Abstract Old-growth forests are optimal habitats for many woodpeckers, which are often themselves excellent indicators of deadwood-associated biodiversity. Old-growth forests are, however, heterogeneous ecosystems in terms of structure, composition, and deadwood characteristics, thus implying a varied use of these forests by woodpeckers. In boreal landscapes, old-growth stands are threatened by forest harvesting; however, there is little information in regard to the consequences for biodiversity with the loss of specific types of old-growth forests. This study aimed to assess how the black-backed woodpecker (Picoides arcticus), a biodiversity indicator species associated with old-growth forest attributes, uses different types of old-growth forests for its foraging needs. We identified woodpecker foraging marks in 24 boreal old-growth forest stands in eastern Canada that were dominated by black spruce (Picea mariana), located within the home range of eight black-backed woodpeckers. We identified the various old-growth forest types using a typology based on the structural attributes of old-growth stands. We classified the sampled stands into four old-growth forest types, corresponding to different successional stages (recent or old, relative to the onset of the old-growth stage), composition (pure black spruce or mixed black spruce–balsam fir [Abies balsamea]), and productivity (ongoing paludification or not). The black-backed woodpecker foraged in all types of old-growth forests, but favored dense old-growth forests that were not paludified and that showed a high temporal continuity (i.e., old-growth dynamics probably started more than a century ago). The temporal continuity of the old-growth state allows for the continuous supply of large, slightly decayed snags, the preferred foraging substrates of the black-backed woodpecker. The old-growth forest type most favored by this woodpecker is, however, also the forest type most often targeted first by logging operations. Protecting the biodiversity associated with recent deadwood in managed areas thus requires maintaining a sufficient area and density of dense, old-growth black spruce-dominated forests in managed areas.

The concept of functional trait-environment relationship posits that species in a local community should possess similar traits that match the selective environment. The present study examines species trait-habitat (using Fourth-corner and RLQ analyses) and habitat occupancy patterns (logistic regression models) of bird assemblages in boreal forest stands following disturbances by forest fire and salvage logging. The stands differed in the amount and composition of residual tree retention, salvage- and aquatic-edges, degree of burn severity (all measured at 100 and 500 m buffers), as well as landscape-level variables such as distance to previously burned forests. Tests of trait-habitat relationships showed that canopy-nesters and bark- and foliage- insectivores required high levels of residual trees of low burn severity, with the feeding guilds showing affinity for different stand composition. In contrast, ground-nesters and omnivores thrived in salvaged areas and associated edges. In addition, cavity-nesting and ground-foragers were associated with severely burned stands. The species’ habitat occupancy patterns were commensurate with trait requirements, which also appeared to be scale-dependent. For example, some fire-associated species had high occupancy probability in severely burned stands at small-scale (100 m buffer), which was consistent with their cavity-nesting trait. This pattern, however, was not evident at large-scale, where their feeding requirement (bark-insectivores) for low-severity burns dominated. Our study suggests that trait-habitat relationships can provide critical information to the complex ways species’ relate to key habitat factors following natural and anthropogenic disturbances.