Other Products and Techniques

The products and techniques in this section are not discussed in the Transport Canada Manual and do not fall readily into any of the preceding categories.

Lure Areas

Lure areas can be established as a means of attracting and holding birds so that they will not move elsewhere where their presence is undesirable (Sugden 1976). The most efficient attractant would be food, although water may also work. Most lure areas in agricultural settings are established near roosting areas to intercept birds, usually waterfowl, that would otherwise feed in surrounding agricultural fields. The lure crops are generally the preferred food of the species involved. The main objective of establishing the lure area is to attempt to concentrate feeding activities inside the lure areas rather than having the birds dispersed among the surrounding fields where they would damage farmer's crops. Lure areas established for airport bird control should incorporate the same principles.

Lure areas that satisfy needs other than food have also been established successfully. Highwater roosts for shorebirds were constructed and successfully attracted wading birds away from an airfield (Saul 1967; Caithness 1970). The most likely candidate groups for lure areas are waterfowl and blackbirds.

Attracting birds to a lure area requires careful consideration. The lure area must be far enough from the airfield and flight paths to ensure that the attracted birds will not create a new hazard. Otherwise, the lure area, by attracting more birds into the area, might increase the risk of bird strikes. The lure area should ideally intercept and "short-stop" the birds at the lure area, well before they would approach the airport. Once the birds arrive at the designated area, adequate supplies of the attractant, such as food, must be maintained. Lure areas must also be positioned so that other disturbances will not affect them. Because lure areas would need to be away from the airfield, the land likely would not be owned or controlled by the airport. This may be a difficult constraint.

Recommendation. - There probably are few airports in Canada where the establishment of lure areas would be warranted and possible. Nevertheless, bird roost and flight patterns should be studied and lure areas should be considered.

Literature Reviewed. - Caithness 1970; Fitzwater 1978; Hooper et al. 1987; Koski and Richardson 1976; Nomsen 1989; Saul 1967; Sugden 1976; Ummels 1983.

Magnets

Two magnetic devices developed by Sho-Bond Corporation (Japan) presently are being marketed as bird deterrents. The "Birdmag" consists of spherical magnets (1.5 cm diameter) strung along a wire at 25-cm intervals. The wire would be strung along ledges where birds would gather to rest, nest, or roost. "Birdpeller" consists of four, 1.5-cm diameter hemispherical magnets attached to a propeller at 6-cm intervals. The manufacturer states that these products generate magnetic fields which disorient birds, and birds avoid areas with these magnetic fields. The Earth's natural magnetic field is used as a navigation aid during migration or homing by many species of birds (Moore 1975; Southern 1974, 1978; Wiltschko et al. 1981). It also is known that anomalies in the Earth's magnetic field, and introduced magnetic fields, can lead to disorientation in birds (Alerstam 1990; Able 1994). However, the ability of introduced artificial magnetic fields to repel birds has not been tested extensively.

Belant et al. (1997) placed magnets with field strength of up to 118 Gauss in nest boxes used by European starlings. This magnetic field was ineffective in deterring starlings from nesting in these boxes. More testing is required before any substantive conclusions can be drawn on the ability of introduced magnetic fields to repel birds. At present, it seems more likely that magnetic fields may disorient but not repel birds.

Recommendation. - Not recommended.

Literature Reviewed. - Alerstam 1990; Able 1994; Belant et al. 1997; Moore 1975; Southern 1974, 1978; Wiltschko et al. 1981.

Microwaves

Description. – Microwaves produce high energy electro-magnetic waves.

Biological Basis. – The electro-magnetic energy associated with microwaves can cause stress, discomfort, and behavioral effects in both birds and mammals (including humans). If the energy is powerful enough, heating and physical damage can occur. The hypothesis is that birds would avoid areas where they were disturbed in this manner.

Literature. – Humans and other mammals can detect microwave energy at average power densities below 1 mW/cm2 and at peak power densities below 100 mW/cm2 (King et al. 1971; Frey and Messenger 1973). At higher power levels, thermal effects occur. In birds, thermal effects may occur at levels as low as 50 mW/cm2 (Byman et al. 1985); in rats thermal effects have been noted at levels as low as 5-10 mW/cm2 (Stern et al. 1979). Evidence reviewed by King et al. (1971) indicates that microwave radiation can produce a wide variety of physiological effects in humans, and that microwaves at densities below the "safety limit" of 10 mW/cm2 accepted in North America can affect nervous activity. This human safety limit has been controversial, in part because of evidence that significant effects can occur at levels well below 10 mW/cm2 (Steneck et al. 1980). In some countries, considerably lower safety limits have been established (Assenheim et al. 1979).

