Snag availability for cavity nesters across a chronosequence of post-harvest landscapes in western Newfoundland

Abstract

We examined the availability and quality of standing dead trees (snags) for nesting habitat in a harvest chronosequence of boreal forests dominated by balsam fir ( Abies balsamea) in western Newfoundland. Snag density declined substantially 10–15 years after harvest, then increased to reach its highest level in 81- to 100-year-old forests that had become senescent. Most (55%) of 1260 snags encountered were balsam fir, which contained 41% of the 81 cavities identified. Cavity presence was most strongly positively correlated to snag diameter at breast height (dbh), followed by decay class, time since harvest and height. Less than 40% of snags available throughout the chronosequence had large enough dbh for cavity nesters. Downy Woodpeckers ( Picoides pubescens) were responsible for 47% of all cavities identified, excavating balsam fir ∼50% of the time. Two larger cavity nesters present, Northern Flickers ( Colaptes auratus) and Three-toed Woodpeckers ( Picoides tridactylus), were more likely to use large-diameter white birch ( Betula papyrifera) snags. Northern Flickers excavated the largest cavities, potentially providing habitat for the greatest variety of secondary cavity nesters. Managing for snags with >30 cm dbh, which flickers target for excavation, has the greatest potential to enhance the broader snag cavity-based community in western Newfoundland.