2013 Bat News

11th December [Geoffroy's Bat caught near Bath]

News has been broken publicly about Jim Mulholland's amazing find of a Geoffroy's Bat Myotis emarginatus at AWT Brown's Folly Reserve near Bath at last. This is the second UK record. Congratulations to Jim and the team who have been monitoring the bats there.

17th November [Nathusius's Pipistrelle Transect Walk]

So far I've carried out three Nathusius's Pipistrelle Pipistrellus nathusii transect walks this month and have yet to record one, though I have recorded Soprano Pipistrelles P. pygmaeus and a few Lesser Horseshoe Bats Rhinolophus hipposideros, with the odd Myotis sp. and Common Pipistrelle P. Pipistrellus thrown in too.

27th October [Passive Monitoring at Blagdon Lake]

I've just run the passive monitoring equipment at the bat house for 3 days recording .wac files, and recorded nearly 2000 calls over that short period, so there is still plenty of bat activity going on. As usual they were split about half and half Nathusius's Pipistrellus nathusii and Soprano Pipistrelles P. pygmaeus with a few Common Pipistrelles P. Pipistrellus for good measure. Interestingly, I recorded a lot of Soprano Pipistrelle social calls and eventually, when listening to the calls using the Kaleidoscope software, I heard a Nathusius's Pipistrelle advertising call made at 18:33 hrs on 24th October.

29th September [Bat Box Checks at Blagdon Lake]

The YACWAG team and I checked the south side bat boxes this afternoon and found a group of Soprano Pipistrelles Pipistrellus pygmaeus at Pipe Bay Copse, a box at Home Bay with a ♂ Common Pipistrelle Pipistrellus pipistrellus and a Soprano Pipistrelle in it, and another box with at least 18 Pipistrelles that we left undisturbed. At Holt Copse there was a box with a ♂ and several Soprano Pipistrelles inside.

27th September [Passive Monitoring at Blagdon Lake]

I collected the SM2BAT+ passive recorder from the Bat House today where it's been since last Saturday. There are an incredible 8259 files to go through. Happy days!

26th September [Bat Box Checks at Blagdon Lake]

The YACWAG team and I planned to check the bat boxes this afternoon, but only managed to do the boxes at the Pumping Station due to finding 11 (2♂,6♀,3unkn) Natterer's Bats Myotis nattereri in the first box and 4 (1♂,3) Soprano Pipistrelles Pipistrellus pygmaeus in the next. Some of the Natterer's had previously been ringed, possibly by Daniel as long as two years ago or more. I'll try and find out.

23rd September [Ad Hoc Recording around Blagdon Lake]

While walking around Butcombe village this evening, trying to locate Nathusius's Pipistrelles Pipistrellus nathusii, I made one very nice recording of a pass by a Greater Horseshoe Bat Rhinolophus ferrumequinum in an area where there could be a potential roost site. I shall have to go back and check. After Butcombe, I drove back to the Bat House at Blagdon Lake and stood for about 100 minutes trying to get a recording of the 'advertisement' call of the ♂ Nathusius's Pip. While I got lots of recordings of the bat, including social calls, I didn't get the 'advertisment' call, which is a bit disappointing. The trilling I heard several times was made by Lesser Horseshoe Bats Rhinolophus hipposideros which is, on the other hand, very encouraging, as we're hoping to attract them to use the house.

13th September [Passive Monitoring at Blagdon Lake]

I've collected the SM2BAT+ bat recorder this afternoon and will spend this evening analysing the information captured. I'm hoping for some good Nathusius's Pipistrelle Pipistrellus nathusii 'advertising/lekking' and Lesser Horseshoe Rhinolophus hipposideros calls. I've been going through some of the previous years data (over 67000 files) in order to isolate some good recordings of Nathusius's Pip echolocation calls for Wildlife Acoustics so that they can create a filter for their new software program Kaleidoscope Pro that Chris Barrington (YACWAG) has been testing on my data.

There were 7213 files recorded (in just ten days) including lots and lots of Nathusius's Pipistrelle calls, with many 'advertisement' calls as I'd hoped, so we can safely say that the Bat House roof is being used this autumn. I also wanted to find out if we had any Lesser Horseshoe Bats approaching the new entrance as well, and sure enough there were a handful of calls recorded, so I remain hopeful that we'll attract them in to use the building as a roost site. I'll put the recorder back out because last year we had a number of Brown Long-eared Bats Lecotus auritus visiting the inside of the Bat House in October. They didn't stick around then, but with the changes made since, perhaps they will be persuaded this year.

