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3 Background This synthesis provides airport managers and biologists with a working reference document that reviews the tools, methods, techniques, procedures, and considerations for reducing air- craft collisions associated with wildlife population control management on airports and in the immediate surrounding areas. Wildlife population control on airports is a unique appli- cation of more broadly defined wildlife damage management that can and should be used as part of an integrated wildlife management strategy. Historically, wildlife damage manage- ment has focused on overabundant species and their effects on property, especially agriculture (Curtis et al. 1996; Conover 2002; Decker et al. 2002; Cleary and Dolbeer 2005). How- ever, wildlife population management on airports often deals with wildlife that may not be overabundant yet pose signifi- cant risks to human safety and health and potentially damage aircraft and facilities (see Figure 1). Thus, when effective use of wildlife population control measures on airports is used, a reduction in wildlife collisions with aircraft and aviation risk to human safety is possible. Wildlife population management on airports has been reported in many formats. Worth noting are the following foundational reference sources pertinent to wildlife manage- ment on airports by Blokpoel (1976), DeFusco and Nagy (1983), Hygnstrom et al. (1994), Harris and Davis (1998), MacKinnon et al. (2001), Transport Canada (2002), Cleary and Dolbeer (2005), Cleary and Dickey (2010), and Belant and Martin (2011). Because airport personnel are legally and professionally obligated to reduce wildlife risks to aviation, these sources provide both diverse and specific information useful to airport personnel relative to wildlife hazards. For the purposes of this synthesis, we have classified the two wildlife population management approaches as either indirect (e.g., habitat modification, harassment, deterrents, repellents, and exclosures) or direct (e.g., lethal and nonlethal trapping; roost, nest, and egg manipulation; chemical and pes- ticide application; and live-ammunition shooting). Integrated airport wildlife population management as a matter of common practice may, and in most cases should, involve a combination of both indirect nonlethal measures and more direct, some- times lethal, wildlife population control techniques. Indirect nonlethal wildlife management methods for birds are specifi- cally addressed in ACRP Synthesis 23 (Belant and Martin 2011) and a review of both methods pertinent to general avi- ation (GA) airports in ACRP Report 32 (Cleary and Dickey 2010). Although indirect methods are more commonly used and are the industry standard for nonlethal wildlife manage- ment on airports, animals may adapt and change behaviors in response to such techniques and may require additional nonlethal and/or direct lethal measures to improve wildlife control effectiveness. Many airports are reluctant to use more direct and often lethal modes of wildlife population control for many reasons including a lack of knowledge of the various direct wildlife population control techniques and methods available; a mis- understanding of such actions on overall wildlife popula- tions outside airport boundaries (metapopulations); a lack of knowledge of permit and license requirements necessary to conduct direct wildlife population control; and fear of public outcry and a lack of public support because of such actions. An integrated approach requires the use of all elements to be most successful. Generally, wildlife management and popula- tion control efforts take a hierarchical approach, with the basis of the program resting on habitat management supplemented by various exclusion and deterrent methods (see Figure 2). Direct removal of animals and especially lethal methods are only effective in the long run when the foundational bases of population management are in place and are most often used as a last resort to reinforce other methods. Nevertheless, a more direct wildlife population control approach can be used on airports that result in the removal, relocation, or lethal reduction of problematic wildlife individuals or populations. It is important that airport managers, operations staff, and their contracted support personnel be equipped with the most current information on the use of direct wildlife popu- lation control methods and their effectiveness. To improve effectiveness, the selection and application of such methods must be consistent with targeted wildlife (vertebrate and invertebrate) ecology. Wildlife and aircraft Conflicts arising from the presence of wildlife and aviation operations remain problematic. Wildlife biologists and avia- tion personnel have been aware of aircraft collisions with birds and other wildlife (wildlife strikes) for decades (Solman 1973; Blokpoel 1976). In 2009, the forced landing of US Airways Flight 1549 in the Hudson River renewed public interest in risks to aircraft posed by wildlife (Marra et al. 2009). The chapter one introduction
