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Home | Bird Damage | Blackbirds and Blackbird-like Birds Blackbirds and Blackbird-like Birds
Red-winged blackbirdsRed-winged blackbirds, common grackles, and yellow-headed blackbirds 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 sunflowers each year in these three states. 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 3 species mix together. Red-winged blackbirds are the most numerous breeding blackbird in the Dakotas and Minnesota and perhaps the most abundant bird in North America. The yellow-headed blackbird is a robin-sized bird, locally abundant in deep-water marshes of the northern Great Plains and western North America. Other blackbird species also feed on seeds, sunflower, corn, and small grains, often in association with redwings and grackles (Linz et al. 1997) 
Common GracklesCommon grackles nest throughout North America east of the Rockies, in shelterbelts, farmyards, marshes, and towns. Grackles have a diet somewhat similar to that of red-wings, but grackles are more predatory, feeding occasionally on small fish, field mice, songbird nestlings, and eggs. In addition to sunflowers, grackles also feed on acorns and other tree fruits in winter (Linz et al. 1997). Grackles will consume blueberries whole and will also forage in cherry and apple orchards, often slashing, and thus damaging, the fruits. They will also eat citrus, tomatoes, watermelons, cabbage, lettuce, grain, corn, peaches, figs, and cantaloupes. Grackles may flock together and roost in trees in urban and suburban areas. They are, thus, not only a nuisance, but may also pose a public health hazard. Accumulations of droppings can harbor histoplasmosis (a respiratory disease) that is indirectly transmissible to humans. Bird droppings also damage cars, and kill lawns and ornamental plants. In addition, grackl es are extremely noisy birds, often making a disturbing racket. The grackle is also a frequent predator at northeastern aquaculture facilities in the spring, foraging on small trout fingerlings initially placed in outside raceways. After fingerlings exceed 5 inches in length, grackles shift their diet to invertebrates and grains and sometimes leave the hatchery altogether. 
European starlingsEuropean starlings sometimes forage in grain and sunflower crops, but the birds are usually searching for insects and do not feed on the crop. Starlings can cause extensive damage to ripening fruit crops. They may descend on orchards in huge flocks and eat small fruits like grapes whole. They will slash some fruits and peck holes in others, including apples, strawberries, and cherries. Cattle feedlots suffer most from wintertime flocks, which can reach as high as 100,000 or more per day. Individual starlings, which weigh approximately 3 ounces, can each eat up to 1 ounce of food per day. A million starlings can consume 27,500 tons of livestock feed during winter months and despoil more feed with their droppings. Starlings also form roosts in residential areas. They are aggressive birds and will often drive other birds away. During nesting season, they may occupy bird houses intended for more desirable species such as purple martins or bluebirds. Brown-headed cowbirdsBrown-headed cowbirds feed primarily on weed seeds and insects, but the females of the species lay their eggs in the nests of other birds. The newly hatched cowbirds often out-compete the biological young of the host species causing declines in species populations (e.g. the Kirtland warbler). 
American crowsAmerican crows may damage crops such as seedling or ripening corn, sorghum, sunflowers, and some fruit crops, however, they are a much lesser problem than blackbirds, grackles and others. Crows have also been known to consume eggs and even the young of nesting birds such as waterfowl or pheasants, though this is usually a localized problem. The main concern about crows is their huge roosts, especially when these roosts are located near residential areas. Odors, noise, and tree damage from droppings are major problems. Roosts may also harbor spores of histoplasmosis (an infectious respiratory disease). Crows are believed to have the potential to spread avian cholera and have been implicated in the spread of transmissible gastroenteritis around swine facilities. 
MagpiesMagpies can damage crops such as cherries, almonds, corn, walnuts, melons, peaches, wheat and figs. Even worse, magpies will pick at open wounds on livestock until the wounds are much bigger and more prone to infection. Also, magpies, like ravens, may pick out the eyes of sick or newly born livestock. Magpies will rob eggs (and sometimes young hatchlings) from nests of other birds and poultry. Magpie roosts, like other roosts, can be troublesome because of excessive noise and odors. ReferencesAVERY, M. L. 2002. Birds in pest management. Pages 104-106 in D. Pimental, editor. Encyclopedia of pest management. Marcel Dekker, New York, USA LINZ, G. M., R. A. DOLBEER, J. J. HANZEL, AND L. E. HUFFMAN. 1997. Controlling blackbird damage to sunflower and grain crops in the northern Great Plains. USDA/APHIS Agriculture Information Bulletin No. 679. Blackbird Links http://ohioline.osu.edu/w-fact/0002.html (Ohio) Cowbird Linkshttp://cowbird.lscf.ucsb.edu/ (California) Crow Linkshttp://www.extension.umn.edu/info-u/environment/BD519.html (Minnesota) Starling Linkshttp://extension.usu.edu/files/natrpubs/starling.pdf (Utah) |
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Content: Laurie Paulik Last updated:
02/05/08 |
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