Robot Bird Wars?

There was a recurrence on the BBC morning news on 19th September of an about the development of a robot Peregrine falcon ( http://news.bbc.co.uk/1/hi/england/merseyside/6469451.stm ) to scare away pigeons from particular locations (notably buildings in city centres that they use like nesting cliffs where they are safe from terrestrial predators). The robot essentially 'sits' in the location, flaps its 'wings' and calls like the falcon (they have been used successfully in a variety of UK locations to deter pigeons and gulls). The objection to the pigeons is that their droppings are unsightly and damages the fabric of buildings. They transmit disease ( some people refer to them as 'flying rats') but other birds, not so objected to, might well do the same. It was claimed that many of these birds are 'failed' homing pigeons. Development of the robot sounds very high-tech and interesting but I wonder why they don't simply periodically display a live bird of prey (like the Harris hawk illustrated) with its handler. This works very well in deterring gulls from nesting on the flat tops of buildings in South Wales and elsewhere. It could be the case that the authorities in cities don't want to risk the bird of prey attempting to make an attack (the public might not like the 'blood and thunder'). If this is the case, one might argue that the approach is purely 'cosmetic' as preventing the pigeons from using successful foraging sites would inevitably condemn some of the birds to starvation and/or reduced breeding efficiency. Employing a real bird of prey at least helps to maintain biodiversity!