Habitat associations of breeding conifer-associated birds in managed and regenerating forested stands.

New Hampshire; Maine

• We examined habitat associations of 18 bird species in managed stands. • Forestry treatments and years-since-harvest were poor predictors of bird abundance. • Vegetation characteristics were excellent predictors of bird abundance. • Forestry treatments influenced important vegetation characteristics for birds. • Managers could target vegetation outcomes rather than forest treatment categories. Forests are often affected by management that could influence demographics of breeding and post-breeding birds that reside within. Numerous studies have focused on immediate effects from management on wildlife soon after forestry treatment (e.g., 0–5 years); however, fewer studies have examined changes in focal species abundance over longer durations as a forest regenerates after disturbance. We examined how forest management influenced 18 conifer-associated birds during breeding and post-breeding over the forest regeneration period in a landscape dominated by forestry. To achieve this, we combined avian detection data from point count surveys conducted in lowland conifer and mixed-wood forests in Maine, New Hampshire, and Vermont with Bayesian distance-removal models and an information-theoretic framework. We estimated abundance and associations with seven common forestry treatment categories applied at the stand scale, years-since-harvest (YSH; 5–120 +), and seven vegetation variables measured within stands. Forestry treatment categories and YSH were poor predictors of abundance. Of 14 species with models having good-fitting statistical distributions while including forestry treatments and YSH as covariates, no species had associations. Of 13 species with models having good-fitting statistical distributions while including vegetation covariates, 12 had important associations between abundance and vegetation variables. Each vegetation variable was associated with abundance of some species, irrespective of the forestry treatment in which the site occurred, including spruce-fir tree composition (seven species), tree basal area (six species), midstory cover (five species), live crown ratio (three species), shrub cover (three species), tree diameter at breast height (two species), and shrub composition (one species). In a companion study, several species assemblages were associated with vegetation variables (i.e., spruce-fir tree composition, tree basal area, and tree diameter at breast height) that were associated with YSH and forestry treatments, suggesting that some forestry treatments may indirectly influence avian abundance when certain vegetation outcomes are achieved. Our results suggest that managers could target species-specific vegetation outcomes rather than more broadly categorized forestry treatment types when managing for individual focal species because of large variations in vegetative outcomes across stands within a forest treatment category. Our study informs management and conservation of biodiversity in regions such as the Atlantic Northern Forest in North America where commercial forestry is the dominant human land use. [ABSTRACT FROM AUTHOR]

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