Occurrence patterns of Black-backed Woodpeckers in green forest of the Sierra Nevada Mountains, California, USA.

Abstract

Black-backed Woodpeckers (Picoides arcticus) are a rare habitat specialist typically found in moderate and high severity burned forest throughout its range. It also inhabits green forest but little is known about occurrence and habitat use patterns outside of burned areas, especially in the Sierra Nevada of California, USA. We used point count and playback surveys to detect Black-backed Woodpeckers during 2011 - 2013 on 460 transects on 10 national forest units. We defined green forest as areas that had not burned at moderate or high severity since 1991 and were more than 2 km from areas burned at moderate or high severity within the previous eight years (n = 386 transects). We used occupancy models to examine green forest habitat associations and found positive relationships with elevation, latitude, northern aspects, number of snags, tree diameter, lodgepole pine (Pinus contorta) forest, and a negative relationship with slope. Estimated occupancy in green forest was higher than previously understood (0.21). In addition site colonization and extinction probability in green forest were low (0.05 and 0.19, respectively) and suggest that many of the individuals detected in green forest were not just actively dispersing across the landscape in search of burned areas, but were occupying relatively stable home ranges. The association with high elevation and lodgepole pine forest may increase their exposure to climate change as these elevation forest types are predicted to decrease in extent over the next century. Although density is high in burned forest, green forest covers significantly more area in the Sierra Nevada and should be considered in efforts to conserve this rare species.