Marblehead Crows
Identification
The American crow is one of America’s best-known birds. Males and females are outwardly alike. Their large size (17 to 21 inches [43 to 53 cm] long), completely coal-black plumage and familiar “caw caw” sound make them easy to identify, even among other types of crows. They are fairly common in areas near people, and tales of their wit and intelligence have been noted in many stories.
Habitat
American crows are widely distributed over much of North America. They breed from Newfoundland and Manitoba southward to Florida and Texas, and throughout the West, except in the drier southwestern portions. Crows in the northern parts of their range migrate southward in the fall and generally spend winter south of the Canada-United States border.
American crows servive the best in a mixture of open fields where food can be found and woodlots where there are trees for nesting and roosting. They commonly live in woodlots, wooded areas along streams and rivers, farmlands, orchards, parks and suburban areas. Winter roosting concentrations of crows occur in areas that have favorable roost sites and abundant food.
Myths
The myth that splitting the tongue allows a crow to talk better is not true and is needlessly cruel.
Fun Facts
Crows are among the most intelligent of birds. Experiments indicate that American crows can count to three or four, are good at solving puzzles, have good memories, employ a diverse and behaviorally complex range of vocalizations and quickly learn to associate various noises and symbols with food.
Crows can mimic sounds made by other birds and animals and have been taught to mimic the human voice.
Crows begin nesting in early spring (February to May, with southern nests starting earlier than northern ones) and build a nest of twigs, sticks, and coarse stems ranging from 18 to 60 feet (5 to 18 m) above ground in oaks, pines, cottonwoods or other trees.
Crow pairs appear to remain together throughout the year, at least in nonmigratory populations, and pairs or pair bonds are likely maintained even within large winter migratory flocks.
The female incubates the eggs and is fed during incubation by the male and nest associates. The young leave the nest at about five weeks of age and forage with their parents throughout the summer. Later in the year, the family may join other groups that in turn may join still larger groups. The larger groups often migrate in late fall or winter.
Few crows in the wild live more than four to six years, but some have lived to 14 years in the wild and over 20 years in captivity. A bird bander reported a crow that had lived 29 years in the wild.
A communal roost site in the Fort Cobb area in Oklahoma holds several million crows each winter. In Nebraska, Wisconsin, and possibly other states, crows appear to be roosting in towns near people. These flocks roost together at night and disperse over large areas to feed during the day. Crows may commonly fly six to twelve miles (10 to 20 km) outward from a roost each day to feed.
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.
Many of the problems caused by crows 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. They may also attack very young calves, pigs, goats and lambs in rare situation. 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. 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.
Large fall and winter crow roosts cause serious problems 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.
Finally, 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.
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Legal Status
Crows are protected by the Migratory Bird Treaty Act, a federal act resulting from a formal treaty signed by the United States, Canada and Mexico. However, under this act, crows may be controlled without a federal permit 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 to constitute a health hazard or other nuisance.”
States may require permits to control crows and may regulate the method of take. Federal guidelines permit states to establish hunting seasons for crows. During these seasons, crows may be hunted according to the regulations established in each state. Regulations or interpretation of depredation rules may vary among states, and state or local laws may prohibit certain control techniques such as shooting or trapping. Check with local wildlife officials if there is any doubt regarding legality of control methods.
Damage Prevention and Control Methods
Exclusion
Netting to exclude crows from high-value crops or small areas. Protect ripening corn in gardens by covering each ear with a paper cup or sack after the silk has turned brown. Widely-spaced lines or wires placed around sites taht need protection may have some efficacy in repelling crows, but further study is needed.
Cultural Methods
Alternate or decoy foods; example: scatter whole corn, preferably softened by water, through a field to protect newly planted corn seedlings.
Frightening
Use with roosts, crops, and some other situations. Frightening devices include recorded distress or alarm calls, pyrotechnics, various sound-producing devices, chemical frightening agents (Avitrol®), lights, bright objects, high-pressure water spray, and, where appropriate, shotguns.
Repellents
None are registered.
Toxicants
None are registered.
Trapping
Check laws before trapping. Australian crow decoy traps may be useful near a high-value crop or other areas where a resident population is causing damage. Proper care of traps and decoy birds is necessary. Capture single crows uninjured in size No. 0 or No. 1 steel traps that have the jaws wrapped with cloth or rubber.
ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).