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Sunday, 29 August 2021

Sunset and sunrise surveys - maximising quality

We're fortunate in the UK to have good practice guidelines for bat surveys, though interpretation of these can cause challenges. Surveys inevitably require numbers of surveyors and ways of sourcing these include:

  • Teams of fully qualified ecologists, usually in larger companies.
  • Office staff and other professionals, given task-specific training.
  • Sub-contractors.
  • Division of a survey into several segments, allowing two or three surveyors to complete it over several nights.
  • Recruitment of a specific team of specially-trained seasonal field ecologists.

Many smaller regional companies like ourselves use sub-contractors. Our experience of this was that it led to inconsistencies in equipment used, levels of experience or training and the quality and accuracy of data recording. Some consultancies achieve excellent standards using sub-contractors, but it wasn't for us.

Our approach to emergence and re-entry surveys is a little different to that practised by many consultancies. The ‘standard’ approach involves each surveyor working individually to watch their section of the subject structure and record what they see, whilst making a digital record of the bat calls heard, allowing for later analysis. Whilst this approach is widely used, we identified several potential weaknesses with it:

  1. When surveyors are asked to record their own data they are forced to take their eyes away from the subject structure for perhaps 30 seconds each time they wish to note anything down (some consultancies use digital audio recorders to avoid this problem). As a non-breeding roost may only contain one-or two animals this may lead to roosts being missed.
  2. Writing down notes also requires artificial light at times, resulting in degradation of the surveyors’ night vision for five minutes or more.
  3. Even the most diligent of surveyors may lose focus without some degree of supervision and encouragement during a two hour survey.
  4. As each segment of the subject structure is effectively surveyed separately, it can be challenging to link movements of bats around the site.
  5. Recreating the entire survey at a later date, based on several sets of notes and recordings is an excellent opportunity for error and misunderstanding to creep in.
  6. It is challenging for the ecologist in charge of the survey to gain a full and broad understanding of the progress of the survey if they also have to focus on one specific section of the building themselves.
  7. If something arises during the survey, which without attention would limit the survey results, for example equipment failure, disturbance by members of the public etc. the ecologist in charge is poorly-placed to react and limit the impact if they are tied to one survey location.
  8. Individual surveyors may feel isolated and gain little from the experience.

To address these concerns and improve our own standards of survey work we implemented our own approach in 2007 and have continually fine-tuned it ever since.

  1. One key difference in our approach is that we deploy a lead ecologist who is usually a licensed bat-worker and who is additional to the surveyors needed to visualise all the relevant parts of the surveyed structure. This may seem profligate, but it allows the lead surveyor to do a much better job of managing the survey:
  2. The lead ecologist is able to build up a full picture of the survey, avoidiong the need to decipher lots of notes at a later date.
  3. They are equipped with a bat detector with live sonogram display, allowing many uncertain bat calls to be identified there and then, reducing the amount of post-survey analysis required.
  4. Supervision of the team is continuous, as the lead ecologist moves around the site, responding to problems, dealing with members of the public. This gives an enhanced level of safety and ensures each surveyor is part of the team.
  5. The lead ecologist is able to spend time with each surveyor, developing their knowledge and ensuring that they gain in experience from every survey.

A further point of difference is our method of communication. Field ecologists are trained not to take their eyes off the structure they are surveying and do not take any notes. Each is equipped with a personal radio and all bat activity is communicated to the lead ecologist using this. Not only does this reduce the risk of roosts being missed, it allows the lead ecologist to build an understanding of the entire survey as it happens, so that any shortfalls or concerns can be immediately addressed. All notes are then taken by the lead ecologist (or by an additional field ecologist at especially busy or complex sites).

Communicating survey data by radio means that all surveyors are aware of everything that is happening during the survey. This assists with remaining focused through a quiet survey and further enhances the survey as a learning opportunity. It also allows individual surveyors to efficiently link bat activity they see with that seen by other surveyors. For example, the risk of confusion between bats emerging from a complex roof structure and those overflying it is reduced. 

