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10 CHAPTER FOUR HARASSMENT, REPELLENT, AND DETERRENT TECHNIQUES We begin this section with a tabular summary of relative efficacy of harassment, repellent, and deterrent techniques for birds at airports. Table 1 is a synthesized literature review providing examples of relative efficacy of each technique. AUDITORY DETERRENTS Ultrasonic Ultrasonic devices likely will not be a viable option as a deterrent for birds. Erickson et al. (1992) surmised that high- frequency sound (>20,000 Hz or cycles per second) devices generally were not effective in repelling birds. Griffiths (1987) tested a commercial ultrasonic unit against numerous bird species in the mid-Atlantic United States and found no apparent effect on bird activity. Martin and Martin (1984) found another ultrasonic device to be ineffective. Woro- necki (1988) reported that an ultrasonic device (Ultrason UET-360) was not effective in reducing rock dove activity during a 20-day treatment period. However, he reported that a combination of a visual device (tested as Deva-Spinning Eyes) and a sonic device (tested as Deva-Megastress II) did temporarily alter rock dove behavior during a 10-day treat- TABLE 1 RELATIVE EFFECTIVENESS OF AVIAN REPELLENT TECHNIQUES Source: Adapted from Cleary and Dickey (2010). Effectiveness: G = Good; F = Fair; P = Poor; N = Not Recommended.
11 poel 1976), agricultural settings, and other locations (Baxter 2000). From the Fieldâ¦Golden Triangle Airport (GTR) The Golden Triangle Regional Airport Authority was established in 1971 through a partnership with the cit- ies of Columbus, Starkville, and West Point, and the counties of Lowndes and Oktibbeha, Mississippi. The airport property consists of 1,000 acres and has ap- proximately 40,000 airplane movements a year. Bird harassment is conducted by the airport firemen, who dedicate approximately 10% of their time to wildlife management. Seasonal influxes of geese in the winter and raptors in the summer are the main problems that arise with wildlife. The staff uses pyrotechnics to move birds from problem areas. Additionally, in the fall, flocks of sparrows and other small flocking birds can create potential hazards. In these instances, personnel have used fire trucks to apply high volume and pressure of water to disperse birds with good success. Mike Hainsey, airport executive director, noted, âHabitat management is a primary line of defense.â Mott and Timbrook (1988) examined the effect of alarm and distress calls on Canada geese. They found a 71% decrease in goose numbers in response to the calls. Addi- tionally, they found a 96% reduction in goose observations when the distress calls were coupled with pyrotechnics (tested as racket bombs, a noise-making pyrotechnic shot from a pistol launcher). Unfortunately, recolonization of the study area occurred shortly after the treatments stopped. In an urban setting, Gorenzel and Salmon (1993) experimented with distress and alarm calls in an effort to deter crows. Ini- tially, crows from nearby roosts were attracted to the calls, but after 30 seconds the crows left the immediate vicinity. Cook et al. (2008) used a modeling approach to assess the effectiveness of nine techniques, including pyrotechnics, handheld distress calls, static distress calls, blank ammu- nition, a combination of blank and lethal use of ammuni- tion, falcons (Falco spp.), hawks (Accipiter spp.), wailers, and kites. These techniques were employed on three spe- cies of gulls at landfill sites. Distress calls were among the most effective; however, when habituation was considered, distress calls were not as effective as other techniques with lethal consequences. Conklin et al. (2009) tested bioacous- tic deterrents for nesting cliff swallows (Petrochelidon pyr- rhonota). Eight unique recordings of alarm and distress calls ment period and reduced the rock dove population present during the onset of treatment. However, this study was not conducted in an airport environment but in a vacant build- ing. Also, the study was not replicated, nor were paired non- treated sites used for comparisons. Gas Exploders Gas-operated exploders, sometimes referred to as gas or propane cannons, offer temporary efficacy for deterring birds from airfields. They have been commonly used to repel pest birds in agriculture and around airports since the late 1940s (Gilsdorf et al. 2002). These devices produce extremely loud, intermittent explosions, usually at fixed 1- to 10-minute intervals as desired, that exceed the blast of a 12-gauge shotgun. Present-day exploders consist of a bottled gas supply, separate pressure and combustion chambers, an igniting mechanism, and a barrel to direct and intensify the noise of the explosion. To alleviate habituation, exploders should be moved periodically (e.g., every 1 to 3 days) within the area needing protection (Littauer et al. 1997; Reinhold and Sloan 1997). Washburn et al. (2006) conducted an experiment with propane exploders at John F. Kennedy International Airport. These authors did not find a significant difference in bird behavior in response to the exploder. Furthermore, the addi- tion of lethal removal did not enhance effectiveness. Con- over (1984a) reported a 77% reduction in bird damage within cornfields in response to exploders. Propane exploders were more cost-effective compared with a chemical technique (tested as Avitrol FC-99) and a visual technique (tested as hawk-kites). In the Mississippi alluvial plain, Mott et al. (1998) described that harassing double-crested cormorants roosting at night