4 following information highlights the real and potential wild- life threat to aviation. Note that the following data are those actually reported and are generally accepted to underrepresent actual losses by between 61% and 89% (Linnell et al. 1999; Cleary et al. 2005; Wright and Dolbeer 2005). Projected total costs are significantly higher than those that are reported in the FAA National Wildlife Strike Database and are esti- mated at $15.787 billion over the period from 1990 to 2011 (Dolbeer et al. 2012): 1. Since the inception of the FAA National Wildlife Strike Database in 1990, 119,917 reported wildlife strikes had projected annual average costs of $718 million in the United States (Dolbeer et al. 2012). In addition, strikes to civil aircraft worldwide have resulted in at least $1.2 billion in loses annually (damage to aircraft and associated costs) and more than 250 human lives lost (Allan 2002). 2. The number of wildlife strikes reported annually has increased more than fivefold, from 1,804 in 1990 to 10,083 in 2011 (Dolbeer et al. 2012). 3. In 2011, 27.6 wildlife strikes per day were reported in the United States (Dolbeer et al. 2012). U.S. airports reporting wildlife strikes increased from 333 in 1990 to a high of 597 (369 airports certificated for passenger ser- vice and 228 GA airports) in 2011 (Dolbeer et al. 2012). 4. Of all aircraft wildlife strikes in the United States, 97.1% involve birds, with terrestrial mammals involved in 2.3%, bats 0.5% (Peurach et al. 2009), and reptiles 0.1% (Dolbeer et al. 2012). 5. From 1990 to 2011, 462 bird species and 38 species of terrestrial mammals were struck by aircraft (Dolbeer et al. 2012) with waterfowl, gulls, and raptors being the species groups with the greatest number of damaging strikes (see Figure 3). Deer (39%) (DeVault et al. 2008; VerCauteren et al. 2009, 2011) and coyotes (34%) are the most frequently struck terrestrial mammals, with deer responsible for 93% of all damaging mammal strikes (Dolbeer et al. 2012). 6. Gulls (16%), doves and pigeons (15%), raptors (13%), and waterfowl (7%) were the most frequently struck bird groups (Dolbeer et al. 2012). 7. From 1990 to 2011, Canada Geese were reportedly involved in 1,351 civil aircraft strikes, resulting in 2 fatalities, 19 injuries, and 5 total aircraft lost. Reported Canada Geese strikes caused a minimum of $2.6 mil- lion in damage each year, with total reported losses exceeding $90 million (Dolbeer and Wright 2008; Dove et al. 2009; Dolbeer et al. 2012). Projected costs FIGURE 1 Canada Goose and American Elk strikes to aircraft (Source: USDA). FIGURE 2 Hierarchy of airport wildlife population control in an integrated program (Source: MSP).
5 crested Cormorants, Sandhill Cranes, Osprey, and Red-tailed Hawks (Dolbeer et al. 2012). 2. In the past 40 years, 13 of the 14 largest-bodied bird species in the United States (>3.6 kg body mass) have shown significant population increases (Dolbeer and Eschenfelder 2003). 3. In North America from 1970 to 2008, migratory and nonmigratory populations of Canada Geese (4.2 kg body mass) have more than quadrupled from 1.2 mil- lion to 5.5 million birds. Resident (nonmigratory) Canada Geese populations appear to have stabilized at approximately 3.5 million birds during the last decade (Dolbeer 2011). 4. Many birds have adapted to urban environments and have found that airports, with their large areas of grass and pavement, are attractive habitats for feeding and resting. Other wildlife such as deer and coyotes are also attracted to airport environments for similar reasons. 5. White-tailed Deer populations (see Figure 5) increased from about 350,000 in 1984 to more than 28 million in 2010 (McCabe and McCabe 1997; VerCauteren et al. 2006, 2011). 6. Further exacerbating the problem, todayâs modern jet turbofan-powered aircraft are much faster and rela- tively quiet compared with their piston-powered pre- decessors, resulting in dramatic changes in the dynam- ics of bird and aircraft interactions (Burger 1983; Kelly et al. 2000). In 1965, 90% of the 2,100 U.S. passenger aircraft had three or four engines. By 2005, the U.S. passenger fleet had grown to 8,200 aircraft, with only 10% having three or more engines. Wildlife strikes most commonly occur on or in close prox- imity to airports. 