Habitat Management to Deter Wildlife at Airports (2014)

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5 Turfgrass is commonly used as ground cover in aviation property because it can be maintained in a way that prevents sight obstruction on the airfield, allows infiltration of runoff from impervious surfaces, and is relatively inexpensive compared to such alternative ground covers as millings or stone (DeVault et al. 2013). However, turfgrass is composed of plants living in soil, which are two resources often used by smaller wildlife such as insects and worms (Reiley and Shry 2007), that in turn may attract potentially hazardous bird species to the airport environment. For example, Canada geese (Branta canadensis) are among the few birds that eat grass blades. Additionally, when turfgrass is taller, it may serve as food and cover for small mammals that may also attract potentially hazardous species, such as rap- tors and coyotes (Washburn and Seamans 2013). Further, turfgrass maintenance can be costly and requires the operation of heavy equipment, which in the AOA can pose safety hazards to personnel and aircraft operations. Consequently, managing a turf area is not as simple a task as it seems; the actual complexity will depend on the species of wildlife attracted to the area and the time of year. Warmer and wetter times of year will require more frequent mowing to maintain a target height of grass, and seasons often influence which wildlife species use these areas (Reiley and Shry 2007). It is important that airport operators consider turf management options that minimize the turf’s attraction of hazardous species based on the suite of potentially hazardous wildlife species in their area. Described here are some ways of managing turfgrass with the goal of minimizing attraction to wildlife. HEIGHT MANAGEMENT Several government organizations have developed specific recommendations for the height at which turfgrass should be maintained on airports, but the idea for all is similar; when grass is very short, it provides foraging areas for birds such as European starlings (Sturnus vulgaris; Figure 1), but when chapter two AIRFIELD TURF FIGURE 1 European starlings attracted to short turfgrass next to an airport runway (Credit: A. Johnson).

6 grass is longer, it may provide food and shelter for small mammals that attract raptors and other predators (Washburn and Seamans 2013). An intermediate grass height is typically recommended to minimize attraction of wildlife to either short or long grass (specific appropriate grass heights depend on the preferences of the wildlife species of concern). Similarly, mowing to prevent grass from seeding will lessen the allure for wildlife attracted to feeding on seeds. The height at which grass flowers and seeds will depend on the type of grass and previous mowing height history. Some grasses can adapt to growing and seeding at shorter heights [e.g., Bermuda grass (Cynodon dactylon)], whereas others typically have taller growth forms [e.g., tall fescue (Schedonorus arundinaceus); Purdue University 2013]. The International Civil Aviation Organization (ICAO 1991) recommends turfgrass height of eight inches or greater, while Great Britain’s Civil Aviation Authority (CAA 2008) recommends grass height between six and eight inches. Transport Canada recommends airports determine an appropriate grass height depending on their unique group of potentially hazardous species (Transport Canada 2002). The FAA in the United States recommends heights of six to 12 inches, but the United States Air Force rec- ommends maintaining grass between seven and 14 inches (Air Force Instruction 91-202, 7.11.2.3). Airport Turf—Height Management: Arlington Municipal (GKY) While short turfgrass may not seem like an obvious attractant, a wildlife hazard assessment at Arlington Municipal Airport in Texas determined that the short grass height was attracting grackles, starlings, mourning doves (Zenaida macroura), mice, red-tailed hawks (Buteo jamaicensis), rabbits, coyotes (Canis latrans), and bobcats (Lynx rufus). Airport operators responded by maintaining grass at the maximum height their mowing equipment allows (4–6 in.). Continued monitoring of wildlife use of these areas will be used to determine the effectiveness of increasing the mowing height. When to Mow Deciding when to mow turfgrass depends on several factors, beginning with the potential inter- ference of mowing equipment and personnel with safe aircraft operations; and the possibility that mowing may itself serve to attract wildlife by disturbing and exposing prey such as insects and small mammals that can lure avian predators such as gulls [Larus spp.], egrets, herons, and raptors (Dinsmore 1973). Mowing grass before it produces seeds will prevent attracting animals that forage on grass seed; such mowing can be scheduled when aircraft operations are less frequent or when wildlife potentially attracted are less active (e.g., at night). Moreover, mowing when the ground is saturated can kill turfgrass and create open areas allowing noxious weeds to develop, which may serve as a new wildlife attractant (Christians 2007). How Often to Mow Mowing turfgrass can be an expensive and time-consuming process, depending on the amount of turfgrass area being maintained. For these reasons alone, most operators only mow turfgrass as often as necessary to maintain the desired height (Christians 2007). And, as suggested previously, reducing the likelihood of creating a wildlife attractant by disturbing potential prey animals is another reason to mow only as often as necessary to maintain desired height (Dinsmore 1973). Mowing too often may also kill areas of grass and, like mowing saturated turf, may create spaces of open ground or noxious weeds to develop, potentially creating new problems with wildlife attraction (Christians 2007). In the Netherlands, turfgrass is mowed just once or twice a year to maintain cover for erosion control while preventing establishment of consistent food or cover sources for wildlife and reducing mowing costs [Koninklijke Luchtmacht (Royal Air Force) 2008]. What Time of Day to Mow At each airport, there are times of day when potentially hazardous wildlife species are less active. For example, cattle egrets have been observed feeding on insects disturbed by mowers and tractors,

