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Open Access Publications from the University of California


The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish &  Wildlife Service.  The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited.  Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.

To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962.  The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years.  It is the most widely-recognized conference of its kind worldwide.

Detailed histories of the development of this Conference are found in these publications:

Marsh, Rex E.  2008.  A History of the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul.  2004.  Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E.  1982.  Twentieth Anniversary of Vertebrate Pest Conferences in California.  Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E.  1962.  Opening Remarks – Vertebrate Pest Control.  Proc. Vertebr. Pest Conf. 1:1-7.


The pest control industry and the challenges ahead

In this Keynote Address, the author challenges the public perception of the “balance of nature.” He discusses the trend toward increasing legislation to regulate pesticides and to protect our environment, including endangered species. He deems the most immediate challenges facing the pest control industry are in relation to the media, the public, and the various legislatures and regulatory entities. He notes that society’s perspective has become “almost entirely risk-oriented rather than benefit-oriented,” concerning such matters as pest control methods. He elaborates on this perspective, challenging those involved in pest control to be in communication with media representatives to convey factual information about the benefits of managing for the good of humans and the environment.

Pesticides, scientists, farmers, and the public: No 'white knight' rescue in sight

The pesticide controversy is much more complicated than simply a disagreement over facts and risk estimates between the "experts" and the "fearful." It is a battle over ideology as much as one over information. This paper discusses the notion of "educating the public" about pesticides, establishing realistic expectations of efforts by industry and academia, and notes some of the limitations, and potential involvement, of scientists as "translators" in dealing with this controversy.

The impact of wildlife damage on wildlife management programs in Wisconsin

Wildlife damage caused by species normally managed as game animals or furbearers should be of major concern to wildlife managers and various user groups: hunters, trappers, and other outdoor recreationists. Real or potential damage may be used as an important factor in determining population levels, harvest goals, and distribution of white-tailed deer and Canada geese in Wisconsin. In any state where private land and agriculture are important, such a strategy could reduce wildlife populations and associated recreational opportunities. Recent surveys in Wisconsin have quantified the amount and distribution of deer, goose, and turkey damage in Wisconsin. These data allow comparisons between wildlife damage and total agricultural production, other causes of crop loss, and the positive economic impact of these species. Additionally, comparisons are possible between perceived losses and maximum potential losses. A review of the problems caused by each animal provides a framework to discuss the issue of wildlife damage to farm crops and the implications for managers and resource users. The double-crested cormorant provides a special example of a resource management problem with wildlife damage.

Animal rights and vertebrate pest control

Many animal rights activists are very vocal in their belief that animals are more valuable or at least equally important to humans. There is little to no compromise in their overall view that the use of animals for food, fiber, teaching, research and testing does not result in improvements for other animals or societal needs. Today's activists are well prepared and very articulate in getting their views across to the public through the press and television media. An increasing number of the public is beginning to believe the activist allegations of inhumane animal practices. The biologist can no longer ignore these allegations: each of us must become active vocal proponents of the benefits of what we are doing and that we are caring people who practice the highest standards of animal welfare.

Controlling wildlife damage: Can computers help?

Expert systems, a new computer field, is presented as a method to make computers more useful and professionally relevant. Expert systems technology is discussed and is demonstrated to be available and affordable. A typical wildlife damage control problem is presented: species identification of a burrowing pest from a verbal description of a mound or burrow. Development of the expert system, BURROW, is outlined in step-by-step fashion, from statement of the problem, through translating knowledge into rules, to testing and review. Emphasis is placed on encouraging others to write simple expert systems to solve routine problems.

Current and future EPA requirements concerning good laboratory practices relative to vertebrate pesticides

In this paper I present a discussion of current Environmental Protection Agency (EPA) policy on ensuring compliance with the Good Laboratory Practice (GLP) regulations as applied to health effects studies submitted to the EPA under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The EPA has recently proposed extending these regulations to essentially all studies submitted to the Office of Pesticide Programs (OPP) in support of a request for a new registration or in response to data requirements issued under Section 3(c) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The potential impact of these proposed regulations as they may apply to vertebrate pesticide efficacy testing is presented and discussed.

Attitude change toward vertebrate pest control

Attitudes of students enrolled in courses on wildlife damage control at two universities were surveyed at the beginning and end of the semester. Attitudes toward wildlife and acceptance of various damage control methods were quantified and compared to responses obtained from the general public in previous surveys. As a result of the class, both groups of students generally became more accepting of current vertebrate control practices, including toxicant use. Student attitudes, as a result of knowledge gained, came to be more realistic and practical. We believe that persons, when presented factual information about wildlife damage and its control, will develop beliefs that are more accurately in tune with the real world. With such information and attitudes, persons will be more supportive of the need to conduct wildlife damage control using today's methods and materials.

Urban wildlife: Can we live with them?

A survey of Extension Wildlife Specialists in the U.S. provided a basis for estimating the magnitude of urban wildlife damage and control in this country. Response to the 9-question mail questionnaire was good (76 percent) following the single mailing to all Extension Wildlife Specialists or people in similar positions listed in the national directory. The majority of questions were answered based upon the experiences and best estimates of these specialists for the interval October 1986-September 1987. Specialists had difficulty providing estimates of damage and costs of prevention and control; 57 percent were not able to provide any data on these topics. Several of the questions dealt with attitudes of people requesting urban wildlife information and/or assistance and wide ranges of responses were received to most of these questions. Most people (78 percent) appeared willing to implement prevention/control measures recommended by these specialists, more than half (61 percent) wanted the animal handled/removed by someone else, and only about 40 percent wanted the damage stopped regardless of cost. Also, slightly over half (55 percent) of clientele represented did not want the offending animal harmed in any way. These results were highly variable from state to state. Several differences were noted in overall responses regarding urban wildlife species. Requests for information were received most frequently for bats and snakes, but both of these groups of animals ranked very low in terms of actual damage reported. The most frequently mentioned groups of animals causing damage in urban areas were roosting birds (including pigeons, starlings, and sparrows), woodpeckers (especially flickers), tree squirrels, bats, and moles. In terms of actual dollar values of damage done, white-tailed deer and pocket gophers apparently caused the most estimated damage. Due to these differences, it is necessary to know which criteria are being used to make an assessment of the relative importance of animal damage control problems. Techniques for controlling urban wildlife damage, such as exclusion, live-trapping, repellents, and poisons, are compared and discussed in some detail in this paper. As urbanization occurs across the nation, concerns about urban wildlife damage will continue; in most cases, we can and will live among these creatures.

