Interesting point about privacy. When I listened in to one of the BirdWeather live streams from Florida, I could hear voices - did the people know their conversation was (albeit quite quietly and indistinctly) being broadcast to the world?
I use passive recorders and from time to have caught conversations of passers by. However, I have always deleted the dialogue, selecting the section of conversation using the sonogram. I have never listened to more than a snippet, just to confirm it is indeed a voice that was accidentally captured. To be honest I have more interesting thing to do than listen to conversations of random strangers, and not enough time to try and clean up recordings by listening and manually deleting sections of human vocals.
I am a fan of passive recorders and think the British Trust for Ornithology should update their monitoring methods to allow recorders to be used in conjunction with other methods. Passive recorders could be especially useful for surveys for owls, woodcock, nightingales - which have all been the subject of recent BTO surveys. Perhaps they could also be used for some remote squares in the Breeding Bird Survey, or for surveys of species that vocalise very early, such as Goshawk. I recall however, that in a passive recorder review, BTO stated that passive recorders should be used where you have the landowners permission. How many amateur sound recordist seek landlords permission before they do any form of sound recording? I certainly don’t. I suppose it doesn’t matter whether the recording device is hidden or visible, whether it is autonomous or manually operated - some people may object to being recorded either by a hidden box or a person waving a directional mic about. As a parallel example, I recently took a photo of my wife, who was taking a photo of a bird. My photo had the bird in the foreground and my wife in the background. Unfortunately my photo also caught another birdwatcher in the background, who took exception. He was perhaps legally correct that I hadn’t asked his permission, although I think from his outburst, I was more troubled that he was about to commit the more serous offence of affray!
Are concerns over the individuals rights of privacy taking things too far? I think this could particularly be the case when considering the occasional and accidental recording of a fragment of a random strangers conversation - which we have no intention of listening to in any case. If I set up a listening device in my garden but not too distant from my neighbours window, it would be a different matter - I then think I would indeed have acted unreasonable and disrespected the rights to privacy.