Parasitized and non-parasitized prey selectivity by an insectivorous bird

The identification and conservation of naturally occurring enemies of crop pests is an important means of improving biological control in cropping systems. One particularly important potential mechanism whereby birds might stabilize and improve pest control is consumption of individual prey that escape mortality from other agents of biological control. We tested the hypothesis that birds prefer to forage upon non-parasitized fall armyworm (Spodoptera frugiperda J. E. Smith) prey via captive feeding trials, where birds were also offered armyworms parasitized by Euplectrus plathypenae (Howard) larvae. While birds were equally willing to eat both parasitized and non-parasitized armyworm prey of the same body size, they strongly preferred larger non-parasitized prey. This preference continued even as this prey item became less numerous than smaller parasitized worms during feeding trials. Our results suggest that birds may contribute to the biological control of arthropod pests that escape control, become larger in body size and, subsequently, a favored prey item.