Evidence concerning the effects of microwaves on birds is conflicting, but it is clear that overt effects can be produced if power densities are sufficiently high. Tanner and his collaborators (1965-1969) have shown that intense microwave fields (average power 10-50 mW/cm2) can cause temporary muscular and neurophysiological disturbances in chickens, pigeons, gulls, and budgerigars. Responses to these fields included extension of legs and wings, unsteadiness of gait, and collapse. Of particular relevance to the deterrent potential were the experiments of Tanner et al. (1969) that showed that the feeding behaviour of caged Leghorns could be changed by radiating at an intensity of 40 mW/cm2 one of two feeding containers. The chickens chose to feed at the non-irradiated food source. After 12 days of irradiation, the hens did not return to the pre-radiation patterns of feeding until four days after the radiation ceased. Furthermore, they immediately avoided the radiated area when radiation commenced again. These levels of radiation, however, are considerably higher than levels that are safe for humans.

A few studies have reported that radars have caused behavioral changes in flying birds (Poor 1946; Drost 1949; Knorr 1954; Hild 1971; Wagner 1972). However, numerous other investigators using both similar radars (Eastwood and Rider 1964; Gehring 1967; Houghton and Laird 1967; Bruderer 1971; Able 1974, and many others) and higher-powered tracking radars (e.g. Williams et al. 1972; Emlen 1974) have not noticed strange behaviours in the birds that they were tracking, even at close distances.

Short et al. (1996) briefly described a study being developed to investigate the ability of birds to detect modulated radar signals, and the possible use of modulated radar signals to deter birds. The strength of this radar would be at levels below those dangerous to birds or people.

Evaluation. – Available evidence suggests that microwave radiation does not deter birds unless power levels are high enough to pose a potential hazard to humans and perhaps the birds themselves. Microwaves have not been adopted as a practical or safe bird deterrent technique (Hunt 1973; BSCE 1988).

Recommendation. – Not recommended.

Literature Reviewed. – Able 1974; Assenheim et al. 1979; Bruderer 1971; BSCE 1988; Burger 1983; Byman et al. 1985; Drost 1949; Eastwood and Rider 1964; Emlen 1974; Frey and Messenger 1973; Gehring 1967; Hild 1971; Houghton and Laird 1967; Hunt 1973; King et al. 1971; Knorr 1954; Koski and Richardson 1976; Poor 1946; Seubert 1965; Steneck et al. 1980; Stern et al. 1979; Tanner 1965, 1966; Tanner et al. 1967, 1969; Wagner 1972; Williams et al. 1972.

Lasers

Description. – Lasers produce high energy electro-magnetic waves.

Biological Basis. – The electro-magnetic energy associated with lasers can cause stress, discomfort, and behavioral effects in both birds and mammals (including humans). If the energy is powerful enough, heating and physical damage can occur. The hypothesis is that birds would leave areas where they were disturbed in this manner.

Literature. – Lasers have been suggested as a technique for dispersing birds (Lustick 1972, 1973; Lawrence et al. 1975). Although Lustick's experiments suggested that starlings, mallards, and herring gulls were disturbed by either pulsed or continuous laser light, the light had to be directed at sensitive areas on the birds. When aimed at the feathers, birds did not react even though the laser was capable of igniting their feathers.

Seubert (1965) described experiments in which caged gulls were exposed to pulsing lasers. Pulsed light at low powers (1-2 joules) produced some flinching but no distress or alarm calls. Light pulses of 100-200 joules directed at the birds singed feathers and caused bleeding in the bird's eyes. However, the gulls reacted no more to the stronger light than to the 1-2 joule light. A continuous laser was also tested (power not stated) but the gulls looked directly into the beam of intense red light with no appearance of discomfort.

More recently, Mossler (1980) tested whether the beam from a helium-neon laser would deter gulls at a landfill from feeding on highly-attractive food. The gulls showed some limited behavioural reactions to the laser beam, but it did not deter them from feeding.

Evaluation. – Although lasers may in some situations be able to disperse birds, the required power levels would be hazardous to humans. Therefore, lasers are not practical as bird deterrents at airfields.

Recommendation. – Not recommended.

Literature Reviewed. – Burger 1983; Frey and Messenger 1973; Koski and Richardson 1976; Lawrence et al. 1975; Lustick 1972, 1973; Mossler 1980; Seubert 1965.

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