Effects of bird predation on some pest insect populations in corn

Intensive agriculture has led to a decrease in biodiversity in many areas of the world. Poisoning birds directly or eliminating habitats suitable for birds within an agricultural landscape, may remove potential control agents of insect pests. The main objective of this project was to investigate the effects of excluding avian species from portions of cornfields through the use of bird-proof netting. Although pest levels were low and exclusion nets failed to affect corn yield, some differences were seen in insect pest population levels, supporting the view that insectivorous birds play a beneficial role in corn fields. Cutworms (Agrotis spp.) and weevils (Sphenophorus spp.) were found at higher density in plots where birds were excluded, especially those situated near the field edge. Data on aphids (Rhopalosiphum maidis) and European corn borer (Ostrinia nubilalis) were more variable but tended in the same direction. Only the adult Northern corn rootworm (Diabrotica longicornis) population was clearly not reduced by birds but infestation levels were extremely low. © 2001 Elsevier Science B.V. All rights reserved.