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3 personnel have been aware of these issues for decades (Sol- man 1973; Blokpoel 1976). Since the inception of the FAA National Wildlife Strike Database in 1990, 99,411 reported wildlife strikes to airplanes have resulted in at least $1.2 bil- lion annually in losses (damage to aircraft and associated costs) to civil aviation worldwide and more than $625 million annually in the United States, in addition to more than 200 human lives lost (Allan 2002; Dolbeer et al. 2010). The vast majority (97.4%) of all wildlife strikes involve birds. Before the jet age of air travel, bird strikes were less com- mon because piston-powered aircraft were noisy and rela- tively slow, and the number of aircraft was comparatively low. Birds could often avoid collisions, and in the event of a strike, damage was minimal. Modern jet aircraft are much faster and relatively quiet compared with their piston-pow- ered predecessors; this changes the dynamics of bird and aircraft interactions dramatically. The skies are becoming increasingly crowded with air- craft and hazardous bird species (Dolbeer 2009). Aircraft movements increased about 3% per year between 1985 and 2004 (Dolbeer 2009). Many species of wildlife also have increased in the last half-century, including those species that pose the most risk to aviation (Dolbeer et al. 2000). Many of these species exceed the airframe and engine cer- tification standards for wildlife strikes [e.g., Canada geese (Branta canadensis)]. These parallel factors create a consid- erable need to employ risk mitigation measures that effec- tively reduce bird strikes. Dolbeer (2006) noted that 66% of wildlife strikes result- ing in substantial damage to aircraft occurred less than 500 ft above ground level (AGL), effectively 10,000 ft from the airfield based on a 3° glideslope (Foundation 2000; Black- well et al. 2009). About 95% of bird strikes occur less than 3,500 ft AGL (Dolbeer 2006). At that altitude, aircraft would be within about 5 miles of the airfield for the busi- est airports (Federal Aviation Administration 2008). Dol- beer (2011) reported that bird-strike rates above 500 ft AGL have increased since 1990, whereas strike rates below 500 ft AGL have decreased during that period. These empirical data suggest that recent wildlife management on airports has reduced strike rates and damaging strikes (Dolbeer 2011); however, airport sponsors and managers are legally obligated [Title 14 Code of Federal Regulations, part 139 (14 CHAPTER ONE INTRODUCTION The impetus for this synthesis is to provide airport managers and biologists with a document that reviews the tools, meth- ods, techniques, and procedures for reducing bird collisions with aircraft (i.e., bird strikes) and their relative effectiveness into a single treatise. The management of wildlife in the con- text of aviation, specifically the reduction of wildlife strikes to aircraft, is a unique application of wildlife damage man- agement. Wildlife damage management typically involves overabundant species and their effect on human property (Conover 2002; Cleary and Dolbeer 2005). However, wild- life damage to aircraft may have immediate implications for human safety. Consequently, airport managers must fre- quently take immediate action to mitigate risk. Wildlife spe- cies involved with aviation hazard may not be overabundant; populations may be within biological and cultural carrying capacity outside of airspace, but their presence within air- space is hazardous and unwanted. Control techniques should be implemented in the con- text of an airport hazard management plan or program. Airport personnel are inherently and legally responsible to reduce aviation risk using a myriad of methods given the constraints of resources and time. Biologists face consid- erable uncertainty regarding the effectiveness of specific techniques under given conditions and circumstances. Fur- thermore, animals adapt and change behavior in response to techniquesâwhat worked last time may not work simi- larly when reapplied. Biologists should be equipped with the most current information on the effectiveness of harassment, deterrent, and repellent techniques, and adequate empiri- cal data should be readily available. For these methods to be meaningful, they must be integrated with principles of avian ecology. Techniques must be founded on ecological principles to be effective, and both managers and biologists should understand and appreciate that relationship. BIRDS AND AIRCRAFT: UNDERSTANDING THE INTERACTION Aircraft collisions with birds and other wildlife (wildlife strikes) pose increasing safety and financial concerns to the aviation industry worldwide. Recent events such as the forced landing of US Airways Flight 1549 in the Hudson River have renewed public interest in risks to aircraft posed by wildlife (Marra et al. 2009). However, wildlife biologists and aviation
4 and/or hazing. We did not limit our review to studies con- ducted within the airport environment because much of the research in this arena has involved captive studies and field studies in agriculture settings. We used numerous databases to find primary and secondary literature, including Google Scholar, DigitalCommons at University of NebraskaâLin- coln, Scopusâ¢, and numerous conference proceedings data- bases (e.g., Vertebrate Pest Conference). We searched for the following terms in article abstracts and keywords: deter- rents, hazing, harassment, repellents, damage management, airports, aviation, frightening devices, and numerous com- binations of the aforementioned. We supplemented searches by examining bibliographies of articles for additional refer- ences. Much of the published literature on the subjects was found in the secondary literature. Guiding Principles of Bird Damage Management Bird management at airports is best considered an adap- tive process of deterrence where species composition and behavior can be expected to change during the day, between seasons, and across years, even when techniques in this syn- thesis are actively employed. Many bird species habituate to deterrent techniques and will return to the area, particularly if the area is attractive to them. Consequently, two critical questions to ask are âWhy are they present?â and âAre they occasional or habitual users of areas on and near the air- port?â Figure 1 depicts a gradient of bird activities along a continuum of fidelity or attractiveness to a particular site. Essentially, as site fidelity increases, difficulty in moving the birds will similarly increase. Matching the type of control technique with the type of bird activity will improve chances of success. Additionally, the more frequently a bird occupies an airport without negative consequences such as control methods, irrespective of degree of site fidelity, the more dif- ficult it will be to disperse the bird. Consequently, effective management is management highly responsive to dispersing birds from airports as soon as they are detected. CFR, part 139)] to make certain the airport environment, including areas near the airport, is safe. Airport managers can use five basic strategies to manage hazardous wildlife at or near the airport (from Cleary and Dickey 2010): 1. Repelling techniques: Use of various audio, visual, or chemical repellents to harass and repel problem wildlife. 2. Habitat modification: Elimination or reduction of food, water, or shelter attractive to wildlife at or near the airport. 3. Exclusion: Use of physical barriers to stop wildlife from gaining access to food, water, or shelter at or near the airport. 4. Population management: Reduction or elimination of wildlife populations that are posing a hazard to aircraft at or near the airport by either capturing (live capture and relocation) or killing the problem animals. 5. Notices to Airmen (NOTAM) of potential wildlife hazards. This synthesis emphasizes numbers 1 and 3; however, the repellent techniques cannot be considered in isolation and typically are applied in conjunction with one or more of the other strategies. METHODOLOGY FOR SYNTHESIS Literature Search We reviewed the literature for papers that included infor- mation regarding bird deterrents, repellents, harassment, FIGURE 1 Gradient of bird activities in increasing order of site fidelity and resistance to control techniques (Source: Adapted from Steve Osmek, SEA Airport).
