Comparing multiscale, presence-only habitat suitability models created with structured survey data and community science data for a rare warbler species at the southern range margin

Golden-winged Warblers (Vermivora chrysoptera, Parulidae) are declining migrant songbirds that breed in the Great Lakes and Appalachian regions of North America. Within their breeding range, Golden-winged Warblers are found in early successional habitats adjacent to mature hardwood forest, and previous work has found that Golden-winged Warbler habitat preferences are scale-dependent. Golden-winged Warbler Working Group management recommendations were written to apply to large regions of the breeding range, but there may be localized differences in both habitat availability and preferences. Rapid declines at the southernmost extent of their breeding range in Western North Carolina necessitate investigation into landscape characteristics governing distribution in this subregion. Furthermore, with the increase in availability of community science data from platforms such as eBird, it would be valuable to know if community science data produces similar distribution models as systemic sampling data. In this study, we described patterns of Golden-winged Warbler presence in Western North Carolina by examining habitat variables at multiple spatial scales using data from standardized Audubon North Carolina (NC) playback surveys and community science data from eBird. We compared model performance and predictions between Audubon NC and eBird models and found that Golden-winged Warbler presence is associated with sites which, at a local scale (150m), have less mature forest, more young forest, more herb/shrub cover, and more road cover, and at a landscape scale (2500m), have less herb/shrub cover. Golden-winged Warbler presence is also associated with higher elevations and smaller slopes. eBird and Audubon models had similar variable importance values, response curves, and overall performance. Based on variable importance values, elevation, mature forest at the local scale, and road cover at the local scale are the primary variables driving the difference between Golden-winged Warbler breeding sites and random background sites in Western North Carolina. Additionally, our results validate the use of eBird data, since they produce species distribution modeling results that are similar to results obtained from more standardized survey methods

Bird response to fire severity and repeated burning in upland hardwood forest

Prescribed burning is a common management tool for upland hardwood forests, with wildlife habitat improvement an often cited goal. Fire management for wildlife conservation requires understanding how species respond to burning at different frequencies, severities, and over time. In an earlier study, we experimentally assessed how breeding bird communities and species responded to fuel reduction treatments by mechanical understory reduction, low-severity prescribed fires, or mechanical understory reduction followed a year later by high-severity prescribed fires in upland hardwood forest. Here, we assess longer-term response to the initial mechanical treatment (M), and a second low-intensity burn in twice burned (B2) and mechanical + twice burned (MB2) treatments and controls (C). Initial (2003) higher dead fuel loadings and consequently high-severity fires in MB2 created open-canopy structure with abundant snags, resulting in much higher species richness and density of breeding birds compared to other treatments. Relative bird density and richness remained much higher in MB2 after a second burn, but few changes were evident that were not already apparent after one burn. The initial (2003) burn in B2 had cooler, low-severity fires that killed few trees. Delayed tree mortality occurred in both burn treatments after one burn, and continued in both after a second low-intensity burn. In B2, this resulted in gradual development of a ‘‘perforated,’’ patchy canopy structure with more snags. Abundance of total birds and most species in B2 was similar to C, but several additional species associated with open-forest conditions occurred at low levels, increasing richness in B2. In both burn treatments, burning temporarily reduced habitat suitability for ground-nesting birds. Bird communities in M were similar to C, as shrubs recovered rapidly. Results indicate that one or two relatively low-intensity burns with patches of hotter fire may result in gradual, subtle changes to canopy cover and structure that may slightly increase bird species richness over time. In contrast, a single high-intensity, high severity fire can create young forest conditions and a heterogeneous canopy structure that can be maintained by repeated burning and increase breeding bird relative abundance and richness by attracting disturbance-adapted species while retaining most other forest species