Could some special window mirror foil work too?
I am hearing a swarm of bees sound almost the whole day, some times it disappears for a few minutes.
How likely is it that someone has a rather high end consumer drone that can stay (rather statically, not moving much) in air for maybe 45 minutes tops. Let it land, put in a pre-charged battery, get the used one out fly back to observation point while charging the empty battery? How many batteries would you need to do this to have it in air constantly apart from the few battery changing boxtops? Is this even realistically?