Faaborg, J., KM Dugger, and W. J. Arendt. 2007. Long-term variation of the winter-resident bird community of Guánica Forest, Puerto Rico: lessons for measuring and monitoring species richness. Journal of Field Ornithology 78:270-278.
This link will direct you to a non-government website that may have different privacy
policies from those of the U.S. Geological Survey.