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The Handbook: Prevention and Control of Wildlife Damage Management, Internet Center Wildlife Damage for

1-1-1994

AMERICAN CROWS

Ron J. Johnson University of Nebraska-Lincoln, [email protected]

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Johnson, Ron J., "AMERICAN CROWS" (1994). The Handbook: Prevention and Control of Wildlife Damage. 60. https://digitalcommons.unl.edu/icwdmhandbook/60

This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in The Handbook: Prevention and Control of Wildlife Damage by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Ron J. Johnson Extension Wildlife Specialist Department of Forestry, Fisheries AMERICAN CROWS and Wildlife University of Nebraska Lincoln, Nebraska 68583-0819

Fig. 1. American crow, Corvus brachyrhynchos (also called the common crow or eastern crow)

Damage Prevention and Frightening Trapping Control Methods Use with roosts, crops, and some other Check laws before trapping. situations. Frightening devices Australian crow decoy traps may Exclusion include recorded distress or alarm be useful near a high-value crop or calls, pyrotechnics, various sound- other areas where a resident Netting to exclude crows from high- producing devices, chemical population is causing damage. value crops or small areas. frightening agents (Avitrol®), lights, Proper care of traps and decoy Protect ripening corn in gardens by bright objects, high-pressure water birds is necessary. covering each ear with a paper cup spray, and, where appropriate, Capture single crows uninjured in size or sack after the silk has turned shotguns. No. 0 or No. 1 steel traps that have brown. Repellents the jaws wrapped with cloth or rub- ber. Widely-spaced lines or wires placed None are registered. around sites needing protection Shooting and Hunting may have some efficacy in repelling Toxicants Helpful as a dispersal or frightening crows, but further study is needed. None are registered technique but generally not effective Cultural Methods in reducing overall crow numbers. Alternate or decoy foods; example: Crows may be hunted during open scatter whole corn, preferably seasons. Check with your state softened by water, through a field wildlife agency for local restrictions. to protect newly planted corn seedlings.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 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 E-33 Great Plains Agricultural Council Wildlife Committee Identification quent steady wing-beat with little or ing grasshoppers, beetles, beetle larvae no gliding. (white grubs, wireworms), caterpillars, spiders, millipedes, dead fish, frogs, The American crow (Fig. 1) is one of Chihuahuan ravens occur in the South- salamanders, snakes, eggs and young America’s best-known birds. Males west, including portions of western of birds, and carrion such as traffic- and females are outwardly alike. Their Kansas, Colorado, Oklahoma, Texas, killed animals. The remainder of the large size (17 to 21 inches [43 to 53 cm] New Mexico, and Arizona and rarely crow’s diet consists of vegetable or long), completely coal-black plumage, in south-central Nebraska. This raven, plant matter. Corn is the principal food and familiar “caw caw” sound make which is smaller than the common item in this category, much of it them easy to identify. They are fairly raven and somewhat larger than the obtained from fields after harvest. common in areas near people, and American crow, can be distinguished Crows also consume acorns, various tales of their wit and intelligence have from the crow by its call, slightly wild and cultivated fruits, water- been noted in many stories. wedge-shaped tail, and flight pattern melon, wheat, sorghum, peanuts, that includes gliding. The white neck Three other crows occur in the conti- pecans, garbage, and miscellaneous feathers, which account for its other nental United States, the fish crow other items. (Corvus ossifragus), the northwestern name, are seldom visible in the field. crow (Corvus caurinus), and the Mexi- General Biology, can crow (Corvus imparatus). Fish Range crows are primarily inhabitants of the Reproduction, and eastern and southeastern coastal Behavior United States, but their range extends American crows are widely distrib- uted over much of North America. into the eastern edges of Oklahoma Crows are among the most intelligent and Texas. Fish crows are somewhat They breed from Newfoundland and Manitoba southward to Florida and of birds. Experiments indicate that smaller than American crows, but in American crows can count to three or the field they appear much alike. They Texas, and throughout the West, except in the drier southwestern por- four, are good at solving puzzles, have can be distinguished, however, by good memories, employ a diverse and their calls — the fish crow call is a tions. During fall, crows in the north- ern parts of their range migrate behaviorally complex range of vocal- short, nasal “ca,” “car,” or “ca-ha.” izations, and quickly learn to associate Northwestern crows, as their name southward and generally winter south of the Canada-US border. various noises and symbols with food. implies, occur in the northwest along One report describes an American the coastal strip from Washington to crow that dropped palm nuts Alaska. They are most often seen for- Habitat (Washingtonia sp.) onto a residential aging along beaches. Northwestern street, then waited for passing automo- crows are smaller than American American crows do best in a mixture biles to crack them. Crows are keen crows, but in Washington state these of open fields where food can be found and wary birds. Consider the number two species may hybridize. Mexican and woodlots where there are trees for of crows that scavenge along high- crows occur in south Texas (Browns- nesting and roosting. They commonly ways; how many have you seen hit by ville area) primarily during fall and use woodlots, wooded areas along autos? Crows can mimic sounds made winter and are fairly small for crows. streams and rivers, farmlands, by other birds and animals and have Their voice is a low froglike “gurr” or orchards, parks, and suburban areas. been taught to mimic the human voice. “croak” or, in some areas, a higher- Winter roosting concentrations of The myth that splitting the tongue pitched “creow.” crows occur in areas that have favor- allows a crow to talk better, however, Ravens are similar to crows in appear- able roost sites and abundant food. is not true and is needlessly cruel. ance. Two species occur in the conti- Crows often post a sentinel while feed- nental United States, the common or Food Habits ing. Although studies indicate that the northern raven (Corvus corax) and sentinel may be part of a family group, Chihuahuan or white-necked raven Crows are omnivorous, eating almost unrelated crows and other birds in the (Corvus cryptoleucus). The common anything, and they readily adapt food area likely benefit from the sentinel’s raven is found from the foothills of the habits to changing seasons and avail- presence. Rockies westward, northward to able food supply. They belong to a Alaska and eastward across Canada Crows begin nesting in early spring select group of birds that appear and some northern U.S. states, and lo- (February to May, with southern nests equally adept at live hunting, pirating, cally in the Appalachian mountains. starting earlier than northern ones) and scavenging. Studies show that Common ravens can be distinguished and build a nest of twigs, sticks, and crows consume over 600 different food from crows by their larger size, call, coarse stems. Crow pairs appear to items. wedge-shaped tail, and flight pattern remain together throughout the year, that commonly includes soaring or About one-third of the crow’s annual at least in nonmigratory populations, gliding. In contrast, crows have a fre- diet consists of animal matter, includ- and pairs or pair bonds are likely

E-34 maintained even within large winter over large areas to feed during the was rural and relatively wary of migratory flocks. The nest, which is day. Crows may commonly fly 6 to 12 people. Will crows that are hatched in lined with shredded bark, feathers, miles (10 to 20 km) outward from a urban areas be habituated to people to grass, cloth, and string, is usually built roost each day to feed. such an extent that they will be more 18 to 60 feet (5 to 18 m) above ground difficult than their rural counterparts Recent radio-telemetry studies indicate in oaks, pines, cottonwoods, or other to disperse from problem sites? that roosting crows may have two dis- trees. Where there are few trees, crows Understanding such factors may lead tinct daily movement patterns. Some may nest on the ground or on the to better options for managing crows fly each day to a stable territory, called crossbars of telephone poles. The aver- in ways compatible with the needs of a diurnal activity center, which is age clutch is 4 to 6 eggs that hatch in people. maintained by four or five birds about 18 days. Young fledge in about throughout the winter and apparently 30 days. Usually there is 1 brood per then used as a nesting site in spring. Damage and Damage year, but in some southern areas there Although these stable groups of crows Identification may be 2 broods. Both sexes help build may stop at superabundant food the nest and feed the young, and occa- sources such as landfills, individuals Complaints associated with crow sionally offspring that are 1 or more within the groups typically fly differ- damage to agriculture were more com- years old (nest associates) help with ent routes and make different stops. mon in the 1940s than they are today. nesting activities. The female incubates Other crows appear to be unattached Although surveys indicate that overall the eggs and is fed during incubation and without specific daily activity cen- crow numbers have not changed by the male and nest associates. The ters or stable groups. Although they appreciably, the populations appear to young leave the nest at about 5 weeks use the same roosts as the activity-cen- be more scattered during much of the of age and forage with their parents ter crows, these unattached birds, pos- year. This change has resulted appar- throughout the summer. Later in the sibly migrants, are not faithful to any ently from the crows’ response to year, the family may join other groups specific location or territory and more changing land-use patterns. Farming that in turn may join still larger regularly feed at sites such as landfills. has become more prevalent in some groups. The larger groups often areas, generally with larger fields. migrate in late fall or winter. Ongoing changes in land-use patterns Woodland areas are generally smaller, may result in associated impacts on Few crows in the wild live more than 4 and trees and other resources in urban crow populations and behavior. His- to 6 years, but some have lived to 14 sites provide crow habitat. Overall, the torically, crow populations have ben- years in the wild and over 20 years in amount and degree of damage is efited from agricultural development captivity. Recently, a bird bander highly variable from place to place and because of grains available as a food reported a crow that had lived an year to year. Several variables enter supply and because trees became incredible 29 years in the wild. Adult into the complex picture of crow dam- established in prairie areas where agri- crows have few predators, although age, including season, local weather, culture and settlement suppressed larger hawks and owls and occasion- time of harvest, amount of crop pro- natural fires. The combination of food ally canids take some. Brood losses duction, and availability and distribu- and tree availability favored crows, result from a variety of factors includ- tion of wild mast, insects, and other and in some areas with abundant food ing predation by raccoons (Procyon foods. and available roost sites, large winter lotor), great-horned owls (Bubo roosting concentrations became estab- Although crows cause a variety of virginianus), and other predators; lished. As the current trend toward damage problems, many of these are starvation; and adverse weather. sustainable agricultural systems con- more commonly associated with other One important and spectacular aspect tinues, which may include a variety of animal species. Crows may damage of crow behavior is their congregation crops and rotations with nongrain seedling corn plants by pulling the into huge flocks in fall and winter. crops, food availability and associated sprouts and consuming the kernels. Large flocks are the result of many patterns of crow roosts may change. Similar damage may also be caused by small flocks gradually assembling as other birds (pheasants, starlings, black- The growing number of crows that the season progresses, with the largest birds) and rodents (mice, ground nest and roost in urban areas also concentration occurring in late winter. squirrels). Crows at times damage rip- raises questions. Are urban habitats The Fort Cobb area in Oklahoma, a ening corn during the milk and dough now selected because of adaptive communal roost site, holds several stages of development. Such damage, changes in crow behavior, or are million crows each winter. In however, is more commonly caused changes in rural settings making urban Nebraska, Wisconsin, and possibly by blackbirds; for further information, sites comparably more suitable? One other states, crows appear to be roost- see Blackbirds. Crows consume pea- study described two neighboring but ing more commonly in towns near nuts when they are windrowed in distinct crow nesting populations — people, resulting in mixed opinions on fields to dry, but other birds, especially one that was urban and somewhat ha- how to deal with them. These flocks grackles, cause the greatest portion of bituated to people and another that roost together at night and disperse this damage. Crows may also damage

E-35 other crops, including ripening grain factors that increase the potential for Lines. Another excluding or repelling sorghum, commercial sunflowers, crows to spread this devastating dis- technique used historically to protect pecans, various fruits, and water- ease. Also, crow and other bird (black- fields from crows is stretching cord or melons. In rare situations, crows may bird, starling) roosts that have been in fine wire at intervals across the field at attack very young calves, pigs, goats, place for several years may harbor the heights about 6 to 8 feet (1.8 to 2.4 m) and lambs, particularly during or fungus (Histoplasma capsulatum) that above the ground. Sometimes alumi- shortly after birth. This problem, causes histoplasmosis, a disease that num or cloth strips or aluminum pie which is more often associated with can infect people who breathe in pans were tied to the wires. More magpies or ravens, is most likely to spores when a roost is disturbed. recently, the concept of stretching happen where livestock births occur in widely spaced lines or wires over or unprotected open fields near large Legal Status around sites needing protection from concentrations of crows. certain birds has received increased Crows are protected by the Migratory attention. Crows were included in two Another complaint about crows is that Bird Treaty Act, a federal act resulting studies at sanitary landfills, but results they consume the eggs and sometimes from a formal treaty signed by the were somewhat conflicting. One report the young of waterfowl, pheasants, United States, Canada, and Mexico. from South Carolina indicated that a and other birds during the nesting sea- However, under this act, crows may 20 x 20-foot (6 x 6-m) wire grid son. Overall, such crow depredation be controlled without a federal permit repelled crows, but another from New probably has little effect on the num- when found “committing or about to York indicated that parallel wires bers of these birds. However, it can be commit depredations upon ornamen- stretched 10 x 10 feet (3 x 3 m) apart a problem of concern locally, particu- tal or shade trees, agricultural crops, and 80 x 80 feet (24 x 24 m) above the larly where breeding waterfowl are livestock, or wildlife, or when concen- ground did not repel them. concentrated and where there is too trated in such numbers and manner to little habitat cover to conceal nests. For constitute a health hazard or other The reason this technique has worked example, nests are more easily found nuisance.” for certain birds is not completely by crows, as well as by other preda- clear, but the wires appear to represent tors, when located in a narrow fence States may require permits to control an obstacle that is difficult for a flying row or at the edge of a prairie pothole crows and may regulate the method of bird to see, especially when rapid that has little surrounding cover. take. Federal guidelines permit states escape may be necessary. Various spe- to establish hunting seasons for crows. cies respond differently to lines, and Large fall and winter crow roosts During these seasons, crows may be generally adult birds are more repelled cause serious problems in some areas, hunted according to the regulations by lines than juveniles. Other factors particularly when located in towns or established in each state. Regulations such as season and/or biological activ- other sites near people. Such roosts are or interpretation of depredation rules ity of the birds, type of lines or wires, objectionable because of the odor of may vary among states, and state or spacing, and height need further the bird droppings, health concerns, local laws may prohibit certain control research and development to better noise, and damage to trees in the roost. techniques such as shooting or trap- understand the potential usefulness of In addition, crows flying out from ping. Check with local wildlife officials lines in bird management. roosts each day to feed may cause if there is any doubt regarding legality agricultural or other damage prob- of control methods. Cultural Methods lems. On the other hand, the diet of crows may be beneficial to agriculture, Damage Prevention and Agricultural Crops. Some reports depending on the time of year and sur- indicate that providing an alternate or rounding land use (see sections on Control Methods decoy food source will reduce crop crow food habits and economics). damage caused by crows. An example Exclusion would be scattering a grain such as Finally, in some situations, large crow Exclusion generally is not practical for whole corn, preferably softened by flocks may become a factor in spread- most crow problems, but might be water, through a field where crows are ing disease. At times, they feed in and useful in some situations. For example, damaging newly planted corn seed- around farm buildings, where they nylon or plastic netting might be useful lings. Although this technique has have been implicated in the spread of in excluding crows from high-value been reported to be helpful in some transmissible gastroenteritis (TGE) crops or small areas. Protect ripening situations, it has not been well tested. among swine facilities. At other times, corn in small gardens from crow or large crow flocks near wetland areas Tree Roosts. Thinning branches from other bird damage by placing a paper may increase the potential for spread specific roost trees or thinning trees cup or sack over each ear after the silk of waterfowl diseases such as avian from dense groves reduces the avail- has turned brown. The dried brown cholera. The scavenging habits of ability of perch sites and opens the silk indicates that the ear has been pol- crows and the apparent longer incuba- trees to weather effects. Such vegeta- linated by the corn tassels, a necessary tion time of the disease in crows are tion management has effectively step in corn grain development.

