Norfolk Wild Nights first 2015 walk

On a mild overcast evening of Saturday 13^th of June we ran our first 2015 Norfolk Wild Nights (NWN) event. Having rained on and off pretty much all day, we were worried that the walk was going to be a wash out. Fortunately, for us the rain stopped and though it was overcast, it was still mild enough for us to run the walk.

 For this gentle amble, we used St Marys Church in Earlham, near the University of East Anglia (UEA) as our hub to start from. 14 people joined us for the walk, from members of the church, to Norwich residents and students from UEA.

Beginning with an introduction on the types of bat species that can be found in the UK, we then described two different bat detectors. Bat detectors are an essential kit when looking out for bats. Calls made by bats when hunting and navigating are too high pitched to fall within our normal hearing range, so we can’t hear them. A bat detector transforms these echolocation calls by lowering the frequency of the sound to something we can hear.

First detector presented was the Batbox Duet, a heterodyne detector, which is tuneable. It allows us to select different frequencies and listen to various bat calls. With practice over time, your ears will pick up the different tones, clicks, and slaps, aiding your identification. Unfortunately with this detector, you can only tune in to one frequency at a time and therefore might miss other bat species that may be flying around. However, the duet can be combined with a MP3 recorder and will then act as a frequency division detector, which will record all sound across the full frequency spectrum.

Second detector introduced was the Anabat, a frequency division detector, which captures the full frequency range and records sound continuously onto a SD card, so bat calls made by different species are unlikely to be missed. The sound files stored on the memory card can be analysed later using sound analysis software called Analook.

Introductions over we then equipped everyone with a bat detector, a head torch and a bat field study council guide (FSC). First we checked out the grounds of St Marys Church and were lucky enough to hear a few Pipistrelles flying around the churchyard. We then headed across Earlham Park taking a gentle stroll alongside the River Yare, stopping at various spots by the riverside, where we heard and saw Daubenton’s and Soprano Pipistrelles. We continued to cross the park heading towards the Sainsbury Art Centre, where our moth traps had been set up ready for our inspection. Along the way, we continued to see and hear Common Pipistrelles, Soprano Pipistrelles, and Daubenton’s, including a Noctule at the bridge close to the Sainsbury Centre.

A sonogram of a Noctule bat recorded on a SM2 and analysed on Sonobat. The deepest and clearest calls of the Noctule are best heard on the peak frequency of 20kHz (frequency range 20 – 45kHz). 

On reaching the Sainsbury Art Centre, surrounded by bats flying overhead in the clearing in the canopy, we found a few moths in our moth traps from the Common Pug to the Snout, which we were able to pot up and bring out so that everyone could get a closer look.

We then headed back to St Marys Church, where thanks to the churchwarden we were able to gain access to the inside and have a quick look at the interior.

Altogether, a successful night with 4 species heard during the evening and a good turn out. Thank you very much to everyone who came along.

More information about bat detectors can be found on the Bat Conservation Trust website. http://www.bats.org.uk/pages/bat_detectors.html