Vertebrate pesticides and nontarget wildlife losses in proper perspective

The use of pesticides as one of the management tools to assist in the prevention and control of damage caused by vertebrate wildlife is certainly not new, nor has it become any less controversial in recent years. In fact, throughout the recent history of pesticide uses for control of vertebrate damage to the production of food and fiber, the prevention of potential epizootic diseases, and other potential threats to man's well-being and to the habitats and management of other wildlife resources, the use of pesticides as well as other management tools have generally been reviewed and monitored by professionals. Justifiably, there has been a significant amount of research conducted to monitor both direct and indirect hazards or potential hazards to nontarget vertebrate wildlife species. It is essential to assess, research and monitor these hazards to other vertebrates, as well as to evaluate the cost benefits and risk benefits of pesticide use. How can we put these concerns or potential occurrences into proper perspective? I'm not sure about many of the potential concerns because knowledge, experience and common sense use by professionals should prevent most nontarget risks. However, I do believe that by providing consideration for a review of nontarget wildlife losses to pesticides as well as other losses to vertebrates we might become more professionally cautious while concurrently improving our competence and confidence in the use of pesticides to prevent and control vertebrate wildlife damage.

Photonovels produced by client/professional partnerships: An educational approach to commensal vertebrate IPM

Since commensal vertebrate pest problems are largely "people problems," a well-planned and executed educational intervention could be the single most important component in an integrated pest management (IPM) program. The basic purpose of educational interventions is to bring sufficient information and understanding to affected clients so that they can and will intercept and control pests in the infested habitat. The encouragement of client participation in producing educational materials is consistent with learning theory and pest management principles. Such production methods allow materials to be closely aligned with client concerns and establish a climate for mutual exchange of ideas between the clients and the IPM professionals. Furthermore, this partnership approach provides an avenue by which a pest management agency may invest its efforts in community-empowering activities aimed at future collective actions which need not depend on professionals, and may be an important step for agency personnel (government vector-control experts, international aid organizations, etc.) in eliminating victim-blaming exercises in futility. The photonovel technique discussed here emphasizes the utilization of client-community resources to enhance the efforts of outside professionals. While the specific example described and analyzed applies to urban rodent control, the concept is applicable to many subjects (including vertebrate IPM and disease prevention programs), to most cultures (in developed and developing countries), and to a broad range of clients (community members, food plant staff, etc.).

Flocoumafen--a new anticoagulant rodenticide

Flocoumafen is a new anticoagulant rodenticide with an acute toxicity between that of bromadiolone and brodifacoum. It has performed well in field tests against house mice and susceptible as well as resistant brown rat populations. Danish lab tests reveal a considerable variation in susceptibility between rodent species and indicate that practical problems in the control of certain Scandinavian bromadiolone-resistant house mouse populations may arise shortly after introduction.

Activity of LM 2219 (difethialone), a new anticoagulant rodenticide, in commensal rodents

Preliminary studies completed on commensal rodents with the new anticoagulant rodenticide difethialone showed very good efficacy, such that 25 ppm baits could be used effectively. New test results presented in this publication confirm the activity as shown under laboratory conditions in choice tests, which represent more severe conditions, as well as its effectiveness against rodents that are resistant and non-resistant to warfarin. In tests where the palatability was only fair the chemical activity resulted in excellent mortality. In a field test against a large population of Mus musculus the results proved very satisfactory. Difethialone is toxic to birds and fish. However, it seems to be better tolerated by dogs and pigs, animals that are frequently on the list of accidental poisonings. Difethialone is stored over a prolonged period in the liver but the risk to non-target species consuming rodents having ingested the compound does not seem to be high. For reasons attributed to the mode of action, difethialone must be handled with precautions as other anticoagulants for which Vitamin K1 is the antidote. In the event of an accidental poisoning, an antidotal therapy plan is proposed. The lower levels of active ingredient in finished baits (25 ppm) should pose a low risk to non-target species.

Status of bromethalin outside the United States

Bromethalin has been extensively researched over the past decade in the United States, Switzerland, England, Denmark, and France. United States EPA registrations were received in 1982 and commercial pelleted formulations containing 0.01 % bromethalin were developed and introduced in the USA by Ralston Purina (ASSAULT®) in 1985 and Velsicol (VENGEANCE®) in 1986. Ciba-Geigy is currently developing new formulations under the tradename DORATID® for use outside the United States. Bromethalin acute toxicity and 14-day subchronic studies are reviewed and data from recently completed 90-day subchronic studies required for registration outside the US are presented. Pharmacodynamic studies have shown that bromethalin acts as an uncoupler of oxidative phosphorylation, thus interrupting the vital production of ATP necessary to maintain essential metabolic functions. Laboratory and field trial data are presented from Switzerland, France, England, and Denmark that indicate the effectiveness of new bromethalin formulations against anticoagulant resistant and susceptible rodents. A comparative rodenticide pen testing system is described from which test results confirm bromethalin's quick action and feed consumption efficiency when compared to second-generation anticoagulants.

Field evaluation of Quintox (cholecalciferol) for controlling commensal rodents

Field efficacy studies were performed on Norway rats Rattus norvegicus), roof rats (Rattus rattus), and house mice (Mus musculus) under a variety of conditions throughout the continental United States. Baits containing .075% (750 ppm) cholecalciferol yielded exceptional results in reducing commensal rodent populations under actual field conditions.

Efficacy and environmental impact of flocoumafen (Storm) wax block baits used for rice field rat control in the Philippines

Two large (approx. 160 ha) trial sites incorporating ricefields and village housing were selected in Laguna Province, Philippines. Flocoumafen 3.5-g wax block baits (Storm®) were applied to one site, initially as two area-wide pulses of 80 to 100 blocks/ha and later as spot treatments, to areas of particularly high rat infestation. Baiting in and around the village houses was already carried out during the first two applications. On average, only 1.175 kg/ha/season of flocoumafen block bait gave good rodent control resulting in significant decreases in crop damage (% cut tillers) compared to the untreated area. The overall yield increase was estimated to be 13 t of grain, equivalent to total added benefit of P39,000 (approx US$ 1,950) or P253 (approx. US$ 13) per ha. Few domestic animals were attracted to the bait and no casualties were reported. Only one dog was seen eating bait but this animal did not develop symptoms of poisoning. None of the wild animals observed regularly during the trial showed significant decreases in numbers after baiting. With the exception of two shrews (Suncus sp.) all animal carcasses found were those of the target rodent pests. It is concluded that flocoumafen gave excellent rat control with no observable effects of non-target animals.

