Frightening devices (harassment)
Frightening techniques are often utilized to disperse gulls, and consist of two categories: noise and visual.
These techniques are most effective before birds become firmly established at a site. If site tenacity is allowed to develop, it will be more difficult to cause abandonment of the site in favor of more peaceful areas. It is also helpful to note that site tenacity is stronger toward feeding and nesting areas, than for loafing areas.
Please remember that gulls are federally protected under the Migratory Bird Treaty Act. Once egg-laying begins, it is illegal to disturb the birds, eggs or nests without a federal permit.
If a harassment campaign is undertaken to control gull numbers at a nest site, it is essential to do so before the onset of egg-laying. For greatest success, it is best to use a variety of methods to prevent acclimation. Places to find materials or devices used in these techniques can be found in the sources for bird control section.
There are a wide variety of noise devices available including
- propane cannons
- pyrotechnics (shell crackers, screamers and bangers)
- other noise makers, such as clappers, motion-activated alarms, and distress alarm call systems
Be sure to check federal and state regulations before using pyrotechnics (a type of explosive) and local noise ordinances to determine if noise-making devices are permitted in your area.
Habituation is the primary drawback to these frightening techniques. With no penalty involved, gulls will quickly learn that most are harmless, especially if they are stationery. They must be moved frequently to avoid habituation. This would include the speakers that deliver distress alarm calls.
Distress alarm call systems
Studies indicate that birds emit distress calls when held by a predator, in an effort to startle the predator into release. It is thought that nearby birds investigate the situation to decrease their chances of also being preyed upon. Initially, gulls may respond to distress calls by coming in to investigate, before eventually dispersing.
Care should be taken when choosing the correct call, as gull distress calls are specific to both region and species. If possible, use calls that were recorded from birds close to your area. Some gulls that reside in mixed flocks may respond to calls of other species which they associate with. Good quality, preferably digital, recordings should be used.
This method is most effective when used in conjunction with other frightening techniques, such as the use of pyrotechnic devices, which are best used when gulls come in to investigate the distress call. After a period of time, birds will return to the site. The time span differs depending on their use of the site (feeding or loafing). It is much more difficult to cause birds to abandon a site if it is a feeding area, as opposed to a loafing area. Be persistent and again, reinforce the distress calls with another form of harassment.
As with all noise-making devices, please check local ordinances before using alarm call systems.
Ultrasonic noisemakers have been suggested by various wildlife control supply companies as being a solution to repelling many species of birds. However, buyers beware! Some research indicates that birds do not respond to the use of these devices, and may not even be able to hear sounds in the ultrasonic range. Some studies indicate that they may be useful for a short period of time, but habituation quickly ensues. Considering the high cost, it may be best to rent such a device initially to determine its effectiveness before purchasing.
There are a wide variety of visual frightening devices on the market including
- predator models
- numerous styles of brightly colored mylar objects, such as flags and streamers and balloons (often decorated with scary eyes or predator images)
- kites resembling avian predators
- dead gull effigies
There are also a number of motion activated devices on the market including sprinklers and self-inflating scarecrows, among others.
Used alone, these will only be effective for a short period of times. As is the case with most frightening techniques, habituation quickly occurs. It is best to use these in conjunction with other types of harassment, such as the use of pyrotechnics or distress alarm calls. Frequently moving and varying the devices used will also help to prevent habituation.
Lasers are considered to be frightening devices which may be useful in dispersing roosting gulls from waterbodies, such as reservoirs. This technique, however, is only effective at night or in low light conditions such as those caused by fog. Research indicates that lasers will not cause complete abandonment of the roosting site, with gulls returning during daylight hours. For most success, sweeps should occur every half hour from dusk to dawn.
Lasers should be used with great caution due to the potential dangers associated with them, and should only be used by trained personnel. The radiation emitted can be a hazard to the skin and eyes, even when directed at a reflective surface. Eye protection should be worn by all personnel in the area where it will be used. Care should also be taken to avoid pointing at occupied vehicles (including aircraft). If the laser is a Class IIIb, danger signs must be posted at all entry points to the area in which it will be used. The exposure limits and dangers associated with various classes of lasers can be reviewed through the following link http://www.asu.edu/radiationsafety/laser/appn_C.html.
Dead gull effigies (fresh carcasses, taxidermic or artificial) as frightening devices have been studied and show some promise as a frightening technique in dispersing birds from feeding and, most successfully, from loafing areas. Gulls will avoid areas containing effigies, but only if
- it is realistic in every detail
- is of the same species as the gulls you are attempting to disperse
- is in good condition (looks freshly killed as opposed to decomposed)
The positioning and posture of the effigy are also details that shouldn’t be overlooked. Taxidermic mounts prepared to mimic agony postures are best.
The use of distress alarm calls used in conjunction with pyrotechnic devices, will enhance the effects of the effigies, and prevent habituation. If used alone, however, habituation is likely to occur within a few days. Federal and state permits would be required for the taking of any gull for use as scaring device. Many airports already have permits to remove various birds and mammals from within their boundaries, and so could use the carcasses for this purpose.
The use of falcons as a frightening technique is becoming more widespread and is seen to be more environmentally friendly by the general public than is lethal removal at airports. This technique, however, may be cost prohibitive to the majority of business/home owners and agricultural producers.
The process requires frequent visits by a falconer with a trained bird of prey, such as a peregrine falcon. The falcon does not hunt the targeted birds, but is flown in a training exercise during which it chases a lure swung about on a tether. The sight of this avian predator flying in the area is enough to cause gulls, and other birds to leave. When used in conjunction with pyrotechnic devices, birds can be trained to connect the sound of the noisemaker with the appearance of the falcon, eventually responding to the noisemaker alone thereby, over time, reducing the number of visits required by the falconer. When used at airports, care should be taken to prevent flocks of dispersing birds from flying in the direction of incoming or outgoing aircraft.
Radio-controlled aircraft can also be useful in dispersing gulls, with some models manufactured to resemble birds of prey. A skilled operator can even control the direction of the dispersing birds. Their use is limited in adverse weather conditions however, and their effects are not long-lasting. Therefore, it is best to use in conjunction with other frightening techniques, such as pyrotechnic devices.
Border collies are also an environmentally friendly way to disperse birds of many species. The approach of an animal that gulls see as a real predator is quite effective. Trained dogs can control the direction of dispersing birds, and over time, is shown to reduce the number of birds landing in the protected area. As with falconry, this method can be expensive, requiring the hiring of an experienced handler with trained dogs. Also, it does little to prevent gulls from flying above airports. It is recommended that this technique is best used in conjunction with other frightening devices.