Daniel,

Please find attached a sample of the sound recordings I made on Sunday. The common pipistrelle has a peak frequency around 45kHz whilst the noctule echolocation calls are in two parts (a chip, chop sound) around 18kHz and 25kHz respectively. Interestingly before they emerged they concentrated on just the ‘chip’ part which can be seen in one of the snapshots. Also there were social calls which have a different function to the echolocation ‘seeing’ calls but the exact nature of them is not fully understood but is believed to be some form of communication.

I have talked with Annette about the roost and she thinks that it is the first record of a noctule roost in the Fens for many years. But, as is usual with bats, it presents many more questions than it answers – where did these bats come from, where was the roost prior to this year, where do they forage, where do they disperse to and how many were there when the roost was at its peak, to name just a few. It will be interesting to see if they return next year and we might be able to answer some of them.

Thank you very much for taking the time to report the bats and also for your time on Sunday, it is much appreciated.

Kind regards

Ian