Canada Warbler Response to Vegetation Structure on Regenerating Seismic Lines

Seismic lines have an extensive footprint in Canada's western boreal forest that alter habitat conditions for many species.  Seismic lines exist within a range of seral states due to changing practices and regulations related to operational needs.  Forest regeneration is often hindered on seismic lines as they are frequently repurposed for recreational or alternative industrial uses.  The Canada Warbler (Cardellina canadensis) is a Neotropical migrant songbird that relies on Canada's boreal region for breeding habitat.  As a species at risk both federally (Threatened) and provincially within Alberta (Sensitive), their response to seismic lines has been a significant gap in our understanding of human impacts on the boreal breeding grounds.  We used playback surveys along seismic lines within Canada Warbler habitat to identify individual territories.  Arrays of autonomous recording units (ARU) were deployed to conduct acoustic source localization (ASL) and map the locations of territorial singing events.  Canada Warblers avoided seismic lines with little to no woody vegetation but were more likely to be observed near seismic lines when shrub cover on the line increased.  Canada Warblers used the seismic line and the edge environment but did not select for the line when compared to its availability.  Use was more evenly distributed across the seismic line as shrub density on the line increased.  However, even the most overgrown seismic lines were still perceived as a feature and influenced Canada Warbler space use and behavior.  For Canada Warblers, ensuring that seismic lines in old-growth deciduous forests are allowed to recover by reducing reuse of lines should mitigate population level impacts, but more work is needed to assess how population dynamics are influenced by seismic lines and other energy sector disturbances.