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22 chapter six AGRICULTURE The FAA discourages establishing any habitat within five miles of an airport/AOA that may attract hazardous species (FAA 2007; Blackwell et al. 2009). This includes agricultural cultivation of row crops and grains [e.g., corn (Zea mays), soybeans (Glycine spp.), and wheat (Triticum spp.)]; and livestock feedlots. While these fields may not always attract a diversity of wildlife, they are often enticements to commonly hazardous species such as white-tailed deer (Odocoileus virginianus; Hein et al. 2012) and birds such as geese, starlings, grackles, allies, and blackbirds (Bent 1965; Dolbeer et al. 1978). Various species of migratory geese will take advantage of grain fields (Patterson 1991); some normally migratory species, including Canada geese, have become successful at finding resources year-round. While many birds eat grain crops at any time, some, such as red-winged blackbirds (Agelaius phoeniceus), may be more of a threat when plants are very young or when soil is turned and insects are exposed (Bent 1965). More research is needed to quantify the risks associated with specific agricultural operations on and near airport property and to examine particular habits of species. Not all wildlife use a crop similarly, and airport operators can observe wildlife use throughout the year to determine how to adapt their management techniques. LIVESTOCK Confined livestock operations such as feedlots and dairy operations concentrate water, food, and waste that may attract potentially hazardous wildlife species such as flocking birds (Cleary and Dickey 2010). While the FAA recommends against allowing confined livestock facilities near airports, free-ranging livestock grazing may be an alternative land use in areas near airports outside of the AOA. Grazing livestock may serve as an alternative method of turfgrass management, providing an economic benefit to the airport and reducing habitat for wildlife that prefer tall grasses and thick vegetation, i.e., rabbits, deer, and rodents. However, livestock themselves can also become a serious hazard if a fence fails and ani- mals enter the AOA, though frequent fence inspection can reduce the risk of this hazard (AC/Cert alert 04-16). This is an example of the complex and seemingly contradictory issues that arise when trying to address all possible wildlife attractants on a landscape. Different methods work well in different regions at different times of year, and can be tested and evaluated over time with proper research and planning. GRAIN CROPS Wheat, sorghum (Sorghum spp.), and rye (Secale cereale) may attract granivorous wildlife such as birds, mice, voles, rats, and larger herbivores such as deer. Again, small mammals can attract other larger, potentially hazardous raptors (Accipitridae), coyotes (Canis latrans), and foxes. Corn and soybeans are also common crops that attract potentially hazardous wildlife such as white-tailed deer (DeVault et al. 2007). Some birds, such as blackbirds, will feed on corn either while the kernels are tender and soft, or after harvest when waste corn is accessible on the ground (Bent 1965). Addition- ally, rice may attract rodents, but also granivorous waterfowl and other bird species that forage in flooded fields. Post-harvest winter wheat is a major enticement for geese and other granivorous birds. HAY CROPS Like grains, hay crops can provide both food and cover for a variety of wildlife species. White-tailed deer are one potentially hazardous species that are attracted to foraging on young legumes such as clover and alfalfa (Medicago sativa; Richer et al. 2005). Mice and rats can also be attracted to hay
23 AgricultureâLivestock: Kansas City International (KCI) KCI owns approximately 9,000 acres of land outside the perim- eter security fence. Until 1997, these fields, as well as portions inside the fence, were used by farmers to raise crops including wheat, corn, soybeans, and sorghum. Then KCI decided to create a 2,000-foot buffer around the perimeter fence, eliminating grain crops and removing some trees, to reduce attractants for white- tailed deer, coyotes, raptors, and foxes. Tall fescue was planted in this area, and once the grass had become established, portions of the buffer were leased for grazing cattle. Now 1,730 acres of this buffer area support over 600 cattle. A separate barbed wire fence encompasses the pastures, and a gravel road between this fence and the perimeter fence allows access for