Hassan some drones are fairlu silent and especially when hovering. It is possible. I prefer a drone drop and pick up of a song meter to record for longer time periods. That also eliminates the drone noise or possible drone interactions with species.

I have no idea about this but I had another question. So far I know, drones make a very high level of noise when they fly. Is it possible to record the call of frogs or birds through this high noise?

My sense is that some drones are rather quiet.

Peter M Narins So sorry Sir. I have very limited knowledge of drones.

No I have tried, frogs go into hiding in fear of overflying predator birds.

It's a good idea, but will only work if you make the drones with a hook or other means of attaching so it's not moving. Meaning that the drone is a transport unit for the mic and cam - then I guess studies could be done this way.

Makes perfect sense, Anders. Sounds like designing a detachable tether for the drone will be a challenge, but possible with some thought. Good luck!

Peter

I'm following the conversation as I'm working on that at the moment. It's not easy but I think it should be working in a few months (when frogs restart calling in the northern hemisphere).

Hi Amaël,

Does your drone avoid the "scare factor" by flying quietly or by alighting on a nearby perch and cutting the engines? Your work sounds fascinating. I have worked on frogs extensively in China- mostly near Huangshan National Park and in Sichuan Province.

Peter

Hassan some drones are fairlu silent and especially when hovering. It is possible. I prefer a drone drop and pick up of a song meter to record for longer time periods. That also eliminates the drone noise or possible drone interactions with species.

Thanks Michael. I have used song meters in Borneo but have not raised them to the canopy with a drone. This could be our next project. What kind of drone can carry a song meter?

Peter

Thank you! I'm working on agricultural landscapes (rice paddies) mostly, so flying slowly, high enough not to scare the frogs is the first approach. For now the purpose is to determine the presence of the species so we don't need high quality recordings, and they can be heard up to 200 m away in the best conditions, so even 50 m high up in quiet pre-monsoon conditions should not be a problem.

I have not been in Sichuan, I'm focused on species in northeast Asia for now

Hi Amaël,

Is one of your target species Pelophylax nigromaculata?

Peter

The focus is on treefrogs (Dryophytes/Hyla) but including syntopic species as well, and P nigromaculatus is most likely to be present at every single site surveyed. So indirectly yes, it is one of the target species.

Amael

Thanks!

Not drones, but I have heard of others using balloons, kites and other soundless areal devices with recorders on them to monitor things like bats.

I'm sure if the payload had a cone or something on it to drown out the buzzing of the drone and listen only in a downward direction it could work.

Some drones come with plastic covers to attenuate the sound of the propellers, and that combined with a directional "downward" microphone is good enough to ID species - based on some trials

I could imagine that adaptive noise filters with pre-recorded noise templates (of the rather uniform drone noise, at least when in a stable position or at constant speed) to be mapped out could work very well in this situation to further improve the acoustic signal quality. Audacity and Adobe Audition both provide such filters.