Any use of full or partial (subset) tree data in research work requires the following citation: Jetz, W., G. H. Thomas, J. B. Joy, K. Hartmann, and A. O. Mooers. 2012. The global diversity of birds in space and time. Nature 491:444-448. For any additional use of the birdtree web tool, please cite “birdtree.org” Studies: