Visual Repellents

Vision-based deterrents present a visual stimulus that is novel, startling, or that the birds associate with danger. The danger can be a predator, a simulated predator, the results of a predator attack (dead bird or model thereof), or some unusual object that birds avoid because it is unfamiliar. Lights, scarecrows, dyes, reflecting tape, predator decoys, kites, balloons, smoke, and dead or live birds are visual stimuli that may disperse birds. Some products incorporate both visual and auditory stimuli.

Many birds discriminate the colour of light at wavelengths between 400 and 700 nm, comparable to humans (Pearson 1972; Martin 1985). In addition, some species, including pigeons, hummingbirds, Mallards, Belted Kingfishers, boobies and some passerines (Martin 1985; Meyer 1986; Reed 1987; Maier 1992) also perceive ultraviolet light (<390 nm). Humans do not detect ultraviolet light. Pigeons and some songbirds have also exhibited sensitivity to the plane of polarization of light (Martin 1985), to which humans have very limited sensitivity. Since birds can apparently detect colour, it could be an important consideration during the construction and development of devices that are used to deter and disperse birds.


Description. – Scarecrows are one of the oldest devices that have been used to control birds (Frings and Frings 1967; Hussain 1990). Most scarecrows are human-shaped effigies; they have been constructed from a wide variety of inexpensive materials such as grain sacks or old clothes stuffed with straw. The more realistic the facial features and the human shape, the more effective scarecrows are likely to be. Painting scarecrows a bright colour can increase their detectability (Littauer 1990a). Commercially-manufactured scarecrows also are available, such as the Scarey Man mannequin. The Scarey Man Fall Guy unit is a 1.46 m tall, plastic mannequin that intermittently inflates with air, bobs up and down, illuminates with an internal light, and emits a high-pitched wail (Stickley et al. 1995 as cited in Andelt et al. 1997).

Biological Basis. – Scarecrows, by mimicking the appearance of a predator (a person), cause birds to respond with prompt flight to avoid potential predation. The greater the realism, in appearance and behaviour, of the scarecrow the greater its effectiveness. Because the threat that birds might associate with scarecrows is perceived rather than real, habituation is likely to occur relatively quickly unless other scare techniques are used in conjunction.

Literature. – In general, scarecrow-type devices have proven ineffective when used in isolation or else effective for only a short time as the target species habituate to the visual stimulus (Blokpoel 1976; Conover 1979, 1983, 1985b; Boag and Lewin 1980; Hothem and De Haven 1982). Scarecrows are more effective if they are moved every 2-3 days (DeFusco and Nagy 1983; LGL Ltd. 1987; Hussain 1990). Scarecrows that move in the wind and that are used with other deterrent devices (e.g. gas cannons) are more effective than immobile scarecrows that are not used with complementary devices. Littauer (1990b) suggested that periodically driving a vehicle near the scarecrow, or placing the scarecrow on a stationary vehicle, could increase its effectiveness. A mannequin tested on Rufous Turtle Doves in a flight cage was found to have a larger effective area than a stuffed crow or kite (Nakamura 1997).

More recently, several types of mechanical pop-up scarecrows have been created. Nomsen (1989) reported that a human-like scarecrow that popped up from a double propane cannon when it fired was very successful in keeping blackbirds from feeding over 4-6 acres of sunflowers. Ducks and geese were observed to be much easier to frighten off than blackbirds.

Another model of scarecrow consists of an inflatable, human-shaped bag that is mounted on a battery-powered compressor or electric fan. It inflates every five minutes. Timers can also be connected to a photo cell switch which would allow the scarecrow-inflation sequence to begin at dusk or dawn. Once inflated, the scarecrow stands up and then emits a screeching, siren-like noise before it deflates (Littauer 1990a; Coniff 1991). Coniff (1991) reported that this kind of scarecrow set up near a catfish pond effectively frightened cormorants. Numbers of great blue herons and black-crowned night-herons initially decreased at a fish hatchery following implementation of two Scarey Man Fall Guy human effigies, but the herons quickly habituated to the devices and numbers increased after the first four nights (Andelt et al. 1997).

Littauer (1990b) described another mechanical scarecrow model with a mannequin head attached to a steel rod. A propane cannon projects the head approximately 30 inches into the air. No information was available on the effectiveness of this kind of scarecrow.

Some species of birds become habituated to scarecrows whether or not they move. Naggiar (1974) reported that scarecrows (stationary) and shooting were not effective in deterring wading birds from fish ponds. After two hours, birds became accustomed to the scarecrow.

Cummings et al. (1986) used a propane cannon and a CO2 pop-up scarecrow to deter blackbirds from sunflowers. They found that most birds were frightened away by the scarecrows; fewer birds returned during the treatment period than were observed during the control period. Cummings et al. speculated that the birds that returned had become habituated to the scarecrow in some cases, and in other cases, that feeding patterns were too well established to allow effective deterrence of the birds.

Scarecrows have been tested for use in deterring birds from landing on oil-contaminated tailings ponds in Alberta. Ward (1978) tested a "bird-scaring raft" with a large fluorescent orange scarecrow, two continually-burning lights, and a gas cannon. The deterrent rafts were not able to exclude all birds. Ducks, in particular Lesser Scaup, were the most sensitive to the rafts. American Coots and grebes were the least affected.

Boag and Lewin (1980) found that a human effigy was effective in deterring dabbling and diving ducks from small natural ponds. When the effigy was present, the total number of ducks on the ponds declined by 95%. Over the same interval there was only a 20% decline on adjacent control ponds, indicating that the effigy was quite effective.

Boag and Lewin (1980) also attempted to evaluate the efficacy of 27 effigies placed around a 150 ha tailings pond. Counts of dead birds found in the pond were compared to counts from the previous year when effigies were not deployed. Although numbers of dead waterfowl were slightly higher in the year with effigies (104 vs. 98), the effigies were still considered effective. More waterfowl and shorebirds were believed to be present in the area during the year when effigies were deployed, and retrieval efforts were more intensive in that year.

Evaluation. – Scarecrows are a flexible deterrent technique. They can be deployed on land or water, are mobile, and are inexpensive to construct. Scarecrows can be used in combination with other control products to enhance the overall deterrent effect. Over the long-term, however, scarecrows have proven to be ineffective. Their best use is in circumstances where temporary and local control is sufficient.

Recommendation. – Recommended only for short-term and local deterrence; not to be relied upon for long term deterrence of birds.

Literature Reviewed. – Andelt et al. 1997; Boag and Lewin 1980; Coniff 1991; Cummings et al. 1986; DeFusco and Nagy 1983; Devenport 1990; EIFAC 1988; Frings and Frings 1967; Kevan 1992; LGL Ltd. 1987; Littauer 1990a,b; Nakamura 1997; Naggiar 1974; Nelson 1990b; Nomsen 1989.

Reflectors and Reflecting Tape

Description. – Reflecting tape is an elastic, 3 layered tape that has a silver metal layer coated on one side and a coloured (usually red) synthetic resin on the other side (Bruggers et al. 1986). This type of tape flashes when it reflects sunlight, and produces a humming or crackling noise when it stretches or flaps in the wind. Because of its noise and reflective features, reflecting tape has been used to deter birds in agricultural settings.

Biological Basis. – There is very little biological basis for the effectiveness of reflectors and reflecting tape. Birds would avoid these products initially because of their natural caution toward unfamiliar objects. They also would exhibit startle responses to the bright flashes of light and sudden noise. Because the biological basis is not strong, however, habituation is likely to occur quickly.

Literature. – Several early studies suggested that reflectors could be used to deter birds from crops and airports. These studies have been summarized by Koski and Richardson (1976). More recent studies have concentrated on the use of reflecting tape rather than just bright flashy objects. Reflecting tape produces noise when it flaps in the wind, and the auditory stimulus is believed to make reflecting tape more effective than other reflectors.

Mylar flags were tested for their effectiveness as gull deterrents by Belant and Ickes (1997). Flags were tested at two nesting colonies and two loafing sites at a landfill. Belant and Ickes (1997) concluded that the reflecting tape was ineffective in deterring the herring gulls (and likely other gulls) from nesting colonies but can reduce herring and ring-billed gull use of loafing areas.

Bruggers et al. (1986) used reflecting tape (0.025 mm thick and 11 mm wide) to deter birds from cornfields, sunflowers and sorghum. The tape was successful in deterring birds when it was suspended above the ripening crops in parallel rows, and when the entry point into the fields was also protected. High winds may have also increased the effectiveness of the tape by increasing the noise it makes. Dolbeer et al. (1986) used reflecting tape to repel blackbirds from crops by stringing tape at intervals of 3, 5, and 7 m. The tape was suspended from poles spaced 3 m apart and the tape sagged 0.5-1.0 m at its low point between poles. The 3 m spacing was more effective at repelling birds than were the 5 and 7 m spacings. Reflecting tape did not deter all species of birds and it was not effective when it became twisted such that the reflecting side was no longer visible.

Summers and Hillman (1990) tested a red fluorescent tape (20 mm wide) in fields of winter wheat in the U.K. to deter Brant. One half of a 20.2 ha field was the control area and the other half was the treatment. A second control field (7.5 ha) was set up in another area that had one gas cannon and two scarecrows. Lines were strung at 40-60 m intervals across the rows of wheat in the experimental field. The tape proved more successful than the cannon and scarecrows in repelling Brant. Geese caused a 1% reduction in grain yield in the taped field, but a 6% reduction in the untaped field. Geese apparently grazed within 2 m of the edges of the fields with tape.

Reflecting tape was ineffective in deterring birds from ripening blueberries (Tobin et al. 1988). Tape was set up in the fields 10 to 12 days before the first bird and berry counts were taken. During this time, the birds could have become habituated to the tape. Also, only 7-10 strands were set up per plot, which may have not been enough to deter birds.

Evaluation. – Reflectors could be useful as bird deterrents in limited applications on airfields. Reflecting tape is easy to set up and is readily moved to other locations. Reflectors could also be placed around the edges of ponds. Improved effectiveness would be achieved by combining tapes with complementary scaring devices (e.g. cannons, scarecrows).

Recommendation. – Reflectors and reflecting tape are recommended only for limited use on airfields.

