AVIAN FORAGING RESPONSE TO JACK PINE (PINUS BANKSIANA) VOLATILE CHEMICALS

Birds benefit trees and other plants by removing herbivores that damage the plant and impede its growth. They can significantly increase the growth and biomass of the trees by foraging on the herbivores that harm plants, and the prey items eaten in turn benefits foraging birds by providing sustenance. This interaction becomes complex when tree volatile chemical communication is added. Trees regularly release volatile organic chemicals (referred to as VOCs) as part of metabolism. The particular VOCs released by a tree can depend on several factors, including water availability, time of year, and damage type (e.g., mechanical damage or insect damage). Therefore, the VOC profile released by a tree has the potential to encode the type of agent causing plant damage, and potentially the infestation level of a species of foraging insect. If birds can sense these VOCs, they could determine which trees will be the most efficient to forage on. I tested this interaction in the jack pine (Pinus banksiana) forests in the Upper Peninsula of Michigan. I measured VOCs released from trees that were favored by foraging insectivorous and omnivorous birds and compared them to VOC measurements from trees that had no avian foraging. Specifically, I focused on both the difference in the α-pinene to β-pinene ratio between preferred and non-preferred trees and the overall VOC composition of preferred and non-preferred trees. I found significant differences in the VOCs released between preferred and non-preferred trees. These differences were consistent with prior research on the differences between insect-damaged and non-insect damaged trees, suggesting the birds were indeed foraging on trees with more insects