Combined long-term effects of variable tree regeneration and timber management on forest songbirds and timber production

Mean stand bird occupancy probability and merchantable timber removed by regeneration success rate (RSR) and harvest prescription for black-throated green. Occupancy probabilities are for year 100 of simulations. Simulations are for 100% sugar maple regeneration. Prescription specifications are presented in Table 1. Error bars are 95% confidence intervals from the standard error of three simulation replicates for each treatment. [Display omitted] ► We simulate centurial bird responses to variable tree regeneration and timber harvest. ► Better canopy-tree regeneration has greatest effect on bird occupancy probability. ► Timber harvests influence timber volume and birds more when regeneration is denser. ► Promoting good regeneration benefits both birds and timber production over long-term. The structure of forest stands is an important determinant of habitat use by songbirds, including species of conservation concern. In this paper, we investigate the combined long-term impacts of variable tree regeneration and timber management on stand structure, songbird occupancy probabilities, and timber production in northern hardwood forests. We develop species-specific relationships between bird species occupancy and forest stand structure for canopy-dependent black-throated green warbler ( Dendroica virens), eastern wood-pewee ( Contopus virens), least flycatcher ( Empidonax minimus) and rose-breasted grosbeak ( Pheucticus ludovicianus) from field data collected in northern hardwood forests of Michigan’s Upper Peninsula. We integrate these bird-forest structure relationships with a forest simulation model that couples a forest-gap tree regeneration submodel developed from our field data with the US Forest Service Forest Vegetation Simulator (Ontario variant). Our bird occupancy models are better than null models for all species, and indicate species-specific responses to management-related forest structure variables. When simulated over a century, higher overall tree regeneration densities and greater proportions of commercially high value, deer browse-preferred, canopy tree Acer saccharum (sugar maple) than low-value, browse-avoided subcanopy tree Ostrya virginiana (ironwood) ensure conditions allowing larger harvests of merchantable timber and had greater impacts on bird occupancy probability change. Compared to full regeneration, no regeneration over 100 years reduces merchantable timber volumes by up to 25% and drives differences in bird occupancy probability ch