E-36 dispersed starling/blackbird roosts, situations. Hanging mylar tape in roost Pesticide and chemical frightening and the same biological concepts indi- trees may be helpful in urban areas. A agent, available in a whole-corn bait cate probable effectiveness in dispers- combination of several scare tech- formulation (Double Strength Whole ing crow roosts. When roosts occur in niques used together works better than Corn) for use in dispersing crows. It is a small number of landscape trees near a single technique used alone. Vary the only for sale to certified applicators or homes or along streets, they usually location, intensity, and types of scare persons under their direct supervision are in fairly dense trees where thinning devices to improve their effectiveness. and only for those uses covered by the the branches will reduce the trees’ at- Supplement frightening techniques applicator’s certification. tractiveness as roosts. Roosts in tree with shotguns, where permitted, to Avitrol® baits contain a small number groves or woodlots usually occur in improve their effectiveness in dispers- of treated grains mixed with many dense stands of young trees. Thinning ing crows. Ultrasonic (high frequency, others that are untreated. Birds that eat about one-third of the trees improves above 20 kHz) sounds are not effective the treated portion of the bait behave the tree stand, especially if marked by in frightening crows and most other erratically and/or give warning cries a professional forester. Such thinning birds because, like humans, they do that frighten other birds from the area. successfully dispersed blackbird/star- not hear these sounds. For a more Generally, birds that eat the treated ling roosts from research woodlots in detailed discussion of frightening tech- particles die. Overall, because of the Ohio and Kentucky, and from at least niques, see Bird Dispersal Tech- type of damage problems associated two problem roost sites in Nebraska. niques. with crows, Avitrol® is unlikely to be In dense cedar thickets, bulldozing Animated “crow-killing” owl models used often. This product is included strips through the roost site to remove can frighten crows from gardens and here, however, because situations may one-third of the habitat has also been small fields. These are made from a arise in which its use would be helpful. successful in dispersing birds, but soil plastic owl model with a crow model Before using this product for crow disturbance with this method may be attached in such a way that the crow control, it is best to contact a qualified hazardous if soils harbor fungal spores appears to be in the owl’s talons. person trained in bird control work of the human respiratory disease Movement is supplied by mounting (someone from the Cooperative Exten- histoplasmosis. For further informa- the model on a weather vane and by sion or USDA-APHIS-Animal Damage tion on roost dispersal, see Bird Dis- adding wind- or battery-powered Control, for example) for technical persal Techniques. wings to the crow. assistance. For additional information on Avitrol®, see Blackbirds and Euro- Frightening Clapper devices (Tomko Timer- pean Starlings. Frightening is effective in dispersing Clapper) have been reported by the crows from roosts, some crops, and Nebraska Game and Parks Commis- Repellents other troublesome sites. In a recent sion as successful in dispersing crows No repellents are registered for crow study in California, crows were suc- from waterfowl concentration areas control. Recent studies show that con- cessfully dispersed from urban crow where crow roosting was destroying a ditioned aversion learning, a form of roosts using tape-recorded “squalling” multiple-row shelterbelt and where repellency, can reduce egg and possi- calls (given by a crow struggling to es- there was concern that crows were bly fruit and grain crop depredation cape from a predator) and a portable aggravating the spread of avian chol- by crows. Further work and registra- tape player commonly used by hunters era. A clapper device