was successful in dispersing cormorants and reducing depredation rates at nearby catfish farms, suggest- ing that it may work on stormwater ponds around airports. Also, Cummings et al. (1986) described that a combination of a gas exploder and a CO2 driven pop-up scarecrow was effective sporadically in a row crop agriculture setting; how- ever, habituation was likely occurring in later tests. Biosonics: Alarm and Distress Calls Biosonic calls, including alarm and distress calls, appear to have some efficacy for deterring birds. However, additional research involving rigorous experimental design is neces- sary to understand efficacy more fully. Biosonics as a repel- ling technique is based on acoustical signals emitted by birds and other animals to convey information to other individu- als of the same species (Boudreau 1968; Conover and Perito 1981; Bomford and OâBrien 1990). Two audible bird-warn- ing stimuli, distress and alarm calls, have been explored or used for acoustically repelling birds from urban and rural roosts (Pearson et al. 1967; Brough 1969), fish-rearing ponds (Spanier 1980; Andelt et al. 1997), airport runways (Blok-
12 were used together in a mix played through an acoustical broadcast unit. Random playback order was used to delay or reduce habitation by swallows. The presence of calls reduced nesting activity by more than 50%. Coates et al. (2010) eval- uated bioacoustics as a deterrent to wild turkeys in Califor- nia vineyards. Broadcast calls of three different types were used independently: wild turkey alarm call, domestic turkey alarm, and crow distress call. No differences in damage rates were found in treated versus untreated plots. Pyrotechnics Pyrotechnics have long been used as deterrents to birds in a variety of settings (Neff and Mitchell 1955; Zajanc 1962; Mott 1980; Tipton et al. 1989; Mott and Boyd 1995; Andelt et al. 1997; Littauer et al. 1997; Mott and Brunson 1997) and can be effective in deterring birds. These devices rely on an explosion or other type of loud noise to deter birds from an area (Mott 1980) and can produce visual stimuli such as a flash of light or burst of smoke. Devices include rifles and shotguns firing live ammunition or blanks and 12-gauge shotguns and flare pistols that shoot exploding or noisy pro- jectiles, including shell crackers, bird bombs, bird whistles, whistle bombs, or racket bombs (Booth 1994; Harris and Davis 1998). Signal flares also have been used at some air- ports but are more expensive than the other devices (Lefeb- vre and Mott 1987). An example of these devices is shown in Figure 4. FIGURE 4 Pyrotechnics (Source: USDA/APHIS/WS Ohio Field Station). Aguilera et al. (1991) reported that screamer shells were effective in dispersing flocks of Canada geese; also, no habituation was reported after treatment. Mott (1980) tested scare cartridges and noise bombs simultaneously to disperse roosting red-winged blackbirds and European starlings in Kentucky and Tennessee. Roosting bird populations of about 1 million birds in five roosts were reduced 96% to 100% dur- ing 3 to 8 evenings of harassment. Mott et al. (1992) tested the effectiveness of pyrotechnics as a dispersant for roost- ing double-crested cormorants (Phalacrocoraxauritis) in the Delta region of Mississippi. Bird-bangers and scream- er-sirens were fired from single-shot pistol launchers on 4 consecutive evenings. Cormorant numbers were decreased from approximately 8,000 birds to 6 during the harassment period. However, Mott et al. (1992) stated that this technique would be less effective if multiple roost sites were available to birds in an immediate area. Logistically and financially, harassing birds in this fashion may not be efficacious. Most bird species become habituated to noises produced by pyro- technics if used repeatedly over time (Littauer et al. 1997; Reinhold and Sloan 1997; Stevens et al. 2000; Ronconi et al. 2004; Ronconi and Clair 2006; Cook et al. 2008). VISUAL REPELLENTS Vision-based deterrents present a visual stimulus that is novel, startling, or that the birds associate with danger. The danger can be a predator, a simulated predator, the result of From the fieldâ¦Sacramento International Airport (FAA code--SMF) Approximately 152,000 operations occur annually at Sacramento International Airport, including commercial, cargo, general aviation, and military operations. Sacra- mento International Airport is located within the Nato- mas basin of California, situated in the Pacific migratory flyway for numerous waterfowl and other bird species. Greg Rowe, senior environmental analyst, described their style of wildlife management as a holistic approach that integrates harassment techniques and animal removal, but most important, working with land use and habitat management to reduce use of the airport landscape by hazardous birds. The airport employs two full-time biolo- gists, and two other employees spend approximately half of their time to reduce hazardous wildlife. Waterfowl are by far the most common problem species, but other birds such as vultures, ibis species, and swallows are also problematic. Additionally, raptors are a growing problem. The most commonly employed deterrent technique is pyro- technics and electronic sound emission devices. These are typically used to scare birds from ponds located near the runway. Greg notes, âOur biologists typically have to ap- ply these techniques to the same group of birds on a daily basis in order to be effective.â Greg also stressed that land management is key and other techniques are secondary in the mission to reduce hazards.
13 a predator attack, or some unusual object that birds avoid because it is unfamiliar. Lights, scarecrows, dyes, reflecting tape, predator decoys, kites, balloons, smoke, and dead or live birds are visual stimuli that may disperse birds. Effigies Effigies have been demonstrated to reduce bird use of target areas; however, their efficacy varies markedly depending on type of effigy used, species being deterred, and resource (nest site, loafing site, foraging area) from which birds are being deterred. Effigies include devices such as scarecrows, scary-eyes, and predator-mimicking devices (e.g., hawk or owl) (Harris and Davis 1998). Scarecrows are one of the old- est devices that have been used to control birds (Frings and Frings 1967). Most scarecrows are human-shaped effigies constructed from various inexpensive materials, includ- ing grain sacks or old clothes stuffed with straw. The more realistic the facial features and the human shape, the more effective scarecrows are likely to be (Gilsdorf et al. 2002). Painting scarecrows a bright color can increase their detect- ability (Littauer 1990). Stickley et al. (1995) demonstrated that a pop-up human effigy reduced double-crested cormorant use of catfish ponds; however, the device was only tried for 7 days. It is unclear if habituation would have occurred later. Nomsen (1989) reported that a humanlike scarecrow that popped up from a double propane cannon when fired was highly successful in keeping blackbirds from feeding over 4 to 6 acres of sunflowers. Ducks and geese were observed to be much easier to frighten from the site than blackbirds. Con- iff (1991) reported that this kind of scarecrow placed near a catfish pond effectively frightened cormorants. Numbers of great blue herons (Ardeaherodias) and black-crowned night-herons (Nycticoraxnycticorax) initially decreased at a fish hatchery following implementation of two human effi- gies (tested as Scary Man Fall Guy), but the herons quickly habituated to the devices and numbers increased after the first 4 nights (Andelt et al. 1997). Boag and Lewin (1980) found that a human effigy was effective in deterring dab- bling and diving ducks from small natural ponds. When the effigy was present, the number of ducks on the ponds declined by 95%. Over the same interval there was only a 20% decline on adjacent control ponds, indicating that the effigy was quite effective. Cummings et al. (1986) used a propane cannon and a CO2 pop-up scarecrow to deter blackbirds from sunflow- ers. They found that most birds were frightened away by the scarecrows; fewer birds returned during the treatment period than were observed during the control period. Cum- mings et al. (1986) speculated that the birds that returned had become habituated to the scarecrow in some cases, and in other cases, that feeding patterns were too well established to allow effective deterrence of the birds. Seamans (2004) reported the effective use of a vulture effigy to deter vultures from a tower in northern Ohio. How- ever, the author reported seasonal differences in effective- ness; in the summer there was no difference in vulture use of the tower during pre-and posttreatment periods. Seamans and Bernhardt (2004) conducted field evaluations of Canada goose effigies. They found an initial decrease in goose abun- dance; however, during a second treatment period no dif- ference was detected. Geese were likely habituated to the effigies after a short time. Figure 5 shows an example of a visual repellent in the form of a dead Canada goose. FIGURE 5 Dead goose effigy (Source: USDA/APHIS/WS Ohio Field Station). Ball (2009) described in an anecdotal note that effigies appeared to be effective in reducing vulture use of the airfield at Cherry Point Air Force Base in North Carolina. Similarly, Tillman et al. (2002) reported that effigies were effective in dispersing vultures from roost sites near livestock produc- tion facilities. Additionally, the authors tested waterfowl decoys painted to resemble dead vultures. They report a continued effectiveness upon switching from the taxidermy effigies to the mock-up decoys. Avery et al. (2002) corrobo- rated Tillman et al. (2002) in the context of vulture [black vulture (Coragypsatratus) and turkey vulture (Cathartes aura)] use of communication towers. They found a 93% to 100% decline in vulture numbers immediately follow- ing installation of the effigies. The authors also noted that effectiveness was independent of species composition of the vulture flock or the vulture species used for the effigy. Most important, Avery et al. (2002) found that the effectiveness was maintained 5 months posttreatment. Effigies appear to be an effective tool to reduce use of an area by both species of vultures. Predator Models Decoys or models have been used to repel birds for decades in agricultural crops, and should be similar in the airport environment (Conover, 1979, 1982a, 1984a, 1985a; Hothem
