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document Historic, archived Do not assume content reflects current scientific knowledge, policies, or practices. #*.< Ow//.•j-yi/cj United States The Denver Wildlife Department of Agriculture Animal and Res^arcli Center Plant Health Inspection Service 1991-92 Miscellaneous Highlights Report, Publication No. 1515 _r U.S. Department ofAgriculture The progpams of the U.S. Department ofAgriculture (USDA) Animal and Plant Health Inspection Service are available to anyone without regard to race, creed, sex, DenverWildlife Research Center disability, religion, national origin, or political belief. P.O. Box 25266 Building 16, Federal Center Mention of companies orcommercial products does not imply Denver, CO 80225-0266 recommendation orendorsement by USDA overothers not mentioned. USDA neitherguarantees norwarrants the Office ofthe Director (303) 236-7820 standard of any product mentioned. Product names are Information and Technology Transfer (303) 236-7873 mentioned solely to report factually on available data and to provide specific information. This publication reports research involving pesticides, rodenticides, and avicides. All uses of such pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans, domestic — animals, desirable plants, and fish or otherwildlife if they are not handled orapplied properly. Use all pesticides selectively and carefully. Follow recommended practices forthe disposal of surplus pesticides and pesticide containers. Issued August 1993 5 Contents Introduction Introduction 3 The past 2 years have been exciting and dynamic ones at the DenverWildlife Research Center (DWRC). Following a Research Highlights 4 reorganization within the Animal and Plant Health Inspection Agricultural Crops 4 Service (APHIS), the Science and Technology division was Endangered Species 12 dissolved and the Centerwas transferred back to APHIS' Nuisance, Safety, and Health Concerns 13 Animal Damage Control program. ALiqvueasctuolctkure1 16 The Center continues to make advances in the field of International Cooperation 18 vertebrate pest management in a numberof areas. Contraceptive Research 21 Reregistration and registration of pesticides important to the operational program in animal damage control continues to be Registration and Reregistration of Pesticides 22 a high pnority. DWRC scientists developed new techniques to control bird damage to fruit and rowcrops. Work continues on Information and TechnologyTransfer 27 resolving the problems birds pose to aircraft. The Center expanded its research to reduce and eliminate bird damage to Outreach Activities 29 fruit and row crops. The search for nonlethal control methods and repellants received high priority, including new research in The Center's Research and Support Staff 33 the areaof immunocontraception forcontrolling the population of problem animals. Publications—Fiscal Years 1991 and 1992 35 DWRC continued to strengthen its cooperative ties between Index 40 universities and the public sectorto offer a cost-effective way to explorethe latest scientific breakthroughs and assess their possible applications to vertebrate pest management. Staff members gave presentations and tours of the facilitiesto many visitors. In 1992, the DenverWildlife Research Centercontinued to meet its commitments tothe needs of its users and position itselfto meet their needs even more effectively in the future. DWRCHighlights Report: 1991-92/3 Research Highlights — Agricultural Crops Modelling the Chemical Attributes of Bird Repellants Interdisciplinary studies by scientists from DWRC and the — Repelling Birds From Dendrobium Orchids A unique Monell Chemical Senses Center have shown that the agricultural crop grown on the Hawaiian islands, dendrobium effectiveness of bird repellants is associated with basicity, the orchidsare severely damaged each year by birds, specifically presence of (1) an electron-donating group In resonance with red-vented bulbuls. One method to protect orchids from bird an electron-withdrawing carboxyllc group on a phenyl ring and damage is the application of a nonlethal chemical repellant. (2) a heterocyclic ring in the same pi cloud asthe phenyl ring. Center researchers cooperated with the Hawaii Governor's Ofthe benzoic acid derivatives tested, methyl, ethyl, dimethyl, Agriculture Coordinating Committee, Hawaii Farm Bureau and linalyl anthranllate, as well as anthranilic acid and Federation, and Hawaii Animal Damage Control to test three 4-ketobenztriazine, were repellentto birds. Models predicting candidate compounds, methiocarb (Mesurol'^'), ziram, and repellancy will permit the efficient identification and methyl anthranllate, in cage and field tnals. development of ecologically sound, nonlethal, taxa-specific repellants to be used foranimal damage control and wildlife In cage experiments, red-vented bulbuls in control groups ate protection. more untreated bird mash than birds presented with bird mash — treated with mesurol, ziram, or methyl anthranllate. Ofthe Reducing Bird Damageto Sprouting Rice Several three repellants, ziram and mesurol significantly reduced food species of