Northern Prairie Wildlife Research Center
Blackbirds often use alternate feeding sites when available. (APHIS photo by George Linz.)
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.
Red-winged blackbird (immature male) on an ear of corn. (Photo courtesy of the U.S. Department of the Interior, Fish and Wildlife Service.)
Red-winged blackbirds are the most numerous breeding blackbird in the Dakotas and Minnesota and perhaps the most abundant bird in North America. The male, a little smaller than a robin, is black with red and yellow shoulder patches. The brownish female, which is smaller than the male, is often mistaken for a large sparrow. Redwings nest throughout North America in marshes, hayfields, and ditches. Often adult males mate with more than one female. Insects are the dominant food during the nesting season (May-July), with the diet shifting to predominantly grain crops and weed seeds in late summer through winter. Redwings from the Dakotas and Minnesota migrate to the lower Great Plains and gulf coast region in winter.
Winter range of red-winged blackbirds, yellow-headed blackbirds, and common grackles breeding in the northern Great Plains
Common grackle (mature male). (USDI, Fish and Wildlife Service, photo by Roger Clopp.)
Common grackles are slightly larger than robins, with iridescent black feathers and a long keel-shaped tail. The male, slightly larger than the female, has more iridescence on the head and throat. Grackles are common nesters throughout North America east of the Rockies, nesting in shelterbelts, farmyards, marshes, and towns. The male grackle usually mates with one female. Flocks feed in fields, lawns, woodlots, and bottomlands. Grackles have a diet somewhat similar to that of redwings, but grackles are more predatory, feeding occasionally on small fish, field mice, songbird nestlings, and eggs. Grackles also feed on acorns and other tree fruits in winter. Grackles often roost in cattail marshes with other blackbirds in late summer, but grackles prefer roosting sites in upland deciduous or pine trees in their wintering locations in the Southern United States.
Yellow-headed blackbird (mature male). (USDI, Fish and Wildlife Service, photo by James Leupold.)
A robin-sized bird, the male yellowhead has a black body with a conspicuous yellow head and breast and a white wing patch seen only when the bird is in flight. The female is smaller and browner with yellow throat and breast and does not have a white wing patch. Yellowheads are locally abundant nesters in deep-water marshes of the northern Great Plains and western North America. Like redwings, male yellowheads often mate with more than one female. This species feeds extensively on insects during the nesting season and in late summer and fall on weed seeds, sunflower, corn, and small grains, often in association with redwings and grackles. An early migrant, yellowheads leave the northern Great Plains area before redwings and grackles, wintering in Mexico.
Other Bird Species
Other birds are sometimes seen feeding with redwings, yellowheads, and grackles but cause only minor damage to agricultural crops. The brownheaded cowbird (Molothrus ater) is a small, sparrow-sized blackbird. The male is black with a brown head, and the female is gray. Cowbirds feed primarily on weed seeds and insects, often in association with grazing livestock. The European starling (Sturnus vulgaris) is robin sized and is dark with light speckles and a distinctively short tail. Although starlings sometimes forage in grain and sunflower crops, these birds are usually searching for insects and do not feed on the crop. However, starlings will damage ripening fruit crops. House sparrows (Passer domesticus) are small brown birds sometimes mistaken for female redwings. House sparrows can cause significant local damage to small grain crops and sunflower grown near farmsteads and towns. Rusty blackbirds (Euphagus Carolinas) are robin sized and can be recognized in fall and winter by their rust-colored plumage. Their diet consists largely of insects. Brewer's blackbirds (Euphagus cyanocephalus) are similar in size to male redwings. Males are black with whitish eyes; females are brownish gray with dark eyes. These birds feed primarily on weed seeds and insects.
Blackbirds are native migratory birds and thus come under the jurisdiction of the Federal Migratory Bird Treaty Act, a formal treaty with Canada and Mexico. Blackbirds are protected by Federal law (Title 50, Code of Federal Regulations, Part 21.43) in the United States except that they may be killed when found "committing or about to commit depredations upon ornamental or shade trees, agricultural crops, livestock, or wildlife, or when concentrated in such numbers and manner as to constitute a health hazard or other nuisance." Some States and local governments may have additional restrictions on killing blackbirds. Starlings and house sparrows were introduced from Europe and are not protected by Federal law.