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National Research Council (US) Committee on Agricultural Land Use and Wildlife Resources. Land Use and Wildlife Resources. Washington (DC): National Academies Press (US); 1970.

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Land Use and Wildlife Resources.

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CHAPTER 7Wildlife Damage and Control

Just as agriculture and land use have changed tremendously in the United States during the past 100 years, so have attitudes toward wildlife. This has been as true of the scientist as of the general public and the agriculturist. The early premise was simple, i.e., animals were either harmful or beneficial, in varying degrees. The government program, begun in the 1880's by the Division of Economic Ornithology and Mammalogy to determine which birds and mammals were harmful and which were beneficial, concentrated for years upon the food habits of birds and mammals in order to establish their economic relationship to man.

These attitudes naturally were reflected in the legislation of that day. State bird protection laws left unprotected or even provided bounty payments for destroying birds considered harmful, such as the hawks and owls that were known to feed upon smaller birds.

Many factors have contributed to the changing attitude toward wildlife, so that no longer can a species be designated simply as friend or foe. Increasing emphasis on ecology and recognition of many of its principles by the public as well as at the congressional level have been important. At the same time there has been an increasingly widespread interest in conservation and a recognition of the value of preserving our natural environment. The Wilderness Act and the Rare and Endangered Species Act reflect the concern of Congress, and President Nixon has established an official council of environmental advisers to the Executive Office.

As public and official attitudes have changed the pressures upon resources have increased and become more complex. These factors combine and result in a number of situations where wildlife and agriculture are in some degree of conflict.


Predation upon livestock by large carnivores is one of the earliest, most sustained, and most widely recognized types of wildlife damage. As early as the 1600's colonists shot, trapped, and offered bounties for the destruction of wolves and cougar to protect their livestock, so these large predators were eliminated rather early over most of the East. Even in the western states the timber wolf has been exterminated, and the red wolf of the South is considered an endangered species. In several states the cougar and the black bear have now come to be recognized as valued game species, rather than pests. The coyote is the species against which most predator control is now directed. In some situations its depredations upon sheep are unquestioned, but unbiased assessments of the extent of damage are difficult to obtain because many sheepmen tend to attribute most or all of their losses to coyotes. Accurate evaluation of coyote damage is complicated by the animal's carrion-eating habits. It is often difficult to determine whether a fed-upon lamb was dead or moribund from some other causes when the coyote found it. The magnitude of the coyote control program is indicated in the Leopold report (1964), which shows that in the federal and cooperative predator control program nearly 90,000 coyotes were taken in one recent year, out of a total of 190,763 predators of all kinds.

Another species widely accused of predation upon lambs is the golden eagle, especially in Texas and New Mexico. After World War II literally thousands of these raptors were killed, largely by private gunners in aircraft. Federal protection was accorded the golden eagle in 1962, but the law provides that governors of states where ranchers could show evidence of eagle predation upon livestock, preimarily young sheep and goats, can obtain permission from the Secretary of the Interior for the ranchers to shoot and trap the birds (but not to hunt them from airplanes or to employ poisons).

The economic effects of golden eagles are being studies by biologists from several agencies. Most recently the National Audubon Society, the National Wool Growers Association, and the Department of the Interior have sponsored a study by Texas Technological College, on the basis of which the subject of golden eagle regulation is being evaluated by the Department. However, more information is still needed on the economics of the golden eagle, and studies should continue.


Birds may often cause severe damage to fruit or agricultural crops, and for several reasons the incidence of damage seems to be increasing. The nature of modern agriculture, with its emphasis upon monoculture and highly specialized crops, and the high cost of bringing the crop to the harvesting stage, when bird damage usually occurs, are among the factors involved.

Accurate estimates of the value of fruit or grain destroyed by birds are extremely difficult to obtain. Numerous field surveys have been made; among the most convincing are those involving ducks and small grain in the Canadian Prairie Provinces and California, blackbirds and rice in Arkansas, and blackbirds and corn in Ohio and several other states.

Losses of grain in Canada have become so serious that major efforts have been made to alleviate them. Devices of various kinds to frighten the birds, and spreading grain near the marshes to lure the birds from the unharvested grainfields, are two methods that have been used. Both are cumbersome and expensive, and they are not always effective.

Another program, inspired by the success of crop insurance against losses from hailstorms and similar “acts of God,” was initiated by Saskatchewan in 1953 and by Alberta in 1961. Paynter (1966) summarized the experience of the first 13 years of the Crop Depredations Insurance program in Saskatchewan, showing that 4,395 farmers had been insured for liabilities totaling $9,557,828. They paid insurance premiums of 2 percent (over $180,000), and claims that totaled more than $745,000 were paid. Claim payments beyond those covered by the 2-percent premiums are covered by a $1 surcharge on each hunting license sold in the province.

The insurance plan alone, however, cannot be considered completely successful in Canada. Many farmers feel they should not be required to pay any premium to defend their interests against legally protected birds, and such a high proportion of those insured are being paid claims for damage that the fund appears likely to be inadequate.

Although waterfowl depredations upon grain in the Dakotas, Minnesota, and Nebraska have been estimated at hundreds of thousands of dollars in some years, the Canadian insurance plan, though considered, has not actually been tried in the United States.

Jahn (1969), in an excellent review of crop depredations by migratory birds, has pointed out that in some counties of the United States the all-risk crop insurance available through the Federal Crop Insurance Corporation of the U.S. Department of Agriculture includes losses to bird depredations among the items eligible for payment. The arrangement is different from that in Canada, since the policy guarantees a specified number of bushels per acre and quality of crop harvested. The number of farmers taking out the all-risk crop insurance has increased since 1937, when it was first made available, so that in 1968 nearly a third of a million farmers insured almost 20 million acres of crops. However, the losses due to wildlife depredations are so minor compared to those from drought, excessive rainfall, hail, insects, and similar causes, that they are included only among the “other causes” that comprise 5 percent of the total.

Farmes (1969) reports that an interagency team, after evaluating waterfowl crop depredations in Minnesota, concluded that with appropriate changes the federal crop insurance program might be more effective in handling losses caused by waterfowl, and that the Federal Crop Insurance Corporation has the staff and experience to deal with a wildlife insurance program.

In California, damage to rice and other small grains by waterfowl has been reduced through a combination of several management procedures. Plantings of waterfowl foods on areas purchased especially for this purpose attract ducks from nearby commercial crops. Improvements in rice-farming practices have also been aided by creating more continuous stands and reducing openings, which are expecially attractive to ducks. Finally, state and federal officials have developed with farmers a “self-help” crop protection program that includes bird harassment and the use of fright devices.

Depredations by several kinds of blackbirds upon rice, especially in Arkansas (Neff and Meanley, 1957), and upon corn in several states in the eastern half of the country are still exceedingly serious and, despite a long-term research program, the problems remain unsolved. Only a few examples of the many other situations in which birds or mammals cause damage to fruit or agricultural crops can be included here.

Lesser sandhill cranes, strictly protected since the Migratory Bird Treaty Act of 1918, have been reported in several western states to cause damage to sorghum, alfalfa, winter wheat, and peanuts. Experimental hunting seasons, in strictly limited areas in New Mexico and Texas, were initiated in 1961, and complaints of damage have decreased. This suggests that the institution of hunting seasons has provided successful control.

In Maine, blueberries are a multimillion-dollar crop on 80,000 acres, and depredations on the ripening fruit by gulls are estimated by specialists at the University of Maine at 2 percent of the crop annually. The total damage appears small, but individual growers may lose the greater part of their crop in a single day.

In California several specialized crops are damaged by legally protected birds of many kinds. Horned larks destroy lettuce; linnets (local name in California for house finch) eat the buds of apricot and almond trees; band-tailed pigeons damage several orchard and truck crops; and coots feed upon hay and truck garden produce.

The problems of bird conflicts with crops are so numerous, complex, and varied that no one solution can be expected. Some effective control measures have been developed, but many more are needed, adaptable to the peculiarities of the problem faced. Nonlethal methods are particularly appropriate, for many of the birds that cause trouble in one situation are valued in others. Where lethal methods are deemed necessary, it is important that they be specific, or selective, so that they will not needlessly destroy nontarget species or have a long-lasting effect upon the environment as do so many of the pesticides now commonly employed.


Damage to the forest by wildlife is widely scattered and usually attracts little attention. Perhaps the commonest effect is upon tree reproduction, because a large number of birds and mammals feed upon tree seeds (Smith and Aldous, 1947). Both artificially seeded and natural forest reproduction have been severely damaged by a variety of small mammals, particularly mice, chipmunks, and squirrels. Areas cleared through logging or fire are particularly vulnerable to wildlife damage during the stage of reseeding and growth of seedlings and saplings, because many species of wildlife are attracted into the openings (Kverno, 1964).

Two other types of damage widespread in the forest are clipping and browsing of timber species by big game, rabbits and hares, and others; and the bark and root damage caused by rodents, such as pocket gophers, mice, and porcupines.

Deer, elk, and other ungulates have frequently become so numerous that their feeding has caused severe damage to forests, especially to seedlings and saplings. In most areas, however, population control is now being achieved through regulated hunting and this type of damage is far less widespread than in the past.

Studies of the effect of rabbit and rodent activity on range forage have shown that rabbits eat mostly leaf and stem material as do meadow voles (Microtus), pocket gophers (Thomomys, Geomys), and some species of ground squirrels (Citellus); most other rodents eat such foods as seeds and insects and may have a beneficial effect on rangelands.

In north-central Colorado studies have shown that the plant genera Vicia, Lathyrus, and Agoseris are important foods for meadow voles; these plants also are consumed by cattle. Pocket gophers eat some of the same plants as do cattle, and show a high preference for certain grasses (e.g., Stipa comata) at the very season when cattle show similar preference. In a variety of areas pocket gophers, ground squirrels, and jack rabbits all compete to some degree with cattle for food.

It is clear that small mammals consume range forage plants, but to what extent? In some annual grassland areas in the Central Valley of California, jack rabbits commonly reach a population level of one rabbit for every two acres. At this level rabbits would eat approximately 115 pounds of air-dry herbage per acre per year. In the same areas pocket gophers occur regularly at population densities of approximately 10 per acre; at this level they would eat about 220 pounds of air-dry herbage per acre per year. The aggregate consumption of these small mammals—about 330 pounds per acre per year—is about a third of the total allowable annual forage utilization.

In the subalpine parklands of the Rocky Mountains the two small mammals of greatest importance as consumers of vegetation are the northern pocket gopher (Thomomys talpoides) and the montane vole (Microtus montanus). In studies made in the summer of 1965 in Colorado, these rodents occurred at population levels of about 20 and 8 animals per acre, respectively. In such numbers, they would consume about 460 pounds of air-dry herbage per acre per year, or approximately one quarter of the yearly herbage production.

Not all of the vegetation eaten by these rodents is suitable for livestock forage and it is likely that their most important effect is not from consumption of herbage, but from their burrowing, mound building, and food storage activities. Jameson (1958) has estimated that the California vole destroys as much vegetation through these activities as in its food consumption. Fitch and Bentley (1949), in their work on the rodents of a California annual grassland, showed that they ate but 10 percent of the vegetation they destroyed. In a 1966 study of subalpine rangeland in north-central Colorado, about 22 percent of the ground was found to be covered with soil brought to the surface during winter or spring by pocket gophers, and only a few plants were able to establish themselves on the fresh workings.

The total ecological impact of rodents on rangelands is clearly the result of a variety of factors. Both native and domestic animals affect vegetation; it is of primary importance to determine precisely what these effects are and how they are brought about. A final and more difficult step is to develop management practices that maintain a vegetational complex such that there will be minimum rodent and rabbit damage and maximum forage for livestock and game animals.


Wild birds and mammals act as carriers or reservoirs for certain diseases of man and domestic animals. A few of these, such as rabies, are of great economic importance, but the majority are local or temporary and do not usually result in control demands of any magnitude.

In certain urban and industrial situations, however, birds have become serious pests and have created unusually difficult control problems. Best known are starling and pigeon roosts on buildings or the roosting in city shade trees of tremendous aggregations of starlings and other birds. A variety of control methods are partially successful, but most are awkward, expensive, and ineffective.

Perhaps the most spectacular conflict between birds and man involves the bird-airplane problem, which was brought dramatically to public attention in 1960 when a jet plane crashed at Logan International Airport, Boston, killing a number of persons. In this instance a flock of starlings was sucked into the jet engines.

In Canada one commercial airline (Air Canada) has maintained records of strikes with birds and costs of repairing the damage. Strike rates are highest during the spring and fall bird migrations, and the greatest annual damage was $350,000, sustained in 1961. Since then the damage and costs have declined as a result of habitat modification and other measures to disperse birds from the vicinity of the airports.

In the United States, records appear to be less accurate, but at 28 of the nation's busiest commercial airports from 1962 through 1966, approximately 1,000 bird strikes were recorded. In 1965 the U.S. Air Force recorded 839 strikes, necessitating 75 engine replacements at a cost of four to five million dollars (Seubert and Solman, 1968; U.S. Air Force, 1966).

More accurate data must be obtained as a basis for remedial action, but the one simple fact that has come through most clearly is that habitat conditions particularly attractive to birds cannot be tolerated in the immediate vicinity of jet airports.


Predators and rodents have positive values as well as the negative ones discussed above. This, in fact, was the first tenet of the Leopold report (Discussed later in this chapter) and it underscores the expressed policy of the Department of the Interior that control measures when instituted must be specific and selective and must avoid destroying the innocent individuals with the guilty.

The American public, as it has become more affluent with more leisure time for recreation, has developed a stronger and more sophisticated interest in nature and the out-of-doors. This interest is expressed in many ways. While the number of hunters and fishermen continues to grow, the number of people interested in the “nonconsumptive” uses of wildlife has shown a far greater increase. National parks and other nature reserves are used far more than ever; and books, binoculars, and cameras sell as never before to the growing number of birdwatchers and other amateur naturalists.

Not many decades ago, few would have challenged the statement that “the only good coyote is a dead coyote,” but today many thrill to hear or see a coyote. It is a common sight in some of the national parks to see traffic jams where motorists have stopped to enjoy the sight of a coyote hunting. The timber wolf population in Algonquin Provincial Park, only 200 miles from Canada's largest city, is regarded by many as the park's proudest possession, and hundreds have gathered in an evening along the road through the park to hear the wolves respond to recorded howling.

While the value is sometimes intangible and difficult to translate into monetary terms, it is clear that the American public has come to place a high premium on wildlife in general, and particularly upon predatory species that only recently were almost universally condemned as pests and that, in certain situations, must still be controlled to prevent damage. In this context the growing interest in the predators for sport has special significance, especially if their use in sport can aid in necessary control.


The value of large predators for sport has received little attention in the United States, though the contrary is true in northern Europe. Where the Europeans hunted such carnivores for sport, the American tradition was to trap, poison, and bounty them. This attitude was understandable on the frontier, where wildlife was more important for food than for recreation; therefore, deer, turkey, or ducks were far more welcome quarry than a fox. Neither economic nor social conditions in the United States favored a leisure class that could afford the luxury of fox hunting.

In recent years, however, the sporting potential of these predators has become more widely recognized. In its 1965 National Survey of Hunting and Fishing the U.S. Bureau of Sport Fisheries and Wildlife included for the first time a survey of participation in the sport of “varmint hunting,” and came up with a surprising estimate of 2,573,000 participants—more even than had hunted migratory game birds that year. The term “varmint” is loosely used; in the sporting literature it includes many species of commonly unprotected wildlife such as crows, magpies, marmots, and jack rabbits as well as predators, but coyotes and foxes are favored on the long list of “varmints.”

The inconsistencies even in adjacent states indicate clearly how our traditions relating to these predators are changing. The mountain lion, for example, is a game animal in Colorado and hunting it requires a special license. In Arizona and South Dakota a bounty is paid on it, and in seven western states it is unprotected. In 1967, Oregon declared the cougar a game animal and provided a year-round closed season pending study to determine if its population was sufficient to merit a hunting season. The previous year eight counties in Oregon had offered a bounty on the cougar.

Although the coyote is a prime target of state and federal predator control programs, it is increasingly a favorite of sportsmen, who have a variety of hunting methods from which to select. “Calling” coyotes is remarkably successful, permitting even close-up photography at times. The use of trained hounds, particularly greyhounds, is not uncommon in the western plains states.

The growing popularity of coyote hunting for sport is indicated in western states by the existence of such groups as the Arizona Varmint Callers Association, which reports seven clubs with a paid membership of 550. California, Colorado, Nevada, and New Mexico report similar clubs and a growing interest in this sport.

In New York State in 1964 and 1965 an attempt was made to coordinate predator hunting with control when the statewide raccoon hunters' organization, as part of its effort to keep the raccoon a legally protected game animal, offered the services of its members in the control of any raccoons causing damage to corn or garden crops. Properly organized, this type of cooperation could accomplish needed control where animals are doing damage, and at the same time provide recreation.

As the recreational value of hunting certain predators becomes more widely recognized, this sport might well replace some of the expensive control efforts. It should be emphasized, however, that the hunting of what are not ordinarily considered to be game animals should be done only when such animals are sufficiently abundant to sustain an annual kill without hazard to their populations or ecological values. Examples of such abundant and successful species, in much of their range, are the woodchuck, crow, coyote, and raccoon. In states where it is still to be found, the status of the cougar should be guarded to make certain that is not overhunted.


Control of predators and rodents by the federal government, in response to state and local requests, is a well-established activity that had its beginnings in the Bureau of Biological Survey, U.S. Department of Agriculture. The Bureau began conducting experiments in control methods for predators in 1909, and for range rodents in 1914. In 1915 Congress appropriated funds to control predatory animals that were killing livestock and transmitting rabies. Since then the activity has grown until in 1964-65 the cost of these programs was nearly $7 million, of which about a third was federal funds. This federal activity was invariably in response to requests by states, lesser divisions of government, and in some cases private organizations; these private organizations provided substantial contributions to the work.

In some areas efforts have been made to provide educational programs on the control of rodents and predators, particularly through established extension agencies. In eastern states the Fish and Wildlife Service developed extension services for landowners and others who needed rodent control, and some of the states employed extension specialists who had as one of their duties the development of educational programs relating to rodent control. In the fruit-growing areas of several eastern states, particularly New York and Virginia, mice and rabbits are a considerable threat to fruit trees; here the states have been active in both research and extension to prevent losses to the orchards.

The concept of having either the state or federal government provide the landowner with information on methods he himself can use to protect his crops, instead of furnishing actual control services, is similar to policies and practices related to disease and insect control. In Kansas and Missouri, state extension specialists in predator control have been operating since before 1950.

There are compelling reasons for continuing the federal control program in some areas. In western states federal land is intermingled with private holdings, and ranchers graze their stock under permit on public lands. Thus animal damage control traditionally has been regarded as a federal responsibility. The lands on which control is practiced are extensive, and the methods used often are potentially dangerous to other animals and man. Given these conditions it is argued that control by professionals is more likely to meet acceptable standards of safety and effectiveness than that by the owners of livestock or other property. The fact that animal control left to nonfederal agencies has often employed the outmoded and inefficient bounty system is a case in point.

The administration of control programs and the setting of control policies face inherent difficulties. Until recently the Fish and Wildlife Service carried on predator and rodent abatement operations where field workers and supervisors judged them to be needed. Criteria for deciding when and where operations were desirable or necessary were not clearly established, and decisions too often reflected the personal ideas and biases of individuals. Under these conditions, and with two thirds of the funds coming from stockmen's associations and local levies, a steadily expanding and not highly discriminating program against predators and range rodents was carried on. The Service was under long-standing demand from both scientists and laymen to increase the objectivity of its methods for determining control needs and to adjust field activities accordingly.

Predator control problems and policies have been reviewed by a number of writers. A few recent representative publications include those of Allen (1963), Balser (1964), Berryman (1966), Hall (1966), U.S. Congress (1966), and Gottschalk (1967).

As a result of the concern at highest levels of government that public programs involving wildlife damage and control be in tune with modern thinking, an important study was conducted dealing specifically with these problems.

The Leopold Report

The so-called Leopold report (Leopold, 1964) on predator and rodent control in the United States was written at the request of then Secretary of the Interior Stewart L. Udall. The board of five that produced this report after a period of intensive study has an impressive record of experience in the biological sciences and in public service in wildlife management, and their conclusions and recommendations have been widely accepted.

Two basic assumptions adopted by the board were that:


All native animals are resources of inherent interest and value to the people of the United States. Basic governmental policy therefore should be one of husbandry of all forms of wildlife.


At the same time, local population control is an essential part of a management policy, where a species is causing significant damage to other resources or crops, or where it endangers human health or safety. Control should be limited strictly to the troublesome species, preferably to the troublesome individuals, and in any event to the localities where substantial damage or danger exists.

After its appraisal the board concluded:

It is the unanimous opinion of this Board that control as actually practiced today is considerably in excess of the amount that can be justified in terms of total public interest. As a consequence many animals which have never offended private property owners or public resources values are being killed unnecessarily. The issue is how to sharpen the tools of control so that they hew only where cuts are fully justified.

The board included in its report six recommendations:


Appointment of a continuing advisory board of predator and rodent control which should be widely representative of the livestock and agricultural interests, conservation organizations, and technical organizations. The Leopold board recognized the controversial nature of animal control programs and the need for a “forum for the wide spectrum of opinions” regarding control.


Reassessment of its own goals by the Branch of Predator and Rodent Control of the Fish and Wildlife Service, and a break with the tradition that it “. . . is primarily responsible to livestock and agricultural interests. . . .”


Some specific suggestions for the control program:


Continuation in the West of the system of trained professional hunters as being most effective.


Continuation of the cooperative arrangement under which at least half of the costs are borne by nonfederal sources.


Requirement of more proof and documentation of the need for any local control program, including statistics on the “true extent of the damage.”


Encouragement of extension educational programs wherever feasible (generally the eastern half of the country).


Replacement of bounty systems with extension programs.


Use, in the eastern United States, of “flying squads of federal control agents” where rabies outbreaks or similar temporary situations occur.


An amplified research program, particularly to develop more specific controls, so that innocent animals are not so often the victims, and also to develop repellents and other protective devices that do not involve killing.


Selection of a new name for the Branch of Predator and Rodent Control—one that suggests a broader management function.


Adoption of stricter legal control over the use of poisons, particularly over 1080, which the report states has resulted in much secondary poisoning. Mentioned specifically were the need to guard against the “ecological abuses” of secondary poisoning of nontarget species, and the need to prohibit export to foreign countries where the danger of misuse is high.

Official Acceptance of the Leopold Report

The Leopold report, released to the public on March 9, 1964, at the North American Wildlife and Natural Resources Conference, was accepted officially by Secretary Udall on June 22, 1965, after 15 months of study, as a “general guidepost for Department policy,” but “. . . not as a policy mandate.” However, several tangible results of the report's recommendations have been evident:

On July 1, 1965, the Branch of Predator and Rodent Control became the Division of Wildlife Services, and new leadership and direction were provided. As the name suggests, the Division has far broader responsibilities than did its predecessor. In addition to control activities the Division has responsibility for surveillance and monitoring of pesticides in the environment, and for “wildlife resource enhancement work,” with emphasis upon migratory species; initial efforts are to be concentrated upon Indian, military, and Interior lands (Berryman, 1966).

