Red-winged blackbird predation on northern corn rootworm beetles in field corn.
Relationships between red-winged blackbirds (Agelaius phoeniceus) and the chrysomelid Diabrotica longicornis were studied in field maize in Cayuga County, New York State. Research was concentrated in 50 maize fields located within 7 km of a large autumn roost of icterids (primarily red-winged blackbirds). Before the maize fields were damaged by the blackbirds (the pre-damage period), more blackbirds were seen and more bird droppings were found in those fields with high populations of D. longicornis. Of the combined crop and proventriculus of 21 blackbirds collected in maize fields during the pre-damage period, 50% contained D. longicornis, while of those of 34 blackbirds collected in fields after damage 81% contained maize and only 5% D. longicornis. Maize fields with high populations of D. longicornis did not receive more maize damage from the blackbirds.