i. Computers

ii. Video Cassette Recorders (VCRs)

Recording sound from the night sky directly to computer hard drive is the most efficient way to document avian night flight calling. Recent increases in the size (and decreases in the cost) of computer hard drives now make it possible to record every night (up to 10 hrs. mono/night) for a whole migration season on a single hard drive. Ten hours of recording (22050 kHz, 16 bit sampling parameters) translates to ~ 1.6 Gigabytes of hard drive space. Internal and external hard drives now cost less than $1.5 per GB (some internals are less than $1/GB). This makes recording to hard drive cheaper than recording to a VCR tape. The one catch is that a computer (~$500+) is more expensive than a VCR (~$75+). 

The extra cost is justified if you plan to use automatic call detection software. Recording directly to a hard drive gives you a digital soundfile that can then be analyzed for bird calls in faster-than-real time (on the same computer) with Old Bird's automatic detection software. Recordings on VCRs (or other audio tape) need to be played back into a computer in real time in order to automatically detect avian flight calls.  In the past, this operation had to be performed multiple times with different call detectors (e.g., Tseep-o and Thrush-o) to detect calls from different species groups. You still have to run the different species group detectors (e.g., Tseep-x and Thrush-x), but because you are crunching a digital file on the same computer, the call detection programs take place in faster-than-real time (typically less than 20 minutes for eight hour sound files on newer computers).

Third party software is available for setting up a computer to record at specific times and automatically name and save sound files to a specific folder on your computer. For example, see Easy H-Q and  I-Sound. automatic recording software. Such software makes it possible to set up a recording station and let it automatically run and record every night for a whole migration season without any maintenance or tape changing. This assumes, of course, that your microphone does not malfunction, and that there are no equipment malfunctions or long power outages. Computers can be set to automatically return to a preset, automatic recording status once power returns. To do this one must go into the computer's BIOS and set up automatic bootup after power outage in the Power Management section. One must also make sure that the option to have the recording software (e.g., Easy H-Q or I-Sound) automatically initiate after the computer restarts is selected. The software can be set to automatically name the nightly files with the date and time of recording. The Easy H-Q recorder allows one to add a specific text name in addition. This is useful if you have multiple stations and want to also label a recording with a site name.

One trick to using both Easy Hi-Q and I-Sound is that once you have selected your settings, you need to quit the program and reboot your computer in order for any settings you specify to carry over if there is power outage. For the Easy Hi-Q recorder, you need version 2.0 or later in order to have the software reinitiate after a power outage. Note: the Old Bird call extraction software only works on mono, 22050 sampling rate, 16 bit, wav files. Be sure to implement these settings in recording software if you want to avoid the step of converting files -- note also that the maximum file size for wav files you create is 2 GB.

There are many different types of computer soundcards on the market. Most PCs come with a soundcard installed. These usually have a microphone input and a line-level input. If you are running directly from your microphone to the computer, you will want to use the microphone level input. In any case, it is important to test the input recording level to make sure it is set at a reasonable level - not too loud or too weak. On most PCs the recording input level adjustment can be set by double clicking the sound level control icon in the lower right of the Start menu bar (little, often gray-colored, megaphone-looking icon). You double click this volume control then select the options pull down menu (upper left on the volume control window). Select properties, then select recording, then select OK (make sure the microphone volume control is selected), and adjust the microphone volume. Many newer computer soundcards have a mic boost option than can be implemented in the volume controls, typically in an advanced controls section (accessible by clicking on options). This adds extract gain to the signal.

You will need some way to assess how loud the signal is. If you have the Easy HiQ or I-Sound Recorder, you can simultaneously adjust the microphone input level and see the input sound level vary in the recorder window. For Easy H-Q, ideally you want the typical night time background noise at your recording site (quiet night) to be a bit to the right of center in the signal strength indicator. For I-Sound, background noise should show about a quarter of the of way up the signal strength indicator. This allows enough room for bird calls that are louder than the background noise to be recorded without being distorted. Inevitably, the calls of some low flying birds will be too loud and distort. In most cases these calls can still be classified to species when spectrographically analyzed (e.g., with Old Bird's GlassOFire software). The goal in setting the input recording is to record the bulk of the calls during a night without distortion. This is something you will want to play around with to make sure you have workable settings before you begin monitoring flight calls.