Efficacy of trimethacarb as a small mammal repellent in no-till corn plantings

Trimethacarb (2,3,5-trimethylphenyl methycarbonate) was evaluated as a mouse repellent in no-till corn plantings. Two studies were conducted. One involved an early spring planting and included 5 treated and 5 control plots. The second involved a late spring planting and included 3 treated and 3 control plots. Species composition and relative abundance of small mammals were determined for each plot by trap and release before treatment. On the 10 early spring plots, species composition was 85% prairie voles (Microtus ochrogaster), 14% deer mice (Peromyscus spp.), and 1% house mice (Mus musculus). On the 6 Iate spring plots, species composition was 66% prairie voles, 28% deer mice, and 6% house mice. Trimethacarb (15% by weight) was applied in a 15-20 cm band on the ground surface over the planted corn seed at a maximum rate of 9.2 kg/ha. Corn seeds consumed by small mammals and intact corn sprouts were counted when the corn was approximately 10 cm tall, or about 17 days after planting. At harvest, the numbers of corn stalks and yield in kg per ha were estimated. In the early spring planting, mice consumed a total of 657 and 755 seeds on the 200 sampling sites (treated and control plots, respectively). In the late spring planting, mice consumed a total of 122 and 87 seeds on the 120 sampling sites (treated and control plots, respectively). Differences between the mean numbers of seeds consumed by mice on the treated and control plots were not statistically significant in either planting. In the early spring plantings, a total of 1,784 and 1,641 intact sprouts were present on the 160 sampling sites {treated and control plots, respectively). In the late spring plantings, a total of 1,267 and 1,114 intact sprouts were present on the 120 sampling sites (treated and control plots, respectively). Differences between the mean numbers of intact sprouts on the treated and control plots were not statistically significant in either planting. The average numbers of stalks per ha at harvest for the early spring planting were 42,230 and 31,604 (treated and control plots, respectively); estimates for the late spring planting were at 42,929 and 40,597 (treated and control plots, respectively). Differences between the numbers of stalks on the treated and control plots were not statistically significant for either planting. Average yield for the early spring planting was 8492 kg/ha and 6267 kg/ha (treated and control plots, respectively); and for the late spring planting was 6618 kg/ha and 6831 kg/ha (treated and control, respectively). There was no statistically significant difference in kg/ha between treated and control plots for either planting. These results indicate that trimethacarb is not an effective mouse repellent in no-till corn plantings.

Vitamin K1 treatment of brodifacoum poisoning in dogs

Twenty dogs received a potentially lethal (15 mg/kg) dose of brodifacoum, a halogenated coumarin-type anticoagulant poison. Eleven were immediately treated with vitamin K1 daily for 5 days, either by intramuscular injections (2 mg/kg) or oral tablets (1 mg/kg). It was necessary to give further doses of vitamin K1 to most of the dogs for up to 2 weeks after the first treatment period to reduce their P times to normal levels (< 10 seconds). Four dogs were not given further vitamin K1 and two of these died of acute blood loss from an intrathoracic hemorrhage. Nine dogs received vitamin K1 (2 mg/kg by intramuscular injection) when clinical signs of anticoagulant poisoning were observed. Two dogs died suddenly without premonitory clinical signs of poisoning. The remaining 7 dogs showed various signs of anticoagulant poisoning 4 to 8 days after dosing and they received a 5 day course of vitamin K1. After this period one dog had a transient rise in its P time but this returned to normal without treatment, while another dog was treated on days 16, 20, 29 and 30. In conclusion, the authors recommended vitamin K1 therapy, 2 mg/kg by tablet or injection, daily for 3 weeks in cases of known or suspected brodifacoum poisoning in dogs.

LD50 determination of zinc phosphide toxicity for house mice and albino laboratory mice

Results showed that wild house mice were more susceptible to zinc phosphide than an albino strain. The LD50 and 95% confidence limits for combined sexes with wild house mice (Mus musculus) were 32.68 ± 3.58 mg/kg, but 53.34 ± 2.64 for the albino mice. The regression equations between the probits of mortalities and the logs of doses are Y= 10.38x -10.72 for wild mice and Y= 6.78x-6.71 for albino mice. Both the individual and sexual variations among albino mice in their susceptibility to zinc phosphide were greater than those of wild mice. The results suggest that attempts to extrapolate toxicity values from albino mice to wild mice may prove misleading.

Attractiveness of carbon disulfide to wild Norway rats

In laboratory experiments, carbon disulfide (CS2) increases the attractiveness of feeding stations to rats and mice. Bait consumption is also increased, and the effects are more pronounced for females than for males. The present study was designed to assess whetherCS2 would enhance consumption of a standard bait formulation by wild Norway rats (Rattus norvegicus). The results showed that consumption was tripled when bait was paired with CS2. We speculate that CS2 could similarly enhance the effectiveness of rodenticide bait formulations to which it is applied. Extensive field tests of CS2 as a rodent attractant appear warranted.

The biology of domestic rats: telemetry yields insights for pest control

In previous studies Norway and roof rats were captured, fitted with radiotransmitter collars, and released into their respective habitats. Detailed observations were made of their locomotor patterns, home ranges, activity phasing, food sources, and general behavior. A summary of micro-ecology, habitat partitioning and other behaviors from those studies which may be of use to persons interested in vertebrate pest control is reported.

Comparative evaluation of tamper-proof mouse bait stations

A method for the evaluation of mouse control using tamper-proof mouse bait stations was developed and efficacy trials conducted to determine if house mice (Mus musculus) would visit and consume rodenticidal baits located within these stations. All stations were rapidly investigated by mice. Variation seen between the individual stations related to animal variation and did not appear to be related to differences in the stations themselves. Station placement was more critical to mouse investigation and subsequent bait consumption from the station than were the various features used to prohibit nontarget access.

Stopping house mice building infestations through exterior control

The author describes problems of contamination of foodstuffs in warehouses by commensal rodents, noting that an estimated 95% of such contamination in the U.S. is due to house mice, rather than commensal rats. Other estimates have stated that between 80% and 98% of the food industry’s rodent problem is due to house mice. Pest control operators have often failed to deal with the issue of exterior mice’s ability to access the interior of such storage facility, but rather have concentrated control methods inside the building, rather than searching for the source of the infestation. A study of 7 food warehouses located in Missouri, Kentucky, and South Carolina over a period from 1980 through 1883 revealed the following: exterior house mice were present virtually year-round and were far more numerous than interior mice as shown by trap captures; exterior mice fed on adult insects and insect larvae as well as weed and grass seed; good interior control of mice prevented breeding of interior mice, so nearly all interior mice originated from exterior populations; some mice traveled >200 ft across closely-mowed grass or pavement to reach the warehouse; mice were rarely carried into the warehouse in shipments of palleted foodstuffs. Mouse-proofing specifications are listed, with the intent of showing that exclusion of mice is possible if attention to detail is carried out. PCOs should provide services to retrofit buildings to be mouse-proof, as building managers are seldom able or willing to make this effort. Exclusion should be undertaken in conjunction with use of control measure such as interior and exterior multi-catch traps, bait stations, and glue boards. Details of case histories of successful house mouse control are provided.

