Date of Completion
Honors College Thesis
Bicknell's Thrush, Multi-season Occupancy Model, New Hampshire, White Mountains, Citizen Science, Mountain Birdwatch
Bicknell’s Thrush (Catharus bicknelli) is a neotropical migrant bird species that breeds in the montane spruce (Picea spp.) and balsam fir (Abies balsamea) forests of Maine, New Hampshire, Vermont, New York, and eastern Canada. This species has a restricted range, a decreasing population, and is facing the significant threat of climate change. I used a multi-season occupancy model to predict the probability of occupancy, colonization, and extinction, of Bicknell’s Thrush, while accounting for the probability of detection. From 2010 to 2021, 597 detections of Bicknell’s Thrush from 276 sampling stations in New Hampshire were recorded. Covariates investigated were elevation, proportion of evergreen forest, deciduous forest, and other landcover types. Detection covariates included survey date, point count start time, and year. The model predicted an overall negative relationship between detection probability and point count start time, where detection declined after 5:00am and then increased after 7:30am. The probabilities of site occupancy and site colonization were best represented by the additive and interactive relationships of elevation and proportion of evergreen forest, respectively. Elevation was the covariate that had the largest beta estimate for occupancy and colonization probability. Probability of local site extinction is best represented by proportion of evergreen forest and has a slight negative relationship. As the White Mountain National Forest of New Hampshire continues to warm, the relationship between a changing climate, upslope movement of the montane spruce-fir forest, and species occupancy will be increasingly important for conservation of the country’s largest concentration of Bicknell’s Thrush habitat.
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Higgins, Garrett Timothy, "Using Citizen Science Data to Predict the Probability of Occupancy, Colonization, and Extinction of Bicknell’s Thrush (Catharus bicknelli) in the White Mountains of New Hampshire" (2022). UVM Honors College Senior Theses. 471.