Tritrophic interactions with avian predators: the effect of host plant species and herbivore-induced plant volatiles on recruiting avian predators

Herbivore-induced plant volatiles (HIPVs) are important signaling compounds released by plants upon wounding. These compounds have been shown to mediate tritrophic interactions in recruiting insect predators and parasitoids. Recent work has begun to show that avian species, which were once thought to have a very limited sense of smell, can cue in on these HIPVs to find insect prey. Here, we test the ability for two general HIPVs, methyl jasmonate and methyl salicylate, to recruit avian predators. We test the recruitment efficacies of these HIPVs across four different host plant species, black walnut (Juglans nigra), red maple (Acer rubum), cattail (Typha latifolia), and wheat (Triticum aestivum), and use clay caterpillars to quantify predation by insectivorous birds. We found no significant differences in predation between treatment groups across any of our host plants. However, there was a nearly significant effect of methyl salicylate in black-walnut trees. Interestingly, our results did show a significant effect of host plant species on predation levels. The two tree species, particularly black walnut, had higher levels of predation than the herbaceous species. We discuss the implications of these results and suggest a number of ideas and suggestions for future studies investigating the role of HIPVs in attracting insectivorous birds.