Management of fruit bat and rat populations in the Maldive Islands, Indian Ocean

The introduced black rat (Rattus rattus) and the endemic giant fruit bat (Pteropus giganteus ariel) are serious depredators of coconuts and fruits, respectively, in the Maldives. Differences in reproductive rate between rats (high) and bats (low) must be considered in implementing control programs. We estimate a rat population can fully recover from an island-wide reduction of 90% in less than 6 months. In contrast, a bat population may require 6 years to recover from a 90% reduction. Crown-baiting of coconut palms with anticoagulant rodenticides is effective in reducing rat damage, but villagers have been-reluctant to adopt recommended baiting programs, allowing rat populations to quickly recover. We substantially reduced bat populations on islands (e.g., from 2.1 bats/ha to 0.7 bats/ha) after a few nights of mist netting and recommend this procedure for managing bat populations. Bat populations should not be reduced below 0.25 bats/ha on islands in the Maldives.

Reduction in rodent populations through intermittent control operations in the cropping ecosystem of the Indian desert

Control operations at 6-month intervals, continued for four years in crop fields, reduced the rodent population to 5.08 percent losses to agricultural production. After eight crop seasons, a significant reduction in rodent density was observed in treated areas when compared with that of the control areas (P < 0.01). Correlation between pre-treatment population index (y) and number of seasons (log of x) was found to be 0.91 (P< 0.01). A relationship was established between y and x: y = 0.804.0-0.9621 log x. From this equation, it can be inferred that rodent population will reach zero level after treating crop fields continuously for 6.85 or say 7 .0 (seven) seasons. After control, the numbers of predominant rodents, Tatera indica, Meriones hurrianae, and Rattus meltada, were significantly reduced and the residual population was composed of Mus booduga, Gerbillus spp., Rattus gleadowi, Golunda ellioti, and Funambulus pennanti.

Rice as a trap crop for the rice field rat in Malaysia

The potential of rice as a trap crop for the rice field rat, Rattus argentiventer, was clearly illustrated by the studies conducted in 60.7 ha of newly rehabilitated rice land in Permatang Pauh and in the MARDI Research Centre's rice fields in Bumbong Lima. The rice crop was very attractive to the rats, especially at the reproductive phase. The combination of a physical barrier and traps was very effective in exploiting rice as a trap crop for rice field rats. The trapping patterns indicated a massive influx of rats from the surroundings for a period of three weeks in Permatang Pauh and of a lesser degree in Bumbong Lima. In Permatang Pauh, adult male rats caught ranged in weights of 116-293 g and females 85-230 g. Very few subadults were caught, only 2.3% or 35/1550 measured, whereas in rice fields cultivated continuously, young and adult rats were caught (84 adults to 116 young, or 58 % of the rats caught were subadults and juveniles) as in the case of the population in Bumbong Lima. The sex ratio in the Permatang Pauh population showed a preponderance of males in the first two weeks but eventually more females appeared in the 4th and 5th week. The overall sex ratio was 1236 males to 1107 females (a ratio of 1.12:1), which did not depart from the expected ratio of 1:1. The total number of rats caught was 2343 in the first season but in the second season only 24 rats, 22 R. argentiventer (16 males and 6 females; sex ratio of 2.7:1) and a pair of Rattus rattus diardii were caught in Permatang Pauh. In the Bumbong Lima population, the sex ratio for adults was 37 males to 4 7 females (0.7:1) and in the young 75 males to 41 females (1.8:1). Rats were attracted to the crop only when the adjacent areas were harvested and, as the crop in the surrounding areas matured, the number of rats caught declined and reached zero at the booting phase. Rice at the early reproductive phase is an effective lure for the rice field rats and thus could be used as an efficient trap crop for its control.

Characteristics of damage by vertebrate pests to groundnuts in Pakistan

Vertebrate pest damage to groundnut (Arachis hypogea) was assessed at harvest in 164 fields selected along road transects in Pakistan. Overall damage in these fields was estimated at 5.3%, of which the lesser bandicoot rat (Bandicota bengalensis) accounted for 2.4%, the short-tailed mole rat (Nesokia indica) caused 1.0%, and the wild boar (Sus scrofa) caused 0.9%. Desert hares (Lepus nigricollis), crested porcupines (Hystrix indica) and house crows (Corvus splendens) together accounted for the remaining 1.0% damage. The damage characteristics of each species are described. Observations indicated that visual above-ground examination of plants for damage underestimated the actual loss because both lesser bandicoot rats and mole rats often remove groundnut pods below ground without killing or otherwise damaging the plants. The yield loss based upon 5.3% damage would equal 67 kg of groundnut per hectare.

Introduced animals in Hawaii's natural areas

The Hawaiian islands provide superlative examples of biological evolution and are perhaps the best sites in the world for biological invasions. Introduced invertebrates such as the Argentine ant (lridomyrmex humilis) and the western yellow jacket wasp (Paravespula pensylvanica) reduce native insects and plant pollinators and may have been a factor in native bird declines. Management of invertebrates in localized areas through use of chemicals such as Tahara and diazinon is being attempted. Research on the long term effects of alien birds on native ecosystems is under way, but management currently is restricted to preservation of intact and large areas of native ecosystems. Black rats (Rattus rattus), small Indian mongooses (Herpestes auropunctatus), and feral cats (Felis catus) are thought to be especially important invaders of natural areas in Hawai'i. Research on ecology and control methods for all 3 species is under way, with registration of diphacinone for mongooses by the Animal and Plant Health Inspection Service nearly complete. Ungulates have been the most prominent alien animals in Hawai'i's ecosystems since shortly after continental man introduced them in the 18th century. Successful control and even eradication of feral cattle (Bos taurus), feral sheep (Ovis aries), mouflon (Ovis musimon), feral goats (Capra hircus), and feral pigs (Sus scrofa) has been accomplished in many areas to date through systematic, long-term programs with salaried personnel. Methods and costs of some of these programs are presented.

