RACING PIGEONS – IMPACT OF RAPTOR PREDATION

Visual deterrents
Static visuals, such as scarecrows and raptor models, are common, traditional methods
used in attempts to scare avian pests. In general, however, motionless devices either
provide only short-term protection or are ineffective; some birds may even come to
associate them with favourable conditions (Inglis 1980). To maximise effectiveness
devices should possess biological significance, appear lifelike, be highly visible and
their location changed frequently in order to extend the period of habituation (Feare et
al. 1988, Mott & Boyd 1995). The effectiveness of scarecrows may be enhanced if
fitted with loose clothing and bright streamers which move and create noise in the
wind (Vaudry 1979) - effectively becoming a moving visual.
Ultimately, however lifelike, under most circumstances scarecrows and raptor models
do not present a threat which is sufficiently alarming to birds (Inglis 1980). Over a
period of time birds learn that effigies or models do not represent an actual threat and
are no longer alarmed by them. To increase the threat, therefore, it is recommended
that these devices are reinforced with other sound-producing or visual deterrents.
Ideally, for example, scarecrows should be periodically reinforced by human activity.
Model raptors
The basis for this deterrent is mimicry of real predators and evocation of fear and
avoidance in the target species. Most potential prey species react to predator models;
the strength of the response, however, varies between species (Conover 1979). In
USA, museum-mounted models of a sharp-shinned hawk Accipiter striatus and
goshawk both reduced the numbers of birds visiting feeding stations. Habituation to
the models, however, was relatively quick with birds re-entering the feeding area after
only 5-8 hours exposure.
Model raptors fail to incorporate behavioural cues which may be critical to the
induction of fear and avoidance in the target species. Falcons which are “in the
mood” to hunt are said to be “sharp set”, such birds are invariably hungry enough to
fly at quarry (Inglis 1980). Although it is difficult for human observers to
differentiate between a falcon when it is sharp set or conversely, well fed, birds will
mob a hawk more frequently when sharp set than when well fed. Thus, model raptors
will be inherently less threatening and consequently less effective than live raptors.
For some bird species the avoidance response to large avian predators appears to be,
in part, a learned behaviour. Juvenile gray jays Perisoreus canadensis showed little
response to a model great horned owl Bubo virginianus, whereas adult jays reacted
intensely (Montevecchi & Maccarone 1987). Interestingly, with repeated exposure
adults habituated to the decoy, whereas juveniles developed a stronger fear toward the
model.
Large predatory owls, such as eagle owls Bubo bubo and great horned owls have been
have been known to kill smaller birds of prey (Newton 1979); such owls, however,
are absent from the UK. In south Scotland the main avian predator of sparrowhawks
is the tawny owl Strix aluco, which in most cases take nestlings but occasionally
adults (Newton 1986). In regions where their ranges overlap, goshawks may prey on
adult sparrowhawks, with probably the more vulnerable recently fledged young
mostly taken (Newton 1986). Finally, sparrowhawks do kill and eat conspecifics, e.g.
juveniles may be predated by larger females after leaving their natal territory (Newton
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