Sadly, it is never possible to separate bat consultancy work from the reality that we operate in a competitive industry and costs are important. It may seem that having an additional person on each survey is an untenable additional cost and is likely that many clients would be unwilling to pay  for this. We do not factor this in when costing work. Better to accept a lower profit margin but be satisfied that we are delivering the very best standards of survey we are able to. We find that, with our approach the amount of ‘post-game analysis’ necessary after each survey is significantly reduced, as less de-ciphering of notes and analysis of recorded calls is required. This saving goes a long way towards balancing any additional cost.

I am not suggesting that our approach to emergence and re-entry survey is the best or ‘right’ way to conduct them. Each consultancy must develop their own approach, based on the resources available to them, the economic framework in which they operate and the scale and complexity of the surveys they carry out. However, good practice can only be good practice when it is openly shared and discussed. Our approach has been developed and fine-tuned over fourteen years and works very well for us. I hope it may be of use to others in helping to form their own approach to these surveys.

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Saturday, 21 August 2021

Looking after your bat detector - guest blog by Andrew Dobson

Andrew Dobson is the UK face of Titley Scientific, the company which makes the Anabat range of bat detectors. I've known Andrew for over a decade and every time I meet him he always has some useful tip, or else a sad tale of us non-engineering ecologists ill-treating his beloved equipment. I persuaded him to distil some of these hints into a guest blog for us.

Deploying a remote download system back in 2013

8 years ago, I found myself taking over Titley Scientific UK & European distribution, selling and servicing Anabat bat detectors. After emigrating to Australia in 2007, it was 2012 and time to come back to the UK - especially with the arrival of a new baby. Around this time, Titley Scientific was being taken over by the Australian company I worked for. They needed someone in the UK to look after things and I thought to myself, ‘why not?’ Moving to Australia in the first place was a massive risk, hence, coming back with a job opportunity this time was hard to refuse. 

By this point, I had almost 20 years experience in electronics. Fortunately, this meant fixing Anabat bat detectors was relatively straightforward for me, just slightly different to work I had done before. As comfortable I may be with anything electronically related, I will admit that I am no salesman. Personally, I do not really believe people working with this equipment need a ‘shiny salesman’, but more of an honest and genuine person who tries their best. People like Chris Corben and Richard Crompton were around well before me, promoting all things Anabat. From this, the community was already aware of Titley products, which gave us the best chance of succeeding. In fact, everything was there for me. The only shortfall I could see was the technical expertise needed in the UK and hopefully I filled that gap.

Since starting, I have had some amazing experiences all over Europe and met many amazing people. In particular, I remember being in a cave in Portugal, where was told to close my mouth if I did not want bat pee in my mouth! This was definitely a highlight for me. 

Like any career serving people, I have had the odd difficult customer or made the odd mistake, but in general I think I have done well. I try my best and most people appreciate that. Chris Corben is the brains behind the original Anabat kit and is still working hard to help along with the team in Brisbane. Chris cannot help enough and I will always be grateful for his help. 

Within a few weeks of starting, I found “David’s Bat Blog”, and decided to make contact. David was a friendly and welcoming contact, so I gravitated to his hospitality. Back in 2013, we deployed a remote download system and solar panel near him, which recorded bats all year round  – I never quite managed to get a go in his glider but hopefully there is still time for that :-)    

8 years in and I have probably taken apart more bat detectors than most, so when David asked for a guest blog post it made sense to try and make it useful and talk about what I know (not bats!). Here are some pointers to help folk care for their field kit and avoid common errors: 

Disclaimer: I only work on Titley products, but in general all bat detectors on the market need a sensitive microphone element and run on batteries, so this info is useful for most bat detectors regardless of brand.  Also, the vast majority of units sold do not fail, I am only talking about a very small number. 


Leaking alkaline batteries and resulting damage in an Anabat Express

Alkaline batteries leak, that is pretty much it. If you would like to use them then that is always the risk. This is mainly due to being run flat, left in kit or get too hot. Electrolyte comes out and eats everything it its path. SD1’s were forever coming back with heavy corrosion. I soon found out people thought leaving them with AA’s in all winter was a good idea as it prolonged the life of the clock battery. This is, in fact, the absolute worst thing to do, as they eventually run flat and leak. There was some myth that leaving them would prolong the clock battery, but this is only true if the unit is turned on. Now we have the Anabat Swift, this has amazing battery life and can work on 4 or 8 AA’s. The downside is, if you fit 8 AAs and have just one the wrong way, it will work fine due to the voltage still being within the correct range, but that one alkaline fitted backwards leaks immediately and can really damage the detector.