Health risks to humans and domestic livestock posed by feral pigs (Sus scrofa) in North Queensland

A sample of 608 adult pigs from Cape York and adjacent islands was examined for parasites and their serum tested for livestock diseases associated with the Queensland tropics. Feral pigs from North Queensland pose a significant health threat to humans with the incidence of Spargana (the plerocercoid of Spirometra erinacei) through the consumption of undercooked pork. Meliodosis (Pseudomonas pseudomallei), Leptospirosis (L. var pomona), and Brucellosis (Brucella suis) are capable of infecting humans directly during unhygienic butchering of infected carcasses. In North Queensland, the widespread intermingled distribution of feral pigs and cattle increases the potential for the transmission of Actinobacillus, Leptospirosis, and Brucellosis from feral pigs to cattle. Both Europeans and Aborigines on Cape York also raise wild-caught feral pigs for meat. It is important to realize that parasites and diseases are present in young pigs and that poor husbandry practices increase the risk of infection from several parasites, i.e., Lungworm (Metastronsylus sp.), stomach worm (Physocephalus sexalatus, Hyostrongylus rubidus), thorny headed worm (Macracanthorrhynchus hirudinaceus), and kidney worm (Stephanurus dentatus). Heavy infection of these parasites reduce growth rates and cause unthriftiness in infected animals.

Predator odors and their potential role in managing pest rodents and rabbits

The snowshoe hare (Lepus americanus), several species of voles (Microtus spp.), the northern pocket gopher (Thomomys talpoides), and the red squirrel (Tamiasciurus hudsonicus) cause serious damage to forest plantations and stands (and voles and pocket gophers in tree fruit orchards) by their feeding activities. Certain synthetic predator odors are reviewed which have produced significant avoidance responses in these pest species and reduced damage to crop trees on an experimental basis. In addition, the specific study reported in this paper was designed to assess the influence of predator odors on population density and survival of montane vole (M. montanus) populations in natural grassland habitat. Vole populations declined significantly in three consecutive winters on an area (and also on a replicated area in the third winter) treated with predator odors. These declines were caused by significantly lower survival in the treatment than control populations. Concurrent feeding damage to young apple trees was significantly reduced on the treatment area. We suggest that the predator odors may have attracted additional predators to the study area thereby increasing predation, as well as perhaps inducing behavioral-physiological stress in the vole populations. This technique could be implemented in forest plantations and tree fruit orchards as a means to disrupt resident vole populations and protect crop trees from damage.

A two year study of the physical and economic impact of voles (Microtus montanus) on mixed maturity apple (Malus spp.) orchards in the Pacific northwestern United States

The physical impact of voles in agriculture and forestry has been duly noted by many researchers around the world. The economic impact of the various species, however, has not received much attention other than to note that losses from these animals can be substantial when population levels become high. This study assesses the economic impact of an extremely high population of Microtus montanus (mountain voles) in a large apple (Malus sp.) orchard in northcentral Washington State (U.S.A.) over a two-year period. In this study, 200 trees were harvested, weighed, graded, and compared by the amount of visual damage that could be seen above the soil surface. These values were then compared with cash values received by growers for the season. Production was decreased a weighted average of 36% (31% for red delicious and 53% for golden delicious) or $3036/ac. ($7500/ha.) during the first year. In the second year, production increased 3.2 fold but still did not reach that of the control orchard. If 30% of the orchards in the state were to suffer the same level of infestation, over $137 million/year could be lost because of poor management and control programs.

A field method for assessing the palatability of rodenticidal baits

Assessments of the palatability of rodenticide baits are usually conducted in the laboratory but little is known of the value of such tests as determinants of the potential performance of formulations in the field. Field bait acceptance tests conducted earlier were either unduly time-consuming or failed to take account of aspects of rodent behavior in relation to baiting regimes which make the interpretation of results difficult. This paper describes a novel, cost effective technique for assessing the palatability of baits in the field and the use of the new method to compare the acceptance of three commercial formulations, containing either difenacoum or brodifacoum, with that of an EPA approved challenge diet. No statistically significant differences were found in the acceptance of the three baits and the challenge diet at three farmsteads harboring infestations of Rattus norvegicus. Similar results were obtained in equivalent laboratory choice tests conducted following an established protocol. A comparison of results from the two environments bestows confidence both in the practical value of the laboratory test method and in the likely performance of the baits when used for rodent control operations. Wider possible uses of the field test methodology are discussed.

Effects of implementing EPA's endangered species protection program on national forest system lands

In 1986, the U.S. Environmental Protection Agency (EPA) initiated an effort to comply more fully with the Endangered Species Act. This effort became their "Endangered Species Protection Program.'' The possibility of such a program was forecast in 1982 when Donald A. Spencer gave a presentation to the Tenth Vertebrate Pest Conference on "Vertebrate Pest Management and Changing Times." This paper focuses on current plans for implementing the EPA's Endangered Species Protection Program as it relates to the USDA Forest Service. It analyzes the potential effects this program will have on the agency, using the pocket gopher (Thomomys spp.), strychnine, and the grizzly bear (Ursus arctos horribilis) as examples of an affected pest, pesticide, and predator.

Rodenticide residues in animal carcasses and their relevance to secondary hazards

Some complexities and limitations of using carcass residue data to determine secondary hazard to nontarget species are discussed. The roles of chemical and toxicological properties of the rodenticide such as metabolism, excretion, organs of retention, site of absorbtion and latent period in secondary hazard are reviewed and examples given. The possible effects of bait composition and application methods, the behavioral response of the nontarget species, and local environmental factors upon secondary hazard are outlined.

Determination of the environmental fate of ground squirrel carcasses

A field study was conducted in Lewis and Clark County, Montana, during the summer of 1986 to determine the fate of Columbian ground squirrel (Spermophilus columbianus) carcasses in the environment. Ground squirrel carcasses were marked with radio transmitters and placed in situations and locations similar to those found in actual rodent control operations. Carcasses were monitored until their fate was determined or until they were no longer considered attractive to scavengers. Red fox (Vulpes fulva) was the primary scavenger in this study. Striped skunk (Mephitis mephitis) and birds (corvids and/or raptors) were the other mammalian and avian scavengers identified. Carrion-eating insects quickly attacked the carcasses and were important in determining the maximum exposure time of the carcasses to scavengers. Factors determining the risks lo scavengers from rodent control operations and management techniques to reduce nontarget hazards are discussed.

The operation of coordinated rabbit control organizations in England and Wales

Rabbit control organizations in England and Wales were studied between 1978 and 1982. A national survey of existing organizations showed that there were 2 types (societies and groups) and that they jointly covered only 2% of farmers and 1.5 % of agricultural land. Three societies were studied for 3 years and were found to be underfunded and increasingly unable to provide coordinated control on adjoining properties. Farmers are provided with recommendations on how to run coordinated rabbit control organizations.

Breeding birches for resistance to rodent and hare damage

Rodents and hares are very harmful pests in forest plantations in the Holarctic zone. No effective way to control damages by these pests is known. There is large variation in resistance of different birch species, origins and families. The resistance does not seem to be correlated to growth of seedlings, thus the prospects for resistance breeding are considered good. There seem to be large variation even within birch families which can partly be explained by morphological differences between seedlings. Also the nursery treatment seems to determine the palatability of seedlings to herbivores. Ways to produce resistant genotypes for the use of practical forestry are discussed.

