Equipment suggestion for recording owls for research (2 Viewers)

[nocturnalbirder]

As part of my Ph.D., I am studying the responses of Tawny owls to dummies placed in their territories, along with playback of territorial calls. The physical responses of the owls will be recorded as video using a thermal camera (which I already have) placed 30 m away on a tripod, and the vocal responses will be recorded using an audio recorder that I plan to tape or fix to the tripod. I expect the resident owl to be flying around and changing positions (on different trees), while it continues to call so a directional microphone would not work. And it may start to call when it could be about 100 m away (or a bit more) and quickly come very close to the dummy. Eventually, I plan to extract some variables like the total number of calls produced by the owl and its peak frequency from the audio recordings. My idea was to get something like the Zoom H5 and using the X/Y capsule that comes with it. But I would really appreciate your suggestions. My budget is 300 euros.

 

[Jon.Bryant]

My budget is 300 euros.

I was going to suggest a WildLife Acoustics SM4 or SM Mini, but they will both blow your budget.

These are both passive recorders, so designed for research and monitoring. They come in a weather tight housing, that can be secured in place with a cable lock (rather like a trail camera).

The mics are omni, so pick up everything in the general area. Gain can be set at different levels, and in a quite area, you can pick up owls at a reasonable distance.

The recorders can be programmed to run at specific times, so for instance you can run a schedule from sunset to sunrise - if you set location and date correctly, the recorder will automatically determine when sunset and sunrise are!

The SM4 can be deployed in the field for a very long time, whereas the SM Mini can be deployed for over a week (dependent on temperature and memory card size).

Given your budget, something to look at may be the WildLife Acoustics SM Micro 2. The only thing to check out would be whether this is great for owls? The mic (at least on the mark 1) had a non-flat frequency response, and was most sensitive at circa 4Khz (so good for most passerines). I am not sure how sensitivity dipped at lower frequency, so you would need to understand whether recording Tawny owl hoots will be a problem. As I say, they are selling the Mk 2 now (or will do shortly), and I think the mic may have been improved.

The other downside with the micro is that is slightly less resistant to humidity, and Wildlife Acoustics suggest that you deploy it in the field with a small desiccant bag in the recorder box.

The device (as per the mini) can be setup using an app on your mobile, which makes setting the date and time, location and recording schedule easy.

WildLife Acoustics are pretty good at helping researchers, so may be worth contacting them for their opinion/confirmation, as to whether the SM Micro 2 will work.

The link to their support form is below

WA Support Form

Finally (and you are probably aware of this), from my own recording work, owls can be non vocal for very long periods. I have frequency had very intermittent calls from Tawny Owls - either hours apart, or in some cases just one vocalization in the night. I am not sure if this is because they are not very vocal, or if they have relatively large ranges. I therefore think that to ensure you capture all nearby vocals, you will need a recorder that can run through the night at least.

 

[nocturnalbirder]

Thanks for the detailed suggestion, Jon.
One thing I did not mention is that I don't need to record throughout the night, but just for half an hour when the dummy owl with playback is set up in the resident owl's territory. Would that change your suggestion?

You are right that they might not call regularly during the night when using passive recorders, but from what I have read and observed in the field, this can depend on the season, stage of the breeding and also the density of owls in the area. But this should not be a big issue in my study since we are conducting the experiment during the early part of the breeding season in predetermined owl territories and the dummies will be accompanied by call playback.

 

[Jon.Bryant]

Would that change your suggestion?

If you are going to be there and operate the recorder, then perhaps you don’t need a passive recorder. An all-in-one would probably suit, but I am not sure of a make and model - they are generally designed for recording music, so may not be very sensitive and able to pick up more distant sounds. Others I am sure can advise on a model that will be OK.

Interesting that I am not certain that owls always respond vocally to playback. As an example, last spring I recorded Himalayan Owl, which is pretty similar to Tawny Owl. I may be wrong, but I recall that the bird flew in to playback, but ‘observed’ and didn’t vocalise straight away. That evening, at least an hour after our encounter, there was an interesting series of vocalisations between presumably a male and female… I am not sure if the early tape luring caused the birds to be more vocal, once the threat of a stranger’ had disappeared.