Literature Reviewed. – Belant and Ickes 1997; Bruggers et al. 1986; Dolbeer et al. 1986; Koski and Richardson 1976; Summers and Hillman 1990; Tobin et al. 1988.

Predator Models

Description. – Predator models are designed to resemble a predator, usually an owl or hawk. Models vary from very poor to very life-like imitations of the predator. One (poor) example is the "plastic owl" commonly used on buildings to deter pigeons, sparrows and swallows.

Biological Basis. – Predator decoys are used to disperse and deter birds by mimicking the appearance and/or action of real predators. Avoiding predators has high survival value and thus there is a strong biological basis for the use of predator models. The model must be realistic, however, or pest birds will habituate.

Literature. – Decoys or models usually have been used to scare birds from agricultural crops (Conover 1979, 1983, 1984, 1985b; DeFusco and Nagy 1983; Crocker 1984). Conover (1979, 1983) found that stationary, mounted hawks and hawk-kites (see below) deterred birds from feeding stations and corn fields but that their effectiveness was short-term. Belant et al. (1997e) found plastic, hand-painted effigies of great horned owls and merlins ineffective in reducing starling use of nest boxes. There was no significant difference among nest boxes with or without the effigies in the proportion of nest boxes with nests, eggs, or nestlings.

Models of predators sometimes attract rather than repel birds (Conover 1983; LGL Ltd. 1987). For example, blackbirds and crows often mob owls or owl models. However, Conover (1982, 1985b) found that a moving plastic owl model with a plastic crow model in its talons repelled crows from gardens and small fields. A stationary version of the same model was not effective at deterring birds.

Evaluation. – Given that models are less realistic than live birds, predator models are limited in their effectiveness. Pest birds will eventually learn that the model is not the real thing and therefore, is not a threat. If short-term deterrence is sufficient, then predator models are a option. They are inexpensive and easy to deploy. Their effectiveness can be enhanced by moving them frequently.

Recommendation. – Recommended only for situations where very short-term and local control is needed. Generally not recommended for use on airfields.

Literature Reviewed. – BSCE 1988; Belant et al. 1997e; Conover 1979, 1982, 1983, 1984, 1985b; Crocker 1984; DeFusco and Nagy 1983; Frings and Frings 1967; Hothem and DeHaven 1982; Inglis 1980; Koski and Richardson 1976; LGL Ltd. 1987; Naef-Daenzer 1983; Saul 1967; Stout and Schwab 1979.

Hawk Kites and Balloons

Description. – Hawk kites are a mobile variation of stationary predator models. Hawk-shaped kites are tethered to the ground or suspended from helium balloons or poles to keep them aloft.

Biological Basis. – Hawk kites work on the principle that prey species will flee an area in response to perceived danger. In the absence of an actual threat, birds will soon learn that there is no need to flee and at that point the kite is no longer effective.

Literature. – Kites that mimic hawks and other raptors have been used to frighten birds from corn and sunflower crops (Harris 1980; Conover 1983) and from grapes (Hothem et al. 1981; Hothem and DeHaven 1982). Usually these kites are suspended from helium-filled balloons or hung from poles in order to keep them aloft with or without wind.

Conover (1983) conducted experiments with four different designs of hawk-kites (Mausebussard, Falke, Steinalder and Habicht). These varied in the species represented, size, wing-span and colouration. Each kite was attached to the middle of a braided nylon line that was strung between two bamboo poles set 3 m apart. The kites did not effectively deter birds from feeding on corn. Because the kites were not attached to balloons, they were less mobile (40 m range of movement for kites with balloons vs. 2 m range for kites only), and therefore, probably less effective at scaring birds. When movement was incorporated into the deterrent (kites were suspended from balloons) the kites became effective at deterring birds from feeding in corn fields (Conover 1984).

Hothem et al. (1981) used four kites, with balloons, to repel birds from vineyards: 1 eagle kite with a 1.35 m wingspan, 1 eagle kite with four circular holes in the leading edge of the wings, 1 kite with a falcon image on the lower side, and 1 eagle kite made of cloth (1.65 m wingspan). All kites were attached to helium balloons (diameter 1.2 m). The balloons were tethered with 23 kg test nylon line; each day the length of the tether was adjusted to be between 8 and 52 m. One kite-balloon was set up per 1.0-1.1 ha of vines for a 7-day evaluation period (treatment), and then removed for another 7-day period (control). To reduce the likelihood of habituation, kites and the colour of balloons (5 different colours) were changed every 1-2 days. Although results suggested that bird damage was reduced during the 7-day period with the kiteballoons, the decrease in damage was not significant. The sample size may have been too small for a meaningful test.

Hothem and DeHaven (1982) tested a "kite-hawk" to reduce bird damage in vineyards. The kite had a 1.3 m wingspan and was coloured to resemble an immature Golden Eagle. The kite was suspended from a blue helium-filled balloon with diameter 1.7 m. Based on six 7 day-on/7 dayoff treatment periods, no difference was found in the percent loss of grapes (2.8% for treatment vs. 2.9% for control). However, damage levels were found to have increased with increased distance from the kite-balloon, suggesting that the deterrent may have been effective over a very small area. Kites were damaged when winds exceeded 8 km/h, but generally lasted up to 14 days.

