Red-winged blackbird and starling feeding responses on corn earworm-infested corn
We examined the feeding behavior of red-winged blackbirds (Agelaius phoeniceus) and European starlings (Sturnus vulgaris) on ears of corn (Zea mays) artificially infested with corn earworms (Helicoverpa zea). In 30-minute aviary tests, redwings and starlings directed 39 to 79% more feeding responses to ears of corn with worms than to ears without worms but they damaged the same proportion of ears with and without worms. In 3-hour aviary tests and a field evaluation, birds damaged more ears with worms than without worms. In spite of more feeding responses directed to ears with worms, the overall damage (number of kernels eaten by birds) was similar in both groups of ears in aviary tests. Our findings indicate that earworms can influence feeding behavior by redwings and starlings on ears of corn. The results generally support the hypothesis that by reducing insect populations in cornfields, one can make the fields less attractive to birds. Also, because redwings and starlings actively sought earworms in corn ears, these abundant birds have the potential for reducing populations of these insect pests in cornfields.