Damage and Damage Identification
Complaints associated with crow damage to agriculture were more common in the 1940s than they are today. Although surveys indicate that overall crow numbers have not changed appreciably, the populations appear to be more scattered during much of the year. This change has resulted apparently from the crows’ response to changing land-use patterns. Farming has become more prevalent in some areas, generally with larger fields. Woodland areas are generally smaller, and trees and other resources in urban sites provide crow habitat. Overall, the amount and degree of damage is highly variable from place to place and year to year. Several variables enter into the complex picture of crow damage, including season, local weather, time of harvest, amount of crop production, and availability and distribution of wild mast, insects, and other foods.
Although crows cause a variety of damage problems, many of these are more commonly associated with other animal species. Crows may damage seedling corn plants by pulling the sprouts and consuming the kernels. Similar damage may also be caused by other birds (pheasants, starlings, blackbirds) and rodents (mice, ground squirrels). Crows at times damage ripening corn during the milk and dough stages of development. Such damage, however, is more commonly caused by blackbirds. Crows consume peanuts when they are windrowed in fields to dry, but other birds, especially grackles, cause the greatest portion of this damage. Crows may also damage other crops, including ripening grain sorghum, commercial sunflowers, pecans, various fruits, and watermelons. In rare situations, crows may attack very young calves, pigs, goats, and lambs, particularly during or shortly after birth. This problem, which is more often associated with magpies or ravens, is most likely to happen where livestock births occur in unprotected open fields near large concentrations of crows.
Another complaint about crows is that they consume the eggs and sometimes the young of waterfowl, pheasants, and other birds during the nesting season. Overall, such crow depredation probably has little effect on the numbers of these birds. However, it can be a problem of concern locally, particularly where breeding waterfowl are concentrated and where there is too little habitat cover to conceal nests. For example, nests are more easily found by crows, as well as by other predators, when located in a narrow fence row or at the edge of a prairie pothole that has little surrounding cover.
Large fall and winter crow roosts cause serious problems in some areas, particularly when located in towns or other sites near people. Such roosts are objectionable because of the odor of the bird droppings, health concerns, noise, and damage to trees in the roost. In addition, crows flying out from roosts each day to feed may cause agricultural or other damage problems. On the other hand, the diet of crows may be beneficial to agriculture, depending on the time of year and surrounding land use (see sections on crow food habits and economics).
Finally, in some situations, large crow flocks may become a factor in spreading disease. At times, they feed in and around farm buildings, where they have been implicated in the spread of transmissible gastroenteritis (TGE) among swine facilities. At other times, large crow flocks near wetland areas may increase the potential for spread of waterfowl diseases such as avian cholera. The scavenging habits of crows and the apparent longer incubation time of the disease in crows are factors that increase the potential for crows to spread this devastating disease. Also, crow and other bird (blackbird, starling) roosts that have been in place for several years may harbor the fungus (Histoplasma capsulatum) that causes histoplasmosis, a disease that can infect people who breathe in spores when a roost is disturbed.
Learn More About:
General Biology, Reproduction, and Behavior
Economics of Damage and Control
Legal Status
Damage Prevention and Control Methods
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