Tried and we thought abandoned years ago, the idea of putting loudspeakers playing bird noises down runways at fixed positions is being discussed again.

We cannot state that it is not at all effective; we can state that vehicle based systems are in major use with proven efficiency.

Fixed systems are not regarded as an efficient, or indeed a safe, method by which to broadcast bird distress calls; by their very nature they are also expensive in hardware and installation.

When the bird control operator takes a mobile bird dispersal device to the problem flock of birds, he is able to hear the broadcast clearly, set the volume according to the task in hand and turn it off if he has put birds up at the wrong moment, or completed his task.

If the speakers are only around the runway, it follows that broadcasts will only be from these fixed locations and habituation is then more likely. A mobile operator necessarily varies the location of broadcast and usually tries to play downwind fixed installations cannot do this.

Depending on the location of the "bird control point", it may not be possible for the operator to hear that bird distress calls are actually being broadcast. If they cannot, how do they know the birds can hear it?

If the birds do not disperse in response to a fixed position broadcast, or non-broadcast, what does the operator then do? Despatch a vehicle to do the job and if so, will aircraft be held while this is done?

Is this more efficient than having the vehicle out on the airfield doing the job in the first place!!