After the trip to Västerbotten, I would say that the my NocMig project was a resounding success. Over the course the nine days spent on Hällögern, sound recording was carried each night. The results, with regard to the total amount of recorded migrant calls, varied from night to night. Naturally, as one might expect, the results were greatly affected by the weather. Over the course of the nine days spent there, the weather varied quite a bit.
In general, I arrived during southeasterly winds and clear skies, which led to a quite superb first recording session. After that, the wind veered around to a more northerly vector, it became much colder and there was much precipitation. Not only was there torrential rain overnight on one occasion, but also, towards the end of my stay, bouts of snow and hail. This was followed by northwesterly winds and showers, again, not good conditions for migration. We cannot control the weather, however, you must play with the hand you are dealt in this regard. All things considered, as a project, it must be viewed as a success, given the following results. Note that all these records were documented during the hours of darkness, that is from 19.00-05.00hrs...
Total 641 calls recorded
- 557 Redwing
- 35 Eurasian Robin
- 19 Song Thrush
- 5 Tengmalm's Owl
- 2 Pygmy Owl (one individual each night, with two at the same time on one occasion)
- 3 Meadow Pipit
- 1 Bullfinch
- 2 Fieldfare
- 3 Reed Bunting
- 8 Common Snipe
- 2 Mistle Thrush
- 2 Black Grouse
- 1 Hawfinch
- 1 Yellowhammer
- 1 White Wagtail
- 1 Long-tailed Tit
As a statistical recording tool, sound recording migrant bird species at night has huge potential. Results are clearcut in general, with the huge majority of calls easily identifiable. Obviously, more difficult species, such as flycatchers, require more experience and care with regard to correct identification. I would expect a wider range of species earlier in the autumn period and this could prove a little more challenging. During the time period I recorded, Redwing made up the vast majority of records. I found all calls were rather simple to identify as a rule, indeed, by the end of the week I could identify most species calls visually, by glancing at the sonograms. I used 'Audacity', which is currently a free software download, to analyze the overnight recordings. I found it hugely time efficient to scroll through recordings, which I had preset to record in fifteen minute time blocks on the Marrantx 661 digital recorder. Picking out calls was simple, simply download a fifteen minute block of recording into audacity and scroll through the sonogram, looking for the very obvious sonograms of migrant birds overhead. In other words, large periods of time can be completely covered without requiring observer's on the ground. The second night was incredibly busy, with just over 400 calls recorded. Even so, it took just a couple of hours to check the results. Quiet nights were very much quicker to check, though a degree of care has to be taken to check the files in a manner that ensures nothing is missed.
Because each call can be logged, documented and assigned an exact time, the potential for statistical analysis is of a very wide scope. Over a longer period of study, not only could totals of various species be scrutinized, other things like peak hours of passage, peak dates and best weather conditions for certain species can be established. Best of all, sound recordings provide hard evidence, which can be logged and saved. It would be difficult not to see this form of bird recording become more and more prevelant in the future. Bird observatories, for example, given their often remote locations, would provide incredibly useful statistics if regular night recording were carried out on a regular basis. Over a period of years, this data would be invaluable.
These were some of my thoughts over the week. It didn't stop at dawn of course, I left the recorder on untill 11.00am each morning and picked up plenty of nice recordings after dawn as well. The period around dawn is excellent and passage for two or three hours afterwards was generally excellent. It was much more difficult to analyze the recordings during this period, simply because of the volume of migrating birds at this time of day. Whilst it is very interesting to go through diurnal calls as well, the beauty of night recording is that, in general, the calls are short, easily identified and there is not a cacophony of local, stationary birds moving around. In short, it provides an outstanding sample of migration.
Apart from being struck by the potential of this type of night recording for study of nocturnal migration, there were several practical lessons to learn. No doubt, every potential location will pose different challenges, but there are certain considerations that should be carefully thought out before placing the equipment out for the the night...
The sound of Redwing migration through the rain high overhead in the dead of night...
Weather conditions are obviously among the most important of considerations when it comes to sound recording migrant birds overnight. Precipitation proved detremental to results, with little moving in such conditions. Not only is it bad for migration, but it presents major difficulties with regard to equipment. Electronic devices and water are simply not good bedfellows. On the island, I was fortunate that I could place the recording equipment under an outbuildings roof, negating any worry of water damage. In this instance, noise became an issue, namely the noise created by rain and hail drumming against the roof over the recording set up.