blackbirds, particularly red-winged blackbirds consumption. In field trials, ziram and mesurol reduced bird congregating in large spring roosts, can cause extensive damage to flowers by about 80 percent. damage to sprouting rice. U.S. Department of Agriculture (USDA) economists estimatethat lossesto rice growers reach Overall, the present findings suggest that any one ofthese $3.7 million annually. The chemical toxicant DRC-1339 has chemical pesticides may be utilized as a bird repellant on been used in the pastto reduce blackbird populations near flowering plants. Center researchers feel that field-test roost sites. However, the Environmental Protection Agency application rates of ziram and mesurol were probably higher (EPA) has concerns about its effectiveness and hazards to than needed for effective control. Therefore, furthertesting of nontarget birds feeding in baited areas. thesechemicalsshould beundertaken atlowerapplication rates. Dunng March and April 1991 rice baits containing DRC-1339 — , Repelling Snow Geese From Cover Crops Snow geese (2 percent active ingredient) were evaluated on blackbird overwinter in New Jersey and other mid-Atlantic States, and staging areas neara 4.7-million-blackbird roost in Evangeline migrant populations are increasing rapidly. As a result, snow Parish, LA. During the prebaiting period, blackbirds geese now cause problems forfarmers and wildlife managers consumed 5,900 lb of untreated rice from 9 bait sites within alike. Unlike Canada geese, whose depredations occur 2 miles ofthe roost site. During the treatment period, primarily In the fall, snow geese do most oftheir damage in blackbirds consumed 4,600 lb of brown ricetreated with DRC- late February and early March as the birds graze In 1339. Based on a consumption rate of 28 particles per bait- anticipation of spring migration. Rye, winterwheat, and turf site visit, an estimated 3.5 million blackbirds consumed are damaged, reducing nitrogen fixation and exposing fields to treated baits. Thirteen days after baiting commenced, the wind erosion. Because geese are Implicated as a primary roost population dropped from 4.7 million to 45,000. vector in the transmission of agriculturally Important pathogens and parasites, even farmers without substantial Centerscientists found that the rice baits treated with DRC- goose damage to crops express concerns overvisits by flocks 1339 caused no mortality to nontarget birds, such as to theirfields. savannah orwhite-crown sparrows, that were present on bait sites during baiting. Birds that could be susceptible to baits Recent cooperative work by scientists from DWRC and Monell treated with DRC-1339 (e.g., mourning doves) were not Chemical Senses Corporation shows that white plastic flags, observed on any baited site until afterthe baiting program was at a density of 1 flag/acre, effectively repel snow geese for concluded. 6-8 weeks at a lowcost ($0.80/unit). Comparably effective mylarflagging costs 50 percent more. In 1992, research was initiated to expand the possible use of DRC-1339 baiting for reducing sprouting rice damage by We speculate that white flagging may be a useful snow-goose blackbirds roosting in coastal marshes in Vermilion Parish, LA. damage-control tool in locations otherthan agricultural fields. Because ofthe difficulty in attracting coastal roosting Forexample, flagging might encourage snow-goose dispersal blackbirds to levee bait sites, Center scientists, with the in marshes where excessive grazing has had substantial assistance of biologists from APHIS' Animal Damage Control negative Impacts. The DWRC-Monell team plans to test this (ADC) unit, evaluated the effectiveness of "simulated nee possibility, as well as a comparative evaluation of white flags, fields" for attracting blackbirds to bait sites on levees. The black flags, and mylarstreamers. potential effectiveness and nontarget hazards of DRC-1339 baiting for reducing spring-roosting blackbird populations underthese conditions was also assessed. Eight of nine 4/DWRCHighlights Report: 1991-92 simulated rice fields, each consisting of prepared rice fields (two of which were found dead), nontarget exposure on levee seeded with approximately 200 kg of dehulled (brown) rice, bait sites appeared minimal. were effective in attracting blackbirds to fields and bait sites — on adjacent levees. Most consistent blackbird use occurred at Reducing Blackbird Damageto Seeded Rice The sixfields located on or near blackbird flight pathsto and from repellancy of a new insecticidal seed treatment, NTN-33893, coastal roosting areas. Approximately 22 percent ofthese was evaluated in cage feeding trials involving red-winged flightline blackbirds visited simulated fields. blackbirds and brown-headed cowbirds. Even at application rates well below those projected for insecticidal use, the From their assessments of 8 baited sites, Centerscientists compound effectively reduced bird consumption of rice seed. estimated that blackbirds consumed from 25 to 112 kg of bait Additional trials are planned to investigate furtherthe potential treated with DRC-1339 per site during 4 to 18 days of baiting. usefulness ofthis compound