Korner-Nievergelt, F., Sauter, A., Atkinson, P.W., Guélat, J., Kania, W., Kéry, M., Köppen, U., Robinson, R.A., Schaub, M., Thorup, K., van der Jeugd, H. & van Noordwijk, A.J. 2010. Improving the analysis of movement data from marked individuals through explicit estimation of observer heterogeneity. Journal of Avian Biology 41: 17. doi:10.1111/j.1600-048X.2009.04907.x