In May 1967 the Bureau of Sport Fisheries and Wildlife issued a statement of policy for animal damage control (Gottschalk, 1967). In announcing it, Director Gottschalk explained that drafts of the statement had been reviewed by “over 30 conservation organizations and agencies, including representative user groups. . . . The finished product is in accord with the majority of the suggestions made and incorporates much of the basic philosophy . . . of the Leopold Report.”

This official document begins with a significant statement of philosophy that recognizes the esthetic value of wildlife resources. In addition, the statement indicates that the Bureau must cooperate with state game and fish agencies in the conservation of fish and wildlife resources for the use and enjoyment of the entire public, that control measures must remain flexible, that when control is needed it shall recognize fully the ecological relationships involved and must emphasize removal of specific offending individuals wherever and whenever possible.

The statement of policy emphasizes demonstrated need for control, selective control, cooperation with state and federal agencies, advance planning, the use of educational techniques where possible, avoidance of hazard to endangered species of wildlife, and a strong program of research “to find new, improved, selective, and humane methods.”

This official policy is evidence that the Leopold report has been adopted to a very considerable extent. Only two recommendations of the report are not mentioned: the one calling for appointment of a continuing advisory board on predator and rodent control, and the final one urging far stricter legal controls governing the use of poisons, over which the Department of the Interior does not have sole jurisdiction.


The variety and magnitude of wildlife damage to man's crops and property are sufficient to demand more effective controls than are available at present, and research is urgently needed to develop them. Changes in agriculture and land use, and changes in wildlife populations and their behavior, repeatedly bring about new situations where damage by wildlife occurs. Furthermore, public attitudes toward wildlife have changed so much that it is more essential than ever that nonlethal types of control be used wherever feasible.

Federal research on wildlife damage control is being conducted in several key points in the country and many effective methods have been developed. But an accelerated program is needed for the important new problems that regularly arise; also all potential avenues to control must be explored. There is need to maintain close contact with work done on control methods in Europe, where some of the same situations have been faced far longer than in the United States.

Methods of controlling or alleviating damage fall into at least four broad categories, and studies should continue to explore all of them—biological or cultural, mechanical and electronic, chemical, and payment for damages. For each of these categories there are examples of successes in particular situations. All deserve additional study.

The biological or cultural category includes some cases, in California, where waterfowl have been lured from rice fields to areas of food planted especially for them. It also covers situations around airports, where habitats have been modified to reduce their attractiveness to birds. And it might well include the development of crop varieties that are resistant to birds, though little has been accomplished so far with this approach.

The electronic and mechanical category includes various types of scaring devices, the herding or harassing of birds, shooting, and various electronic devices, of which the most successful to date have used recorded alarm or distress calls of gregarious birds. This last technique has been used with considerable success against starlings in vineyards in Germany and France.

Chemical methods have been and are being given much attention. Several classes of chemicals offer possibilities—toxicants, repellents, soporifics or stupifacients, and the antifertility agents that are being considered as a way of holding some animal populations in check.

Payment for damages, as exemplified by the waterfowl depredation crop insurance plan used in Canada, may have applicability to some conditions in the United States. From the summary by Boyd (1963), it appears that state game agencies have had experience with this method, since 10 states were paying landowners for game damage to crops, although the programs in most cases were very limited.


Wildlife damage and nuisance situations may be expected to continue and probably to increase. The development of successful methods of controlling or mitigating damage already offers a challenge to the natural scientist or social scientist who is interested in tackling it. In the past it has been difficult to interest capable young scientists in these problems, because of the somewhat unfavorable public image of the traditional predator and rodent control programs. Those interested in wildlife management usually preferred the role of producing, rather than destroying or controlling, wildlife.

As research in bird and mammal control becomes more sophisticated, and it is more widely recognized that it draws upon many basic sciences—ecology, physiology, behavior, biochemistry, electronics—the art of controlling wildlife damage may be expected to achieve greater stature, attract more research attention, and be more frequently successful.

