Portugal, Steven J.; Murn, Campbell P.; Sparkes, Emily L.; Daley, Monica A. (2016). "The fast and forceful kicking strike of the secretary bird". Current Biology. 26 (2): R58–R59. doi:10.1016/j.cub.2015.12.004.
McNab, J. M. (1973). "The avian caeca: a review". World's Poultry Science Journal. 29 (3): 251–263. doi:10.1079/wps19730014.
Mayr, G.; Clarke, J. (2003) "The deep divergences of neornithine birds: a phylogenetic analysis of morphological characters" Cladistics19 527–553
The Depression of Reptile Biomass by Large Herbivores – Janzen, D.H., American Naturalist, 110, 71–400 (1976)
Allan, D.G.; Harrison, J.A.; Navarro, R.A.; van Wilgen, B.W.; Thompson, M.W.(1997) "The Impact of Commercial Afforestation on Bird Population in Mpumalanga Province, South Africa – Insights from Bird-Atlas Data" Biological Conservation79 173–185