Brant reportedly were repelled from a large area (5 km in radius) when a helium-filled diamond-shaped kite was tethered to a line on the ground and moved along that line in an erratic pattern (DeFusco and Nagy 1983). The Brant apparently did not habituate to this device.

High winds can decrease the effectiveness of kites. Harris (1980) reported that kite-balloons could not withstand high winds on the Manitoba prairies. The rate of habituation is not clear; some workers have reported slow or no habituation (DeFusco and Nagy 1983), whereas others have reported more rapid loss of effectiveness. Inglis (1980) reported that Wood Pigeons habituated to a kite-balloon after only 4 hours.

Evaluation. – Kites and balloons can be useful as bird deterrents on airfields, but their usefulness is limited by habituation. Kite-balloons are easy to set up and can be moved relatively easily to other locations. They could be effective around a small pond or temporary wet area that attracts birds, for example. Kites and balloons have some practical limitations. Balloons may be difficult to keep inflated. High winds (a problem on open airfields) and rain could destroy their effectiveness. It would be necessary to use other complementary scaring devices (e.g. cannons, scarecrows) to extend the effectiveness of hawk kites and balloons.

Recommendation. – Hawk kites and balloons are recommended only for situations where shortterm and local control is sufficient.

Literature Reviewed. – Conover 1983; DeFusco and Nagy 1983; Harris 1980; Hothem et al. 1981; Hothem and DeHaven 1982; Inglis 1980.

Gull Models

Description. – Gull models in this context refer to replicas or actual specimens of dead gulls, typically presented on the ground as though they have fallen and died there.

Biological Basis. – Dead birds, either actual or models, serve as a warning that some form of danger is, or recently has been, present in the area. Initially birds often approach a dead bird to look at it, but they usually leave the area after discovering the unnatural position of the bird.

Literature. – Bird bodies have been used to repel and scare birds from agricultural areas (Naef- Daenzer 1983) and from airports (see Koski and Richardson 1976, Inglis 1980, and DeFusco and Nagy 1983 for reviews). Models of dead birds also have been useful in scaring birds in certain circumstances. For example, models of dead gulls, or actual dead gulls displayed prominently, have been useful in scaring gulls away from some airports (Saul 1967; Stout and Schwab 1979; Howard 1992). However, in most countries these methods have not been found to be sufficiently effective to be adopted operationally (BSCE 1988).

Some success has been achieved by using dead gulls or gull models deployed in unnatural positions or in positions assumed by dead or injured birds. Stout et al. (1974) used model gulls to disperse glaucous-winged gulls from an airfield at Shemya in the Aleutian Islands and ring-billed gulls from a landfill near an air force base in Pasadena, Texas. In the latter case it was necessary for the gulls to be airborne so that they all could see the model gull on the ground. Distress calls were played to make the gulls fly. In the Netherlands, stuffed gulls in injured positions were found to be effective only if they were frequently moved to avoid habituation (Hardenberg 1965). Crucified corpses and polystyrene gull models were successful at keeping gulls off loafing areas at Auckland and Wellington airports in New Zealand. The secret to success here was that alternate loafing areas were available. At a third airport with no alternate loafing areas, the gull models were less successful (Caithness 1970).

Mock gulls were used as part of the intensive gull control program conducted annually at the large ring-billed gull colony at Toronto's Leslie Street Spit. The mock gulls consisted of gull wings tied to a plastic bottle. They were thrown into the air to simulate injured gulls. The mock gulls were used in conjunction with falconry, pyrotechnics, and distress calls in a program that successfully prevented ring-billed gulls from nesting in large parts of the area (Watermann 1985, 1986, 1987; Watermann and Cunningham 1989). Several airport and landfill control programs kill gulls that are then thrown up into the air when pyrotechnics are used. This reportedly reinforces the effectiveness of the pyrotechnics.

Evaluation. – As with many of the visual deterrent products discussed thus far, dead gulls and models of dead gulls (or other species) will deter some birds but the period of effectiveness is limited by habituation.

Recommendation. – On their own, gull models are recommended only for situations where shortterm and local control is sufficient. However, models of dead birds (or stuffed birds) can be an effective component of an integrated bird control program.

Literature Reviewed. – BSCE 1988; Caithness 1970; DeFusco and Nagy 1983; Hardenberg 1965; Inglis 1980; Koski and Richardson 1976; Naef-Daenzer 1983; Saul 1967; Stout and Schwab 1979; Stout et al. 1974; Howard 1992; Watermann 1985, 1986, 1987; Watermann and Cunningham 1989.


Description. – Trained falcons and other hawks are used by professional falconers to chase birds from specific areas by pursuing and occasionally killing them.

Biological Basis. – Most birds have evolved well-developed escape behaviours that are triggered by the sight of those species of falcons and other hawks that could prey on them. There is a sound evolutionary basis for prey species to avoid falcons.

Literature. – Raptors have been used to disperse birds from a number of airports, including some in Canada (Blokpoel 1976; Koski and Richardson 1976; DeFusco and Nagy 1983; Blokpoel 1984; Hild 1984; BSCE 1988; Erickson et al. 1990). Peregrine falcons were flown against gulls at an airfield in Britain in a two year study in the late 1940's (Wright 1965). The falcons were successful but needed to be flown at least once, and sometimes more often, each day to keep gulls away.