ranchers. Ranchers use freeze-proof watering tanks in the pastures filled by well water, be- cause open water can be a major enticement to many wildlife spe- cies. Not only do the cattle maintain a shorter grass height in the buffer area, they also reduce browse habitat along tree lines that normally attracts deer. The shorter grass height has also figured into an integrated small mammal control effort in the airport buffer area by reducing the cover habitat of thick long grasses. While 14 deer were observed on the airfield in 1997, KCI has not had a confirmed sighting of a deer on the airfield since 2007. Grazing cattle outside the perimeter fence at KCI (Credit: B. Johnson). AgricultureâGrain Crops: Victoria Regional (VCT) Victoria Regional Airport in Texas is surrounded on three sides by agricultural land. The most common uses for this land are pasture and rice. Pastures often are overgrown and provide habitat for deer, wild pigs, and coyotes. The rice is usually in a two- to three-year rotation, but there is some rice grown every year, attracting waterfowl, cranes, gulls, and passerines such as blackbirds. Other species of concern on the property include mourning doves, barn swallows (Hirundo rustica), sparrows, vultures, and killdeer. The airport has been issued a federal depredation permit for migratory birds and a state permit for culling deer. Airport personnel also use non-lethal techniques such as pyrotechnics and acoustic devices to deter potentially hazardous birds. Snow geese (Chen caerulescens) are most common on agricultural fields in the southern United States during winter after harvest of grain. Flocks of snow geese flying over Victoria Regional (left) and loafing in an agricultural field nearby (right) (Credit: A. Johnson and S. Brammell).
24 fields in large numbers, attracting other potentially hazardous species such as raptors and carnivores (Kaufman et al. 2000). If hay is cultivated on or near airport property, operators can work with farmers to determine ways to minimize the risk of attracting wildlife, such as harvesting at night when avian and insect activity is reduced. Other ways of reducing risk may include increasing the distance from the airport perimeter where hay crops are allowed; installing deer-proof fencing around the AOA; and orienting hay fields in such a way that deer and other wildlife will not attempt to cross the AOA to get to other fields or forested areas. NON-TRADITIONAL FRUITS AND NUTS Fruits and nuts are major attractants to many wildlife species. Few deterrents other than physical obstructions (fencing and netting) have proven very effective in keeping birds from seeking out berries and smaller fruits, including grapes (Way 1961). However, some chemical deterrents such as anthraquinone have been used on seed crops such as sunflowers with some success against feeding, but not necessarily against attracting grackles and blackbirds (Werner et al. 2011). Apple orchards have been shown to attract deer and small mammals such as moles and voles (Phillips et al. 1987). Fruit and nut crops are a challenge for airport operators in deterring wildlife, and require persistent efforts to reduce wildlife foraging. GRASS SEED HARVESTING The grass seed industry faces many of the same challenges as other grain crops: deterring larger her- bivores such as deer and elk and rodents (Bartuszevige and Endress 2008; Sivy et al. 2011) as well as geese (Alisauskas et al. 1988) and other granivorous birds. If grass production is maintained adjacent to airport property, potentially hazardous wildlife may enter the AOA. Grass seed can be treated like other grain crops in an airportâs WHMP depending on the particular wildlife species of concern. BIOFUELS Like agricultural cultivation, biofuel production is an alternative land use for airports (Martin et al. 2013). Exotic plants such as Miscanthus (Miscanthus giganteus) and native warm-season grasses are candidate species for biofuels (Tilman et al. 2006; Heaton et al. 2008; Tilman et al. 2009; Somerville et al. 2010). While airport production of biofuels is unlikely to meet the needs of a production facil- ity, it can contribute to a larger collaboration of sources of biofuels materials (Kocoloski et al. 2011; DeVault et al. 2012). Biofuel fields dominated by grasses may attract dense populations of small mammals, but further research is needed on the potential for such areas to attract potentially hazardous wildlife to airport AOA (Blackwell et al. 2009; Martin et al. 2011; DeVault et al. 2012).