Of course, different aspects of the weather need to be considered. Wind is a major consideration. Light winds lead to the best recording results. Strong winds may buffet the microphone and it is advisable to give careful thought to the placement of the recording gear. A sheltered position can make all the difference to recording quality. Tucking the microphone on the sheltered side of a low wall or alongside a large rock can help shelter the microphone, for example. If using a parabol, a windshield can help greatly, a cotton or polyester shield can be stretched across the parabol and used to cut wind noise. I am told stretching clingfilm over a parabol has little effect on the recording quality, but can help prevent water damage. Always study the weather forecast, in order to be able to foresee potential problems should the wind shift direction or strengthen during the night.
Wind and it's effect on the immediate surroundings also needs to be considered carefully. Placing the recorder beside trees is fine in calm weather, but should the wind increase overnight, wind buffeted foliage can produce a lot of noise and make identification of calls a lot more difficult. Often, with regard to NocMig, the less background noise there is, the more calls can be easily picked up and identified. On occasion, natural background noise can be desirable. It is nice to have some background noise with more conventional sound recording, say in a woodland setting. The recording below was made just after dawn, after a long NocMig session. The wind was quite fresh by that stage.
2. Power Supply
One of the most important considerations with regard to recording all night, is the power source. Regardless of the set up in use, recording all night demands enough power to see the entire night through, which in the case of Hällögern, during my visit, was just over twelve hours. Careful thought had to be given to the fact that four lithium Aa batteries were not going to cover it. If I went with internal batteries, I would be forced to change them out every four hours, perhaps less.
Obviously, mains electricity was the way to go. This presented no problem on the island, as I could run a cable up to twenty metres from the lower cabin. My digital recorder, a Marrantz 661 PDM, as well as the DC Adapter were laid upon on a small, raised piece of wood, then covered by an upturned plastic bucket.
Given more remote locations, power presents more difficulties, where mains power will not be available. In order to record all night, some sort of external high capacity battery will be required in order to ensure a full night of recording.
By position, I mean, the exact location of the recording gear, as well as the direction in which it is trained. Whilst a remote, quiet location may provide better quality recordings, there is no reason why recording cannot be carried out almost anywhere. Often, the dead of night is quiet, even in urban areas. I found it best to train the parabol directly upwards toward the sky overhead. Pointing towards the horizon also yielded records, but the quality of recording was often not as good. Also, training the gear directly upwards picks up less noise, such as wind blowing through trees, the noise of the sea or distant dogs barking.
For any long term study, I would think it best to decide on one precise location, perhaps after a few trials and then leave the recorder in the same location repeatedly, pointing in the same direction. More random recording, in order to find out what species may be moving through the night skies, also has much merit.
4. Human Disturbance
Sound recording gear is relatively expensive. Leaving a sound recording set up out overnight unattended brings the risk of theft or vandalism. Again, remote areas offer the advantage of being less disturbed. Even in remote areas, returning to leave gear repeatedly may be noticed by others.
There are a couple of things to consider. Firstly, there is no need to go to great expense to record at night and there are cheaper options that won't break the bank should gear suffer damage or theft. Secondly, recording from around your home is always an option, especially if you have a private garden. Even in an apartment block, you can attach recording gear to various mounts designed by companies such as Ram or GoPro, which will affix to windows by suction cup. Brackets can be attached to walls, or windows can simply be left open, with the recording gear inside, where it will be safe from the elements. Recording from under a roof through an open attic window would also provide superb results...
5. Noise Pollution
For anyone who has ever sound recorded, it is quite incredible how much noise pollution affects recording and how difficult it can be to escape it. Aeroplanes, Helicopters, Traffic, Dogs, Power Tools, the list is seemingly endless. When setting up for a night recording, give thought to potential sources of noise pollution. Often, things go quiet in the middle of the night, the small hours of the morning see most human activity stop and even in urban areas, it may be possible to record migrants at this time. In more remote areas, there may me less noise in general. Again, the beauty of night recording lies in the fact that, even in residential areas, the relative peace of the twilight hours can mean sound recording can be extremely rewarding.
So that's my thoughts for now. Personally, I thoroughly enjoyed recording at night an would warn you that it is potentially addictive. It adds a new dimension to birding, is an incredible recording tool and is very rewarding. Why not give it a try? You never know what might be passing overhead while you sleep, until you do...