• Abstract and Figures
• Public Full-text

U.S. Department of Agriculture Animal & Plant Health Inspection Service Wildlife Services August 2016 Bird Dispersal Wildlife Damage Management Technical Series Techniques Thomas W. Seamans Supervisory Wildlife Biologist USDA-APHIS-Wildlife Services National Wildlife Research Center Sandusky, Ohio Allen Gosser State Director USDA-APHIS-Wildlife Services Rensselaer, New York Figure 1. Photo of a frightened wild turkey (Meleagris gallopavo). Human-Wildlife Conflicts Quick Links Conflicts between humans and birds likely Successful dispersal techniques should have existed since agricultural practices capitalize on bird sensory capabilities. If Human-Wildlife Conflicts 1 began. Paintings from ancient Greek, birds cannot perceive the dispersal Habitat Modification 2 Egyptian, and Roman civilizations depict technique, it will not be effective in Frightening Techniques 4 birds attacking crops. In Great Britain, dispersing birds. recording of efforts at reducing bird Bird Management 7 damage began in the 1400s, with books Birds rely primarily on their vision and Examples on bird control written in the 1600s. Even hearing to find food, avoid predators, and Conclusion 8 so, the problem persists. Avian damage to locate mates. Bird vision is quite different crops remains an issue today, but we also from human vision; birds can see colors Glossary & Key Words 10 are concerned with damage to homes, that humans cannot perceive (including Resources 11 businesses, and aircraft, and the the ultraviolet range), and and they detect possibility of disease transmission from and use polarized light. Bird response to birds to humans or livestock. scare devices (Figure 1) that rely on vision Page 2 WDM Technical Series—Bird Dispersal may depend on the visibility of the object to the bird, as present. You must be aware of the birds in the area “visual noise” could be ignored. With regard to hearing, because the height and density of vegetation may attract birds generally are capable of hearing frequencies between or deter birds, depending on the species. Tall and dense 1,000 to 3,000 Hertz, which is narrower than normal vegetation may interfere with the birds’ ability to capture human capabilities. Since this range does not include the prey. In addition, other species may avoid taller vegetation ultrasonic range, ultrasonic devices will not scare birds. because it hinders their ability to detect approaching Birds also use tactile (touch) and olfactory (smell) senses, predators. For those species, tall vegetation may reduce but to a lesser degree. Devices based on these senses are some bird conflicts. not generally used for dispersal. Some birds, however, prefer tall vegetation for nesting and Not only must birds be able to perceive a dispersal feeding. For example, European starlings (Sturnus vulgaris) technique, they also must interpret the technique as a frequent areas with tall grass when in large flocks, but threat to their safety. A technique that worked initially may avoid these same areas when alone or in small flocks. On fail later as birds habituate to it and no longer perceive the the other hand, brown-headed cowbirds (Molothrus ater) technique as threatening. For some species, the prefer short grass because, although there may be fewer introduction of limited lethal control reinforces non-lethal insects available, the birds have easy access to them. dispersal techniques, as the birds again perceive the non- Before modifying herbaceous vegetation, try to understand lethal technique as potentially dangerous. For other why a bird is using the area. For example, if birds are species, changing techniques is necessary, because they feeding on insects you may want to use an insecticide to may not react to the death of a flock member and remove the food source. If birds such as eastern therefore still not interpret the scare technique as a threat. meadowlarks (Sturnella magna) are nesting in taller In either case, changing techniques and using multiple vegetation, you could mow the vegetation to remove techniques in an integrated manner are essential for nesting habitat, but realize this may make the area deterring birds from sensitive areas. attractive to those birds (e.g. American robin [Turdus migratorius]) that prefer feeding in shorter grass. No single technique or tool will deter birds in every instance or situation; there is no silver bullet. Successful It also is possible to change the attraction of an area by bird dispersal involves a combination of tools and timing of working directly with the plants that attract offending birds. use, as well as the skill and persistence of biologists and For example, not all herbaceous vegetation is equally wildlife control operators (WCOs). The following sections desirable as a food source. Chemical makeup and mineral offer overviews of various techniques that have been used content of vegetation will influence the foraging on grasses to