased from 1993-2019 and diverged from their declining occupancy of natural sites. Species assemblages of restored and unrestored sites differed significantly from those of natural sites soon after peat extraction ceased or post restoration. But assemblages from restored and unrestored sites became progressively similar to those of natural sites during the first 20 years, especially in restored sites. We conclude that bird species assemblages of restored bog sites are converging toward those of natural sites, and that restoration provides novel habitats for regionally declining species, e.g., Savannah Sparrows.