intermittently tion of an appropriate agent for pro- to attract animals. Such dispersal “claps,” producing a sound much like ducing a conditioned aversion allows crows to be moved from prob- a twig snapping or like two boards response are needed. lem sites to sites where they are less clapping together. The device can be likely to interfere with people. placed up in trees or at other sites close to crow perches, making it perhaps Toxicants In addition to recorded distress or more significant to crows as a frighten- No toxicants are registered for crow alarm calls, frightening devices include ing device. Clappers have also been control. Special Local Needs 24(c) gas-operated exploders, battery- used to frighten and disperse other registrations have been sought for operated alarms, pyrotechnics, (shell- birds (starlings, grackles, swallows) DRC-1339 (3-chloro p-toluidine hydro- crackers, bird bombs), chemical and to repel deer at night. Like many chloride) by USDA-APHIS-ADC for frightening agents (see Avitrol® other frightening techniques, clappers limited, small-scale use. below), lights (for roosting sites at appear to be most effective with wary night), bright objects, clapper devices, populations. Populations that have Trapping and various other noisemakers. Beat- habituated to people or disturbance to ing on tin sheets or barrels with clubs such an extent that they have lost their Trapping is often less attractive than can help in scaring birds. Spraying wariness, may not respond. other techniques because of the wide- birds as they land, with water from a ranging movements of crows, the time Avitrol®. hose or from sprinklers mounted in Avitrol® (active ingredient: necessary to maintain and manage the roost trees, has helped in some 4-aminopyridine) is a Restricted Use traps, and the number of crows that

E-37 can be captured compared to the total number in the area. Trapping and removing crows, however, can be a successful method of control at loca- tions where a small resident popula- tion is causing damage or where other techniques cannot be used. Examples include trapping damage-causing crows near a high-value crop or in an area where nesting waterfowl are highly concentrated. Two types of traps can be used to successfully capture crows. First, individual crows may be captured uninjured with No. 0 or No. 1 steel traps that have the jaws wrapped with cloth or rubber. These sets are most successful if placed at vantage points in areas habitually used by crows or if baited with a dummy nest containing a few eggs. Check such traps at least a twice daily. Crows captured in this way might be used, if necessary, as ini- tial decoys in the Australian crow trap 16" described below, but the small number of captures is otherwise unlikely to affect a damage situation. A second and more commonly used trap for crows is the Australian Crow 2' Trap (Fig. 2), a type of decoy trap. These traps are most successful if used during the winter when food is scarce. Australian crow traps should be at b least 8 to 10 feet (2.4 to 3 m) square and 5 to 6 feet (1.5 to 1.8 m) high. If 10' desired, construct the sides and top in panels to facilitate transportation and storage. Place the trap where crows are likely to congregate. The most attractive bait is meat (such as slaugh- c 6" terhouse offal, small animal carcasses) or eggs. Whole kernel corn, milo heads, watermelon, and poultry feed 10' may also work and may be preferred where carnivores such as feral dogs might be attracted to the trap. Place Fig. 2. Australian crow trap: (a) completed trap, (b) end view, and (c) plan of “ladder” opening. the bait under the ladder portion of the trap. Also provide water. After the first baiting, the trap should not be vis- ited for 24 hours. Once the birds begin to enter the trap, it should be cared for daily. Replace the bait as soon as it loses its fresh appearance. Remove all crows captured except for about five to be left in the trap as decoys. Remove captured crows after sunset when they are calm (to facilitate handling).