14 and DeHaven 1982) (Table 1). Conover (1979, 1982a) found that stationary, mounted hawks and hawk-kites deterred birds from feeding stations and cornfields but that their effective- ness was short-term. Conover (1984a) elucidated that hawk- kites reduced red-winged blackbird (Aegaeileus phonecius) damage by 83% in an agriculture setting. Belant et al. (1998) found plastic, hand-painted effigies of great horned owls (Bubo virginianus) and merlins (Falco columbarius) inef- fective in reducing starling use of nest boxes. There was no significant difference in starling activity among nest boxes with or without the effigies. Conover (1983) found that black- birds and crows often mob owls or owl models, increasing use of an area by hazardous birds. However, Conover (1982b, 1985b) found that an animated plastic owl model clutching a plastic crow in its talons repelled crows from gardens and small fields, while a stationary version of the same model was not effective. Seamans and Helon (2006) tested a lightweight plastic device that forms a spiral when suspended and contains pig- ments that allow the device to change color depending on viewing angle (tested as the ChormaFlairâ¢ Crow Buster) to repel starlings at nest sites. There was no difference in the presence of nest material between treated and control nest boxes. Also, clutch size was similar between treated and controls, but a slight delay in egg laying was observed in the treated boxes. Balloons or modified balloons have been tested on numerous occasions as a deterrent for birds in various set- tings (Conover 1982a; Avery et al. 1988; McLennan et al. 1995; Nakamura et al. 1995; Mott et al. 1998). Seamans et al. (2002) tested a balloon with a kite and stabilizer attached to deter gulls near a landfill in New York. Under various circumstances the device was effective in decreasing gull use. However, Seamans et al. (2002) reported high mainte- nance costs and time requirements to deploy such devices. They maintained that devices such as these should be used as a part of an integrated management program for gulls. Figure 6 shows an example of a visual repellent in the form of a balloon. FIGURE 6 Helikites in action (Source: USDA/APHIS/WS Ohio Field Station). Lasers Lasers (such as the device shown in Figure 7) have been demonstrated to deter birds; however, efficacy varies across species and with wavelength (i.e., color) of transmitted light. Relative efficacy increases with decreasing ambient light. The use of lasers to disperse birds is relatively new (Lus- tick 1973; Gilsdorf et al. 2002). Glahn et al. (2000) tested the efficacy of lasers to disperse double-crested cormorants from night roosts in the Mississippi Alluvial Valley during winter. Two types of lasers were tested: the Desmanâ¢ laser [red (632.8 nm) helium-neon laser] and a Dissuaderâ¢ laser security device that is also a red beam (650 nm) but is a diode laser (Glahn et al. 2000). The authors pretested the lasers on wild-trapped cormorants, but results of that study were inconclusive. However, the field trial portion demonstrated significant reductions in cormorant populations by â¥90%. No difference was found between laser types. FIGURE 7 Laser used for dispersing birds (Source: USDA/ APHIS/WS Ohio Field Station). Blackwell et al. (2002) tested the efficacy of a 10-mW continuous-wave, 633-nm laser to repel brown-headed cow- birds and European starlings while perching. They tested a 68-mW, continuous-wave, 650-nm laser in dispersing star- lings and rock doves from perches; also, they tested this laser on Canada geese and mallards in grass plots. There were mixed results; brown-head cowbirds or European star- lings were not repelled from their perch, whereas rock doves demonstrated avoidance during the first 5 min of the 80-min dispersal periods, suggesting weak efficacy. Geese demon- strated the strongest avoidance behavior, 96% of birds dis- persed from the laser-treated plots. Mallards were dispersed initially but habituated to the beam after 20 min. Gorenzel et al. (2002) found similar results with Ameri- can crows. Most crows were dispersed from roosts by the laser, but returned within 15 min. Lasers are a relatively unobtrusive device to humans and show promise as a repel- lent for birds, but results are species specific (Blackwell et al.
