Puerto Rico Bicknell's Thrush Surveys, 2014

A predictive model of the distribution of wintering habitat for Bicknell’s Thrush (Catharus bicknelli) (McFarland et al. 2013) indicated that a considerable extent of potentially suitable habitat for Bicknell's Thrush exists in the central highlands of Puerto Rico. This region has never been surveyed for the species. To test the predictions of the winter habitat model, and to better clarify the species’ distribution during the winter, we conducted surveys in areas throughout Puerto Rico identified as potentially suitable habitat. We conducted field surveys from January 2015 through March 2015. We visited 44 1-km2 cells that we selected from the winter habitat model using a generalized random tessellation stratified (GRTS) sampling approach. An equal number of cells in each predicted probability of occurence class (low [<25% predicted probability of Bicknell's Thrush occurrence], medium [25%-50% prredicted probability of occurrence], and high [>50% predicted probability of occurrence) were selected for surveys. Within each cell, we surveyed a minimum of 3-5 points that were >250 meters apart. The location of points within each cell was determined systematically based on accessibility - all points were in forest adjacent to roads - and to ensure an even distribution of points across the cell. At each point, a single observer counducted a 10-minute count divided into four 2.5-minute intervals. A 1-minute playback of Bicknell’s Thrush vocalizations was broadcast before the second and fourth periods. Individuals of all species detected in each interval of the count were registered. Each interval was treated as a new count, so the same individual bird could be recorded in each interval of the 10-minute count. References McFarland KP, Rimmer CC, Goetz JE, Aubry Y, Wunderle JM Jr, Sutton A, Townsend JM, Sosa AL, Kirkconnell A. A winter distribution model for Bicknell's Thrush (Catharus bicknelli), a conservation tool for a threatened migratory songbird. PLoS One. 2013;8(1) e53986. doi:10.1371/journal.pone.0053986. PMID: 23326554; PMCID: PMC3541143.