E-38 Should any nontarget birds be cap- Crow hunting during open season can near people appear to be increasing. tured, release them unharmed imme- be encouraged in areas where crows Individuals experiencing damage diately. Euthanize captured crows cause problems. The helpfulness of problems should weigh the costs of humanely by carbon dioxide exposure hunting as a control technique varies control against the amount of damage, or cervical dislocation. A well-main- depending on crow movements, the then work with the proper authorities tained decoy trap can capture a num- season in which the damage occurs, to develop a control program. ber of crows each day, depending on and other factors. Another consider- On the beneficial side, the crow diet in- its size and location, the time of year, ation is that crows tend to be more cludes large numbers of insects consid- and how well the trap is maintained. wary of people when they are hunted ered harmful to agriculture, as well as and thus more easily dispersed from A recent study in Israel of hooded mice and carrion. In addition, their roosting or other areas where their crows (Corvus corone), which are about consumption of waste grain left in presence is a problem. Further study is the same size as American crows, indi- fields may help prevent undesirable needed to better understand the rela- cated that decoy crows were more volunteer corn in the following year’s tionships between hunting and important than bait to trap success. crop. The fact that crows also eat wariness, and whether a pattern exists Using one hooded crow decoy bird, snakes may be considered a benefit by that might be used to improve crow however, appeared to be as effective as some people. management programs. using three to four, and fleshy baits Overall, crow and other bird problems did increase success in some cases. To can be difficult or frustrating to resolve prevent hooded crow escape, the lad- Economics of Damage satisfactorily with the methods and der gap width of the American model and Control understanding currently available. was reduced from 18 to 12 inches (45 Persistence and use of a variety of to 30 cm), and 1.5 x 0.8-inch (4 x 2-cm) The economics of crow damage often techniques may be necessary to help square rungs were used instead of center around a widespread contro- prevent damage. In addition, further 3-inch (8-cm) diameter metal rods. The versy over whether crow feeding research is needed to develop damage potential response of American crows habits are harmful or beneficial. Some control methods based on an under- to such trap modifications is unknown say that crows earn their keep by tak- standing of bird problems in relation but merits study. ing harmful insects and cleaning up carrion. Others say the damage done to agricultural and urban landscapes Shooting and Hunting far outweighs any beneficial aspects. and other natural resource systems Despite some studies of the crow diet, where damage occurs. Shooting is more effective as a disper- little quantitative information is avail- sal technique than as a way to reduce able on the overall economic impacts crow numbers. Crows are wary and Acknowledgments of crows. In addition, it appears likely thus difficult to shoot during daylight that the economics of crows in relation hours. They may be attracted to a con- The references listed under “For Additional to agriculture or people have changed Information” and many others were used in cealed shooter, however, by using from what they were 30 or more years preparing this chapter. Gratitude is extended to crow decoys or calls, or by placing an ago when many crow studies were the authors and the many researchers and owl effigy in a conspicuous location. observers who contributed to this body of done. Generally, the number of crows killed knowledge. I extend special appreciation to R. W. Altman, retired Oklahoma State University by shooting is very small in relation to At one time several state legislatures extension wildlife specialist, for his contribu- the numbers involved in pest situa- appropriated funds for bounties on tions as co-author of the first edition of this tions. However, shooting can be a crows and for bombing crow roosts, chapter. I also thank M. M. Beck, R. M. Case, R. helpful technique to supplement and and suggested all-out efforts to eradi- Kelly, and R. Ross for comments and helpful advice on the first edition; J. Andelt provided reinforce other dispersal techniques cate the crow. Now, most state wildlife typing and technical assistance. I gratefully when the goal is to frighten and dis- and agriculture departments report acknowledge M. M. Beck, C. S. Brown, R. M. perse crows rather than specifically to only a few scattered complaints of Case, and R. L. Knight for valuable reviews of reduce numbers. For more details on crow damage each year. At times, this second edition. dispersal, see Bird Dispersal however, individual farms or crops do Figure 1 by Emily Oseas Routman, University of Techniques. suffer severe damage, and concerns Nebraska-Lincoln. about large crow roosts in urban areas Figure 2 from E. R. Kalmbach (1939).