15 for blackbirds. However, red mirrors reduced the capture rate compared with the control. Furthermore, more brown-headed cowbirds (Molothrus ater) and common grackles (Quiscalus quiscula) were captured more often in control traps versus treated traps with mirrors. Numerous types of lights have been used to deter birds at feeding, roosting, and loafing sites (Koski et al. 1993; Seamans et al. 2001). Larkin et al. (1975) observed that migrating birds reacted to searchlight beams at distances of 200â300 m. In the same study, birds took evasive action to approaching small aircraft with landing lights. Blackwell and Bernhardt (2004) tested the efficacy of pulsing white and wavelength-specific aircraft-mounted light during day- light hours. Their experiments involved captive brown-head cowbirds, Canada geese, European starlings, herring gulls, and mourning doves. Cowbirds were the only species that exhibited a response to the landing lights, but responses were sporadic. Blackwell and Bernhardt (2004) contended that more research was needed on specific light wavelengths and pulse frequencies. Specifically, understanding object lighting in the context of avian antipredator responses, and how antipredator behavior varies among bird species, may improve efficacy of lighting as a control technique (Black- well et al. 2009). Dogs and Falconry The use of dogs to deter and haze birds is promising and gen- erally appears effective, but more experimental research is needed. The use of dogs has received attention and research as a tool to deter birds from airports (Carter 2000a,b; Cas- telli and Sleggs 2000; Patterson 2000). Castelli and Sleggs (2000) reported a retrospective analysis of the efficacy of a border collie program to repel and haze geese. At the local scale of the airport, the program was effective at reducing geese overabundance, but at the larger regional scale it did not contribute to the solution. Carter (2000b) reported sev- eral case studies on the use of border collies. Most strikingly, in Delaware the use of dogs reduced bird numbers by 99.9%, and damage was reduced from $600,000/year to $24,000/ year. Figure 8 shows an example of a dog on bird-deterrent duty at an airport. FIGURE 8 Border collie at work in Florida [Source: Marc Beaudin, The News-Press (Ft. Myers, Fla.)]. 2002; Gilsdorf et al. 2002; Gorenzel et al. 2002). Although green and blue lasers were ineffective at deterring white- tailed deer (Odocoileus virginianus) (VerCauteren et al. 2006), they have not yet been tested for efficacy in repelling birds. However, qualitative evidence at some airports sug- gests green lasers can be highly effective at dispersing birds such as rock doves and European starlings. Reflecting Tape, Reflectors, and Flags Reflecting tape and similar devices appear to have limited efficacy in most circumstances. Summers and Hillman (1990) tested a red fluorescent tape (20 mm wide) in fields of winter wheat in the United Kingdom to deter brant. The tape proved more successful than the cannon and scarecrows in repelling brant. Compared with control fields, a 1% reduc- tion in grain yield in the taped field was found compared with a 6% reduction in the untaped field. Belant and Ickes (1997) tested mylar flags (reflective material) for their effectiveness as gull deterrents. Flags were tested at two nesting colonies and two loafing sites at a landfill near Lake Erie. The authors concluded that the reflecting tape was unsuccessful in deter- ring herring gulls from nesting colonies but can reduce her- ring and ring-billed gull use of loafing areas. Reflecting tape was ineffective in deterring birds from ripening blueberries (Tobin et al. 1988). In this study habituation was considered likely, and reportedly not enough tape was used to elicit a response. Conover and Dolbeer (1989) found similar results with red-winged blackbirds in cornfields. Fields treated with reflector tape had similar damage rates to untreated fields. These results contrasted with those of Dolbeer (1981), Brug- gers et al. (1986), and Dolbeer et al. (1986), who found reflec- tive tapes to be effective in grain fields. Conover and Dolbeer (1989) attributed the possible differences to variation in row spacing of tape. Gilsdorf et al. (2002) further suggest that closer spacing of ribbons of tape may be more effective, but likely not cost-effective. Lights and Mirrors Lights and mirrors appear to have application for dispersing birds from airport environments, but additional research is necessary before specific recommendations can be made. Few studies have evaluated the effectiveness of mirrors to deter birds. Seamans et al. (2001) evaluated mirrors to deter nesting starlings in northern Ohio. Various combinations of mirror types and the addition of lights (green and red flashing) were tested. Fewer nests were found in treated nest boxes in the first year of study. During the second year lower occupancy rates of nest boxes were also found, specifically in the mirror and light combination treatment. The authors concluded that even though slight reduction in starling use was found, mirrors were not a practical repellent. Seamans et al. (2003) followed up the previous study with a similar experiment testing rotat- ing mirrors as a deterrent for decoy traps. Capture rates did not differ between treated (rotating mirror) and untreated traps
