6 September 2013: Bat Walk on Abbey Meadow

Leader: Ben Carpenter 

Thirty-eight of us met at the Abingdon Well-Being Centre car park on the 6th September before heading over the bridge into Abbey Meadows. Unfortunately it was one of the first evenings that was slightly cooler than the previous few days, which could have had the potential to reduce bat activity (cooler weather equals lower insect activity).
Whilst waiting for bats to appear at Abbey Meadows we went over some basic information about bats, this included: that bats are the only true flying mammals, there are currently 17 resident species of bat in the UK, and that they can be incredibly long-lived for such a small size. We also covered echolocation; this is where bats emit high pitch calls that enables them to produce a ‘sound picture’ which in turn allows them to hunt for food (mosquitoes and moths). Using bat detectors we are able heard these high pitch calls, and by tuning the detectors we are able to tell the difference between most bat species (due to different species emitting at different frequencies). We also went over the five main species that would be expected to be encountered around Abbey Meadows; these were noctule, common pipistrelle, soprano pipistrelle, brown long-eared bat and Daubenton’s bat. Whilst going over this information we were occasionally interrupted by the sharp whistling calls of kingfishers from the River Thames; these may have been birds communicating before going to roost. A tawny owl could also be heard hooting in the distance, possibly from near Waitrose car park.

We first started getting common pipistrelles and soprano pipistrelles flying over next to the River Thames; these common species emit their peak frequency at around 45kHz and 55kHz respectively (detectors set at 45kHz and 55kHz will sound like wet slaps for these two species), they can catch around 3000 mosquitoes a night, and tend to fly above two metres. The next species we saw was Daubenton’s bat flying like a small hovercraft very close to the water’s edge, and visible in the torch light was the bat’s white front. The calls of this species on the bat detector are regular and sound like short bursts of a machine gun. The detector picks up calls between around 35kHz and 85kHz, with the loudest sound occurring between 40kHz and 50kHz. These three bats were the main species encountered throughout the evening; however, noctule was also heard by a couple of people at the back of the group. Noctule are generally the first bat species encountered of an evening (around sunset), as they make straight high flights. Whilst walking around we had good views of Daubenton’s foraging low over Abbey Stream, with pipistrelles producing social calls near the end of the walk. We also visited Abingdon lock where we had the occasional bat pass before we headed back to the car park. Abbey Meadows is a good place to see bats as the meadows are surrounded on all sides by the River Thames and Abbey Stream; aquatic habitat which provide foraging opportunities for many bats. The following table provides the percentage of calls of species which have been recorded on Abbey Meadows over three visits in early September. This will give you an idea of what to look for should you go for a nocturnal walk in the area:

SpeciesPercentage of Calls
Common pipistrelle 39
Soprano pipistrelle 25
Pipistrelle species1 18
Daubenton’s bat 11
Myotis species2 3
Noctule 3
Nathusius’ pipistrelle 1

1 Where calls are around 50kHz these have been noted as Pipistrelle species, as it is not possible to directly attribute the calls to either common or soprano pipistrelle.

2 Identification of Myotis species (of which Daubenton’s bat belongs) can be difficult and it is not always possible to reach species level.

Ben Carpenter