The food of the silvereye, Zosterops gouldi (Aves : Zosteropidae), in relation to its role as a vector of a granulosis virus of the potato moth, Phthorimaea operculella (Lepidoptera : Gelechiidae)

Abstract

The silvereye feeds in farmland in south-western Western Australia, eating mainly arthropods. Larvae of the potato moth are regularly a major summer food, and the silvereye shows a well-defined functional response to larval density. The silvereye functional response curve differs from the characteristic vertebrate sigmoid-shaped curve in that it lacks the initial positively accelerating portion. This is attributed to the occurrence of prey in many discrete habitats, combined with silvereye mobility and its sensitive response to low potato moth larval densities. The number of potato moth larvae that are eaten is reduced when a larger alternative prey is available, but the numerical proportion of larvae in the food remains unchanged. The silvereye is a potential vector of a granulosis virus of the potato moth through its regular predation on larvae of the potato moth, its large numbers, and its mobility.