There is a building on a site that we have obtained planning permission and a European Protected Species licence to demolish. There had been a single Common Pipistrelle in there last year and we had designed and constructed new roosting opportunities on site for the Common Pips using the building. The bats were roosting between the underfelt and the large interlocking concrete roof tiles. Access was through a gap in the verge where the concrete had fallen out at the junction between the roof tiles and the ridge tile.
The demolition, originally scheduled for the early part of 2008, was put on hold because of funding issues, so the building was put into the monitoring programme for this year. It was quite a surprise therefore to find 11 bats emerging during mid July from the same spot. The bat detectors showed that they were all Common Pipistrelles. Because of the possibility of them being part of maternity roost we thought it best not to hand net them until late August, when the juveniles would all be flying.
So, there we were last night on the roof waiting for the bats. The building has two adjoining pitched roofs with a large, 1.5 metre wide, valley gutter between them. Plenty of space when we’d got up on the roof to move around safely. Luckily the interlocking tiles are all laid on a shallow pitch so it was possible to walk up the tiles and lie down close to the ridge. I could then hold the hand net just below the entrance to the roost without getting too close myself. It was much easier than trying to hold a hand net in place from the ground. With 5 metres of extensions on to reach the ridge hand nets soon get very heavy, and they also wobble a lot, putting off bats they may be waiting to emerge.
The weather was good. 16 degrees Centigrade, light winds and overcast, but dry. A perfect night to find out more about the bats in the roost. It was still a good night an hour and a quarter later when I was still lying on the roof and Anna was listening to a Noctule and Common Pipistrelles on the bat detector, but no bats had emerged. All the preparation and the bats had moved on!
Saturday, 30 August 2008
Friday, 29 August 2008
Swarming bats.
A return to site for a dawn survey to find out if the bats are returning to roosts in the building being surveyed sounds great until the alarm goes off at 03.50. It is even harder to drag yourself out of bed if you only got back from an evening bat survey at 22.30.
One of the wonderful sights of dawn surveys is of groups of bats ‘swarming’ around before they enter their roost. This morning was slightly different. From 04.30 there were a few Common Pipistrelle bats flying past the building, continuing to feed, and a few Natterer’s bats feeding around a two storey entrance to an open section of the barn. From 04.52 the Natterer’s bats increased in number until there were seven ‘swarming’ around the entrance to the barn at one point. The bats circled around the entrance to the barn before flying inside and then flying around inside the building. This included flying around in the roof space and flying into the open first floor storage areas.
The bats continued to fly in and out of the barn until around 05.30. Standing in the entrance to the barn I had counted 26 bats entering but only 22 leaving. There are other entrances to the barn so they may have exited elsewhere or it may be that some remained, roosting in the cavities in brickwork and splits in the beams that can be found throughout the building.
I’ll have to return to site with the night shoot video recorder for another dawn survey to film the ‘swarming’ and try and take some of the Trainee Volunteer Bat workers along to practice with their bat detectors and to see ‘swarming’ bats.
One of the wonderful sights of dawn surveys is of groups of bats ‘swarming’ around before they enter their roost. This morning was slightly different. From 04.30 there were a few Common Pipistrelle bats flying past the building, continuing to feed, and a few Natterer’s bats feeding around a two storey entrance to an open section of the barn. From 04.52 the Natterer’s bats increased in number until there were seven ‘swarming’ around the entrance to the barn at one point. The bats circled around the entrance to the barn before flying inside and then flying around inside the building. This included flying around in the roof space and flying into the open first floor storage areas.
The bats continued to fly in and out of the barn until around 05.30. Standing in the entrance to the barn I had counted 26 bats entering but only 22 leaving. There are other entrances to the barn so they may have exited elsewhere or it may be that some remained, roosting in the cavities in brickwork and splits in the beams that can be found throughout the building.
I’ll have to return to site with the night shoot video recorder for another dawn survey to film the ‘swarming’ and try and take some of the Trainee Volunteer Bat workers along to practice with their bat detectors and to see ‘swarming’ bats.
Thursday, 28 August 2008
Evening emergence surveys.
I was surveying a set of buildings last night. Building surveys had found evidence of bats using the building. This had included droppings, individual and in small clusters, as well as butterfly wings. The butterfly wings indicated that bats may have been returning to the building to perch and eat some of their larger prey. In order to gather further evidence on the species and numbers of bats I initially arranged to visit the site and undertake an emergence survey.
