Changes in species interactions within the cavity-using community in managed forest landscapes of the boreal mixedwood forest in eastern Canada

Abstract

Over the last 50 years the intensive use of even-aged management practices in the boreal forest of Canada has generated extensive landscapes of aggregated clear-cuts, which have considerably skewed the age structure of the forest towards regenerating and young stands. In contrast, mature and old forests in these landscapes become fragmented and rarefied. Moreover, since these habitats often have a linear shape (riparian buffers and cutblock separators), they become vulnerable to secondary disturbances such as wind throw, which can jeopardize the persistence and recruitment of standing decaying and dead trees. There is thus concern for organisms that rely on these forest attributes for nesting and foraging, particularly members of the vertebrate cavity-using community. In the boreal forest, woodpeckers are the primary cavity formation agents for the entire cavity-using community. Knowledge of their distribution in linear habitats of managed landscapes is thus critical for understanding the nest web structure of cavity users in such environments. We present a 10-year investigation on woodpecker habitat occupancy, reproductive success and productivity in linear habitats (ranging from12 to 45 sites) of managed landscapes and permanent study plots in an unmanaged continuous forest tract (3000 ha) in the boreal mixedwood forest of Québec, in Canada. In each linear habitat, we conducted systematic ground surveys and direct inspections of tree holes with a 15-m telescopic pole on which we mounted a camera that could fit into holes with a diameter of >2 cm. We found that linear habitats in managed landscapes harboured all five species of woodpeckers that are nesting in the unmanaged boreal mixedwood forest. Apart from the Pileated Woodpecker (Dryocopus pileatus), for which sample size was to small to conduct statistical comparisons, the reproductive success and mean number of fledglings of most woodpecker species was not significantly different in linear habitats than that of breeding pairs in the unmanaged forest. We also found that species richness of non-cavity excavators, particularly those that occupy large cavities, was less in linear habitats of managed forest landscapes than in the unmanaged continuous forest tracts. We evaluate how habitat loss and fragmentation in managed landscapes affects the nest web structure of the cavity-using community particularly with regard to woodpecker species persistence in linear habitats. We discuss how this knowledge can assist stakeholders and policy makers in the development of sustainable conservation strategies for the cavity-using community. .