16 tested as Avitrol, has been effective against gulls, starlings, crows, rock doves, and house sparrows (Passer domesticus) (Seamans 1970). Avitrol also has been used successfully on loafing gulls and pigeons (Blokpoel 1976). Sweeney and McLaren (1987) demonstrated its effectiveness on gulls at landfills. However, Dolbeer (1981) found Avitrol not to be cost-effective in grain crops. Knittle et al. (1988) found 4-AP to be effective for reducing blackbird damage to sunflowers, but it was mostly ineffective in fields greater than 2 miles from a roost. Avitrol is toxic and can be difficult to admin- ister in a dose sufficient to cause the desired effect but not to kill the bird immediately (Harris and Davis 1998). Death may be delayed and affected individuals may be able to fly away before dying elsewhere (Holler and Schafer 1982). Methyl Anthranilate Methyl anthranilate (MA) has been tested on numerous occa- sions as a deterrent for birds in a variety of settings (Avery 1992; Cummings et al. 1992, 1995; Dolbeer et al. 1992; Vogt 1994; Avery et al. 1995; Belant et al. 1995, 1996, 1997). Both dimethyl and MA were strongly avoided by captive mallards and Canada geese when birds were offered both treated and untreated grain (Cummings et al. 1992). When offered only treated grain, both ducks and geese reduced their food intake, but mallards, and to a lesser extent, Canada geese, gradually increased consumption during the 2 to 4 days of the experi- ment. Cummings et al. (1992) assumed that the birds were habituating to the chemical, but they were not given an alter- native food source, and the increased consumption may have been caused by increased hunger. Cummings et al. (1995) tested another formulation of MA, REJEX-IT AG-36, as a grazing repellent for Canada geese. In the pen trial, 59 kg/ha of the chemical applied reduced goose activity on treated grass plots for less than 4 days. Similarly, Cummings et al. (1995) evaluated the effectiveness of MA, tested as ReJex-iT AG-36, as a deterrent for blueberries. In Michigan, MA applied at 16.1 kg/ha did not reduce overall damage by birds, but did offer ephemeral control for 7 days. In the same study, Cummings et al. (1995) tested MA at a rate of 32 kg/ha in Florida to caged cedar waxwings (Bombycilla cedrorum). Results were similar for waxwings in Florida to those in Michiganâberry consumption did not differ. Belant et al. (1995) tested two for- mulations of MA (tested as AP-50 and TP-40) to repel gulls and mallards from water. Overall, gull activity was reduced in pools treated with the MA (tested as AP-50, a free-flowing powder) formulation compared with untreated pools. The MA formulation tested as TP-40 (containing a surfactant), with 1.6-3.0 times greater concentration of MA at the water surface, was slightly more effective in reducing bird activity. Conversely, Belant et al. (1996) found MA in a 14.5% vol/vol formulation was ineffective in reducing geese foraging activ- ity. Also, Belant (1997) found MA ineffective in reducing woodpecker activity on wood siding of residential buildings. Dolbeer et al. (1992) investigated MA (tested as ReJeX-iT) at two different concentrations. Both concentrations were effec- The use of falconry has received some attention as a bird deterrent and appears to have limited efficacy. Some falconry is employed in the United States, but it has mostly occurred in the United Kingdom (Blokpoel 1976; Hild 1984; Erick- son et al. 1990; Dolbeer 1998; Walker 2003; Bryant 2005; Kitowski et al. 2010;). Peregrine falcons (Falco pereqrinus), gyrfalcons (Falco rusticolus), and goshawks (Accipiter gen- tilis) are the species most frequently used (Blokpoel 1976). At John F. Kennedy International Airport, Dolbeer (1998) tested the use of falconry to reduce laughing gull use and strikes to aircraft. Falconry in this case did not provide additional efficacy to a shooting program, but did provide increased public acceptance of the management program at the airport. CHEMICAL REPELLENTS Chemical aversion agents have been used to control birds in a wide range of settings (Guarino 1972; Rogers 1974; Crase and Dehaven 1976; Conover 1984b; Greig-Smith and Rowney 1987; Bomford and OâBrien 1990; Clark and Shah 1991, 1993; Clark et al. 1991; Avery and Decker 1994). Their efficacy is highly variable and depends on chemical use, mode of action, species being deterred, and resource (e.g., loafing site, feeding area) being protected. 4-aminopyridine and 3,5-dimethyl-4-(methylthio)phenyl methylcarbamate Chemical frightening agents and repellents such as 4-amin- opyridine (4-AP) (e.g., tested as Avitrol) and 3,5-dimeth- yl-4-(methylthio)phenyl methylcarbamate (e.g., tested as methiocarb) are poisons that, in sublethal doses, may cause disorientation and erratic behavior. They are usually added to bait. Typically only a portion of a bait presentation (e.g., 10% of corn kernels) is treated with the chemical so that only a small number of the birds to be dispersed are affected. When the treated bait is ingested, a distress response occurs (DeFusco and Nagy 1983; White and Weintraub 1983). Dis- tress calls from affected birds can start 15 min after ingestion, and can last up to 30 min after first effect. Besides emitting distress calls, affected birds may become disoriented and exhibit erratic behavior, often flopping about on the ground. This behavior often alarms other birds and causes them to fly away. If too high a dose is ingested, the bird will die. Trem- ors and convulsions occur before death if birds receive an overdose of the aversion agent, and these may induce other birds to leave the area. Dolbeer et al. (1976) and Woronecki et al. (1989) tested the effectiveness of 2 aminopyridine (chemically similar to 4-AP) in sweet corn fields. Overall, no reduction in dam- age was observed. However, Avitrol has been proven use- ful in dispersing birds (Goodhue and Baumgartner 1965; Woronecki et al. 1989; Gadd 1992; Swindle 2002). 4-AP,