E-39 For Additional Houston, C. S. 1977. Changing patterns of Pochop, P. A., R. J. Johnson, D. A. Agüero, and Corvidae on the prairies. Blue Jay K. M. Eskridge. 1990. The status of lines in Information 35:149-155. bird control — a review. Proc. Verteb. Pest Conf. 14:317-324. Ignatiuk, J. B., and R. G. Clark. 1991. Breeding Arvin, J., J. Arvin, C. Cottam, and G. Unland. biology of American crows in Saskatchewan Schorger, A. W. 1941. The crow and the raven in 1975. Mexican crow invades south Texas. parkland habitat. Can. J. Zool. 69:168-175. early Wisconsin. Wilson Bull. 53:103-106. Auk 92:387-390. Johnsgard, P. A. 1979. Birds of the Great Plains, Stouffer P. C., and D. F. Caccamise. 1991. Bent, A. C. 1964. Life histories of North breeding species and their distribution. Capturing American crows using alpha- American jays, crows and titmice. Dover Univ. Nebraska Press, Lincoln. 539 pp. chloralose. J. Field Ornithol. 62:450-453. Pub., Inc., New York. 495 pp. Kalmbach, E. R. 1937. Crow-waterfowl Stouffer P. C., and D. F. Caccamise. 1991. Chamberlain-Auger, J. A., P. J. Auger, and E. G. relationships. US Dep. Agric., Cir. 433, Roosting and diurnal movements of radio- Strauss. 1990. Breeding biology of American Washington, DC. 36 pp. tagged American crows. Wilson Bull. crows. Wilson Bull. 102:615-622. 103:387-400. Kalmbach, E. R. 1939. The crow in its relation to Conover, M. R. 1985. Protecting vegetables from agriculture. US Dep. Agric., Farmer’s Bull. Sullivan, B. D., and J. J. Dinsmore. 1990. Factors crows using an animated crow-killing owl No. 1102, rev. ed. Washington, DC. 21 pp. affecting egg predation by American crows. model. J. Wildl. Manage. 49:643-645. J. Wildl. Manage. 54:433-437. Kilham, L. 1989. The American crow and the Dimmick, C. R., and L. K. Nicolaus. 1990. common raven. Texas A&M Univ. Press, Terres, J. K. 1980. The Audubon Society Efficiency of conditioned aversion in College Station. 255 pp. encyclopedia of North American birds. reducing depredation by crows. J. Appl. Alfred A. Knopf, Inc., New York. 1109 pp. Ecol. 27:200-209. Knight, R. L., D. J. Grout, and S. A. Temple. 1987. Nest-defense behavior of the American crow Weeks, R. J. 1984. Histoplasmosis, sources of Good, E.E. 1952. The life history of the American in urban and rural areas. Condor 89:175-177. infection and methods of control. US Dep. crow, Corvus brachyrhynchos Brehm. Ph.D. Health Human Serv., Public Health Serv., Diss., The Ohio State Univ., Columbus. Knopf, F. L., and B. A. Knopf. 1983. Flocking Centers for Disease Control, Atlanta, 203 pp. pattern of foraging American crows in Georgia. 8 pp. Oklahoma. Wilson Bull. 95:153-155. Goodwin, D. 1976. Crows of the world. Yahner, R. H., and A. L. Wright. 1985. Comstock Publ. Assoc., a div. Cornell Univ. Maccarone, A. D. 1987. Sentinel behaviour in Depredation on artificial ground nests: Press, Ithaca, New York. 354 pp. American Crows. Bird Behav. 7:93-95. effects of edge and plot age. J. Wildl. Manage. 49:508-513. Gorenzel, W. P., and T. P. Salmon. 1993. Martin, A. C., H. S. Zim, and A. L. Nelson. 1951. Tape-recorded calls disperse American American wildlife and plants, a guide to crows from urban roosts. Wildl. Soc. Bull. wildlife food habits. Dover Publ., Inc., New 21:334-338. York. 500 pp. Friend, M. 1987. Avian cholera. Pages 69-82 in Mott, D. F., J. F. Besser, R. R. West, and J.W. Editors M. Friend, ed. A field guide to wildlife DeGrazio. 1972. Bird damage to peanuts and Scott E. Hygnstrom diseases, Volume 1. General field procedures methods for alleviating the problem. Proc. Robert M. Timm and diseases of migratory birds, US Dep. Verteb. Pest Conf. 5:118-120. Gary E. Larson Inter., Fish Wildl. Serv., Resour. Publ. 167, Moran, S. 1991. Control of hooded crows by Washington, DC. modified Australian traps. Phytoparasitica 19:95-101.

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