Feeding behaviour of avian dispersers of mistletoe fruit in the Loskop Dam Nature Reserve, South Africa

Abstract

The dispersal of three mistletoe species [Tapinanthus (formerly Loranthus) leendertziae, T. natalitius ssp. zeyheri and Viscum combreticola by birds was studied in the Loskop Dam Nature Reserve, South Africa. Eight of the 27 species of frugivorous birds present were observed feeding on mistletoe fruit. The yel-lowfronted tinker barbet Pogoniulus chrysoconus was the most important single disperser of mistletoes, consuming 64%, 80% and 94% of the fruit of the above mistletoe species respectively, and being behaviourally most suited to the dispersal of mistletoe seed. The other seven avian species were incidental mistletoe fruit eaters. Seasonal variations in mistletoe eating by different birds are mainly related to the preference for Tapinanthus fruit by species other than the tinker barbet. Three ways of handling mistletoe seeds are described: regurgitation (in more than 80% of the cases), defaecation and ‘pecking’. Very few interactions between birds occurred on mistletoe plants. No interspecific aggression was observed but intraspecific aggression was evident in the tinker barbet. Less than 50% of Tapinanthus and less than 20% of V. combreticola seeds were carried away from the parent plant or its host. Few seeds were carried away more than 50 m from the parent plant. Regurgitation is most important for mistletoe dispersal generally, but defaecation may be more important for long-distance dispersal and dispersal of the smaller-seeded Viscum species.