Further studies of falconry have been conducted on a variety of species (Seaman 1970; Heighway 1970; Mikx 1970). Heighway (1970) reported on an operational study of peregrines at a Royal Naval Air Station on the north coast of Scotland. A team of eight peregrines flown by two full-time trainers took two years to establish control over the resident gull populations that used the area. Pyrotechnics and carbide cannons were used to supplement the falconry efforts. On average, it was necessary to replace two falcons each year. A team of four goshawks was successfully used at an airbase in Holland to clear the runways of gulls and other species. Again, techniques such as pyrotechnic devices were employed to supplement the raptors. It is important to note that the gulls showed no signs of habituating to the goshawks during the two-year study (Mikx 1970). On the other hand, Hahn (1996) reported on the use of falcons at a military airfield in Germany and concluded that "we cannot recommend falconry as a routine method for bird control at civil airfields."

Operational bird control programs at five Canadian airfields use, or have used, falconry as a key element. The airports are Lester B. Pearson International Airport (Toronto), Dorval Airport (Montreal), North Bay Airport, CFB Trenton, and CFB Shearwater (Blokpoel 1980; Mason 1980; Transport Canada 1984; LGL Limited, per. obs. 1998). All of these programs involve the use of supplementary techniques in addition to the falconry - including shellcrackers (pyrotechnics), distress calls, and killing. In addition, the gulls have learned to associate the patrol truck with danger and the truck itself becomes a scaring device (the gulls are able to distinguish the bird patrol control truck from other vehicles that are present [Mason 1980]). Overall, the falconrybased programs at these airports have been considered to be successful (e.g. Environmental Assessment Board 1987a,b; Mason 1988). In fact, Mason (1988) believed that gulls learned not to fly over the airport because of the bird deterrent program.

Recently raptors, along with other deterrent methods, have been used to restrict the nesting area of ring-billed gulls at a large colony at Toronto (Blokpoel and Tessier 1987). Various species of raptors were tethered on perches for most of the study, and only occasionally allowed to fly free. The raptors plus other techniques (pyrotechnics, mock or model gulls, killing, distress calls) were successful in keeping the gulls from nesting in certain areas, but some other species, such as Canada geese were not affected (Watermann 1985, 1986, 1987). In 1997 and 1998, a significant portion of the large Eastport (Hamilton, Ontario) Ring-billed Gull colony was denied to nesting birds through the use of falconry (U. Watermann and M. Givlin, Bird Control International, pers. comm. 1998).

Falconry techniques have been applied at sanitary landfill sites (SLS) in Trenton and North Bay (Blokpoel 1980). A quantitative study of the effectiveness of the gull control program was conducted at the Quinte SLS (Trenton, Ontario) in spring 1983 (Risley 1983; Risley and Blokpoel 1984). The bird control team visited the landfill at least twice per day and applied a variety of control techniques including flying of falcons or other hawks, firing various shell crackers, throwing dead gulls in the air, and firing live ammunition. The methods used and time of day varied and gull habituation appeared to be low (Risley 1983). The study concluded that the gull control program at Quinte SLS was very effective. The effectiveness seemed to derive from the cumulative effects of several bird control episodes (Risley and Blokpoel 1984). Falconry is presently part of control programs at the Halton Regional Landfill and the Niagara Road 12 Landfill in Grimsby, Ontario and at a landfill near Montreal.

In a study by Kenward (1978, in Inglis 1980), Goshawks were unsuccessful in deterring Wood Pigeons from Brassica fields. After repeated attacks by the Goshawk, the pigeons usually resettled and continued to feed.

The use of falconry in conjunction with other deterrent techniques has been shown to be effective at dispersing gulls, with little sign of habituation. However, several workers have noted that falconry has several shortcomings that need to be considered before employing the technique (Wright 1965; Blokpoel 1980; Mason 1980; Transport Canada 1984; Environmental Assessment Board 1987a). Falcons and hawks used to be hard to obtain and many of the most effective performers (e.g., peregrine falcons) were/are endangered species. However, the recent great expansion in captive breeding programs have made raptors, even peregrines, easily available. Several raptors are required for any successful control program. Transport Canada (1984) suggests that the optimum number for control at Lester B. Pearson International Airport, for example, is 20 individual raptors of 5 species. This allows for raptors of different sizes to specialize on each of the problem species at the airport. Where gulls are the main concern, a few individuals of a single species of large falcon would be sufficient. Several individuals are needed because falcons cannot be flown continuously. Falcons become tired; they cannot be flown for a day after eating a full meal; and they cannot be properly flown when they are moulting. In addition, falcons can become injured or lost when they are being flown.

Falconry is successful only if it is conducted by well-trained and dedicated falconers. Falconry is an art, and the training, flying, and care of the birds requires strong dedication and skill (Blokpoel 1980). Because of the long hours involved, and the potential for sickness or missed time by the falconer, a multi-person crew of falconers is preferable. Finally, falcons cannot be flown during bad weather such as fog, heavy rain, or high winds (Wright 1965; Blokpoel 1980; Transport Canada 1984). These are conditions that often encourage gulls to use inland feeding and loafing areas. The lack of falcons at these times could make control of gulls difficult.

