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10 CHAPTER FOUR HARASSMENT, REPELLENT, AND DETERRENT TECHNIQUES We begin this section with a tabular summary of relative frequency sound (>20,000 Hz or cycles per second) devices efficacy of harassment, repellent, and deterrent techniques generally were not effective in repelling birds. Griffiths for birds at airports. Table 1 is a synthesized literature review (1987) tested a commercial ultrasonic unit against numerous providing examples of relative efficacy of each technique. 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- AUDITORY DETERRENTS necki (1988) reported that an ultrasonic device (Ultrason UET-360) was not effective in reducing rock dove activity Ultrasonic during a 20-day treatment period. However, he reported that a combination of a visual device (tested as Deva-Spinning Ultrasonic devices likely will not be a viable option as a Eyes) and a sonic device (tested as Deva-Megastress II) did deterrent for birds. Erickson et al. (1992) surmised that high- 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.
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11 ment period and reduced the rock dove population present poel 1976), agricultural settings, and other locations (Baxter during the onset of treatment. However, this study was not 2000). 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. From the Field...Golden Triangle Airport (GTR) Gas Exploders The Golden Triangle Regional Airport Authority was Gas-operated exploders, sometimes referred to as gas or established in 1971 through a partnership with the cit- propane cannons, offer temporary efficacy for deterring ies of Columbus, Starkville, and West Point, and the birds from airfields. They have been commonly used to counties of Lowndes and Oktibbeha, Mississippi. The repel pest birds in agriculture and around airports since airport property consists of 1,000 acres and has ap- the late 1940s (Gilsdorf et al. 2002). These devices produce proximately 40,000 airplane movements a year. Bird extremely loud, intermittent explosions, usually at fixed 1- to 10-minute intervals as desired, that exceed the blast of a harassment is conducted by the airport firemen, who 12-gauge shotgun. Present-day exploders consist of a bottled dedicate approximately 10% of their time to wildlife gas supply, separate pressure and combustion chambers, an management. Seasonal influxes of geese in the winter igniting mechanism, and a barrel to direct and intensify the and raptors in the summer are the main problems that noise of the explosion. To alleviate habituation, exploders arise with wildlife. The staff uses pyrotechnics to move should be moved periodically (e.g., every 1 to 3 days) within the area needing protection (Littauer et al. 1997; Reinhold birds from problem areas. Additionally, in the fall, flocks and Sloan 1997). of sparrows and other small flocking birds can create potential hazards. In these instances, personnel have used Washburn et al. (2006) conducted an experiment with fire trucks to apply high volume and pressure of water to propane exploders at John F. Kennedy International Airport. disperse birds with good success. Mike Hainsey, airport These authors did not find a significant difference in bird behavior in response to the exploder. Furthermore, the addi- executive director, noted, "Habitat management is a tion of lethal removal did not enhance effectiveness. Con- primary line of defense." 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 Mott and Timbrook (1988) examined the effect of alarm hawk-kites). In the Mississippi alluvial plain, Mott et al. and distress calls on Canada geese. They found a 71% (1998) described that harassing double-crested cormorants decrease in goose numbers in response to the calls. Addi- roosting at night was successful in dispersing cormorants and tionally, they found a 96% reduction in goose observations reducing depredation rates at nearby catfish farms, suggest- when the distress calls were coupled with pyrotechnics ing that it may work on stormwater ponds around airports. (tested as racket bombs, a noise-making pyrotechnic shot Also, Cummings et al. (1986) described that a combination from a pistol launcher). Unfortunately, recolonization of the of a gas exploder and a CO2 driven pop-up scarecrow was study area occurred shortly after the treatments stopped. In effective sporadically in a row crop agriculture setting; how- an urban setting, Gorenzel and Salmon (1993) experimented ever, habituation was likely occurring in later tests. with distress and alarm calls in an effort to deter crows. Ini- tially, crows from nearby roosts were attracted to the calls, Biosonics: Alarm and Distress Calls but after 30 seconds the crows left the immediate vicinity. Biosonic calls, including alarm and distress calls, appear to Cook et al. (2008) used a modeling approach to assess have some efficacy for deterring birds. However, additional the effectiveness of nine techniques, including pyrotechnics, research involving rigorous experimental design is neces- handheld distress calls, static distress calls, blank ammu- sary to understand efficacy more fully. Biosonics as a repel- nition, a combination of blank and lethal use of ammuni- ling technique is based on acoustical signals emitted by birds tion, falcons (Falco spp.), hawks (Accipiter spp.), wailers, and other animals to convey information to other individu- and kites. These techniques were employed on three spe- als of the same species (Boudreau 1968; Conover and Perito cies of gulls at landfill sites. Distress calls were among the 1981; Bomford and O'Brien 1990). Two audible bird-warn- most effective; however, when habituation was considered, ing stimuli, distress and alarm calls, have been explored or distress calls were not as effective as other techniques with used for acoustically repelling birds from urban and rural lethal consequences. Conklin et al. (2009) tested bioacous- roosts (Pearson et al. 1967; Brough 1969), fish-rearing ponds tic deterrents for nesting cliff swallows (Petrochelidon pyr- (Spanier 1980; Andelt et al. 1997), airport runways (Blok- rhonota). Eight unique recordings of alarm and distress calls