Recent approaches to controlling mountain beavers (Aplodontia rufa) in Pacific Northwest forests

Biologists of the Denver Wildlife Research Center are currently investigating ways of managing mountain beaver (Aplodontia rufa) populations and are developing methods for alleviating mountain beaver damage to conifer trees being grown for timber in the Pacific Northwest. Studies initiated in I 986 indicated that aversive conditioning with Big Game Repellent Powder (BGR-P) dusted on cull Douglas-fir (Pseudotsuga menziesii) seedlings placed in burrows significantly reduced mountain beaver damage to planted seedlings treated with BGR-P and to untreated seedlings. Trials also showed that strychnine-sword fem (Polystichum munitum) baits prepared with a 4.9% (active) strychnine paste concentrate (SLN Reg. No. ID-870003) are very effective and selective for mountain beaver control. Other subjects discussed include results of several probes with toxic baits and phosphine gas, trials with a drug and a wetting agent to induce hypothermia, destruction of underground nests to prevent reinvasion, and mountain beaver behavior associated with controlling damage.

Recognizing black bear damage to second growth redwoods

Black bears, Ursus americanus, have been known to cause severe damage to second-growth redwoods (Sequoia sempervirens). The damage is seasonal and is often associated with logging roads, skid trails or other openings in the forest. Signs of damage are characteristic and cannot easily be confused with other species of wildlife that damage redwoods.

Problems associated with beaver in stream or floodway management

In California, beaver (Castor canadensis) were first recognized for their value as a furbearer. Additionally, in many areas, beaver are considered desirable if not essential components of stream and wetland ecosystems. Where beaver and human activity overlap, beaver have become nuisance animals causing direct damage through dam building, flooding, bank denning, and loss of agricultural crops. Other problems such as the threat of levee failure and subsequent flooding, increases in undesirable brush growth due to a raised water table, restricted access due to flooding, and an increased mosquito population resulted in the Department of Water Resources (DWR) developing a beaver management program. In 1984, DWR entered into a long-term agreement with the U.S. Department of Agriculture (USDA) Animal Damage Control (ADC) program to eliminate a large existing population of beaver and remove subsequent reinvading individuals from a 20-mile stretch of man-made Cherokee Canal in Butte County, California. In addition, existing dams, lodges, dens, and heavy brush growth were removed in an attempt to insure the flood safety of the project and modify the existing habitat making it less suitable for reinvading beavers. Both the costs and results of this program are discussed, as well as the long-term management strategy for this project

Terrestrial mammalian pests in Argentina--an overview

In Argentina, 41 of the country's 300 native or introduced land mammals are legally considered as pests: 31 are indigenous and 10 exotic. The types of problems arising are described and the principal species causing them are reviewed. Although inflicting damage, several wild animals are also valuable for commercial hunting enterprises.

Badgers as occasional pests in agriculture

The badger (Taxidea taxus), because of its strong propensity for digging, is considered North America's fossorial carnivore, feeding mostly on ground squirrels, pocket gophers, and mice throughout much of the western and midwestern continent. Badger excavations, primarily in search of food, produce mounds and deep holes which can damage alfalfa and other crops and damage farm equipment and water systems. Depredations include poultry, waterfowl, and eggs. Overall, the badger is considered a relatively minor vertebrate pest. As a furbearer it is considered a renewable natural resource. Most local pest problems are currently reduced through leghold trapping and shooting. Habitat modification through continuous rodent control is effective and a long-lasting badger control method.

A decade of use of livestock guarding dogs

Results from a ten-year study of livestock guarding dogs show that the dogs are an effective tool for reducing predation. Average reduction attained by five strains of dogs (Anatolian Shepherds, Maremmas, Shar Planinetz, Anatolian/ Shars, Maremma/Shars) was 64%, with predation reduced to zero for 53% of reporting producers in 1986. Variations in trustworthy, attentive and protective behavior of the dogs were breed-specific, and offer mechanisms for improving the system.

Large livestock protection collars effective against coyotes

A small (30-ml 1080 solution) livestock protection (LP) collar has been registered by the U.S. Environmental Protection Agency (EPA) to help control coyote (Canis latrans) predation on sheep and goats. However, the small collar does not adequately cover the throats of large livestock. We pen tested large (60-ml 1080 solution) LP collars on large sheep for effectiveness against coyotes and determined sodium fluoroacetate (FAC) residues in coyotes and sheep to estimate nontarget hazards. The large collar was effective. In 5 tests, all 5 collars were punctured and all attacking coyotes died. Time to death averaged 25 h. Coyotes received more toxicant from large collars and had higher FAC residues in stomach contents and muscle compared to coyotes killed by small collars. Despite usually higher FAC residues from large LP collars, our assessment indicated minimal primary and secondary hazard to nontarget species.

M-44 sodium cyanide ejectors in the animal damage control program, 1976-1986

This paper summarizes Animal Damage Control (ADC) program records relating to M-44 use during Fiscal Years 1976-86. During these years, M-44s were used in 14 western states to take 103,255 animals, including 92,843 coyotes, 5,544 other target canids, and 4,868 nontarget animals. More animals were taken in Texas than in all other states combined. Program-wide during FY 1977-81, M-44 effort averaged approximately 5,600 unit years annually and 1.2 target animals were recovered per M-44 year. M-44s accounted for 12.3 percent of all coyotes taken by the ADC program during FY 1976-86. The coyote take by M-44s doubled from FY 1981 through 1986. In FY 1986, more coyotes were taken by M-44s than by any other method in Texas, New Mexico, and Nebraska. Program-wide in that year, aerial hunting ranked first, the leghold trap second, and the M-44 third in numbers of coyotes taken. The M-44 has increased in importance since its reregistration in 1971, but the coyote lake by M-44 has not approached the peak reached in 1971.

Field evaluation of padded jaw coyote traps: effectiveness and foot injury

A field study of unpadded and padded foothold coyote traps was undertaken in six western states in 1986-1987. Tests were designed to determine the capture efficiency and extent of foot injury caused by different trap modifications. Results were similar to an earlier study undertaken in 1984-85 that showed padded traps reduced foot injury but captured and held fewer animals than did unpadded traps. Both studies showed that unpadded long-spring traps used operationally by Federal Animal Damage Control specialists were the most effective (75-78% capture rate) but caused more foot injury. Padded long-spring traps were intermediate in efficacy (52-57%) and foot injury, while padded "Soft Catch''™ traps were the least effective (30-58%) but caused the least injury to captured coyotes.