Evaluation. – There is a sound biological basis to the use of falconry for bird control. Pest birds are readily dispersed by falcons and will not habituate because the threat is real. Allowing a falcon to kill a pest bird on occasion strengthens the threat. The fact that falconry is a "hands on" technique that is deployed selectively further enhances it effectiveness over an automatic product that is controlled by a timer.

Experienced handlers and trained raptors are required; neither may be available on short notice. Raptors can not be used at night, or during periods of high winds or heavy rains.

Recommendation. – Falconry is recommended as a highly effective component of an airport bird control program. Falconry can be used in conjunction with other deterrent techniques.

Literature Reviewed. – Blokpoel 1976; Blokpoel 1980; Blokpoel 1984; Blokpoel and Tessier 1987; BSCE 1988; DeFusco and Nagy 1983; Environmental Assessment Board 1987a,b; Erickson et al. 1990; Heighway 1970; Hild 1984; Kenward 1978 in Inglis 1980; Koski and Richardson 1976; Mason 1980; Mason 1988; Mikx 1970; Risley 1983; Risley and Blokpoel 1984; Seaman 1970; Transport Canada 1984; Watermann 1985, 1986, 1987; Wright 1965.


Aircraft, both fixed wing and helicopters, have been used intentionally to chase or haze birds from an area, especially in agricultural situations. Regulations exist in Canada to prevent close aircraft approach to seabird colonies because of the disturbance this can wreak on the nesting birds. However, many birds obviously have adapted to the noise and visual stimuli associated with aircraft at airports and are not dispersed or harassed. Although it is clear that birds can be dispersed or harassed by aircraft in many situations, probably including airports if the hazing is intentional, this technique is not practical at airports where the chase aircraft would themselves become hazards to aircraft safety. Also, bird-aircraft collisions are a potential hazard. At least one aircraft has crashed during a bird-hazing flight, apparently when manoeuvring to avoid a bird flock (U.S. National Transportation Safety Board, file no. 1612).

Recommendation. – Not recommended.

Radio-Controlled Model Aircraft

Description. – Standard remote-controlled model aircraft can be used to harass or scare birds. The aircraft can be enhanced by painting a raptor shape on the body. Falcon-shaped model aircraft have been used.

Biological Basis. – Model aircraft imitate falcons and other hawks and can be used to harass and chase birds out of specific areas.

Literature. – Radio-controlled (RC) model aircraft have shown some promise in scaring birds away from airports, agricultural areas, aquaculture operations, and landfill sites (e.g. Saul 1967; Ward 1975a; DeFusco and Nagy 1983; Parsons et al. 1990). RC model aircraft require skilled operators (Littauer 1990a). For that and other reasons, they have not been widely adopted in dispersing birds at airports (BSCE 1988).

Model aircraft have been used to deter piscivorous birds, such as cormorants and herons, from aquaculture operations (Coniff 1991; Parsons et al. 1990). Flying one model plane for every 200-300 acres has been recommended for larger land-based fish farms (Littauer 1990a). Model aircraft have proven to be useful in reducing numbers of gulls visiting a landfill site in the southeastern United States (R. Davis, LGL Limited, unpubl. obs.). In this situation, large-winged slow-moving model aircraft circled over the landfill continuously during daylight hours. The program was successful but very labour-intensive. Model aircraft with supplementary noisemaking devices have been used to disperse problem birds in Israel (Yashon 1994).

An experimental falcon-shaped aircraft was successful at deterring starlings and killdeer at Vancouver International Airport and ducks and geese at Westham Island, Vancouver, B.C. (Ward 1975a; Solman 1981). Most birds exhibited avoidance behaviours similar to those caused by a real falcon. However, a falcon-shaped model aircraft is difficult to fly and requires a highlyskilled operator. Another effective approach is to paint a raptor design onto a more conventionally-shaped model aircraft (Saul 1967).

Disadvantages of using radio-controlled aircraft are that the direction of dispersal of birds often is not controlled, and that damage to planes and birds may result if birds and model aircraft collide (Coniff 1991). Good weather and suitable landing and fuelling areas are necessary. A major concern is that flying of model airplanes near active runways could pose a hazard to the full-sized aircraft.

Evaluation. – Model aircraft would be effective only over the relatively small areas that can be seen by the operator. Other advantages and limitations are noted below.


  1. Birds may habituate only slowly to a model aircraft that actively hazes them, especially if it is falcon-shaped.
  2. Circling model aircraft can be used to prevent birds from returning to, and landing in, an area.
  3. This technique is likely to be less species specific than are many others.


  1. Skilled operators are necessary.
  2. The technique is labour-intensive.
  3. Nearby landing and refuelling areas are needed.
  4. Direction of bird dispersal is not easily controlled.
  5. Model aircraft cannot be used in heavy winds, rain or snow.
  6. Safety concerns about operations near active runways.

Recommendation. – Recommended, but only for areas of the airport that are not adjacent to active runways and taxiways. It may be difficult to employ the technique because of the need for skilled operators.