mitigate bird problems in various situations, as well as by Canada geese (Branta canadensis). By planting turf examples that highlight successful bird dispersal grasses that are not desired by grazing birds (e.g., high- programs. endophyte fescue, centipedegrass, St. Augustine grass, and zoysiagrass), a landowner can make an area unattractive for birds which, in turn, can make birds easier to scare away using an audio or visual scare technique. Habitat Modification Likewise, a landowner can plant trees or shrubs that do not provide food for birds. In cases where long established All birds need some combination of food, water, cover, and trees are the attraction, thin or prune the vegetation back space to survive. Modify one or more of these features, by about a third to make the area less desirable. and birds will often move to an area that better suits their needs. Management of vegetation can affect food, cover, and in some cases, space. Before starting to manage vegetation, survey the location to identify the species U.S. Department of Agriculture Page 3 Exclusion Techniques Exclusion methods may be divided into two categories: area and ledge. The exclusion of birds from areas typically involves using nets or wires suspended to prevent bird ac- cess. The mesh size of the net depends on the species you are attempting to exclude. Netting with a ¾-inch mesh will keep most pest birds from accessing protected areas. Failure to install nets properly, however, can increase sur- face areas for nesting or loafing. In addition, poorly in- stalled nets can trap birds, leading to the death of birds and increased damage to the protected area while birds try to escape. When nets are hung over high value crops such as blueberries or grapes, the manner in which birds are attacking the crop (e.g., from the ground up or from the top down) will influence how the net should be deployed and the ultimate success or failure of the netting. Use overhead lines made of wire, nylon strings, or monofil- ament to prevent birds from using specific areas. The exact reasons why lines work are unknown but the placement of lines in grid, parallel, or random patterns has worked to prevent bird access to food, loafing, or nesting areas. Spac- ing of the lines varies by the species that is to be excluded. In general, wider spacing of about 10 feet is effective for birds with wingspans of around 2 feet, whereas narrower spacing has worked for birds of smaller wingspan. Various species of gulls (Laridae), geese, sparrows (Passeridae), and swallows (Hirundinidae) have been excluded from feeding or loafing areas. However, some species, such as Figure 2. Top to bottom. Daddy long legs, netting (different mesh sizes), bird coil, bird wire, and bird spikes. mallard ducks (Anas platyrhynchos), have not been de- terred from using protected areas as they are willing to that make a bird uncomfortable when it tries to use a ledge pass through even narrow overhead grids. or some similar perching area by causing minimal amounts Birds can be deterred from small water bodies such as of pain. A variety of anti-perching spikes are available that retention ponds by covering the water surfaces with float- work (in theory) either by preventing birds from perching on ing discs or balls. This technique will reduce evaporation, the spike with their feet or by pricking birds that attempt to however, and may change water chemistry by preventing land on them. air from mixing with the water. Unfortunately, no single device will be effective against all You can exclude birds from loafing or nesting on ledges in species of birds. In general, larger birds require different several ways using a variety of products (Figure 2). Metal devices than smaller birds due to the ability of different flashing, wood, or stone placed on ledges at a 45° angle or sized birds to fit within a series of spikes or grasp them in a more will exclude birds. Additionally, products are available manner that allows them to perch. Some larger hawks Page 4 WDM Technical Series—Bird Dispersal (Accipitridae) have learned to grab hold of the spikes and alarm and distress calls are available. Use them at a use them as a perch. volume that birds are accustomed to hearing. It is not helpful to play calls louder than how the birds normally As with any mechanical device, to be effective, spikes must hear or perceive the call. be maintained and used against species for which they are intended. For example, when a series of ledges are Birds habituate to repeated alarm and distress calls in the involved, if spikes on lower ledges are covered with absence of any threat. Calls are more effective in material dropping down from upper ledges, they will be dispersing birds when used with other methods (e.g., ineffective. Some birds actually learn to drop nesting pyrotechnics, limited lethal control) that present a clear material onto the spikes so that the spikes help to form a threat.

Load more

  12

Copy Link