as a nonlethal means for Theoretically, if 432 kg of treated bait were consumed, controlling blackbird damage to seeded rice. approximately 500,000 blackbirds would have been killed. In — response to baiting and migration, blackbird roosting Evaluating Sucrose To Control Fruit-Eating Birds Recent populations in the treated area were reduced by discoveries regarding bird feeding behaviors and digestive approximately 70 percent. Yet for blackbird roosting physiology suggestthat conditioned aversions may develop in populations in one untreated control area, reductions response to fruit chemistry. Majorfruit-eating pests such as exceeded 90 percent, precluding any inferences about European starlings and American robins cannot digest treatment effects. sucrose, a minorcomponent of blueberries, cherries, and other small fruits, because these birds do not have sucrase, Although 28 nontarget species, primarily shorebirds, were the necessary digestive enzyme which splits the sucrose observed in simulated rice fields at a rate of 20.2 birds/h, molecule. Developing techniques that would substitute baiting only levees and field edges appeared to limit nontarget sucrose forthe simpler, digestible sugars naturally more bait exposure. Species such as killdeer, meadowlarks, and prevalent in fruit (glucose and fructose) could reduce bird cardinals were observed at a rate of 0.5 birds/h on levees and damage. This avenue was explored on two fronts in 1991: field edges, significantly less than their rate of appearance in biochemical alterations of fruit chemistry and repellancy actual fields. Based on these data and except forcardinals investigations. DWRCHighlights Report: 1991-92/5 — Through a cooperative research agreement between the Birds and Blueberries Blueberry and cherry growers University of Florida and DWRC, fruit crop researchers at the continue to experience high fruit loss to birds in most areas of university investigated enzymatic reactions that occurwithin the United States. The use offnghtening devices is costly, blueberries that regulate sucrose breakdown. This research is and they have limited effectiveness. The recent cancellation continuing in hopes ofdetermining biotechnological means to of Mesurol®for use on fruit came about in part because of elevate the sucrose level in fruitto bird-deterrent levels. concerns over residue levels. One approach to reducing residues is to lowerthe application rate. Center biologists Because ingestion of concentrated sucrose solutions makes evaluated Mesurol on blueberries in an aviarytrial at sucrase-deficient birds ill, scientists have speculated that application rates of 0.6, 1.1, and 1.6 kg/ha and in the field at sucrose might represent an environmentally safe avian 1.1 and 1.6 kg/ha. Biologistsfound thatthese application repellant. During 1992, Russ Mason and Larry Clark rates afforded limited reduction of bird damageto blueberries. compared the repellancy of sucrose to that of methyl However, Center biologists continue to evaluate other anthranilate (MA), a known avian repellant. They alsotested potential bird repellants such as MA and Imidan for use on different combinations of sucrose and MA to investigate small fruits. whether repellancy could be enhanced by mixing thetwo compounds. The results show that birds strongly avoided MA In the summer of 1992, Center biologists evaluated two MA in both feeding and drinking trials. Yet only light sucrose formulations (Bird Shields and ReJeX-iTF) and Imidan in solutions were avoided, and then solely in dnnking trials. No blueberry fields near Fennville, Ml. Birds had consumed combination of MA and sucrose was as effective as MA alone. between 12 and 19 percent ofthe crop at harvest; however, results suggested that the rate ofdamage was reduced during Additionally, feeding experiments were used to assess the the first 7 days posttreatment. behavioral responses offruit-eating birds to foods with high sucrose content. Robins and starlings avoided consuming Reducing Blackbird Damageto Sunflowers in the North- — aqueous solutions with more than 11.25 percent sucrose, Central States Throughout Minnesota and the Dakotas, mixed with less than 3.75 percent digestible glucose and millions ofcommon grackles, red-winged blackbirds, and fructose. yellow-headed blackbirds congregate in dense cattail marshes during midsummer, feeding on early ripening sunflowers. The These data suggestthat the development of high-sucrose value of annual sunflower losses due to blackbirds amountsto fruits as special bird-deterrent cultivars is promising as an millions of dollars. Chemical repellants, mechanical scare integrated pest managementtechnique to deterfeeding by devices, avicides, and altered cultural practices have been some species of birds. tested to reduce these losses. Each was found to have — limitations because of high cost in relation to benefits, Repelling Birds From Fruit With ImidanS^ The North logistical considerations, limited effectiveness, and/oradverse American Blueberry Council conducted a DWRC-funded environmental effects. DWRC scientists are testing new nationwide questionnaire surveyto determine the extent of