Garamszegi, L. Z., Donald, J. W., Francis, C. D., Fuxjager, M. J., Goymann, W., Hau, M., et al. (2018). Species-specific means and within-species variance in glucocorticoid hormones and speciation rates in birds. Integrative and Comparative Biology, 58(4), 763-776. doi:10.1093/icb/icy086.