Surveys of Forest Birds on Puerto Rico, 2015

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 43 1-km2 cells that we selected from the winter habitat model using a generalized random tessellation stratified (GRTS) sampling approach. 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. Forest cover within a 50-m radius around each point was at least 50%. At each point, a single observer counducted 4 repeated surveys. Each survey lasted for 2.5 minutes, and repeated surveys were conducted in sequence, one after another. A 1-minute playback of Bicknell’s Thrush vocalizations was broadcast before the second and fourth surveys; there was no delay the second and third surveys. Individuals of all species detected during each survey were registered.

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.