Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
25 chapter seven OTHER VEGETATION ON AIRPORT PROPERTY COMPOSITION Some wildlife species are generalists, and will eat many different types of food or use many different habitats for shelter. However, many are attracted to specific foods and habitats, which can make wildlife management a little easier. Airport operators can observe and learn the habits of the species that pose a risk to aircraft safety at their airport. Potential risks of wildlife to aircraft operations may change seasonally each year or over time as habitats and conditions evolve. As plants produce new Other VegetationâComposition: John F. Kennedy International (JFK) Changing conditions to maintain safe air operations at airports may include changing plant species in and around the AOA. Operators at JFK noticed a few areas of vegetation on airport property that attracted concentrations of potentially hazardous wildlife, and developed plans to eliminate or greatly reduce the attractant. One risk was posed by migrating flocks of tree swallows that would visit the airport each fall and appeared to be attracted to areas of bayberries (Myrica pensylvanica) near runways. Examination of crop contents of some of the birds confirmed that they were eating predominantly bayberries, which convinced operators to remove the shrubs (Bernhardt et al. 2009). In another area of JFK, ornamental pear trees (Pyrus callyeryana) that attracted starlings were replaced with less appealing species, including Japanese zelkova (Zelkova serrata), American redbuds (Cercis canadensis), fringe trees (Chionanthus virginicus), golden rain trees (Koelreuteria paniculata), and Atlantic white cedars (Chamaecyparis thyoides). JFK also planted trees in large open areas of turfgrass, which deterred geese from grazing. This is an example of vegetation management that can meet multiple needs, but operators should also be careful not to create a new, potentially more risky allure when making changes to vegetation. Bayberry shrubs formerly inside the AOA (left) and trees used to break up areas of turfgrass at a northeast airport (right) (Credit: L. Francoeur).
26 growth or fruit, wildlife may use them differently, affecting aircraft safety. Diversity in vegetation will likely attract a greater diversity of wildlife (Tews et al. 2004). However, a mosaic of vegetation in a landscape can also help to break up large areas of habitat that would otherwise be attractive to wildlife (MacArthur and Pianka 1966). If wildlife have to spend more time searching for food than they would somewhere else, or if they do not feel safe in an area because of limited views of oncoming threats, they may prefer to go elsewhere (Charnov 1976; Brown 1999). SPATIAL CONSIDERATIONS Separation from the AOA is an important consideration with any habitat modification that might attract wildlife, and the FAA has criteria for allowable structures within certain distances of the AOA (FAA AC 150/5200-33). These distances range from 5,000 ft to five miles, depending on aircraft involved and type of aircraft operations. Density Dense vegetation is a common nesting habitat for many bird species, but it can also serve as excellent cover for both birds and mammals, who use it to hide from predators or take refuge from the cold; while predators may use it to ambush or hunt prey (Shake et al. 2011). Other wildlife are deterred by thick brush and plants, which may interfere with inter-flock communication and the view of approaching predators (Brown 1999). Tall vegetation is normally effective in long thin rows and does not need to be thick, which prevents attraction to other wildlife for use as cover. Other VegetationâSpatial Considerations: Midwest, United States An airport in Ohio contacted the U.S. Department of Agriculture Wildlife Services for wildlife management advice. The air- port owns 150 acres approximately 4,000 ft from its AOA which it has allowed a non-profit organization to use as a grassland conservation area. Though this property may appear well outside the area of risk to the airport, it is a potential attractant for hazardous wildlife, and is still being monitored for use by potentially hazardous birds, primarily smaller passerine birds. This property is an example of a conservation effort that airports can support, using property outside of the AOA that does not appear to increase wildlife strike risk. Grassland conservation area owned by a nearby international airport (left), and bobolink (Dolichonyx oryzivorus) observed in that grassland (right) (Credit: B. Washburn).
27 Patch Size As a general rule, smaller areas of habitat will be able to support fewer animals (Fahrig 2013). However, several small patches of high-quality habitat close to each other can create a mosaic that is able to support more animals. Animals tend to move from a patch as resources are depleted or if the risk of being in a patch increases (MacArthur and Pianka 1966). Larger patches will be easier for airport operators to manipulate and maintain compared to several smaller patches of various habitats requiring various management techniques. Additionally, several small patches have more edge habitat than one large patch, and edge often supports greater diversity of wildlife species (Koh et al. 2010). Operators will need to determine if small or large patches are more alluring to the specific wildlife of concern to them. CONSERVATION AREAS Conservation areas on airport grounds may take the form of wetlands, grasslands, or more forested areas. These areas can be valuable habitat for threatened and endangered species such as insects and grassland birds that pose little risk to aircraft safety (Blackwell et al. 2013). However, it is helpful to consider the species attracted to these habitats in a specific region before implementing any conservation efforts. Mammal conservation on or around airports is less likely to be safe at any spatial scale, because of the risk of enticing animals that are prey for larger, more hazardous wildlife, or of attracting larger animals (e.g., deer and coyotes) themselves (DeVault et al. 2011; Blackwell et al. 2013). Other VegetationâSpatial Considerations: Midwest, United States A Midwest airport was having trouble with waterfowl attracted to open standing water in shallow ditches. It elected simply to allow a strip of vegetation to grow up along the waterâs edge, thereby making the surface water much narrower and less attractive to ducks and geese. The vegetation consisted of naturally-occurring species such as reeds and grasses that cost the airport nothing other than occasional mowing; and that have additional benefits of removing some pollutants from runoff and slowing water runoff rates to reduce erosion and sedimentation of ditches. The vegetation strip is kept narrow and along the waterâs edge or over the water surface to prevent its becoming a travel corridor for other potentially hazardous species such as deer and carnivores. This particular airport reports the program has resulted in fewer waterfowl using the ditches, and is satisfied with the results. Alternative techniques for deterring the birds from this ditch would include use of pyrotechnics or the frequent presence of humans or other threats such as dogs. Open surface water in broad shallow ditches (left) can be less attractive when lined by a strip of dense vegetation (right).
28 WOODLOTS Wooded areas in most parts of the world are closely associated with high-quality habitat for many species of vertebrate wildlife (Kays et al. 2008; Quinn et al. 2013). The variety of plants in these areas provides not only food but excellent cover. Airports with adjacent forested areas can minimize the impacts these habitats have on safety by learning what wildlife are supported in the woodlot and determining best management practices for those species. A generally effective strategy for reducing risk associated with wooded areas is to separate them from the AOA using quality fencing (AC/Cert alert 04-16). Fences can be designed to prevent coyotes, deer, and other wildlife going over and/or under the barriers; for guidance on exclusive fencing techniques, see VerCauteren et al. (2013).