If you must use Alkalines, here are some musts!

1.      Check and double check they are fitted in the correct orientation.

2.      Take them out when not in use.

3.      Avoid the pack of 40 that are unbelievably cheap.

 You can even see what the battery voltage is in the menu, so maybe its worth spending a few seconds checking its around 12v with new batteries.

I recommend Eneloop rechargeables where possible, and to clean the contacts with a pencil eraser from time to time. If you cannot get Eneloop, stick with well-known brands. Why risk buying “amazing value sponsored batteries” that Amazon are trying to push on you?  


By definition, microphones are delicate sensors that convert sound waves into an electronic signal.  Pointing one of these to the sky for 6 months in all weather, and expecting it to be consistently sensitive from start to finish is probably a mistake! All manufacturers say, “weatherproof/waterproof”, but also caveat that with, “avoid something or other”. In my experience, it is best to avoid all rain to get the most out of them. Obviously, this is not always possible, so pointing away from prevailing weather and slightly down (omnidirectional mics pick sound up from all around anyway) is your best bet. Water building up on the microphone will also block the sound from getting through until it dries out, so your recording quality will suffer. Make sure you read and follow any microphone care instructions provided with your equipment.


Most passive detectors (the type that you leave out in the field) are now waterproof, so prevent wetness getting inside. This generally means they are pretty good at preventing moisture getting out as well (some now have vents for this). Opening them in the pouring rain, then getting the inside wet and closing the waterproof case traps the moisture inside. This is when it can go to work corroding everything, but mainly the power connections, as they can get slightly warmer than elsewhere. Active detectors (the type you use while carrying around) are generally not waterproof and care should be taken to avoid getting them wet.

SD cards

They get old and slow, then slow detectors down and cause issues. It helps to re-format them from time to time. For tiny zero crossing files this is usually not an issue, but full spectrum .wav files are 1000 times bigger, so speed is king. Go with class 10 and a write speed of over 120mb/s. Also, never EVER use those horrible micro SD cards in those crappy holders, you are introducing another dozen tiny connections that can fail!

It’s not working

If it is not working, unfastening, or responding to your presses; generally using 10 times more force is not the answer. If the microphone does not unscrew, it is probably not a good idea to use enormous pliers. When things do not work as normal, just give it a few seconds and try again. Maybe even take the batteries out, give it a few minutes and try again. Bat detector manufacturers do not have the resources of Apple or Samsung, but will always help you to get issues sorted out as soon as possible. With bat detectors, generally check for firmware updates at the start of every season, unless the product is brand new. You could also subscribe to email notifications for firmware updates where possible (Titley does this).

Service in Winter

Requesting your kit to be checked or serviced the day before the season starts does not help anyone. Particularly, since, whoever is servicing them probably already has plenty of work to do. Sending kits to be serviced in winter gives plenty time to have them looked at and fixed. They can also have their alkaline batteries that were left inside since September removed and disposed of.

Respect your kit

It’s that simple, just look after it. Store it in a dry place at room temperature, keep it clean and take batteries out when not in use. After use, if the case & mic are wet, leave it open with the mic still fitted for a day or two if possible. If it comes to the point you need to return something, wrap it accordingly – couriers like to damage things!

Hopefully, that helps a little to get the most out of your kit and save yourself some money in repairs. Each new product we release has improvements on the last, so progress is being made to help. Our latest will be the Chorus, which is our entry level passive detector. Its design builds further on our years of experience making and servicing bat detectors.

The new Titley Chorus bat detector & acoustic recorder

Titley Scientific on Facebook

Titley Scientific website

Andrew has kindly lent me a prototype Chorus to try out - I'll post some thoughts about it very soon.