An example of the attention paid to bird damage and its control in Europe is provided by the discussion at a symposium held in London in 1967 (Murton and Wright, 1968). Sir Landsborough Thomson and Professor V. C. Wynne Edwards, Department of Zoology, University of Aberdeen, two of the most distinguished zoologists in the United Kingdom, acted as chairmen of sessions that reviewed bird problems on a worldwide scale. The latter concluded with remarks that are as valid in the United States as in the United Kingdom:

Given enough knowledge, rational decisions can be taken. But if people blindly take sides on questions of bird control as a matter of principle and insist on forcing the issue one way or the other by trial of strength, the decisions reached must necessarily be political decisions; and they may do quite unnecessary harm or injustice to the least appreciated interests on the other side.

Sir Landsborough Thomson's opening remarks to the session for which he acted as chairman are also pertinent:

It is to be hoped that the title, “Problems of Birds as Pests”, will not lead anyone to think that this symposium has been conceived in a spirit of hostility to bird-life. Most of those taking part are in fact ornithologists or conservationists, or both. The perspective in which the topic should be viewed is that control is an aspect of conservation, requiring study like any other. In an environment where the balance of nature has been greatly disturbed, mankind has a responsibility for wildlife management; this properly includes reasonable defence of human material interests.

Birds are to a large extent economically beneficial; they are also, of course, scientifically interesting and aesthetically delightful. Yet some species tend to be harmful, and others become pests when present in excessive numbers or in the wrong places. The task is, dispassionately and objectively, to determine the facts and consider what to do.

The extent of interest in Europe in these problems also is exemplified by the organization of an international society of economic ornithologists and the appearance of its technical journal Angewandte Ornithologie, which deals with the positive as well as the negative economic impact of birds. It appears that in western Europe the attitudes of the public and of scientists toward wildlife damage and control have matured to a point where constructive discussion and research on the problems proceed more objectively than in the United States. The chief goal, of course, should be alleviation of the damage, rather than destruction of animals.


  • Allen, D. L. 1963. The costly and needless war on predators. Audubon Mag. 65(2): 85-89, 120-121.
  • Balser, D. S. 1964. Management of predator populations with antifertility agents. J. Wildl. Manage. 28(2): 352-358.
  • Berryman, J. H. 1966. Trans. N. Amer. Wildl. and Natur. Resour. Conf. 31: 246-258.
  • Boyd, R. J. 1963. A brief summary of game damage data and forage requirements in the United States. A report to the Colorado Game, Fish and Parks Commission. 14 p. (mimeo.)
  • Farmes, R. E. 1969. Crop insurance for waterfowl depredation. Trans. N. Amer. Wildl. and Natur. Resour. Conf. 34: 332-337.
  • Fitch, H. S., and J. R. Bentley. 1949. Use of California annual-plant forage by range rodents. Ecology 30(3): 306-321.
  • Gottschalk, J. S. 1967. Man and wildlife (a policy for animal damage control). U.S. Department of the Interior, Washington, D.C. 12 p.
  • Hall, R. E. 1966. Carnivores, sheep, and public lands. Trans. N. Amer. Wildl. Conf., 31: 239-245.
  • Jahn, L. R. 1969. Migratory bird crop depredations: A naturalist's views of the problem. Presented at the Migratory Bird Crop Depredation Workshop, University of Maryland, July 15-16, 1969. 32 p . (mimeo.)
  • Jameson, E. W. 1958. Consumption of alfalfa and wild oats by Microtus californicus. J. Wildl. Manage. 22: 433-434.
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  • Murton, R. K., editor; , and E. N. Wright, editor. (ed.). 1968. The problems of birds as pests. Academic Press, New York. 240 p.
  • Neff, J. A., and B. Meanley. 1957. Blackbirds and the Arkansas rice crop. Agricultural Experiment Station Bulletin 584, University of Arkansas, Fayetteville, Arkansas, February 1957, 89 p.
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  • Seubert, J. L. 1966. Biological control of birds in airport environments. Interim report, Proj. Agreement FA65WAI-77, Proj. No. 430-011-01E, SRDS Report No. RO-66-8, U.S. Department of the Interior, Bureau of Sport Fisheries and Wildlife, Washington, D.C. 41 p.
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Copyright © National Academy of Sciences.
Bookshelf ID: NBK208754


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