managementtechniques for reducing blackbird damage to bird damage to bluebernes. Tabulation and analysis ofthe sunflowers. responses suggested annual bird damage in excess of $8 million. The pesticide Imidan® (active ingredient, phosmet) is In currentexperiments, blackbirds are dispersed by removing currently registered for use on numerous fruit crops. In orthinning cattails in theirpreferred roosting habitat, marshes. feeding trials, starlings and cedarwaxwings avoided Imidan- To accomplish this task efficiently, an EPA-registered aquatic treated fruit mash at concentrations of 30 p/m and 100 p/m. herbicide (RodeoB) is applied aeriallyto the cattails from These findings suggestthat this currently registered fixed-wing aircraft. Research on the amount of habitatthat insecticide treatment may be a useful component of strategies must be altered to disperse blackbirds and thereby reduce to control bird damage to fruit. sunflower damage is being conducted. In addition, the benefits of enhancing wetlands for other birds, especially Two other bird-repellent materials yielded less satisfactory waterfowl, through the use of interspersed vegetation and results. Although low applications rates of methiocarb (1.1 water are being assessed. and 1.6 kg/ha) successfully repelled birds from blueberries in aviarytrials, neitherapplication rate provided adequate In August 1989, cattails in four marshes used by large protection from bird damage in Michigan and Flonda field populations of blackbirds were aerially sprayed in strips with trials. MA was applied at rates of 2.3 and 9.1 kg/ha to Rodeo herbicide at 3.0 qt/acre. This rate was very effective blueberries in flight pen and field trials in Florida. Even atthe for killing mature stands ofcattails. Blackbirds did not roost in higher rate, neitherofthe two formulations tested was these marshes during 1990. 1991. or 1992. Populations of effective in reducing damage by birds. soras and Virginia rails, marsh wrens, waterfowl, and shorebirds were used to indicate possible effects caused by the application of Rodeo. The numbers of marsh wrens, soras, and rails, which depend on dense vegetation, declined SIDWRCHighlights Report: 1991-92 significantly between 1989 and 1992. The numbers of North Dakota State University scientists have developed a waterfowl and shorebirds remained the same. bird-tolerant hybrid sunflowercontaining morphological features thatthwart blackbird feeding. Features that may In 1990 and 1991, 24 marshes were selected to (1) test the make sunflower heads less accessible to feeding blackbirds effectiveness of removing cattails to discourage blackbirds include concave heads facing downward, thicker hulls, long from roosting, (2) determine the effect of altering cattail head-to-stem distances, and long, inward-pointing bracts. marshes on nontarget avian populations, and (3) determine Completed research showed that these morphological traits the effectof Rodeo on aquatic organisms. In July, strips of are consistent among planting environments. Thus, hybrids cattails in varying widths were sprayed with Rodeo across four possessing these traits can be developed forcommercial use. marshes. Eight untreated marshes served as controls. Few Experiments have been conducted whereby captured red- blackbirds roosted in the treated marshes in 1992. Sunflower winged blackbirds are fed whole sunflower heads showing damage was minimal (< 3 percent) in sunflowerfields various morphological features. It appearsthat concave- surrounding treated and untreated marshes, making the shaped or nearlyflat heads facing the ground arethe most effectiveness of cattail management difficult to evaluate. effective for conferring bird resistance. A commercial hybrid Numbers of marsh-dwelling birds observed, density of cattails bird-tolerant sunflower should be available within 3-4 years. in treated marshes, and the amount of sunflower damage surrounding test marshes will be analyzed. Development and Testing Rodenticides—DWRC researchers conducted a study in Texasto evaluate Preliminary research on the development of a computerized strychnine bait concentrations for control ofthe plains pocket mapping and imaging system to assess the effects of gopher. Strychnine baits were applied by hand, and pocket- herbicide sprays on marsh vegetation began in 1991 and gopher mortality was determined by monitoring radio- continued in 1992. Aerial photos were taken of45 marshes equipped animals aftertreatments. The highest mortality DWRC treated with herbicide and 12 control (untreated) marshes. occurred at the 0.75-percent concentration rate. Ultimately, the system will be used to predict likely blackbird submitted a final report regarding these data to EPA in 1992. roost sites and to pinpoint areas ofthe marsh preferred by blackbirds. DWRCHighlights Report: 1991-92/7 — Laboratory studies ofcholecalciferol as a rodenticide for use Evaluation of Cholecalciferol Baitfor Pocket Gophers with norttiern pocket gophers were completed. Cholecalciferol Cholecalciferol-treated oat bait (0.15 percent active ingredient) concentrations as low as 0.01 percent are effective. wasfound effective against