DETERRENT DEVICES 



Table 1 presents a preliminary evaluation of the usefulness of most of 

 the deterrent devices or methods that have been considered for use in aquatic 

 or marine environments. These devices are described in detail in the report 

 to PACE (Koski and Richardson 1976), but the descriptions are not repeated 

 here. Rather, the devices and methods that may be most useful in oil spill 

 areas or that have been useful in terrestrial areas are briefly discussed 

 below. 



DYES 



One test has suggested that waterfowl tend to avoid water that contains 

 greenish-yellow dye. If this is true (further tests are required to confirm 

 this observation), then dyeing oil (if economically possible) would be a useful 

 method for reducing numbers of birds that land in or swim into oil. The advan- 

 tages of this method are that the dye could be applied quickly and over a 

 wide area from an aircraft, and that an oil-soluble dye would remain in the 

 oil as it drifted. Disadvantages are that the dye would not be visible at 

 night; that, as dyes break down, the deterrent effect would wane; and that 

 some species may be attracted to dyed oil. 



SEARCHLIGHTS AND FLASHING LIGHTS 



Searchlights are at least partially effective in dispersing feeding and 

 flying waterfowl at night; however, some species of birds are attracted to 

 lights at night, especially during conditions of rain, fog, or heavy cloud 

 cover. Flashing lights and strobes may also be useful in dispersing waterfowl 

 at night, and apparently are less likely to attract other birds. Neurophysio- 

 logical tests of strobes using three species of birds suggest that the optimal 

 color may be red and that the optimal flashing rate may be 6 to 12/sec. How- 

 ever, flash rates of 6 to 12/sec can trigger epileptic seizures in susceptible 

 people. In general, the efficacy of lights as a deterrent has not been proved 

 in any situation for species except ducks and gulls, and even for these birds, 

 effectiveness has not been demonstrated in areas of open water. 



HAWKS AND FALCONS 



Hawks and falcons have been used successfully to disperse birds from 

 airports. Raptors, however, are useful only by day and during fair weather. 

 They require extensive care and training and are not readily available. Further- 

 more, efficacy over water is unknown, but is suspected to be less than that 

 over land. In fact, the immediate response of most water birds to the appearance 

 of a falcon nearby is to land on the water and/or dive, and these behaviorial 

 responses would increase the probability that birds would become oil-soaked. 



DISTRESS AND ALARM CALLS 



Recorded alarm and distress calls of various species, when broadcast 

 in the vicinity of the same species, often cause the birds to disperse. These 

 calls are generally effective longer than most other deterrents, because birds 

 accommodate to them slowly. The most important limitation of this method 

 is that distress calls are usually species-specific and that some species 

 rarely, if ever, utter distress calls. Attempts should be made to identify 



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