Abstract
C. J. Fiss. Avian Community and Species-specific Response to Management Targeting Improvement of Forest Age-class Diversity. 201 pages, 4 tables, 26 figures, 2023. APA style guide used.
The concept of forest-age class mosaics has gained considerable traction in recent years as a potential tool to increase structural complexity of forest landscapes, and a means of improving habitat diversity and quality for birds. Calls for such a management strategy have come in the wake of well documented forest bird population declines, which parallel the homogenization of forest-age classes in the eastern US. For the avian community, homogenization of forest ageclasses could represent a loss of niche space thereby reducing avian richness, diversity, and overall conservation value provided by forests. From the species level, forest-age class mosaics may improve habitat quality for a growing group of species understood to make habitat-shifts during the post-fledging period. Despite the potential implications for forest bird conservation, the effect of forest age-class mosaics on bird communities and the habitat quality of individual species is not well tested, especially at landscape scales at which mosaics need to be implemented. I used data gathered from three regions of Pennsylvania from 2019 to 2021 to determine the effects of forest age-class mosaics on bird communities and Wood Thrush (Hylocichla mustelina), a declining songbird with dynamic habitat use across the breeding season. I found evidence to support that increasing forest age-class diversity within 600-ha landscapes could increase avian community conservation value, especially for habitat-shift species. I did not find support that maintaining some optimal proportion of 0-6, 7-20, and/or 21- 39 year-old stands within landscapes would benefit the entire forest bird community. Management scenarios simulated at the landscape level revealed that Wood Thrush could benefit from even-aged management that promotes age-class diversity by increasing in unmanaged stands throughout the landscape, but also within treated stands for at least 20 years after overstory removal. I found that Wood Thrush abundance was relatively high in riparian zones up to 100-m away from streams, therefore, these should be preserved when possible. Wood Thrush nest success was higher in forest age-class mosaic landscapes, but fledgling survival was similar between these and homogenous landscapes. Forest age-class mosaics could be a useful way to restore avian diversity and habitat quality in degraded landscapes.