Predators and sheep management practices in Sonoma County, California

Over the last twenty-five years, sheep numbers have been declining in Sonoma and Marin Counties, California, at the same time the number of predators has increased. With the removal of most chemical control methods, livestock producers have had to turn to other methods of preventing livestock losses. The objective of this project was to survey livestock producers to determine the levels of predation, type of predator involved, and the management methods being used to reduce these losses. This information is essential to develop a sound extension program to help livestock producers better deal with the predator problem.

Development and testing of the coyote lure operative device

A new device for orally delivering substances to coyotes (Canis latrans) has been under development for approximately 10 years. The development of the coyote lure operative device (CLOD) is described along with some recent field evaluations of the CLOD system. In general, the results of these field tests indicate that the CLOD shows potential and merits further development.

Distribution and magnitude of eagle/livestock conflicts in the western United States

Problems with golden eagle (Aquila chrysaetos) and bald eagle (Haliaetus leucocephalus) depredation on livestock in western United States were investigated by surveying Animal Damage Control field personnel. One hundred forty-three individuals from 14 states identified areas where they had observed eagle damage to livestock in the past 10 years. Most field personnel believed golden eagles (both residents and migrants) were the most important species causing livestock depredations. The highest livestock losses to eagles were associated with open range lambing operations. Eagle numbers were reported to be increasing throughout the West, but livestock losses to eagles were staying at about the same level.

Photographic records--their importance in today's environmentally sensitive bird management programs

We are living in a day of change. Environmental awareness is a part of our everyday life in a way unprecedented in history. The courts, in their infinite wisdom, have initiated the joint and several liability (deep pocket) rules that make everyone at risk in almost all situations. Bird management programs, by their very nature, are extremely sensitive. Any project, if not evaluated, planned, carried out, and documented properly can result in adverse regulatory agency action, bad publicity, and even fines or lawsuits. Proper photographic documentation can play a vital part in helping to provide the necessary records to help prevent problems and/or defend yourself in case of lawsuit or regulatory action. In the preparation of this paper, we surveyed state pesticide lead agencies, state Department of Conservation (Fish and Wildlife) agencies, some U.S. Fish and Wildlife Law Enforcement personnel, and several individuals to get their reaction to and their comments about this concept of supplemental recordkeeping. Of those responding, a majority thought the concept of supplemental photographic recordkeeping would be an asset to individuals and organizations conducting bird management projects.

An evaluation of modified 4-aminopyridine baits for protecting sunflower from blackbird damage

Bait preference studies with red-winged blackbirds (Agelaius phoeniceus) in North Dakota sunflower fields indicated that sunflower seeds and a combination of sunflower seeds and chopped corn (MIX) were more successful in producing affected blackbirds, primarily red-winged blackbirds, than pearl barley or chopped corn used separately. A subsequent study compared the effectiveness of commercial Avitrol FC corn Chops-99S to 4-aminopyridine-trealed MIX-99S baits for reducing blackbird damage to ripening sunflower. Both baits significantly reduced damage in fields nearest a blackbird roost (within two miles), but were largely ineffective in fields farther than two miles from a roost. The ramifications of these results are discussed.

Solution to urban bird problems

A survey of municipalities across the country indicated that pigeons were the most widespread aerial nuisance in urban areas. These were followed in order by: blackbirds, starlings, house sparrows, woodpeckers, crows/ravens, swallows/swifts, waterfowl (Canadian geese, mallards, and coots), and gulls. With somewhat lesser frequency were robins, vultures, raptors, herons/egrets, mockingbirds, waxwings, and monk parakeets. Local bird problems were mostly handled by: USDA-APHIS-ADC, Health Department, City/County Animal Control, Landowner/householder, PCO, State Wildlife Agency, Police Department, and Mayor's office.

Observation of woodpecker damage to electrical distribution line poles in Missouri

Woodpecker damage to electrical distribution poles was monitored in Saline and Pettis Counties, Missouri. Damage increased over the four-year monitoring period. There was an increase in both the number of poles damaged and the amount of damage to individual poles. When woodpecker-damaged poles were replaced, the replacement poles proved highly vulnerable to attack. A pole repair and replacement program in Dekalb and Gentry Counties was monitored. The objective was to determine if plastic mesh would effectively protect poles from woodpecker attack and if efficacy could be reliably determined within one year of installation. Plastic mesh failed to provide an acceptable level of protection. It was not possible to get an accurate evaluation of efficacy at the end of one year. Recommendations are made for protecting distribution line poles from damage by woodpeckers.

Effect of ultrasonic, visual, and sonic devices on pigeon numbers in a vacant building

Three bird scaring devices, ultrasonic, visual and sonic, were evaluated for repelling pigeons from inside a vacant building. After 10-30 days of treatment, none of the devices reduced the pigeon population from levels recorded in pre- and post-treatment periods. However, both the visual and sonic devices altered pigeon behavior during their 10-day treatment periods and temporarily reduced the pigeon population during the first 2 days of treatment. The ultrasonic device was completely ineffective; no change in pigeon activity was observed during a 20-day treatment period.

Aerial treatments against starling roosts in France with chloro-para-toluidin (CPT): Results of eight years of experiments

The starling is one of the major pest birds in France. During the winter, starlings coming from other parts of Europe gather in the Northwest of France and cause extensive damage in the corn silage distributed to the cattle, by eating and spoiling the grains. As it is impossible to protect the cattle food by physical means in most of the situations, the persons in charge of resolving the problem have chosen to turn towards chemical roost treatments. Between 1980 and 1988, nearly 40 treatments have been carried out on 25 different roosts. The chemical used is CPT (chloro-para-toluidin) applied at the rate of 100 kg per hectare. Water is added to the formulated product and a volume of 1000 liters per hectare of the treatment mixture is applied with a fixed-wing aircraft. Results usually ranged from 30% to 80% of the birds killed. No phytotoxic problems have been reported on the roost sites, and only light wildlife adverse effects arc mentioned. Studies are going on with the following points: degradation of CPT in the soil, and reduction of the amount of CPT and/or water without drop of effectiveness.

Flight pen evaluations of eyespot balloons to protect citrus from bird depredations

The effectiveness of eyespot balloons in discouraging boat-tailed grackle (Quiscalus major) use of a simulated orange grove was investigated in a series of 4-day trials. The mean distance to the trees of 6-bird experimental flocks was the same with a plain white balloon present as with no balloon. A white balloon with red and black eyespots kept birds at a greater distance from the trees throughout the trial. The presence of a black balloon with orange and yellow eyespots did not repel the birds from the grove. Observations of birds using the area within 1 m of the trees revealed no effect due to the eyespot balloons nor was the number of oranges pecked reduced in the presence of the eyespot balloons. These results were primarily due to a single bird that consistently ignored the white eyespot balloon during the 4-day trial, entered the grove, and avidly pecked the fruit. In combination with other crop protection devices, eyespot balloons may prove effective in deterring bird use of citrus trees.

