PS 18-45 - Red-naped sapsucker (Sphyrapicus nuchalis) preference for canopy cover and insect abundance on aspen trees (Populus tremuloides) in City of Rocks, Idaho

Tuesday, August 8, 2017
Exhibit Hall, Oregon Convention Center
Erika Alvarado1, Kerri T. Vierling2 and Jamie Jarolimek2, (1)Doris Duke Conservation Scholars Program, (2)Department of Fish and Wildlife Science, University of Idaho, Moscow, ID

City of Rocks in southern Idaho is a temperate desert ecosystem containing aspen trees (Populus tremuloides). The presence of Red-naped Sapsuckers (RNSA) in this area can be important because their presence increases biodiversity. RNSA activity is indicated by the presence of sap wells. I observed that RNSA demonstrate a preference for certain trees in a stand. Canopy cover may play a role in this observed tree selection. I hypothesized that RNSA choose trees based on percent canopy cover. I predicted that RNSA select trees with higher canopy cover. Canopy cover was measured for trees across seven different stands to determine if it plays a role in tree selection by RNSA. Ten trees in each stand were measured, five trees with sap wells and five trees without sap wells. A densitometer was used to measure the canopy cover for each tree.

The presence of RNSA affects other organisms in aspen tree ecosystems, including insects. I observed insects on aspen trees with sap wells. I tested the hypothesis that sap wells play a role in insect abundance on aspen trees. I predicted that trees with sap wells would have a larger number of insects compared to trees without sap wells, and that trees with sap wells would also have a higher diversity of insects. Insect data was collected three times throughout the day on each tree measured for canopy cover. Data was collected by observing a tree for ten minutes and insects that landed on the tree were written down, collected, or captured in a photograph. Insect orders were recorded to determine insect diversity on aspen trees.


Based on the data collected canopy cover does play a role in the presence of Red-naped Sapsuckers. On average the trees selected by Red-naped Sapsuckers had 9.04% more canopy cover than the random trees that were selected for measurement. This could be because increased canopy cover may provide protection from predators or shade during the hot summer months. Preliminary data collected on insects indicates that insects prefer trees without sap wells. This is contrary to what I predicted for insect abundance. A possible reason for observing a high number of insects on trees without sap-wells could be that insects could face increased predation on trees with sap wells due to other animals being attracted to the sap well. The results did not indicate that insect diversity varied between trees with and without sap wells.