Monday 6 November 2017

Sound Recording - Cowley Woods 1st November

I have spent many years recording and analysing bat calls as part of my work and have often considered experimenting with bird sound recording but have never done so. Having read the recent article on night sound recording in Birdwatch magazine and seeing the various samples posted on the Portland Bird Observatory website I thought I would finally give it a try. Initially I borrowed a Tascam DR05 from work but I quickly found that this recorder was not suitable (despite good reviews) for recording bird sounds. I found that the recordings were low level and that the playback on the recorder was poor, I considered that the ability to playback a recording at reasonable volume was important. After some research I opted for the Olympus LS-14 and although I tested the inbuilt microphones i found that these were not good enough for anything but the closest of birds. So I then tested a Sennheiser video-microphone that I have had for years but I couldnt get this to work. Finally after digging around I found my Sennheiser ME66 microphone which, again, I have had for many years but barely used. This was, and I believe still is, considered to be one of the best directional microphones for recording bird sounds. My research indicated that the Telinga set-up is the ultimate but this is a considerable financial outlay for one just commencing in bird sound recording.

I then investigated software for analysis of recorded bird sound and after some fairly quick research I decided that the Raven software was a good starting point. Having downloaded the free Raven Lite and watching a number of tutorial videos and reading some of the user manual I found this a fairly straightforward piece of software to get to basic grips with. I then opted to download the Raven Pro one year licence for USD100 with a view to extending this licence if my interest took off.

On 1st November I had my first opportunity to test my kit and here are a few recordings from wandering around Cowley village and to Cowley Woods near to Cheltenham. The calls were uploaded to Sound Cloud and the sonograms were generated in Raven Pro.

First I encountered a flock of Long-tailed Tit and recorded their 'zerrr' call. The sonograms generated remind me of horse heads with the higher pitched 'ze' element of the call forming the head and the lower pitched trilling 'rrr' the body of the horse.

 I then recorded this singing Robin. The recording levels are a little high and therefore there is some distortion to this recording but the sonogram shows some of the complexity of the song.

Here is a fairly distant (c.200m) Great-spotted Woodpecker showing its broadband 'pic' call.

I then encountered a flock of around 50 Redwing and in this sonogram the familiar 'seep' calls at around 7kHz and and low inverted 'V' of the 'gack' call at around 2.50 kHz at 0.4 and 2,5 seconds can be seen and heard,

Finally, at sunset this flock of House Sparrow were socialising just before settling down to roost. The sonogram is so busy that its simply fuzz from the shear level of calling by the birds.

So, I think that this is a fair start but initially I notice that there is a lot of noise to my recordings particularly in the lower frequency. I suspect this is simple background noise from the recording device as the frequency of this noise seems to be consistent across all recordings. There is a way to filter this noise in Raven Pro and I began to get to grips with this in the Robin recording, this reduced noise can be seen in the sonogram above which has a reduced fuzz along the bottom of the sonogram. During my investigations to find suitable kit to commence sound recording I found the following websites very useful and I hope they are useful for you if you decide to embark on this rapidly evolving element of birding.

ABA Blog - How to Record Birdsong Part 1
Audubon - A beginners Guide to Recording Bird Vocalisation's
Ear Birding Blog
How to Visualise Bird Sounds
Macaulay Library - Audio Recording Techniques
Raven Sound Analysis Software
Sound Approach
Understanding Sonograms
Wild Mountain Echoes