Literature Reviewed. – Coniff 1991; BSCE 1988; DeFusco and Nagy 1983; Inglis 1980; Littauer 1990a; Parsons et al. 1990; Saul 1967; Solman 1976, 1981; Ward 1975a.


Description. – Attempts to use lights to disperse or repel birds have involved flashing, rotating, strobe and search lights (Krzysik 1987).

Biological Basis. – The biological basis for the deterrent effectiveness of lights is unclear. Lights have not been a long-term feature of the environment that birds would have evolved a natural reaction to. It may be that lights in certain situations are a novel stimulus and thus elicit an avoidance response. This would seem to be most true of flashing, rotating, or strobe lights. Lights at night may blind or otherwise disorient night-active species. Lights may also serve to warn birds of an approaching danger, such as an aircraft.

Literature. – Searchlights have been used to deter ducks from landing and feeding in grain fields, and tests have shown that some nocturnal migrants illuminated by light beams take evasive action (see Koski and Richardson 1976 for review). Although searchlights are effective deterrents in some situations, they sometimes attract birds at night, especially when it is cloudy or foggy.

Most information on the use of strobe lights in deterring birds has involved aircraft and airfields where birds pose serious safety hazards. Recent information on the use of strobe lights in airfield situations indicates mixed levels of success. Lawrence et al. (1975) reviewed various types of evidence - anecdotal, statistical and experimental - and concluded that strobe lights have some deterrent effect. A study in the UK in 1976 revealed that the use of aircraft landing lights during the daytime produced a decrease in bird strikes. The simultaneous use of strobe anticollision lights, produced a further decrease in bird strikes. Strobe lights appeared to be more effective at deterring lapwings than gulls. However, Zur (1982) found no significant reduction in the number of bird strikes on DC 9 aircraft with strobe lights versus those without strobe lights.

Briot (1986) observed the reactions of crows, magpies and jays that were tethered to the ground to overflights by low-flying aircraft with and without white 100,000 candela strobe lights flashing at 4 Hz. The distance between the bird and aircraft when a bird attempted to fly was recorded. No significant difference was observed in the flushing distance between overflights with and without strobe lights. However, a slight increase in scare distance with an increase in flash frequency was recorded. However, the experimental procedure may have affected the results. The tethered birds may have been reluctant to fly as the aircraft approached.

In a study of the effects of strobe lights on Laughing Gulls and American Kestrels, Bahr et al. (1992) found that strobe light frequencies of 50 Hz elicited faster responses in heart rates than frequencies of 5, 9 and 15 Hz. However, the lower strobe frequencies appeared to produce the greatest overall increases in heart rates. A study by Briot (1986) hinted that scare distance increased with an increase in strobe frequency. Laty (1976) suggested that frequencies not exceed 100 Hz. Gauthreaux (1988) used a frequency of 1.3-2 Hz in laboratory studies with migratory sparrows. Other studies have shown that frequencies from 8-12 Hz produce stress in gulls, pigeons, and starlings (Belton 1976; Solman 1976). Belton (1976) found that gulls delayed approaching a feeding area by 30 to 45 min when it was illuminated by a white or magenta strobe at 2 Hz. No repellant effect was observed when the strobe light flashed at higher frequencies to 60 Hz.

In a comprehensive, laboratory-based study using laughing gulls and American kestrels, Green et al. (1993) investigated responses to strobe lights of varying wavelengths (colour) and frequency. The tests clearly demonstrated that the test birds were aware of and responded physiologically (increased heart rates) to strobe-light stimuli. However, overt avoidance reactions were not observed. The authors concluded that while strobe lights may attract the attention of birds, they do not result in obvious fright responses, at least in the absence of other threatening stimuli. If birds were to associate the strobe light with a threat, such as an approaching aircraft, evasive responses might be initiated by the birds. Suggested frequencies, colours, intensity, and elements of motion were recommended for testing.

A few studies using strobe lights, amber barricade lights, and revolving lights on aquaculture facilities (Salmon et al. 1986; Nomsen 1989; Littauer 1990a) indicate that these lights are effective in deterring night-feeding birds (e.g. herons). The lights probably produce a blinding effect so that birds become confused and cannot easily catch fish. In some cases, birds became habituated to the lights, and even learned to avoid the lights by landing with their backs to them. Andelt et al. (1997) found bright rotating lights to be ineffective in frightening night-feeding black-crowned night-herons and great blue herons from a trout hatchery. The herons shifted to the unlit portion of the hatchery, but caught fish as effectively in lighted and unlit sections.

Mossler (1979) experimented with the use of flashing lights at a refuse dump. A "light board" was constructed with car lamps flashing (0.75 Hz) in sequence from the centre of the board outwards. This pattern was thought to mimic the flapping of wings. The flight board was carried by a person walking toward a flock of gulls, and flight responses were monitored. The strongest responses noted were to red and blue lights. However, the use of the flashing light board provided no significant change in flight responses compared to that elicited by a person approaching the gulls without the light board. Use of the light board mounted on a car elicited a lesser flight response by gulls than had been observed to a car without the light board.

