PS 26-123 - The influence of vegetation on Red-naped Sapsucker selection of aspen trees for sapwell excavation

Tuesday, August 8, 2017
Exhibit Hall, Oregon Convention Center
Alyssa Gomez, Jamie Jarolimek and Kerri T. Vierling, Department of Fish and Wildlife Science, University of Idaho, Moscow, ID

Red-naped Sapsuckers (Sphyrapicus nuchalis: RNSA) are a keystone species that excavate cavities and sapwells in quaking Aspen (Populus tremuloides: POTR5). While there has been research on RNSA tree selection for cavity excavation, selection criteria for sapwell excavation has yet to be identified. Determining what factors affect sapwell tree selection could lead to a better understanding of the species requirements. The goal of this study was to determine if surrounding vegetation influences which trees RNSA chose for sapwell excavation. We predicted that trees with sapwells would be surrounded by smaller, less established vegetation. We identified 8 stands with RNSA active cavities at City of Rocks National Reserve, Idaho. We randomly selected 5 trees with sapwells, and 5 trees without sapwells, within a 50m radius of each focal RNSA cavity tree. Within a 5m radius of each sapwell and non-sapwell tree, we measured the height of each surrounding shrub and the diameter at breast height (DBH) for each surrounding tree. We used these metrics to differentiate between less established and established vegetation.


Snowberry (Symphoricarpos oreophilus: SYOR) at a height interval of 0-0.5m was found more frequently around sapwell trees than non-sapwell trees. POTR5 of 2.5-8cm DBH were more frequent around sapwell trees than non-sapwell trees. These results support the hypothesis that vegetation does influence sapwell tree selection. The results of SYOR at height intervals of 0-0.5m found more often around sapwell trees may suggest that shorter ground coverings allow for more visibility of predators. Future studies on predator prey interaction may further support this hypothesis.