Response of Vegetation and Avian Communities to Retention Harvests in a Mixed-pine Forest in Northern Alabama

Abstract

Retention harvests are commonly used silvicultural methods that mimic natural disturbance and create a mosaic of mature and early-successional habitats which may simultaneously provide habitat for both mature-forest and disturbance-dependent birds. My objectives were to assess how vegetative structure affects bird occupancy and population dynamics before and after a retention harvest which removed 43% to 69% of stand basal area. I constructed species-specific, robust design occupancy models to assess the effects of microhabitat variables on bird occupancy, colonization, and local extinction within a retention-harvested mixed-pine forest in northern Alabama during 2011 and 2012. Before harvest, sites with greater density of understory vegetation <1m tall were more likely to be occupied by three disturbance-dependent species: indigo buntings (Passerina cyanea), white-eyed vireos (Vireo griseus), and yellow-breasted chats (Icteria virens). Following harvest, indigo buntings were more likely to become locally extinct on sites with greater basal area. Sites with greater post-harvest basal area were more likely to be colonized by wood thrushes (Hylocichla mustelina), but less likely to be colonized by red-eyed vireos (Vireo olivaceus) and red-headed woodpeckers (Melanerpes erythrocephalus). This research examined pre- and initial post-harvest conditions, creating a baseline for future research exploring shifts in forest bird communities across developmental stages of a retention-harvested mixed-pine forest.