Despite the gloomy forecasts for the weather earlier in the week it was a good warm evening with little wind and with plenty of insects available for the bats to eat. From the car park we descended to the nearest viewpoint over the water to sit and wait. A heron flew in and perched on the top of the pines to our left and was beautifully silhouetted against the sky. The first surprise of the evening was that our first bat at 8.23 was a Noctule . This was clearly visible feeding above us with its characteristic ‘chip’chop’ call coming from the bat detectors. It was soon joined a by a second, and these bats continued to feed high over the valley for most of the time we were present. After 10 minutes and with no other bats other than the feeding Noctules we headed off down the lake to see what else we could find. Our first pipistrelle, a Common, did not appear until 8.39, soon to be followed by a Soprano pipistrelle at 8.41. By the time we reached the dam at the far end of the lake there was still little activity from any bats apart from the Noctules. A few pipistrelles of both species passed through and we then headed back half way up the lake towards the car park, disturbing a toad off the track as we went, and sat at another view point. Despite it now being quite dark there was still no sign of any Daubenton’s bats over the water which was the second surprise of the evening, as it seems a very suitable site. A few Common and Soprano pipistrelles were feeding in front of us but it was relatively quiet. As a last resort we returned to our starting point at the top of the lake where we found Common and Soprano pipitsrelles in numbers, regularly having 2+ bats in front of us. At last the rattle of a Myotis bat on the detectors and, turning on the light, we had some good views of Daubenton’s bats flying low over the water for the next 10 minutes. There was probably only one or two Daubenton’s present judging by the timing of their appearances.
Analysis of the calls from the two recorders the following day did show that we had missed 2 passes by Daubenton’s bat earlier in the evening, one near the dam and the other half way back up the lake. The second ‘missed call’ was particularly interesting as it revealed those characteristic reverse hook pattern of a Daubenton’s social call which I have not seen as clearly as this recording for some time.
There were also some nice Noctule calls with changes from the short flat calls, when little information on their surroundings is required in a large open area, to steep sweeping calls when they got closer to the side of the valley and more navigational information was required.
A good finish to the Nats outdoor programme for 2017.