radio-collared pocket gophers in a tree seed orchard near Olympia, WA. A followup baiting of In laboratory studies, bromethalin grain baits were evaluated control animals with equal parts of untreated oats and for black-tailed prairie dogs. The prairie-dog mortality data cholecalciferol-treated oats was also effective. suggested that additional testing ofthis compound is desirable. Several pocket gophers in the study area were taken by avian predators. Further evaluation of cholecalciferol bait is In cooperation with the State of Nevada, strychnine-alfalfa indicated if sufficient data are developed to assure that no baits were formulated with a 3.2-percent strychnine hazards exist for raptors and ifthe food base forthreatened concentration and were tested on Townsend pocket gophers raptors is notjeopardized by baiting rodents on forest lands. in the laboratory. Data were inconclusive, and a field test scheduled for September 1991 was canceled. Additional Alternativesto Lethal Baits for Mountain Beavers in testing with a reformulated strychnine concentrate has begun. Forests—DWRC researchers conducted studies oftrapping and habitat modification by mechanical thinning and by use of Evaluation of Strychnine Baitfor Control of Mountain herbicides on forest plantations damaged by mountain — Beaver Field evaluations ofoperationally applied, pelletized beavers. Evaluation ofthe removal of mountain beaver nests strychnine baits forcontrol of mountain beavers on forest indicated that reinvasion ofthese systems is delayed several lands showed that at three experimental concentrations, years, possibly long enough to establish new plantations. The strychnine had very little effect on mountain beavers. initial herbicide applications applied to mountain beaver Evaluations on 24 study areas in Washington and Oregon habitat were not effective in reducing growth oftargeted indicated thatthe beavers readilytake baitfrom burrows but vegetation. apparently do not eat it. Pen studies at Olympia showed that one baited pellet (with 0.9 percent strychnine) was lethal but Response of Mountain Beaverto Conspecifics in Their — was not readily eaten. The manufacturer (Oreo) does not plan Burrow System Artificial burrow systems were constructed to renew registration ofthe bait pellets for mountain beaver. to study interactions among mountain beavers. Encounters There appearsto be a significant correlation between within the system were agonistic, and resident animals telemetry evaluations ofthis pelleted bait, which showed good aggressively evicted intruders. Though mountain beavers efficacy when it was placed where radio-collared animals were exhibited scent-marking behaviors, the marks did not prevent known to be active compared to poorefficacy for operational intrudersfrom entehng and exploring occupied burrow evaluations where the actual locations ofthe mountain systems. We speculate that marking serves to enhance the beaverswere unknown to the people applying bait. terntorial confidence ofthe established mountain beaver. Evaluation of Diphacinone Bait Blocks for Pocket Gopher Relative Intake of Selective Forage Species bythe — — Control Radio telemetry and operational evaluations of Mountain Beaver Foraging by mountain beavers is registered paraffin bait blocks containing diphacinone for economically important because it hinders reforestation efforts control of pocket gophers and pocket gopher reinvasion in the Pacific Northwest. Species of hanyested forage have indicated that there was no reduction of reinvasion within been identified through obseiA/ational studies and stomach 6 months or 1 yearafterthis bait was applied to forest lands in analyses. Unfortunately, scientists know little aboutwhy southwestern Oregon. Radiotelemetry applications, including mountain beavers selectthese plants. In an ongoing study, the use oftransmitters embedded in bait blocks, showed that attempts were madeto identifyfactors that influence the blocks were fed on and were transported inside burrow foraging habits of mountain beavers. Mountain beavers are systems. There was less control, however, of radio-collared periodically offered a variety of plants from which to forage for pocket gophers with the diphacinone blocks than with food and/or nesting matenal. Relative changes in which registered strychnine-treated oat bait used forcomparison plants are selected by mountain beaver may reflect changes (62 percent v. 72 percent). Overall control after 1 month with in a plant's nutritional constituents orchemical defenses. A diphacinone was 36 percent, versus 61 percent with cursory review ofthe data reveals that conifers are taken less strychnine bait. Alternatives to baiting are being sought frequently in the spring and summerthan they are during the because of possible impacts on threatened or endangered fall and winter. Conversely, red alder is taken more often in species associated with lands under reforestation. the spring trialsthan in the wintertrials. Foxglove and ginger are generally avoided, while mountain beaver routinely select for salal, cat's ear, sword fern, bracken fern, and red huckleberry. BIDWRCHighlights Report: 1991-92