7 yet they also regularly leave foraging areas shortly before sunset to return to roosting sites (Dinsmore 1973). Thus, mowing at night can effectively minimize prey availability to daytime foraging species that are hazardous. Operators can schedule mowing when hazardous wildlife is not present to be attracted to exposed prey, but may need to adapt mowing schedules depending on species present at different times of year. SURFACE AREA Many airports are restricted by local regulations on how much impervious surface area they have on their property [FAA Advisory Circular (AC) 150/5300-13]. This may influence decisions to replace hard surfaces with turfgrass. However, if an airport already has issues with attracting wildlife to areas with turfgrass, adding more would only increase the problem. Alternative covers that are not wild- life lures may be considered instead (DeVault et al. 2013). Also, although larger areas of turfgrass may be easier to maintain than several small parcels, wildlife may feel more secure and efficient foraging in larger areas of turf (Fernández-Juricic and Beauchamp 2008). PLACEMENT FAA AC150/5200-33B recommends against large areas of turfgrass within separation criteria, suggesting a five-mile buffer between the aircraft approach/departure space and any wildlife habitat attractant. Turfgrass is most often used around airport buildings and in the AOA; however, airports having issues with turfgrass attracting potentially hazardous wildlife have replaced some of their turf in these areas with alternative ground covers such as artificial turf and asphalt millings. Sports fields and golf courses are alternative land uses near airports as well and create large areas of turfgrass adjacent to AOAs (Figure 2). This land use practice may be a good alternative to wetlands or agriculture, but may need special treatment with chemical deterrents (e.g., anthraquinone; Ayers et al. 2010) or physical barriers to reduce attraction to wildlife. Operators need to strive to ensure that when replacing one habitat with another they do not create a new attraction that draws in the same or other species of wildlife. Breaking up areas of turfgrass may reduce their attractiveness to wildlife such as geese (as described in chapter three). COMPOSITION Regional variation in climate, growing season, and soil conditions determine the turfgrass able to establish and survive in a given area (Christians 2007; Washburn and Seamans 2013), as well as a cover’s ability to compete with noxious species (i.e., weeds). While operators cannot control the weather, they can use fertilizers and mulches to their advantage to encourage better establishment of a thick turfgrass density when seeding (Washburn and Seamans 2013). In addition, certain species of grass are less palatable to wildlife that pose safety concerns such as Canada geese. Washburn and Seamans (2012) found that creeping bentgrass (Agrostis stolonifera), FIGURE 2 Canada geese grazing on turfgrass at a sports field adjacent to a California airport (Credit: A. Johnson).