17 tive in repelling mallards and ring-billed gulls. Stevens and Clark (1998) tested MA in an aerosol form as an irritant for captive starlings. The MA aerosol was effective as an irritant and starlings did not habituate to repeated exposure. Aerosols may hold promise as a hazing technique for some species of birds; however, more research is needed on their effectiveness and proper application concentrations. Anthraquinone Dolbeer et al. (1998) evaluated an anthraquinone formulation [tested as Flight Controlâ¢ (FC)] as a feeding repellent for Canada geese and brown-headed cowbirds. The formulation was applied to turf within small pens housing captive geese. They found 2.5 times more bill contacts/min observed on untreated plots compared with treated plots during a 7-day trial. Presented with untreated millet or millet treated with FC, caged cowbirds avoided the treated seed and lost body mass during the 3- to 4-day trials. Cummings et al. (2002) conducted a field evaluation of anthraquinone (tested as FC) in newly planted rice fields. Seed was treated with FC at a 2% (g/g) concentration at day of planting. Blackbird abun- dance and seed damage were significantly lower in treated fields compared with untreated fields. Blackwell et al. (1999) tested the possible enhancement of anthraquinone (tested as FC) with the addition of a plant growth regulator [tested as Strongholdâ¢ (SH)]. The plant growth regulator alone was not effective in reducing herbivory of grass by geese. However, a combination of anthraquinone and the plant growth regulator reduced geese presence by 62% and reduced foraging activ- ity by 88%. Blackwell et al. (1999) also reported a continued effect of the treatments 22 days after initiation. The plant growth regulator (tested as SH) greatly enhanced anthraqui- none (tested as FC) as a repellent for geese on turf grass. Blackwell et al. (2001) again used anthraquinone (tested as FC) and methyl anthranilate (tested as ReJeX-iT AG-36), but in this instance sandhill cranes (Grus canadensis) were used in pen trials with corn. Both chemicals were effective in reducing corn consumption by cranes. Cranes consumed 8.6 times more corn in the untreated pens compared with corn treated with MA (tested as FC) and consumed 9.8 times more untreated corn compared with corn treated with MA (tested as ReJex-iT AG-36). Methyl anthranilate applied with a plant regulator appears to provide repellency against birds at food sources for up to several weeks (Blackwell et al. 1999). Miscellaneous Chemicals Dolbeer et al. (1988) tested the effectiveness of naphthalene as a repellent for starlings around structures. No differential use was found in treated or untreated nest boxes. No recent inves- tigations of napthalene as a repellent have been conducted. Belant et al. (1997a) compared the effectiveness of d-pulegone and mangone, both taste aversives, on captive brown-headed cowbirds. The 0.01% d-pulegone lowered cowbird feeding activity, but at lower rates did not. Man- gone was slightly more effective at lower concentrations, but consumption of mangone-treated millet was similar among one-choice tests. Dolomitic limestone has been hypothesized as a taste aversive for birds (Clark and Belant 1998). Belant et al. (1997) tested if adding limestone in the form of a dry substance or slurry reduced consumption of grain. Results were mixed, as reductions of total food intake decreased for both cowbirds and geese during one-choice tests with lime and grain. How- ever, body mass was not affected during two-choice tests. In treated grass plots, goose feeding was reduced for 2 to 3 days after application of lime in both forms. Similarly, tests of dolomitic lime, activated charcoal, a silica-based compound (tested as Nutra-lite), and white quartz sand as taste aver- sives on cowbirds and Canada geese revealed that lime and charcoal showed potential as repellents (Belant et al. 1997b). However, Belant et al. (1997b) reported short-lived efficacy of the silica-based compound for geese. Chemical-based Tactile Deterrents Tactile deterrents are perhaps the least studied bird deterrent approach. Most tactile repellents are sticky substances that deter birds from sitting on perches, such as building ledges, antennas, and airfield lights and signs. Reidinger and Libay (1979) tested glue applied on perches to deter birds near rice- fields. The authors found the glue to be effective during the short treatment period (5 to 8 days). Clark (1997) tested sev- eral dermal contact repellents to deter starlings from using structures. In theory, these repellents cause irritation to the bird through contact with the dermis on the foot and birds avoid such areas subsequently. Starlings demonstrated agita- tion in response to 5% oil extracts of cumin, rosemary, and thyme (Clark 1997). Furthermore, starlings avoid perches treated with R-limonene, S-limonene, or Ã-pinene. Conklin et al. (2009) tested surface modifications in an effort to deter cliff-swallows from nesting on highway structures. Polyethylene sheeting proved to be effective in reducing nesting activity; however, swallows were still able to build nests. EXCLUSION METHODS Various devices and materials have been used to provide perceived or actual barriers to exclude birds from unwanted areas to prevent loafing, nesting, foraging, and other activi- ties. Exclusion methods used include razor wire, overhead wires, netting, covers (floating and other), and floating balls such as those shown in Figure 9 (Harris and Davis 1998). Total exclusion measures for birds are generally impractical and cost prohibitive; therefore, other partial exclusory tech- niques and âvirtualâ barriers are more typically employed.