1. From 1990 to 2011, 72% and 75% of bird strikes for commercial and GA aircraft, respectively, occurred accounting for underreporting rates may conserva- tively total as much $2.97 billion based on estimates in Dolbeer et al. (2012). In addition, Canada Geese were responsible for the loss of a USAF AWACS aircraft in 1995 that killed 24 aircrew and cost in excess of $280 million (Gresh 1996). 8. From 1990 to 2011, 897 U.S. civil aircraft incidents with white-tailed deer were reported resulting in 1 of 24 human deaths and 25 of 256 injuries reported for all wildlife incidents during this period. Although deer incidents for all species represent only 0.9% of all wildlife strikes reported, they account for 5.4% of estimated costs, resulting in a minimum of $75 million in total reported damages and as much as $852 million in projected damages (Biondi et al. 2011; Dolbeer et al. 2012). Aircraft movements have increased approximately 3% per year (17.8 million aircraft movements in 1980 to 25.2 million in 2011) with passenger enplanements in the United States increasing from 310 million in 1980 to 715 million in 2011. In addition, the numbers of wildlife species have increased over the same period, including many species that pose the greatest risk to aviation (Dolbeer et al. 2000). As a result, the skies are becoming increasingly crowded, with aircraft and hazardous bird species occupying the same space (Dolbeer 2009). In addition, highly successful programs funded by the U.S. government during the past 40 years (e.g., pesticide regulation, expansion of the wildlife refuge systems, and wetlands restoration), coupled with land-use changes, have brought about dramatic increases in the populations of many larger-bodied bird species in North America (Dolbeer et al. 2000; Dolbeer and Eschenfelder 2003) as highlighted here: 1. Large bird species increased significantly from 1980 to 2011, including Bald Eagles, Wild Turkeys, Canada Geese (see Figure 4), American White Pelicans, Double- FIGURE 3 Eagle strike at MinneapolisâSt. Paul International Airport (MSP) (Source: MSP). FIGURE 4 Canada Goose strike on GA aircraft (Source: Trans- port Canada).
6 below 3,500 ft above ground level (AGL) (Dolbeer 2006; Dolbeer et al. 2012); effectively within 10,000 ft from the airfield based on a 3° glideslope (Blackwell et al. 2009). At that altitude, aircraft would be within about 5 miles from the airfields of the busiest airports (Federal Aviation Administration 2007). 2. Above 500 ft AGL, the number of strikes declined by 33% for each 1,000-ft gain in altitude for commercial aircraft and by 41% for GA aircraft. Strikes above 500 ft were more likely to cause damage than strikes at or below 500 ft (Dolbeer et al. 2012). 3. Dolbeer (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. 4. After striking wildlife, a precautionary or emergency landing was the most commonly reported negative effect on a flight (4,353 incidents), including 46 incidents where pilots dumped fuel to lighten aircraft weight and 76 inci- dents where an overweight (heavy) landing was made. An aborted takeoff was the second most common nega- tive effect (1,922 incidents), which included 805 aborted takeoffs at greater than 80 knots (Dolbeer et al. 2012). 5. Fifty-seven wildlife strikes resulted in destroyed air- craft, with 56% of these occurring at GA airports (see Figure 6) (Dolbeer et al. 2012). From 1990 to 2011, empirical data suggest that recent wild- life management on airports may have contributed to a reduc- tion in wildlife strike rates and damaging wildlife strikes on airports (Dolbeer et al. 2012). Since 1990, wildlife manage- ment actions to mitigate wildlife risk have been implemented at many airports and these actions are likely responsible for the general decline in reported wildlife strikes with damage on airports from 2000 to 2011. Damages to aircraft and accidents remain a problem in the off-airfield environment and it is evi- dent that more needs to be done to address those problems. Future management actions at airports should be prioritized based on the hazard level of species observed in the aircraft operating area (Dolbeer et al. 2012) and in surrounding air- space. Because airport sponsors and managers are legally obli- gated under 14 CFR Part 139 to make certain that the airport environment and areas near the airport are safe, continued and improved integrated wildlife population management remains a necessity (see Figure 7). In ACRP Report 32, Cleary and Dickey (2010) suggested that airport managers can use five basic strategies to manage hazardous wildlife at or near the airport: 1. Habitat modification: Elimination or reduction of food, water, or shelter attractive to wildlife at or near the airport. 