Bats emerge in the evening to catch insects. Some species emerge around dusk, while others wait until it is nearly fully dark. Standing outside a building from just before sunset you can see any bats that roost in the building emerging. As it gets darker this becomes more difficult and the use of aids such as night vision binoculars or night shoot video recorders can help. The best aid to finding where bats are roosting, where they are going to eat and what species they are is a bat detector. One type of bat detector commonly used is the heterodyne bat detector. These detectors take the echolocation that the bats use to locate their prey and convert it into a sound that can be heard by humans. The differences in the calls, their frequency, repetition rate and tonal qualities can all be used to help distinguish different species.
During the survey last night I had Common Pipistrelle bats visiting from 20.27, 18 minutes after sunset. They continued to feed until around the building until 21.30 when they became more intermittent visitors to the site. The best part of the survey however was the arrival of a Myotid species of bats. These bats produce sounds on the heterodyne bat detector that are sharper ticks compared to the wetter slaps of the Pipistrelles. They continued feeding around the buildings until around 21.50 when they became intermittent. Their echolocation calls on the Pettersen D200 bat detector was a series of fast tiks, with a tonal quality similar to walking over straw. They are probably Natterer’s bats but I’ll have to return to site to gather more evidence before being sure.
Bats emerge in the evening to catch insects. Some species emerge around dusk, while others wait until it is nearly fully dark. Standing outside a building from just before sunset you can see any bats that roost in the building emerging. As it gets darker this becomes more difficult and the use of aids such as night vision binoculars or night shoot video recorders can help. The best aid to finding where bats are roosting, where they are going to eat and what species they are is a bat detector. One type of bat detector commonly used is the heterodyne bat detector. These detectors take the echolocation that the bats use to locate their prey and convert it into a sound that can be heard by humans. The differences in the calls, their frequency, repetition rate and tonal qualities can all be used to help distinguish different species.
During the survey last night I had Common Pipistrelle bats visiting from 20.27, 18 minutes after sunset. They continued to feed until around the building until 21.30 when they became more intermittent visitors to the site. The best part of the survey however was the arrival of a Myotid species of bats. These bats produce sounds on the heterodyne bat detector that are sharper ticks compared to the wetter slaps of the Pipistrelles. They continued feeding around the buildings until around 21.50 when they became intermittent. Their echolocation calls on the Pettersen D200 bat detector was a series of fast tiks, with a tonal quality similar to walking over straw. They are probably Natterer’s bats but I’ll have to return to site to gather more evidence before being sure.
Wednesday, 27 August 2008
How many species of bats are there in South East Staffordshire?
There are 9 species of bats that have been recorded in South East Staffordshire. These are;
Brown Long Eared bat. Plecotus auritus.
Common Pipistrelle. Pipistrellus pipistrellus.
Soprano Pipistrelle. Pipistrellus pygmaeus.
Noctule. Nyctalus noctula.
Leisler’s bat. Nyctalus leisleri
Whiskered bat.Myotis mystacinus.
Brandt’s bat. Myotis brandtii.
Daubenton’s bat.Myotis daubentonii.
Natterer’s bat.Myotis nattereri.
All bats are protected by law.
Some of these bats can be seen and heard when attending bat walks arranged in conjunction with the South East Staffordshire bat group. These walks start at sunset and carry on for an hour or more. The bat group members will take groups of people on the walk and help them to look for bats and listen to them using bat detectors.
Brown Long Eared bat. Plecotus auritus.
Common Pipistrelle. Pipistrellus pipistrellus.
Soprano Pipistrelle. Pipistrellus pygmaeus.
Noctule. Nyctalus noctula.
Leisler’s bat. Nyctalus leisleri
Whiskered bat.Myotis mystacinus.
Brandt’s bat. Myotis brandtii.
Daubenton’s bat.Myotis daubentonii.
Natterer’s bat.Myotis nattereri.
All bats are protected by law.
Some of these bats can be seen and heard when attending bat walks arranged in conjunction with the South East Staffordshire bat group. These walks start at sunset and carry on for an hour or more. The bat group members will take groups of people on the walk and help them to look for bats and listen to them using bat detectors.
Thursday, 21 August 2008
What is the optimum time to conduct a bat survey?
Bat surveys should be conducted between May and September. This is when bats are most likely to be present and not hibernating.
Tuesday, 19 August 2008
How many bats are there in South East Staffordshire?
There are 17 species in the UK but in this part of the country there are just 9 which are:
- Common pipistrelle
- Soprano pipistrelle
- Brown long-eared bat
- Whiskered bat
- Brandt's bat
- Natterer's bat
- Daubenton's bat
- Noctule
- Leisler's bat
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