In most cases, even using the mic boost option on newer sound cards, running the signal from your microphone directly into the microphone input of your computer will produce too weak a signal.  You should consider buying a preamp (see "Rolls MP13" preamp in video cassette section below) and boosting the signal from your microphone before you run the signal into your computer.

Another recording option is to run the microphone signal directly to the computer while a detector program is operating. In this case, the computer will only record snippets of sound when specific bird calls are detected (species recorded depend on the detector used). This does not use much hard drive space (typically much less than a 100MB for a whole migration season). The problem with this strategy is that you only get what the detector picks up and there are no detectors that pick up all types of bird calls. So, this method is only recommended if you are looking at a specific subset of birds (e.g., warblers and sparrows). This type of call detection can be set up to run automatically using a PC's task scheduler and the simple scripts below: 

Start and Stop Detector

Click links to download zipped MS-DOS batch file

The Start detector is set up to automatically start the Tseep-x warbler and sparrow flight call detector if that program is located on the C: drive (e.g. C:/Tseep-r.exe). To schedule the start of a different detector, right click on the Start Detector icon, select Edit in the popup menu, and simply change the Tseep-r text to the text name of the detector you would like to start and save the file.

Once you have downloaded the Start and Stop detector batch files, create a folder named Batch on your C: drive. Then, access the Scheduled Tasks icon in your PC's Control Panel, select add scheduled task and follow directions for setting up the automatic task scheduling.

The cheapest way overall to record night flight calls of migrating birds is with a video cassette recorder (VCR) though, as mentioned above, analyzing the night flight calls on VCR tapes is somewhat tedious. You have to either listen back to the tape and log the calls manually or play the audio tape into a computer that is running call detection software. If you have a computer, you might as well record directly to your hard drive.

VCRs now sell for less than $75. The problem is that VCRs typically do not have microphone inputs. They have line level inputs that are geared for receiving a much stronger signal. Therefore, in order to use a VCR to record night flight calls, the signal from the microphone needs to be amplified. The easiest way to do this is to find an audio cassette player that has a microphone level input as well as a line level output. The signal from your microphone goes into the audio cassette player’s microphone input and out this machine’s line level output into the line level input of the VCR. Typically, in order to do this, the audio cassette player needs to be paused in the record mode so the signal will run through the machine. Inexpensive audio cassette players that have microphone inputs are getting hard to find in stores as they are being rapidly replaced by CD and DVD players which don't have microphone inputs. You might be able to pick up a used or broken cassette deck in a local electronics repair store. The tape drive doesn't need to work. The deck just needs to power up and amplify a signal.

If you can't find a cassette deck, the next option is to buy a microphone preamp. Rolls makes one called the Rolls MP13 which has XLR and 1/4 in. phone plug inputs and outputs, and an AC power connector. The XLR connectors allow you to get the most gain. If you search the web you will find it for prices varying from $60-$75. (See Microphone Design for more info on XLR connectors).

Typically, you will want to record as much of an evening’s flight as possible. To do this the T-160 VCR tapes (~$2/tape) are the most economical. You can find these in most department stores that have consumer electronics. These tapes will record for eight hours if the VCR is set to record in the EP (Extra long play) mode. The cheapest 8 hr. tape in the US market is the Sony T-160 (four pack for < $7 US).

One of the common problems people have in getting their VCR recording working is that they do not set the VCR input channel correctly. If the RCA input jacks on the back of the VCR are used, then the VCR will need to be set to record on Line 1 (L1).  Line 1 is typically just before Channel 1 on the VCR. You can use the buttons on the face of the VCR or the remote control to set the channel.  Note: in many cases with today's VCRs, you will also need to use the remote to set the VCR to record in EP mode (Extra long play). Older VCRs often had a button on the face of the VCR to set the length of play mode.

To hear the VCR recordings you make, run the audio signal from the VCR’s line outputs to the line inputs of another audio device that is connected to speakers or that has headphone jacks so you can listen with headphones. The audio signal can also be run into a computer for analysis.