Bat Survey at All Saints’ Church

A survey was taken in October 2022 of the bat activity in All Saints’ Church.

Gareth Harris came to speak about the results on March 14th.

If you missed his talk it can be downloaded by the following link until 19th April 2023

https://share.icloud.com/photos/0e9WAScHaXo-KUhx7bXJ6p3kQ

Information gathered in October 2022

The first chart shows the information gathered from a detector on one of the central pillars in the nave, roughly pointing towards the piano (where there were some accumulated bat droppings).

The detector recorded 7 nights of activity before the batteries ran out. The numbers in the following table relate to “bat passes” i.e. the number of times the detector was triggered by that species. So the numbers don’t relate to numbers of bats, but they are a proxy for activity levels.  This largely confirms what we suspected, that pipistrelle bats, long-eared bats and Lesser horseshoe were present.

This shows that Lesser horseshoes are indeed flying around the inside of the church and they are typically doing so in the middle of the night – the fact that they aren’t recorded at dusk or dawn, suggests they aren’t day roosting here, but somewhere else, and come here only in the middle of the night. This is characteristic of what’s called “night roosting” behaviour. This is a good definition of a night roost: “a sheltered area where the bats can hang up, groom, and digest their food between foraging bouts. These are particularly important for heavily pregnant females and for bats foraging at a distance from their normal day roost. Many night roosts are structures which would be too light and exposed to the elements to be suitable as day roosts, but during darkness provide the bat with sufficient shelter and security against inclement weather and/or predators. Examples of these include church porches, derelict old-fashioned outside toilets, or open sided sheds.”

Basically, the day roost is somewhere else and the bat (its likely an individual) comes here only in the middle of the night. The places where the droppings are found are well-lit locations too, so this fits nicely.

Species	03/10/2022	04/10/2022	05/10/2022	06/10/2022	07/10/2022	08/10/2022	09/10/2022	Grand Total
Lesser horseshoe bat			1		1		5	7
Common pipistrelle	15	6	119	45	15	15	6	221
Soprano pipistrelle			4					4
Brown long-eared bat	13	66	6	7		6	2	100
Grand Total	28	72	130	52	16	21	13	332

Similarly, the decent number of Brown long-eared bat passes, indicate that a roost is present, and that they were warming up inside the church before leaving the church to forage in the wider landscape. Additionally, the time of year, and the types of calls that were recorded indicate that they were also courting and displaying too – we often record this type of behaviour in September and October inside large buildings such as churches, cathedrals, barns and large houses. Again, this fits with what we know – we suspect the roost closest to the main door is long-eared bat.

Common pipistrelle were also very vocal – and the calls recorded also relate to courting bats. All British bats mate and court in the autumn months.

Secondly – we left a detector in the outbuilding where we suspected the Greater horseshoe. Here we recorded 10 nights of data.

Species	03/10/2022	04/10/2022	05/10/2022	06/10/2022	07/10/2022	08/10/2022	09/10/2022	10/10/2022	11/10/2022	12/10/2022	Grand Total
Greater horseshoe				133				1	52	93	279
Noctule bat	2	1		2	1					2	8
Serotine bat			1				1				2
Common pipistrelle	71			21	13	3	52			30	190
Brown long-eared bat										1	1
Grand Total	73	1	1	156	14	3	53	1	52	126	480

Astonishingly, we recorded 279 passes of Greater horseshoe bat – so they are clearly using it. Not every night and sometimes not very much – but other nights, they used it a lot (e.g. the 6^th).

In the following graph, I’ve plotted the number of passes recorded for each hour (1800hrs, 1900hrs, 2000hrs etc). This highlights where the main activity is. During the 3^rd to the 12^th October, sunset was between 1838 and 1821…….and sunrise was 0710-0725.

We don’t think the Greater horseshoe bat is day roosting in the outbuilding (because we’ve never seen it there – and it’s a big bat, you’d have noticed it!). And our data shows it is using the outbuilding through the night……but the timings of the recordings show the bat is using the site a lot shortly after sunset and an hour before sunrise……in fact, some of the passes are within minutes of sunset. Which means that the Greater horseshoe bat is roosting somewhere VERY close by. Its perhaps worth canvassing nearby residents to see if anyone has outbuildings, stables, cellars etc that it could be using for day roosting.

I also suspect, judging by the numbers of calls and of the constant echolocation calls, that this bat was actually perched and was warbling at the same time – i.e. it may have been singing to attract females. (I’ve seen them do this in the entrances to roosts before). And if that’s the case, I wonder if it was successful!?