Songbird response to seismic lines in the western boreal forest: a manipulative experiment

Abstract

Millions of kilometres of seismic lines have been created for hydrocarbon exploration in the boreal forest and their impact on songbirds is unknown. I conducted a replicated before–after control–impact (BACI) field experiment in southern Northwest Territories to evaluate the impact of 6 m wide seismic lines on songbirds. Territories of all birds on six pairs of 12 ha control and treatment plots were mapped for one year before and one year after seismic lines were cut through the treatment plots. The songbird community was not dramatically affected by seismic lines. At the community level, birds did not decline in abundance or move their territories relative to the seismic lines, and they included the seismic lines in their territories. However, ground and shrub nesting species that had territories spanning the seismic lines increased the size of their territories. At the species level, only the Ovenbird ( Seiurus aurocapilla (L., 1766)) showed a consistent response to seismic lines. Ovenbirds declined in abundance, moved their territories away from seismic lines, and were not observed crossing the lines. Pressure on industry from land managers to reduce the width of seismic lines should continue to minimize the impact of these clearings on all species.

Regional habitat needs of a nationally listed species, Canada Warbler (Cardellina canadensis), in Alberta, Canada

“…Although forest clearing for oil and gas development reduces the amount of trees on the landscape, the effects of fragmentation from linear features and small disturbances (e.g., well sites) were not important predictors of Canada Warbler abundance in this study. Machtans (2006) found that Canada Warblers did not avoid seismic lines in the Northwest Territories but included these features within their territories. However, linear features were treated as unusable, and territory size was expanded to compensate.…”

“…However, studies also report the Canada Warbler in early seral vegetation with brushy edges and residual patches of live trees , Schieck and Hobson 2000, Schieck and Song 2006; reviewed by Reitsma et al 2010). Canada Warblers also may not avoid edges created by human development, but may increase territory size and incorporate smaller clearings within their defended space (Machtans 2006). Clearly, refined understanding of the local habitat needs of Canada Warblers and how these are influenced by various types of human activities that alter the age structure, spatial pattern, and composition of their habitat is needed, particularly at large spatial extents.…”

Edge influence on forest structure in large forest remnants, cutblock separators, and riparian buffers in managed black spruce forests

“…Forest regeneration occurs in many energy sector disturbances; however, human use often keeps seismic lines and pipelines open (Figure 1). Soil compaction and mixing from construction and ground disturbance, as well as shading by surrounding vegetation, also inhibit tree regeneration (Lee andBoutin 2006, Lankau et al 2013; but see Machtans 2006). Unlike forestry, where tree planting and natural regeneration result in rapid regrowth, changes in boreal forest bird habitat may persist for years in many types of energy sector disturbance (Lee andBoutin 2006, Lankau et al 2013).…”

How well do regional or national Breeding Bird Survey data predict songbird population trends at an intact boreal site?

“…Industrial activity peaked in 1995-2000 and has been essentially nonexistent since 2007. Most of that disturbance produced small effects that a regional study like ours would not detect (Machtans 2006). Finally, we collected detailed vegetation data twice during our study, separated by 11 years, and succession was not changing the study stands in any significant way (C. S. Machtans, unpublished data).…”