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Friday, 13 August 2021

Whither goes woodcrete? A new source of robust bat-boxes

A Lunar Environmental bat box
(Image copyright Lunar Environmental)

I've long been an advocate of woodcrete or woodstone bat boxes (the terms appear to be interchangeable, though may be trademarks for all I know). German-made Schwegler bat boxes have been around for many years, in a wide variety of shapes and sizes, have become pretty much the standard for good quality bat boxes and are widely used.

Moulded of a wood-fibre and cement mix, these boxes have better insulation than more traditional wooden boxes and a much longer life-span. Unlike wooden boxes, which rarely last much more than a decade (poorer ones often rot even more quickly), these last pretty much forever, unless some brat decides to lob half-bricks at them - they tend to break if a direct hit is scored - so they're an ideal solution for mitigation/compensation schemes. 

Some Schwegler boxes, destined for a development site several years ago

The weakness of Schwegler boxes has always been their price. At about £35 for the simplest type (2F), which Blue tits can find their way into, and about £15 more for ones with a wooden baffle (2F-DFP), which discourages the blue and yellow feather-rats, they're not cheap. However, the cost is mitigated by their higher take-up rate - I've often found them to have two or three times the occupancy level of wooden boxes, probably aided by their better insulation properties and consequent slower changes in internal temperature.

So what's not to like? Nothing, except that they disappeared off the market several years ago. All the suppliers still list them, but are perpetually out of stock. I've heard numerous claims that this has been caused by a fire at the factory, problems with raw materials, Brexit, massive demand elsewhere in Europe etc. Whatever the cause, you simply can't get them. So what to do?

CJ Wildlife sell a Vivara Pro bat box, made from a similar material. Their price point is much more reasonable than the Schwegler boxes, at around £20-25. But I'm not a huge fan of these - they are less robust than the Schwegler products and have to be mounted using a rather feeble attachment, which does not inspire confidence and makes it impossible to hammer a nail in and bend it over (my preferred way of attaching a box to a tree, to prevent is blowing down in winter). In fairness I haven't seen one fail...yet. They also look a bit like a twee bird-house, but that probably bothers me much more than it would a bat!

Two Vivara pro boxes, in position

So for the last couple of years I've been using Vivara Pro boxes and hoping that Schwegler would sort themselves out. But now I've found an alternative that I'm rather impressed with. And they're based in Scotland. Given that these things are pretty heavy, carbon footprint is a factor.

Lunar Environmental, a small firm based in Aberdeenshire, are moulding their own woodcrete boxes and selling them direct. What's more their price-point is good, with a micro box at £25 and a macro one at £35.  The macro is 31cm tall and 15cm diameter, whilst the micro is 26cm tall and 10cm diamter. The boxes do not have an openable door, but instead have a sloping floor, leading to an entrance slot in the base, making them self-cleaning. They have a curved back, helping them to sit against a tree-trunk, but seem to work ok mounted on a wall as well. The attachment is a loop of rust-proof cable, moulded into the top of the box.

Dimensions and internal shape of the Lunar boxes 
(Image copyright Lunar Environmental)

I really like these boxes - they have a solid, well-made feel. Kevin Wright not only understands bats, he also worked in concrete moulding in a previous career and has been able to combine these two disparate skill-sets. What I really like is that he's thinking about the product and how to perfect it. Interestingly, these boxes have a lower wood content than the other types on the market and use vermiculite instead, to enhance the insulation properties of the boxes.

One of the Lunar boxes, mounted on the gable end of my house

Incidentally, they also make bespoke boxes. Kevin is currently working on a batch of crevice bricks for me, for an artificial hibernaculum project we're working on. 

So, if you need a batch of boxes for a project, I'd suggest giving Lunar a try. 

Lunar Environmental

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Saturday, 7 August 2021

The bat identification song (with apologies)

For everyone who has ever peered myopically through a hand-lens at a small, wriggling, angry bat by the light of a failing head-torch I bring you... the bat identification song.

To the tune of "My favourite things" from "The Sounds of Music".

All together now...

Ridges on noses and hairy wee calcars,
Pale furry bellies and separated ears,
Varied veination on Pipistrelle wings
These are a few of my bat ID things.

