Verwantskap tussen groepgrootte en voedingsukses van vee-reiers ( Bubulcus ibis ) in die sentrale Vrystaat : research and review article

Relationship between group size and feeding success of cattle egrets (Bubulcus ibis) in the central Free State Regardless of habitat or time of day, cattle egrets feeding independently of hosts generally occur in larger groups than those feeding in close association with ungulates. The average group size of three individuals feeding in association with hosts stays remarkably constant with regard to divergent situations. Based on the type of habitat and the grazing speed of the host concerned, cattle egrets achieve the highest feeding success (number of prey items) with the least energy inputs (number of paces) in association with cattle, and to a lesser extent with the closely related buffalo. Compared to solitary birds, cattle egrets feeding in groups experience without exception a higher feeding success. Results of feeding experiments, as well as the exceptional occurrence of so-called feeding lines, confirm the phenomenon that the feeding success of cattle egrets correlates closely with the size of the feeding group. Ongeag habitat of tydstip van die dag kom vee-reiers wat onafhanklik van gashere voed oor die algemeen in groter groepe voor as die wat in noue assosiasie met hoefdiere voed. Die gemiddelde groepgrootte van drie individue wat in assosiasie met gashere voed, bly merkwaardig konstant met betrekking tot uiteenlopende situasies. Gebaseer op die tipe habitat en weispoed van die betrokke gasheer behaal vee-reiers die hoogste voedingsukses (aantal prooi-items) met die minste energie-insette (aantal tree) in assosiasie met beeste, en in 'n mindere mate met die naverwante buffel. Vee-reiers wat in groepsverband voed, ondervind sonder uitsondering 'n hoer voedingsukses as enkelinge. Resultate van voedingseksperimente, asook die uitsonderlike voorkoms van sogenaamde voedingslinies, bevestig die verskynsel dat die voedingsukses van vee-reiers ten nouste verband hou met die grootte van die voedingsgroep.