 

[Dave Boyle]

I use a zoom H5 a lot for nocturnal recording, mostly seabirds not owls, haven't seen a owl for years! The recorder is great but the XY capsule isn't brilliant, unless birds are very noisy and close, so you'll need an external mic if you want to get recordings from 100+m away

 

[nocturnalbirder]

If you are going to be there and operate the recorder, then perhaps you don’t need a passive recorder. An all-in-one would probably suit, but I am not sure of a make and model - they are generally designed for recording music, so may not be very sensitive and able to pick up more distant sounds. Others I am sure can advise on a model that will be OK.

Interesting that I am not certain that owls always respond vocally to playback. As an example, last spring I recorded Himalayan Owl, which is pretty similar to Tawny Owl. I may be wrong, but I recall that the bird flew in to playback, but ‘observed’ and didn’t vocalise straight away. That evening, at least an hour after our encounter, there was an interesting series of vocalisations between presumably a male and female… I am not sure if the early tape luring caused the birds to be more vocal, once the threat of a stranger’ had disappeared.

Thanks for the suggestion again, Jon. Call playback usually works very well for owls. It could be possible that individual you encountered was a floater (a non-territorial individual) or perhaps the call playback was done outside the border of the owl's territory. Then maybe the owl just came to check but wasn't bothered enough to respond vocally. Many times, I also see that Tawny Owls first arrive and 'check out' the source of the playback, but almost always they respond vocally within a couple of minutes.

 

[nocturnalbirder]

I use a zoom H5 a lot for nocturnal recording, mostly seabirds not owls, haven't seen a owl for years! The recorder is great but the XY capsule isn't brilliant, unless birds are very noisy and close, so you'll need an external mic if you want to get recordings from 100+m away

Thanks for the suggestion, Dave!

 

[Jon.Bryant]

I use a zoom H5 a lot for nocturnal recording, mostly seabirds not owls, haven't seen a owl for years! The recorder is great but the XY capsule isn't brilliant, unless birds are very noisy and close, so you'll need an external mic if you want to get recordings from 100+m away

Yes. Lots of consumer all-in-one recorders have scant detail on mic sensitivity, but Zoom do seem to publish a reasonably detailed specification. The H5 mic is stated to have a sensitivity of -45 dB, 1 kHz at 1 Pa (which is 5.6234 mV/Pa). If you compare this with most external mics it is pretty low - as an unfair comparison the old Senheisser ME67 long gun had has a sensitivity of 50 mV/Pa (which is -26 dB dB re 1 V/Pa).

Mic sensitivity conversion tools are available on the web, to convert between dB re 1 Pa and mV/Pa, but generally a more sensitive mic has a smaller negative number in dB re 1 Pa and a larger mV/Pa figure.

I think that possibly for picking up owls at distance, you would need a sensitivity probably in the 30 mV/Pa range.

 

[Vollmeise]

@nochurnal birder: as Jon mentioned, the sensitivity of your microphone determines whether the signal levels of your recordings are strong enough to meaningfully measure and compare the amplitude.

You should try to get an external Mic using one of those condenser mic capsules, which both are high sensitive and low noise:

Primo EM272 (39,8 mV/Pa)
PUI AOM5024L (63 mV/Pa)

Shops like veldshop.nl or NHBS and others offer them at a reasonable price.

If you wanted to use the signal amplitudes to determine the owl's flight movements, this would not be a particularly accurate or even reliable method.

To locate the owls' calls, you can place three precisely located recorders and then calculate the exact position of the calling owl using time differences in post analysis. This requires either recorders that start synchronously to within 1 ms (AudioMoth Dev with GPS module, Frontier Labs BAR-LT, Wildlife Acoustics SM4 TS), or subsequently synchronized recordings. To do the last, you can take any three precisely located recorders and then output a located reference signal at the beginning and end of the recording via your speaker. Using these reference signals, the recordings can then be synchronized by offsetting, stretching and compressing. If you have any questions, please feel free to PM me.

@jon: the sound meter mini is capable of recording up to 1.000 hours if You place 6 Lithium batteries in it (as I do both with my Mini I and II versions. The Mini I has to be equipped with a special battery lid to do so). This will last for months, if you need it.