Feeding association between cattle egrets (Bubulcus ibis) and mammal hosts in the central Free State

Abstract

Field observations undertaken during October 1995 to April 2001 in agricultural areas and nature reserves of the central Free State, indicate that cattle egrets mainly feed in commensalistic association with ungulates or even farm implements. A higher percentage farm animals than game was involved herewith. Based on calculated preference indices only three species, namely cattle, buffalo and white rhino, qualified as key hosts. Eland, gemsbok, impala and horses were classified as major hosts, while the rest of the thirteen observed host species were identified as minor hosts. More than half of all feeding associations (58,4%) occurred during the early mornings followed by a decrease during the middle of the day with a slight increase again later in the afternoon. Depending on the host species involved, notable differences occurred in the time of association. Cattle were the only host species with which cattle egrets associated during any time of the day. Evidently, cattle egrets associated most often with larger host species which were actively grazing. In grassland habitats the birds mainly fed in front of grazing hosts, but behind those that moved too fast.