24th August [ UK National Nathusius's Conference]

Organised by Daniel Hargreaves and Dr. Jon Russ at Ubley Village Hall, the Street, Ubley, Bristol, BS40 6PN. Run in conjunction with the Bat Conservation Trust and sponsored by Bristol Water.

In the evening delegates split into 6 teams and trapped at various points around the lake. 87 bats of 8 species were caught, including 5 new ♂ Nathusius's Pipistrelles Pipistrellus nathusii. The full list was:

For more information about the UK National Nathusius's Conference please email Daniel Hargreaves at: or Lisa Worledge at:

For more information about Nathusius' Pipistrelle in the UK see Jon Russ' Website.

9th August [Nathusius's Pipistrelle Survey at Blagdon Lake]

A breezy day settled down at dusk, so Daniel Hargreaves, Matthew Hobbs, Adrian Bayley, David Cottle, Irene Mills & Phil Rundle ran 4 Harp traps with lures along Butcombe Bank. Quite a few local birders/naturalists came along, including Melanie Patch, Philippa Paget, Mervyn Pearce, Jack Willmott, Pete Massey, Mike Jenkins, Prof. Robert Kelsh, John Martin, Phil & Lucy Delve, Chris, Gary & Kieran Mott and a few others that I didn't get the names of (please let me know who you were). It was an excellent evening with quite a few bats caught at dusk, and although the action slowed later, the quality got steadily better and we finished the session on a high capturing the first ever Leisler's Bat Nyctalus leisleri (a breeding ♀) at Blagdon Lake. The list was:

25th May [Nathusius's Pipistrelle Survey at Blagdon Lake]

It was a lovely calm evening and we set up two harp traps and two nets along Butcombe Bank hoping to catch more Nathusius's Pipistrelles, but after lots of activity as it got dark the catch droppped off sharply and we didn't catch any of the target species. It was nice to see quite a few Serotine's Eptesicus serotinus flying along the water's edge and we did catch 3 ♀ Lesser Horseshoe Bats Rhinolophus hipposideros that were quickly released to avoid any extra stress to them. Local ecologist David Gibbs joined us, with a view to looking at ectoparasites, and took a Spinturnix mite from the ♀ Daubenton's Bat Myotis daubentonii that he identified as Spinturnix myoti by host association.

19th May [Nathusius's Pipistrelle Survey at Blagdon Lake]

This evening during a trapping session at Ash Tree, we caught the first Brandt's Bat Myotis brandtii for the site. She was a parous ♀. We also caught 2 more ♂ Nathusius's Pipistrelles Pipistrellus nathusii, that were ringed and fur-clipped.

18th May [Nathusius's Pipistrelle Survey at Blagdon Lake]

Just like buses, we caught 2 more ♀ Nathusius's Pipistrelles Pipistrellus nathusii, both of which were ringed and fur-clipped as part of an ongoing investigation into population dynamics using stable isotope analysis. One weighed 9.0 grams and the other 8.1 grams (non-parous). You have to suspect that there must be a maternity roost somewhere close by.

14th May [Blagdon Bat House Update]

I went to take some pictures inside the Bat House as work nears completion today:

Bat House, entrance modified to cut light exposure when the outside door is opened © Nigel Milbourne, 2013

Bat House, windows blocked inside to make it dark © Nigel Milbourne, 2013

Bat House, new floor & hatch to cool damp space for hibernation © Nigel Milbourne, 2013

Bat House, roughened wooden beams for bats to hang on © Nigel Milbourne, 2013

Bat House, new entrance for bats to fly through e.g. Lesser Horseshoe © Nigel Milbourne, 2013

Bat House nearing completion © Nigel Milbourne, 2013

14th May [Blagdon Bat House Update]

Daniel and I met with Bristol Water and their contractors again today as the work on converting the old Venturi House alongside Park Lane into a Bat House is nearing completion. There is a bit more work to be done this week on securing the roof structure and creating an opening suitable for bats to fly into the building, including Lesser Horseshoes, which don't fly to an opening and crawl in like many of the others. Then the scaffolding can come down and we will start monitoring again, both inside and outside the roost. The plan is do very little else and just see what happens in the first year before we consider adding things like roost boxes and a hot box for a maternity roost. It's all very exciting and I will keep you up-to-date with events as they unfold over the coming year.