Lefebvre and Mott (1983, in Krzysik 1987) found that flashing amber lights, in combination with movable owl decoys, were successful in dispersing a starling roost. Gauthreaux (1988) observed that Savannah Sparrows maintained in outdoor cages with a view of the horizon oriented themselves directly away from a red strobe light. However, they did not show any significant response to white strobe light or constant red or white light.

Lights have had limited success at deterring birds from oil spills. Blinking lights were found to be 50-60% effective at dispersing all birds from oil spills (U.S. Dept. Interior 1977, in DeFusco and Nagy 1983). Some tests have shown lights to be effective in dispersing waterfowl, waders, sparrows, gulls, and other species (DeFusco and Nagy 1983). Other tests, however, have shown lights to be ineffective against waterfowl (Boag and Lewin 1980), gulls, blackbirds and starlings (DeFusco and Nagy 1983).

During the 1970s, Syncrude Canada experimented with weather-proof lights in combination with human effigies to deter migratory waterfowl from tailings ponds near the Athabasca River. Functional problems and high costs led to the eventual abandonment of this system in the late 1970s (T. Van Meer, pers. comm.). SUNCOR Inc. also experimented with flashing lights in an attempt to deter migratory waterfowl from similar, smaller tailings ponds. Beacons were added to an existing deterrent system consisting of effigies and propane cannons. Their subjective evaluation was that lights did not increase the success of the system, and the use of the beacon lights was subsequently discontinued (J. Gulley, pers. comm.).

Evaluation. – Flashing and strobe lights could be useful in deterring birds from an airport at night and during twilight periods. A steady light, such as a searchlight, is not as effective as flashing and revolving lights and may attract birds during some weather conditions.

Flashing or strobe lights could be set up around an airport. They are most likely to be useful in combination with other deterrent devices such as cannons, Phoenix Wailers, and effigies. Flashing lights might increase the effectiveness of these other techniques at night.


  1. Lights are easy to deploy and require very little maintenance.
  2. Lights could be effective for deterring certain birds in certain situations at night.


  1. Lights can be used only in very specialized circumstances at an airport. They must not interfere with the vision of the aircraft flight crews and air and ground traffic controllers.
  2. Lights may not be effective for some species during daylight hours.
  3. Lights may attract birds on foggy, misty nights.
  4. Effectiveness on large water bodies has not been tested.

Recommendation. – Lighting systems are recommended only for testing and selected limited use. They are as yet an unproven bird control technology and should not be a core component of an airport bird control program.

Literature Reviewed. – Andelt et al. 1997; Bahr et al. 1992; Belton 1976; Boag and Lewin 1980; Briot 1986; Gauthreaux 1988; Green et al. 1993; Koski and Richardson 1976; Laty 1976; Lawrence et al. 1975; Littauer 1990a; Lefebvre and Mott 1983; Mossler 1979; Nomsen 1989; Salmon et al. 1986; Solman 1976; Thorpe 1977; Zur 1982.


Description. – The literature contains many observations on the use of coloured objects, such as scarecrows, flags, and balloons to frighten and repel birds from agricultural crops and aquacultural operations. However, there is little research on the use of coloured dyes as a method to deter birds.

Biological Basis. – The biological basis for any avoidance by birds of certain colours is unclear. Any initial avoidance may be as a reaction to a strange novel stimulus. Avoidance reactions to coloured water may be associated with previous experience with bad tastes and/or polluted/oiled areas.

Literature. – Coloured runways had no deterring effects on birds (ACBHA 1963), but a pond dyed greenish-yellow was reported to have temporarily deterred waterfowl as long as "dye-free" ponds were present nearby (Richey 1964). When all the ponds were dyed, the colour had no repelling effect and ducks landed in the dyed water.

Lipcius et al. (1980) tested young mallards' responses to coloured water. The ducks were deprived of food for 24- and 48 h periods, and then placed in a pen adjacent to a pool. Across from the pool was a feeding tray. The mallards were exposed to clear and coloured water (dyes were water-soluble); the colours tested included red, yellow, orange, green, blue, indigo, violet and black. Orange was the most effective and consistent colour in delaying mallards from entering water. Other colours were generally less effective and showed less consistency in mallard responses. Among colours, black was one of the least effective in deterring or delaying mallards from entering water. The results suggested that black water may even attract mallards. Lipcius et al. (1980) suggested that it would be worthwhile to conduct further related research, including tests of orange dyes or coloured objects as a method of deterring seabirds from oiled waters.

Evaluation. – Dyes, if effective, would be useful to deter birds from landing in puddles and ponds on airfields. Dyes would be easy to apply and require little maintenance except perhaps occasional re-application. They would not be effective at night. Dyes are still an unproven approach to bird control, however. They show some promise but have not been tested adequately yet.

Recommendation. – Not recommended for situations where control is essential. Suitable for testing only.

Literature Reviewed. – ACBHA 1963; Koski and Richardson 1976; Lipcius et al. 1980; Maier 1992; Martin 1985; Meyer 1986; Pearson 1972; Reed 1987; Richey 1964; Salter 1979.


Smoke has been used to disperse birds from nesting and roosting sites (see Koski and Richardson 1976 for review) but is not practical for use on airports.

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