2. Exclusion: Use of physical barriers to stop wildlife from gaining access to food, water, or shelter at or near the airport. FIGURE 6 Canada Geese at Illinois GA airport (Source: BASH Inc.). FIGURE 5 (left) White-tailed Deer strike with Piedmont Dash 8 at CharlotteâDouglas International Airport (CTL); note aircraft maximum braking tire tracks (Source: CTL); (right) Cessna Citation 550 destroyed by White-tailed Deer strike at Greenwood County Airport (GRD), South Carolina (Source: FAA).
7 Survey Fifteen representative airports from all nine FAA regions were sent a wildlife populations control and management sur- vey (Appendix D). All responded; a 100% survey response rate. The qualitative and quantitative information from the returned surveys were then compiled to discuss the various lethal and nonlethal wildlife population control techniques currently practiced by U.S. airports and their perceived effec- tiveness (as reported in chapter six). chapter outlineS Chapter two provides a general discussion of wildlife popu- lation management from an historical, biological, and eco- logical framework. In addition, federal and state agencies with wildlife oversight responsibilities, legal requirements and responsibilities, and the requirement for depredation permits are addressed. A general overview of specific direct wildlife population control methods and techniques is also covered. Chapter three addresses specific wildlife population control alternatives. Chapter four addresses federal and state threat- ened and endangered species and game species issues. Chap- ter five discusses wildlife population control issues directed at specific âhigh riskâ bird and mammal species and more general wildlife control techniques targeted at avian and mammalian guilds where species-specific discussion was less appropriate. Chapter six provides the results of airport- provided survey information and âlessons learnedâ relative to specific and general wildlife control measures and their overall effectiveness. This information is intended to pro- vide an experienced perspective that includes suggestions to airports when developing, planning, and implementing an integrated wildlife population control strategy and program. Chapter seven summarizes the successful practices and pro- vides recommendations for further research in the area of airport wildlife population management. 3. Repellent techniques: Use of various audio, visual, or chemical repellents to harass and repel problem wildlife. 4. Population management: Reduction or elimination of wildlife populations 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 primarily emphasizes strategy 4âpopulation management; however, the use of indirect habitat modification, deterrent, repellent, and exclusion techniques cannot be consid- ered in isolation and typically are applied in conjunction with an integrated wildlife population management strategy. SyntheSiS Methodology literature Search A review of the literature was conducted for papers that included information regarding wildlife population control methods. Most of the literature review focused on studies conducted within the airport environment because they pro- vide more relevant information about methods, techniques, and effectiveness needed by airport personnel, although the overall scientific basis for these studies is well supported in other literature. Numerous databases were used to find primary and secondary literature including Google Scholar; DigitalCommons at the University of Nebraska, Lincoln; JSTORâ¢; Web of Scienceâ¢; as well as numerous con- ference proceedings databases (e.g., ecological societies, Vertebrate Pest Conferences, and Bird Strike Committeeâs proceedings). The following terms and keywords were searched for in article abstracts: bird strike, damage man- agement, airports, aviation, wildlife control, population control, and population management, alone or in combi- nations. These searches were supplemented by examining bibliographies of articles for additional references. FIGURE 7 Sandhill Cranes pose potential risk at Orlando International Airport (MCO) (Source: MCO).
