Assessing 100-meter-wide loblolly pine corridors as breeding habitat for landbirds

Abstract

I evaluated the suitability of 100-meter-wide loblolly pine (Pinus taeda) plantation corridors as breeding habitat for landbirds. The study was located within the Lower Coastal Plain of South Carolina on land owned by Westvaco Timber Corporation. The typical rotation-age within the landscape was 20 years. Work was conducted within post-rotation-age (24-31 years) corridors (100-meter-wide linear loblolly pine plantation stands) and patches (typical Westvaco stands). Work was also conducted in rotation-age patches (18-22 years). Vegetation, point count and nest monitoring data were used to compare corridors against patches. Point count surveys were conducted from 1995-1999, and vegetation and nest surveys from 1997-2000. Vegetation data was collected between 1997-2000 within post-rotation-age corridors and patches (24-31 years) and rotation-age patches (18-22 years). I used 10th acre plots to quantify the following variables: pine, hardwood, and snag basal area; pine, hardwood, and snag dbh; canopy cover (%) and shrub cover; overstory and midstory height; and cane and vine cover. Cluster analysis of individual plots found that post-rotation-age corridors and patches were not significantly different (p = 0.1178) from each other, but were significantly different from rotation-age stands (p < 0.0001). Individual comparisons between classifications (post-rotation corridors and patches, rotation-age patches) found most significant differences between post-rotation-age and rotation-age stands. However, post-rotation-age corridors and patches differed significantly in pine basal area (p < 0.0001), pine DBH (p < 0.0001), hardwood basal area (p = 0.0153) and shrub percent cover (p = 0.0358). Point count data was collected from 1996-1999 within post-rotation-age corridors and patches. A total of 94 corridor points and 116 patch points were surveyed from 1996-1999. Corridors had greater species richness (N=44) than patches (N =38). However, species composition was similar between corridors and patches. For all species, the Spearmans rho correlation coefficient on species ranked abundance was highly correlated (r = 0.7877, p <0.0001). In individual species comparisons, only the Red-eyed Vireo was found in lower abundance within corridors (0.213 birds/plot) compared to patches (0.440 birds/plot, p =0.0011). The Brown-headed Cowbird and Blue-gray Gnatcatcher were significantly more abundant within corridors relative to patches. Nest searching was conducted within post-rotation-age corridors and patches, and rotation-age patches from 1997-2000. Three species were compared: the Acadian Flycatcher (n = 132), Hooded Warbler (n = 37), and Northern Cardinal (n = 52). Across all years, no significant difference in nest survival was found between nests within post-rotation-age corridors and nests within post-rotation-age patches for all 3 species. However, when compared to rotation-age patches, Acadian Flycatchers had significantly higher nest survival in both post-rotation-age corridors and patches (p < 0.05). Hooded Warblers had marginally higher nest success in both post-rotation-age corridors and patches relative to rotation-age patches (p = 0.05-0.10). Nest survival was also compared by distance to edge (with loblolly stands aged 0-5 years), distance to road, and distance to edge+road. No significant differences were found in nest survival for the Acadian Flycatcher, Hooded Warbler, and Northern Cardinal based on a nest's distance to edge, road, or road+edge. The Hooded Warbler had 10 out of 37 nests (27%) parasitized by the Brown-headed Cowbird. Nine were within patches and 1 within a corridor. Parasitzed nests were not significantly different from non-parasitized nests based on distance to edge (p = 0.7100), distance to road (p = 0.2111), or distance to edge+road (p= 0.2492).