8 Kentucky bluegrass (Poa pratensis), and fine fescues (Festuca spp.) were preferred by Canada geese over other commercially available turfgrasses such as zoysiagrass (Zoysia japonica), centipedegrass (Eremochloa ophiuroides), or St. Augustine grass (Stenotaphrum secundatum). One commonly used turfgrass in the United States today is tall fescue (Schedonorus arundinaceus), a cool season grass that forms thick continuous strands and is often infested with the fungal endophyte Neotyphodium coenophialum (Washburn and Seamans 2013). The infested fescue is often more tolerant of drought and less preferred for food by grazing wildlife and insects (Clay et al. 1985; Vicari and Bazely 1993; Malinowski and Belesky 2000). The FAA has more standards on turfgrass establishment in AC 150/5370-10E. Some broadleaf plants such as forbs and clovers may invade turfgrasses and can attract grazing wildlife. These plants may be treated with an herbicide, such as 2,4-D, if the desired turfgrass is resis- tant to that herbicide (Hartman et al. 1994; Washburn and Seamans 2004). Application of chemicals would need to be more cost-effective than other deterrence methods and might require additional permits for environmental protection (Washburn and Seamans 2004). Other good cover may not be very attractive to wildlife in airfield areas; for example, Linnell et al. (2009) found wedelia (Wedelia trilobata) to be a useful cover plant in tropical areas. Pochop et al. (1999) found that geese from an airforce base in Alaska preferred Kentucky bluegrass (Poa praten- sis) and flightline turf (Bromus sp., Rumex acerosella, and Festuca rubra) over lupine (Lupinus noot- Airport Turf—Composition: John F. Kennedy International ( JFK) Types of grasses vary in their structure and palatability, which are important characteristics to foraging wildlife. Replacing grasses that have more desirable shapes, lengths, tastes, and textures can reduce turf appeal to potentially hazardous wildlife species. To reduce the various bird species attracted to areas of turfgrass both in and outside of the AOA, operators at JFK replaced some grassy areas entirely with artificial turf. The benefits of artificial turf are that it needs very little maintenance, requires no water, and does not produce seeds or attract insects that might attract larger, more hazardous wildlife. However, operators need to be cautious that artificial turf and the substrate in which it is “planted” may not allow drainage as real turf does, and should plan for proper drainage before installation. Also, operators will want to consider the cost/benefits of replacing turfgrass with artificial turf. A second technique JFK has used to reduce wildlife attraction to turfgrass areas is planting tall fescue in place of grasses more palat- able to geese. Tall fescue helped reduce goose use of a baseball field and adjacent areas on airport property, but the temporary snow-drift or silt fencing in these fields eliminated winter use. JFK has also established areas of tall fescue inoculated with a noxious endophyte. This grass has helped eliminate presence of black-tailed jackrabbits (Lepus californicus) and occasional goose grazing at the approach end of one of the runways. Artificial turf installed next to a runway at a northeast airport (Credit: L. Francoeur).

9 Airport Turf—Composition: Salt Lake City International (SLC) Faced with a number of bird species—raptors, gulls, waterfowl, shorebirds, and passerines foraging on other prey animals or the vegetation itself—that were attracted to fallow fields near its runways, SLC implemented a project to reduce grasses and broadleaf vegetation on approximately 100 acres, using asphalt millings from runway overlays. While a runway overlay can be expensive, leftover millings can be useful and cheap for projects such as this. The scheme was approved by the FAA, airport environmental staff, and engineers. SLC reports greatly reduced wildlife use of these areas, and would use this technique again. One concern with loose material such as asphalt millings in the AOA is the potential for foreign object damage. Operators from SLC report that one area replaced with millings was treated with a tack spray, while others that were not treated did not pose increased risk of foreign object damage compared to vegetated areas. Asphalt millings left over from runway overlay projects (left ) can be used to replace vegetation that may attract wildlife (right) (Source: SLC). katensis), bluejoint reedgrass (Calamagrostis canadensis), and beach wildrye (Elymus mollis). See FAA CertAlert No. 98-05 for more information on grasses attractive to hazardous wildlife (http:// www.faa.gov/airports/airport_safety/certalerts/). GROUND STRUCTURES Many species of wildlife rely on areas of relatively soft soil to dig nests and dens (Lauro and Burger 1989). Shorebirds and waterbirds such as killdeer (Charadrius vociferus), gulls, oystercatchers, and terns prefer to nest on bare ground (Colwell and Oring 1990). These areas do not provide vegeta- tion that may attract many other herbivorous or granivorous species, but still provide an important resource that these nesting birds use.

10 Airport Turf—Composition: John F. Kennedy (JFK) In order to accommodate larger aircrafts, JFK had to expand the width of its runway. This construction left exposed areas alongside the runways of mostly soft sandy soils, creating a desirable habitat for nesting by American oystercatchers (Haematopus palliates). Though the bare ground was reseeded with fescue, the turf did not take hold and oystercatchers were quickly attracted to the area. However, over the course of a few months, other herb and forb vegetation began to grow in the bare areas; and as these plants grew taller and thicker, oystercatchers were deterred from nesting in the vegetated area and moved elsewhere. This is an example of how management techniques intended to deter wildlife may not work as planned; but the unexpected consequences may allow operators to adapt to local conditions and develop effective measures for their species of hazard concern. American oystercatcher nesting at JFK (Credit: J. Mastantuono).