Avian assemblages and Red-eyed Vireo nest survival within mineland forest

Field: Agricultural and Biological Sciences (Life Sciences)

Since the passage of the Surface Mining Control and Reclamation Act (SMCRA) in 1977, mined lands have generally been reclaimed to an environment characterized by severely compacted minesoils, a growth medium comprised largely of unweathered materials, and a predominance of aggressive groundcovers that inhibit native species colonization. Under these conditions, succession is arrested. Within landscapes that are fragmented by traditionally reclaimed surface mines, forest patches are smaller and forest cover on the landscape scale is reduced. As a result, forest songbirds that require large, continuous blocks of forest are negatively affected.;Some pre-SMCRA abandoned minelands contain areas of uncompacted minesoils on which hardwood forest has developed in the absence of aggressive groundcovers. Despite potential differences in tree species composition, study of the relationship between habitat structure and the avian assemblage within pre-SMCRA mineland forest could provide insight into the species assemblages that future mineland reforestation efforts might yield. Study of the reproductive success of forest songbirds within pre-SMCRA mineland forest may provide some indication as to whether this habitat is capable of sustaining breeding songbird populations. In chapter two of this thesis, I detail research in which my objectives were to: 1) examine patterns in avian assemblage structure within mineland and reference forest and to link the avian assemblage response to variables describing habitat structure and composition, and 2) contrast nest survival of Red-eyed Vireos (Vireo olivaceus) breeding within mineland and reference forest.;I conducted this research in 2011 within New River Gorge National River in southern West Virginia. I surveyed avian assemblages and sampled stand structure and composition along 28 fixed-width line transects (14 mined and 14 reference) established within four pre-SMCRA abandoned minelands and adjacent, unmined forest. Minelands within these study areas were relatively wide (80-100 m wide on average) and contained mature forest (60-65 years old) that had developed from areas of loose-dumped spoil mounded atop benches and also within outslopes.;Using an information-theoretic approach, I developed a priori models containing habitat and temporal covariates that I hypothesized to influence the nest survival of Red-eyed Vireos. Within the same study area, I monitored vireo nests within three mineland forest plots and three reference forest plots.;Ordination of avian assemblages using non-metric dimensional scaling (NMDS) showed clear discrimination between mineland and reference assemblages. Linear and surface fitting of habitat variables showed strong correlations between the ordination and groundcover gradients, but generally non-significant relationships for gradients describing forest structure. Mineland assemblages were associated with lower levels of litter cover and depth and also had lower abundance of Ovenbirds (Seiurus aurocapillus), a ground-nesting and foraging species. Within mineland assemblages, the absence of a consistent pattern of relationships among species suggested a wider habitat gradient relative to reference forest.;I monitored 45 Red-eyed Vireo nests, 21 within mineland forest and 24 within reference forest. Nest survival for Red-eyed Vireos was similar within mineland and reference forest and nest patch characteristics (overstory cover and vertical foliage density) had minimal effect on nest survival. Classification tree modeling using forest type as the response variable indicated that reference nest sites were characterized by greater vertical heterogeneity.;In chapter three, I report on research initiated with the objective of examining patterns in avian assemblage structure in response to the presence of two broad classes of minelands on the landscape, compacted bench minelands and loose-dumped bench minelands. This research was conducted in 2010 and indicated the approach taken in 2011 (chapter two). I conducted fieldwork within five study sites in New River Gorge National River and Plum Orchard Wildlife Management Area (WMA). Point count transects were classified as loose-dumped benches, unmined plateau, compacted benches, and unmined steep slope. NMDS ordination indicated that minelands with loose-dumped benches had minimal effect on assemblage structure. The assemblage associated with compacted bench minelands was not discrete, but was largely discriminated from the other assemblage types. Species that use the subcanopy and midcanopy for nesting and foraging were discriminating components of compacted bench assemblages. Relative abundance of the closed-canopy guild was lower within mined forest than within unmined forest.;In total, this research has shown that failure to establish mineland stands in which heavy-seeded species are a component has important implications for avian assemblage structure. Within minelands, heterogeneity in edaphic conditions and the corresponding variation in forest structure likely contributed to an inconsistent pattern in avian assemblage structure.