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16 The use of falconry has received some attention as a bird tested as Avitrol, has been effective against gulls, starlings, deterrent and appears to have limited efficacy. Some falconry crows, rock doves, and house sparrows (Passer domesticus) is employed in the United States, but it has mostly occurred (Seamans 1970). Avitrol also has been used successfully on in the United Kingdom (Blokpoel 1976; Hild 1984; Erick- loafing gulls and pigeons (Blokpoel 1976). Sweeney and son et al. 1990; Dolbeer 1998; Walker 2003; Bryant 2005; McLaren (1987) demonstrated its effectiveness on gulls at Kitowski et al. 2010;). Peregrine falcons (Falco pereqrinus), landfills. However, Dolbeer (1981) found Avitrol not to be gyrfalcons (Falco rusticolus), and goshawks (Accipiter gen- cost-effective in grain crops. Knittle et al. (1988) found 4-AP tilis) are the species most frequently used (Blokpoel 1976). to be effective for reducing blackbird damage to sunflowers, At John F. Kennedy International Airport, Dolbeer (1998) but it was mostly ineffective in fields greater than 2 miles tested the use of falconry to reduce laughing gull use and from a roost. Avitrol is toxic and can be difficult to admin- strikes to aircraft. Falconry in this case did not provide ister in a dose sufficient to cause the desired effect but not additional efficacy to a shooting program, but did provide to kill the bird immediately (Harris and Davis 1998). Death increased public acceptance of the management program at may be delayed and affected individuals may be able to fly the airport. away before dying elsewhere (Holler and Schafer 1982). Methyl Anthranilate CHEMICAL REPELLENTS Methyl anthranilate (MA) has been tested on numerous occa- Chemical aversion agents have been used to control birds sions as a deterrent for birds in a variety of settings (Avery in a wide range of settings (Guarino 1972; Rogers 1974; 1992; Cummings et al. 1992, 1995; Dolbeer et al. 1992; Vogt Crase and Dehaven 1976; Conover 1984b; Greig-Smith and 1994; Avery et al. 1995; Belant et al. 1995, 1996, 1997). Both Rowney 1987; Bomford and O'Brien 1990; Clark and Shah dimethyl and MA were strongly avoided by captive mallards 1991, 1993; Clark et al. 1991; Avery and Decker 1994). Their and Canada geese when birds were offered both treated and efficacy is highly variable and depends on chemical use, untreated grain (Cummings et al. 1992). When offered only mode of action, species being deterred, and resource (e.g., treated grain, both ducks and geese reduced their food intake, loafing site, feeding area) being protected. but mallards, and to a lesser extent, Canada geese, gradually increased consumption during the 2 to 4 days of the experi- 4-aminopyridine and 3,5-dimethyl-4-(methylthio)phenyl ment. Cummings et al. (1992) assumed that the birds were methylcarbamate habituating to the chemical, but they were not given an alter- native food source, and the increased consumption may have Chemical frightening agents and repellents such as 4-amin- been caused by increased hunger. Cummings et al. (1995) opyridine (4-AP) (e.g., tested as Avitrol) and 3,5-dimeth- tested another formulation of MA, REJEX-IT AG-36, as a yl-4-(methylthio)phenyl methylcarbamate (e.g., tested as grazing repellent for Canada geese. In the pen trial, 59 kg/ha methiocarb) are poisons that, in sublethal doses, may cause of the chemical applied reduced goose activity on treated grass disorientation and erratic behavior. They are usually added plots for less than 4 days. Similarly, Cummings et al. (1995) to bait. Typically only a portion of a bait presentation (e.g., evaluated the effectiveness of MA, tested as ReJex-iT AG-36, 10% of corn kernels) is treated with the chemical so that as a deterrent for blueberries. In Michigan, MA applied at 16.1 only a small number of the birds to be dispersed are affected. kg/ha did not reduce overall damage by birds, but did offer When the treated bait is ingested, a distress response occurs ephemeral control for 7 days. In the same study, Cummings (DeFusco and Nagy 1983; White and Weintraub 1983). Dis- et al. (1995) tested MA at a rate of 32 kg/ha in Florida to tress calls from affected birds can start 15 min after ingestion, caged cedar waxwings (Bombycilla cedrorum). Results were and can last up to 30 min after first effect. Besides emitting similar for waxwings in Florida to those in Michigan--berry distress calls, affected birds may become disoriented and consumption did not differ. Belant et al. (1995) tested two for- exhibit erratic behavior, often flopping about on the ground. mulations of MA (tested as AP-50 and TP-40) to repel gulls This behavior often alarms other birds and causes them to fly and mallards from water. Overall, gull activity was reduced away. If too high a dose is ingested, the bird will die. Trem- in pools treated with the MA (tested as AP-50, a free-flowing ors and convulsions occur before death if birds receive an powder) formulation compared with untreated pools. The overdose of the aversion agent, and these may induce other MA formulation tested as TP-40 (containing a surfactant), birds to leave the area. with 1.6-3.0 times greater concentration of MA at the water surface, was slightly more effective in reducing bird activity. Dolbeer et al. (1976) and Woronecki et al. (1989) tested Conversely, Belant et al. (1996) found MA in a 14.5% vol/vol the effectiveness of 2 aminopyridine (chemically similar to formulation was ineffective in reducing geese foraging activ- 4-AP) in sweet corn fields. Overall, no reduction in dam- ity. Also, Belant (1997) found MA ineffective in reducing age was observed. However, Avitrol has been proven use- woodpecker activity on wood siding of residential buildings. ful in dispersing birds (Goodhue and Baumgartner 1965; Dolbeer et al. (1992) investigated MA (tested as ReJeX-iT) at Woronecki et al. 1989; Gadd 1992; Swindle 2002). 4-AP, two different concentrations. Both concentrations were effec-