Bird damage to sprouting rice in Louisiana: Dynamics of the Millers Lake blackbird roost

In spring 1986 and 1987 I examined the relationship between blackbird abundance and sequence of rice planting near a very large roost in southwestern Louisiana to identify factors that contributed to bird damage in newly planted rice fields. Millers Lake, an eutrophic man-made lake of approximately 2,500 ha, attracts a winter roosting population that peaks at 10 to 25 million blackbirds annually. By March and April the roost declines to several thousand birds. Female redwinged blackbirds (Agelaius phoeniceus) were responsible for most rice seed losses, predominating both the roost and feeding flocks in rice fields in spring. Number of flocking birds in fields decreased with roost size, date of year, and distance from the roost. Surveys corroborated recommended planting practices: planting after 24 March coincides with decreased numbers of blackbirds in rice fields, thus reducing the potential for damage to seeded rice by foraging blackbirds.

Prolonged seed handling time deters red-winged blackbirds feeding on rice seed

Theoretical concepts from foraging ecology were studied to identify elements of blackbird foraging strategies that may be manipulated to deter blackbirds feeding on rice. Seed-handling time was identified as one such vulnerable element. Consequently, we developed seed coatings for rice that increased handling time per seed, allowed a satisfactory germination rate, and persisted for several days postplanting. Test coats included hydrophilic binders with several starches, clays, plaster of paris and chemical grout in various combinations. Consistent repellency was achieved in feeding trials with captive red-winged blackbirds.

Using aircraft for controlling blackbirds/sunflower depredations

Although not a new idea, using aircraft to control blackbird damage to sunflowers has provided some relief for sunflower growers in North Dakota. The numerous scaring devices and limited frightening agents have not proven effective in controlling blackbird damage to sunflowers. In response to a congressional directive to provide assistance in controlling blackbird/sunflower depredations in North Dakota, a blackbird hazing program was developed. The program utilized fixed-wing aircraft and shooting to expedite the migration of blackbirds through North Dakota.

Controlling shiny cowbirds in Puerto Rico

A program to trap and remove shiny cowbirds (Molothrus bonariensis) was conducted during two successive passerine nesting seasons at Roosevelt Roads Naval Station in eastern Puerto Rico. It sought to improve existing trapping techniques and to determine the effect cowbird removal has on the reproductive success of the endangered yellow-shouldered blackbird (Agelaius xanthomus). Decoy traps of two basic designs were used to capture 2449 cowbirds in 1162 trap-days (average 2.1/trap-day) in June-September 1985 and 850 cowbirds in 1571 trap-days (average 0.5/trap-day) in March-August 1986. The lower capture rate in 1986 suggests that cowbirds removed in 1985 were not being replaced during the non-trapping period. Trapping data from yellow-shouldered nesting areas in mangrove swamps indicated that cowbird capture rates were significantly higher (P=0.02) for large (14.2-14.8 m3) traps than for smaller (4.2 m3) ones. The effect of cowbird removal on the nesting success of the yellow-shouldered blackbird could not be directly determined because only one nest could be found. Cowbird removal, however, greatly reduced parasitism rates of another parasitized species, the yellow warbler (Dendroica petechia).

Alleviating nuisance Canada goose problems with acoustical stimuli

Alarm/distress calls of Canada geese (Branta canadensis) were evaluated by themselves and in combination with racket bombs to determine their effectiveness in frightening Canada geese from nuisance situations at 2 Corps of Engineers campgrounds in Tennessee. Results based on goose censuses showed a significant (P<0.05) reduction in goose numbers from nontreatment to treatment periods at both sites. Goose numbers were reduced an average of 71% when the calls alone were used. The combination of the calls and the racket bombs produced a 96% reduction in goose observations. Although a reduction in geese was observed during the treatment periods, continual harassment would appear to be necessary as reinvasion was noted after treatment was stopped. The scarcity of alternate feeding and loafing sites may have contributed to this lack of long-term control.

Characteristics of bird-resistance in agricultural crops

The use of biochemical or morphological genetic traits in a crop to protect ripening seeds or grain from bird damage remains a promising tool under certain situations. Research on bird-resistance in crops has focused on grain sorghum, com, sunflower and rice. This crop protection method involves feeding behavior of granivorous birds and its effectiveness depends on the availability of preferred alternate foods. That is, bird-resistant traits provide protection to the crop when other food choices are readily available; however, when alternate food is scarce or high bird populations create serious feeding competition, they are less effective. Several practical factors (i.e., efficacy expectations, agronomic considerations, and cost-effectiveness) were discussed that should be considered in adopting this bird damage control strategy.

Innovative approaches in the control of quelea, Quelea quelea lathimii, in Zimbabwe

Ever since crops have been grown, quelea have been a threat to summer subsistence crops and winter commercial wheat/barley cropping in Zimbabwe. Control techniques spraying toxicant Queletox through ground spray units and aircraft, developed in Zimbabwe, have produced 90% kills keeping the level of depredation down to acceptable levels. Zimbabwe, like most developing countries, faces protein shortages, and utilization of dead quelea by the rural population has always occurred even from sprayed colonies despite repeated warnings of possible side effects. Traditionally quelea have been sold on the black market for 10-20 Zimbabwe cents/bird and recently a far wider potential, even export, has been realized with a potential value increased to 40 cents/bird. Several applications for permits to harvest large numbers have been processed by the Department for export and local consumption provided a suitable method of capturing large numbers could be perfected. The recognition of quelea as a potentially economic renewable resource has intensified research in this area and several mechanical systems have been tried over the years finally culminating in the promising development of the "Impact" trap. The method potentially provides large numbers of uncontaminated quelea for the market. With careful monitoring and the parallel development of the trap roost concept, it is possible this approach could also sufficiently reduce toxic control beneficial to the environment as a whole while providing a source of food and revenue to Zimbabwe.

Behavioral response of cattle egrets to population control measures in Hawaii

We monitored behavior of cattle egrets (Bubulcus ibis) during a population control program to reduce egret-aircraft strike hazards from a small heronry near the Hilo, Hawaii, airport. Results verified that attempts to move egrets from undesirable roost sites should be undertaken before nesting begins. Although possibly compounded by previous treatments, our observations also indicate that 1) egrets may abandon a new roost in response to a few dead egrets placed in clear view around the roost, and 2) shooting at egrets as they attempt to land at a traditional feeding site causes long-term avoidance of the area. Rapid repopulation after control indicates that techniques to move roosts and prevent congregations are more likely than population control to resolve problems.