18 maximum of 16 m spacing on a food warehouse roof. Nest- ing by ring-billed and herring gulls was reduced by 76% and 100% in the first year and 99% and 100% in the second year, respectively, compared with pretreatment data. FIGURE 10 Overhead wires on water source (Source: USDA/ APHIS/WS Mississippi Field Station). Clark et al. (2004) experimentally tested how overhead lines affected red-winged blackbird nest survival. Collec- tively, the presence of overhead wires decreased daily nest survival probabilities, but inferences on line spacing could not be elucidated. Lowney (1993) tested overhead wires as a deterrent to Canada geese around water sources. An 8.3 m grid was placed over small ponds on multiple sites. This sys- tem was successful in deterring geese from water sources. Antiperching Wire or Metal Antiperching devices, such as that shown in Figure 11, appear to be effective for large birds, but less so for smaller species. As larger birds are generally more hazardous to aircraft (Dolbeer et al. 2000), use of antiperching devices FIGURE 9 Bird balls at Heathrow (Source: USDA/APHIS/WS Ohio Field Station). Overhead Wires Overhead wires, such as those shown in Figure 10, are likely the most researched and used exclusion method for birds (Amling 1980; Blokpoel and Tessier 1984; Laidlaw et al. 1984; Lefebvre and Mott 1987; AgÃ¼ero et al. 1991; Belant and Ickes 1996) and can be highly effective. The use of over- head wires is typically effective at deterring use of an area by birds; however, most tests have been conducted on small water bodies or rooftops. The logistics and costs associated with using this technique on larger areas will likely limit its application at airports. McAtee and Piper (1936) produced the initial work on excluding birds from water resources in the early part of the last century; subsequently, several other authors have published material on overhead wires (McLaren et al. 1984; Pochop et al. 1990; AgÃ¼ero et al. 1991; Clark et al. 2004); in many cases wires proved to be effec- tive. Belant and Ickes (1996) evaluated the effectiveness of overhead wires to reduce roof-nesting by ring-billed (Larus delawarensis) and herring gulls (Larus argentatus). In this instance, wires were configured in a spoke-like pattern at a Netted/Bottom-Lined Ponds Mitigate Attractiveness of Stormwater Ponds to Hazardous Birds at Seattle-Tacoma Airport The SeattleâTacoma International Airport (SEA) uses netted/bottom-lined storm- water detention ponds to minimize vegetation growth, reduce attracting hazardous waterfowl, and lower long-term maintenance costs. The use of netting and pond liners is preferred to use of a floating ball or blanket cover because unrestricted access to the ponds was an important design criterion for these facilities. Research was needed to ensure that this practice did not compromise aircraft safety by caus- ing birds to repeatedly fly over ponds when attempting to get below the netting. During fall 2008, 1,000 hours of sampling effort was archived from three avian radars and postprocessed to compare the average time (seconds) targets spent over each of three netted/bottom-lined ponds compared with a paired control site. Paired sites were located an equal distance from the radar antenna. Radar data collected from altitudes 0â450 ft above runway level suggested bird use of netted/ bottom-lined ponds was similar or less than control sites.
19 FIGURE 11 Antiperching devices used to deter birds from a low level windshear alert system (Source: Steve Osmek). is common. Birds perching on fences, signposts, light fix- tures, ledges, or any structure in the airport environment can lead to problems with aircraft (Federal Aviation Adminis- tration 2007, 2008). Avery and Genchi (2004) tested anti- perching devices in an effort to deter birds from perching on the FAAâs Low Level Wind-shear System (LLWAS). Six different antiperch devices were tested on five bird species. No single device proved effective for all species involved in tests. Categorically, larger birds such as owls and vultures require different devices than do smaller species [e.g., cow- birds and fish crows (Corvus ossifragus)]. The combination device (Figure 11) provided the best protection for all species; however, 100% deterrence was not achieved. Seamans et al. (2007) tested an antiperching device to deter brown-headed cowbirds, European starlings, red-winged blackbirds, rock pigeons, and common grackles. In this case a commercial antiperching device (tested as Birdwireâ¢) was tested in an aviary setting. The device was effective in reducing perch use by all species. Blackbirds and starlings were, however, capable of using the perches, but only for a short time. Miscellaneous Techniques A wide variety of control techniques have been employed to reduce bird use of airports but not formally evaluated. Examples include use of remote-controlled vehicles such as radio-operated model aircraft and boats, in addition to many varieties of nonlethal projectiles, including rubber slugs and paint balls. Also, lasers emitting green beams, personnel in vehicles, and various forms of netting have been used. Although several of these techniques may actually be effec- tive in reducing bird use, the lack of quantitative and rig- orous assessments precludes categorizing their utility and application to wildlife damage application.