Digestion of fruit of invasive alien plants by three southern African avian frugivores

Many highly invasive plants are fleshy-fruited and owe their invasiveness largely to mutualisms formed with local dispersers. The energetic benefits gained by frugivores from ingestion of fruits of invasive alien plants remain poorly documented. We assess whether avian frugivores process fruits of invasive alien plants effectively to meet their daily energetic requirements. Four fleshy-fruited plant species that are invasive in southern Africa were considered – Solanum mauritianum, Cinnamomum camphora, Lantana camara and Psidium guajava. Their fruits were fed to three common generalist frugivores – Red-winged Starling Onychognathus morio, Speckled Mousebird Colius striatus and Dark-capped Bulbul Pycnonotus tricolor – to determine the efficiency of digestion. Energetic parameters calculated for all fruit diets varied significantly between frugivore species. Speckled Mousebirds and Dark-capped Bulbuls maintained body mass and efficiently processed all four fruit types, whereas Red-winged Starlings only did so on C. camphora and S. mauritianum diets. These results explain why these fruits are attractive to local avian frugivores. Furthermore, these avian frugivores processed large quantities of invasive fruits, thereby serving as potentially efficient dispersers