Responses of songbirds to diameter-limit cutting in the central Appalachians of West Virginia, USA

Abstract

Diameter-limit harvesting is a commonly-used forest harvesting technique among landowners in West Virginia as opposed to silviculturally-accepted systems such as clearcutting, single-tree selection, and two-age harvesting. Songbird species respond both negatively and positively to these systems, and ornithologists suggest these techniques can be used when managing for songbirds at the stand and landscape levels. However, little is known about the effects of diameter-limit harvesting on songbird abundances and their reproductive success. We evaluated the effects of this technique on songbird populations at the Westvaco Wildlife and Ecosystem Research Forest (WWERF) in the Allegheny Mountains of West Virginia. The area is an industrial forest composed predominantly of Appalachian hardwoods 60–80 years old. We examined songbird abundances throughout the forest and nesting success on four 40 ha plots in 1996. In 1997, two plots were harvested using the diameter-limit technique where most trees ≥45.7 cm were removed. Abundance and nesting success were monitored again in 1997 and 1998. Results indicate that the abundances of most songbird species present prior to harvest changed little after the timber removal. Two species, the Canada warbler ( Wilsonia canadensis) and dark-eyed junco ( Junco hyemalis), were more abundant in harvested areas than unharvested forest. One habitat group, interior/edge species, and total abundance of songbirds also had higher abundance in harvested areas. Overall nest survival in harvested areas was higher both 1- (37.7%) and 2-years (46.4%) after harvesting than before harvesting (14.9%). Only large-diameter trees were removed on the WWERF, and intermediate and subcanopy trees remained standing, retaining considerable structural heterogeneity. Stands that were harvested differed from unharvested stands by having more snags, higher density of trees ≥8–14.9 cm, and a higher percent cover of down wood. Canopy cover over 24 m, density of saplings, and the amount of leaf litter decreased after harvesting, while canopy cover ≥0.5–3 m and the percent of bareground increased. Diameter-limit harvesting at the low intensity in our study might not adversely affect forest-dwelling songbirds in the central Appalachians in the short-term and forest bird communities could be retained.