Clark’s Nutcracker Occurrence, Whitebark Pine Stand Health and Cone Production in the Waterton-Glacier International Peace Park

Scott, Jennifer

Clark’s nutcrackers (Nucifraga columbiana) are the main seed dispersers for whitebark pine and primarily responsible for whitebark pine regeneration through their seed caching behavior. On-going losses of whitebark pine (Pinus albicaulis) in the Crown of the Continent Ecosystem, from white pine blister rust (caused by the exotic fungus Cronartium ribicola), historical losses of whitebark pine to mountain pine beetle (Dendroctonus ponderosae), as well as successional replacement of whitebark pine by fir and spruce exacerbated by fire suppression, may together diminish the likelihood of stand visitation by nutcrackers. In the absence of seed dispersal, management strategies are needed to maintain whitebark pine communities. Here, I focus my studies on the Waterton-Glacier International Peace Park to determine: 1) if nutcrackers occur in whitebark pine communities in the park and at what density, 2) if nutcracker densities vary with whitebark pine cone production, 3) how whitebark pine cone production varies with density and health, and 4) whether the relationship between the likelihood of nutcracker visitation and whitebark pine cone density in the park is predicted by the models in McKinney et al. (2009) and Barringer et al. (2012). To address these objectives, I selected five study areas across the park to examine stand condition and sample nutcracker visitation. Within each study area, I delineated one to three transects per study area, each with two 500 m2 stand assessment plots. For this study, I developed a protocol for estimating both nutcracker (2009, 2010) and whitebark pine cone densities (2010) using line transect distance sampling. Values were calculated by combining numbers for both plots on each transect (1,000m2). Stand assessments revealed average diameter at breast height (dbh) ranging from 6.5 cm to 37.4 cm across transects, blister rust infection levels ranging from 33% to 80%, and live basal area (LBA) per hectare, ranging from 0.42 m2/ha to 11.05 m2/ha. Across all transects, I found total numbers of live whitebark pine and dead whitebark pine ranging from 20 to 330 and 0 to 290, per hectare, respectively. Over the 2009 and 2010 field seasons, I detected 65 nutcrackers over a total of 5.25 km .Over the study, combining detections, I generated a density estimate of 0.85 nutcrackers per ha with a 95% confidence interval of 0.37-2.62. We detected a total of 1338 whitebark pine cones for 2010 alone over the same transect distance. We generated a density estimate of 66.7 cones per ha with a 95% confidence interval of 28.1-158.5. Both cone production per hectare and proportion of observation hours with one or more nutcrackers were similar to previous studies in the Northern Divide region, including the Waterton -Glacier International Peace Park, and the relationships determined by McKinney et al. (2009) and Barringer et al. (2012). Our study is the third to indicate a low likelihood of visitation of whitebark pine communities by nutcrackers in the Waterton-Glacier International Peace Park.