Blackbirds migrating through North Dakota in late summer damage sunflower crops shortly after the yellow ray petals begin to wither and fall (Besser 1985). DeHaven (1982) reported bird damage losses of $7.4 million on 2.2 million acres in 1980. Various behavioral, chemical, and mechanical strategies have been employed over the past decade to reduce the damage. Although some of these methods have effectively dispersed or reduced blackbird populations, many have proven to be ineffective over time, economically infeasible, or culturally unacceptable (Guarino 1984).
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