11th May [Nathusius's Pipistrelle Survey at Blagdon Lake]

Despite the gale force winds during the day, the evening turned into one of celebration as we caught the first ever ♀ Nathusius's Pipistrelle Pipistrellus nathusii at Blagdon Lake after a couple of years of trying. She was a good weight and apparently not pregnant, so Daniel decided that here was the chance to ring and fit a radio tag that might help us work out where she is foraging and, more importantly, roosting. Both ♂ Nathusius's Pipistrelles were also ringed, and we noticed that one of them had a bad injury scab on its shoulder that appeared to be healing, thankfullly. I have added some more information to the Nathusius's Pipistrelle species description including example spectrograms that I've recorded at the lake and some photos of identification features.

During the evening we also checked some known Daubenton's roost sites, deployed the passive monitoring equipment, and Daniel was able to demonstrate identification features of six species and data collection techniques to a happy group, that included Denise and David that I travelled with in Trindad recently, and who had driven down from the Midlands for the session. The next survey date is Saturday 18th and all are welcome. Of course, there will be many sleepness nights before then, tracking 'Natalie' the Nathusius Pipistrelle!

28th April [Passive Monitoring at Blagdon Lake]

The passive monitoring equipment has been running at Ubley Hatchery and so far my analysis has turned up:

13th April [Bats in Trouble due to Cold Weather]

Last summer, bats had a particularly hard time due to the poor weather, and many went into hibernation in less than ideal condition. So, with the cold spell during March prolonging hibernation, it has compounded the problems for them. The unfortunate Daubenton's Bat Myotis daubentonii that was caught out in the cold on 2nd April at Blagdon dam, that subsequently died, was underweight. In addition, a Lesser Horseshoe Bat Rhinolophus hipposideros that was taken into care at Chew Valley Lake on 12th April must have had trouble finding food when it came out of hibernation too, because it weighed just 4 grammes (right on the lower end of the normal weight range). It died shortly afterwards. So, if you come across a bat out in the open in an exposed place, on an outside wall or on the ground, please call the BAT HELPLINE on 0845 1300 228 for further advice. Do not handle the bat unless absolutely necessary to contain it, in which case wear gloves to prevent being bitten (there is a small risk from a rabies-type virus EBLV2).

7th April [Nathusius's Pipistrelle Survey at Blagdon Lake]

We are planning Nathusius's Pipistrelle surveys at the lake, subject to suitable weather and agreement with BW, on:

5th April [Blagdon Bat House Update]

Daniel and I met with Bristol Water and their contractors at Pipe Bay to look at the structural work that's being carried out on the Venturi House prior to its conversion into a new Bat House. It's surrounded with scaffolding at the moment:

Venturi House, Pipe Bay on 5th April © Nigel Milbourne, 2013

The floor has been replaced and an entrance made to the space underneath which should make a fantastic cool room. The windows will be blocked, and a lobby built to prevent light flooding in when the door is opened. The bargeboards will be replaced and new bat tiles fitted to permit access under the tiles to the space between them and the roof. A hot box will be fitted inside the house under the ceiling. The hope is that we can provide a maternity and day roost and hibernation site all in the same building over three levels.

Daniel and contractors discussing roof modifications on 5th April © Nigel Milbourne, 2013

We've recorded Brown Long-eared Bats Lecotus auritus inside the empty building in the past, with a possible visit by Lesser Horseshoe Bats Rhinolophus hipposideros and the tiles have provided roost sites for Pipistrelle Pipistrellus spp. as well. The hope is that with some slight entrance modifications the Bat House will attract more of the species present at the lake to utilise the accommodations year-round. It's a very exciting project that we will keep you updated about as work progresses.

2nd-15th March [Trinibats 2013]

I went on a bat research trip to Trinidad organised by Daniel Hargreaves and Geoffrey Gomes of Trinibats. We had an excellent time and caught 42 species, see the Trip Report with some of my pictures.

9th February [Looking for Woodland Bat Roosts at Blagdon Lake]

Avon Bat Group and friends did some 'cold-searching' for bat tree roosts today. We explored a number of holes and cracks etc in the trees on Butcombe Bank. We found a number of promising potential roost sites without finding direct evidence of previous use. However, one hole in a Beech Fagus sylvatica tree did actually contain a dead, rather desiccated Daubenton's Bat Myotis daubentonii. We also checked the bat hibernaculum that we put up last year, but there was nothing in it, and had a quick look up into a few of the bat boxes from below using a torch, one of which contained a Common Pipistrelle Pipistrellus pipistrellus. Daniel also checked a known Daubenton's summer roost but there was no sign of anyone at home at this time of year.