I bought a bat recorder recently (a BatBox duet). Last night I went back to Gilston to try to record some bat sounds.
Myself and D#1 stood by the lane down to the Marina and waited for the bats to appear. At 9:05 pm the first one came down the lane from the village, and a slow procession continued until we had counted 9 come from the village down. By 9:30 there was a regular flow of bats up and down the road.
The recorder was great – easy to use, fits in the pocket, and was giving us a clear ticking sequence as the bats approached. A sonic burst coincided with a bat flipping round in mid-flight to catch its prey. Finally we went back to the car, and the recorder alerted us to another bat round some trees, and we caught a glimpse of it round our heads. On a number of occasions we would have missed bats without the recorder.
I’m still none the wiser what the bats were. The peak (lowest sound) recording frequency seemed to be around 30 KHz, but was audible over a wide range of frequency settings. I managed to record a several bursts of the full spectrum onto my MP3 player, and on return got them onto the Laptop, but before I can analyse them with the Bat diagnostics program I need to convert the file from .wma to .wav first.