I've been reading an article in the environment section of the Guardian newspaper this evening on the internet that the RSPB have started to use drone's with camera's {just as the army has done in Afghanistan for the war effort} to protect rare and vunerable birds in the UK and of course they are absolutely silent. I think this is an excellent idea and hopefully the birds and other wildlife will have a much better chance of protection and no disturbance by any individual.
Check out the article here.