Study reports on breeding bird responses to harvest of logging residues

Southern pine forests that are regenerating following clearcut harvest provide abundant herbaceous vegetation and down wood for bird species associated with open-canopy conditions, some of which are of high conservation priority. With increased interest in using wood for energy, however, questions have arisen about the influence that removing logging residues for bioenergy purposes might have on breeding birds and other animal species.

A recent publication presents results from a study addressing this question. The paper, which appeared in PLoS ONE, was authored by Steven Grodsky, Christopher Moorman, and Sarah Fritts of North Carolina State University; Steven Castleberry of the University of Georgia, and T. Bently Wigley of NCASI.

The authors report that the bird community in the young pine forests was affected more by the developing vegetation than availability of harvest residues. The abstract for the paper follows.

“Forest regeneration following timber harvest is a principal source of habitat for early-successional birds and characterized by influxes of early-successional vegetation and residual downed woody material. Early-successional birds may use harvest residues for communication, cover, foraging, and nesting. Yet, increased market viability of woody biomass as bioenergy feedstock may intensify harvest residue removal. Our objectives were to: 1) evaluate effects of varying intensities of woody biomass harvest on the early-successional bird community; and (2) document early-successional bird use of harvest residues in regenerating stands. We spot-mapped birds from 15 April± 15 July, 2012±2014, in six woody biomass removal treatments within regenerating stands in North Carolina (n = 4) and Georgia (n = 4), USA. Treatments included clearcut harvest followed by: (1) traditional woody biomass harvest with no specific retention target; (2) 15% retention with harvest residues dispersed; (3) 15% retention with harvest residues clustered; (4) 30% retention with harvest residues dispersed; (5) 30% retention with harvest residues clustered; and (6) no woody biomass harvest (i.e., reference site). We tested for treatment-level effects on breeding bird species diversity and richness, early-successional focal species territory density (combined and individual species), counts of breeding birds detected near, in, or on branches of harvest piles/windrows, counts of breeding bird behaviors, and vegetation composition and structure. Pooled across three breeding seasons, we delineated 536 and 654 territories and detected 2,489 and 4,204 birds in the North Carolina and Georgia treatments, respectively. Woody biomass harvest had limited or short-lived effects on the early-successional, breeding bird community. The successional trajectory of vegetation structure, rather than availability of harvest residues, primarily drove avian use of regenerating stands. However, many breeding bird species used downed wood in addition to vegetation, indicating that harvest residues initially may provide food and cover resources for early-successional birds in regenerating stands prior to vegetation regrowth.”  

Reference 

Grodsky, S.M., C.E. Moorman, S.R. Fritts, S.B. Castleberry, and T.B. Wigley. 2016. Breeding, early-successional bird response to forest harvests for bioenergy. PLoS ONE 11(10):e0165070. https://dx.doi.org/10.1371/journal.pone.0165070