Reyer, Hans-Ulrich Verhaltensphysiologie, Seewiesen, Max Planck Institut für Ornithologie, Max Planck Society;
Reyer, H.-U., & Westerterp, K. (1985). Parental energy-expenditure: A proximate cause of helper recruitment in the pied kingfisher (Ceryle-rudis). Behavioral Ecology and Sociobiology, 17(4), 363-369. doi:10.1007/bf00293214.