Invasive fruits, novel foods, and choice: An investigation of European starling and American robin frugivory

We compared the feeding choices of an invasive frugivore, the European Starling (Sturnus vulgaris), with those of a native, the American Robin (Turdus migratorius). Using captive birds, we tested whether these species differ in their preferences when offered a choice between a native and an invasive fruit, and between a novel and a familiar food. We examined willingness to eat fruits of selected invasive plants and to select a novel food by measuring the time elapsed before feeding began. Both species demonstrated significant preferences for invasive fruits over similar native fruits in two of three choice tests. Both starlings and robins ate autumn olive (Elaeagnus umbellata) fruits significantly more willingly than Asiatic bittersweet (Celastrus orbiculatus). Starlings, but not robins when choosing between a novel and a familiar food, strongly preferred the familiar food. We found no differences in willingness of birds to eat a novel food when it was the only food available. These results suggest that some fleshy-fruited invasive plants may receive more dispersal services than native plants with similar fruits, and that different frugivores may be seed dispersers for different invasive plants.