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Red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula), and yellow-headed blackbirds (Xanthocephalus xanthocephalus) cause severe damage to ripening crops in North Dakota, South Dakota, and Minnesota. Scientific surveys show that blackbirds damage $4 million to $11 million worth of sunflower each year in these three States. On occasion, blackbirds have destroyed entire fields of sunflower in a few days. Preventing this magnitude of crop damage requires knowledge about the blackbird’s habits and various methods available to prevent damage. In late summer, after the nesting season, blackbirds form flocks and roost at night in numbers varying from a few to over a million birds. These flocks and roosting congregations are sometimes comprised of a single species, but often all three species mix together. Although some blackbirds roost in trees in the northern Great Plains, the birds prefer to roost in dense cattail marshes. Between 40 and 50 percent of the blackbird population dies every year. But these mortality figures are offset by the birds’ reproductive success. On average, a female produces two to four fledglings per year. The three common blackbird species have many differences in their nesting biology, food preferences, feeding habitats, and migration patterns.