Lobes beyond calcars and mushroom-shaped tragus,
Bulbous bat willies and horseshoe-shaped faces,
Measured thumb length beside London Zoo rings, 
These are a few of my bat ID  things.

When I don’t know,
When I can’t tell,
When I’m feeling thick,
I simply remember these bat ID things,
And they usually do the trick.  

Digital callipers and Pesola scales,
Finger-end tragi and extended tails,
Pelage that’s golden-brown, chocolate or grey,
These make the bat ID blues go away.

Fur that is shaggy and ears that are lengthy,
Pinkish bare faces and feet that are hairy,
Losing the will to work out what it could be,
Maybe these things will be helpful to me.

When I’m fed up,
When I’m  unsure,
When it’s just not clear
And all I can do has simply gone flat,
I’ll declare that the wretched creature’s…  a bat!

With profuse apologies to Julie Andrews, to Rogers and Hammerstein and especially to you, if someone has just sung this to you!

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Thursday, 5 August 2021

The bat aviators of Portmoak airfield

You might think that flying a glider would have little to do with bats, but there are interesting comparisons to be made between man-made aircraft and bat morphology!

I fly at the Scottish Gliding Centre at Portmoak, near Kinross. In an articel I recently wrote for the club newsletter I compared the various bat species found on the airfield with types of aircraft in use. To help it make sense to a non-aviation audience I've added some footnotes and photos of the gliders described.

Apparently, Portmoak is the second busiest airfield in Scotland, after Prestwick. Unlike Prestwick, we only fly in daylight, but did you know Portmoak is home to another group of skilled aviators, for whom IFR flight (1) is the norm? 

My day job is as a consultant ecologist, specialising in working with bats and several years ago I and a group of students spent some time studying the bats who make the airfield their home. We erected bat boxes around the workshop and caravan site to encourage bats to roost, set up passive acoustic monitors to record their calls and spent several nights using a large ‘harp trap’ to catch bats in flight (and release them afterwards). The outcome of this is that we now know that five bat species hunt around the airfield for the insect prey at night, one of them rare. They use ultrasonic echolocation to navigate and find their prey in the dark.

The 'Goliath' harp trap in place at Portmoak airfield, with Bishop Hill in the background.

The UK’s two commonest bat species are very similar (it was only in the 1990s that they were realised to be separate species) - the Common and Soprano Pipistrelle both hunt around the trees at the edges of the airfield and at the workshops. Think of these as the Schleicher K21s of the bat world (2) – widespread generalists with dependable, middle of the road flight characteristics. Like the K21, if anything is flying it’s probably one of them. Unlike the K21 they do us the service of hoovering up 2-3,000 midges each per night.

A Soprano pipistrelle, expressing some strong opinions

A K-21, a reliable and ever-present training glider, the Pipistrelle of the gliding world. 
(photo credit Alexander Schleicher GmbH)

The rare species at Portmoak is related to them. The Nathusius’ pipistrelle is usually found near large water bodies and Loch Leven is home to a colony of them, one or two of whom are often to be found hunting above the track beside the caravan park. They often migrate over very long distances to hibernate, so possibly they equate to a Discus Turbo (3) in the hands of one of our cross-country pundits.

The Brown Long-eared Bat is also present at Portmoak, hunting amongst the workshop trees and is a bat with very different flight characteristics. As well as ridiculously large ears (so it can listen for insects) it is probably the K-8 (4) of the bat world. It has broad wings and a large tail surface, enabling it to fly very slowly and turn on a sixpence. This enables it to manoeuvre close to vegetation and pluck off insects to eat. Perhaps a step too far for members of the DRV syndicate (5) - bats don’t have to worry about being summoned for a ‘chat’ with the CFI (6).

G-DDRV, a much-loved K-8 glider - slow and maneuverable

A highly specialised species present at Portmoak is the Daubenton’s bat. These are water specialists, hunting low over the Leven Cut for aquatic insects and scooping them from the water’s surface with their feet. I was struggling for a glider comparison, until I recalled that a Slingsby Falcon was fitted with floats during World War II and launched from Windermere by boat-tow. I understand it’s now on show at the Windermere Steamboat Museum.

A Daubenton's bat, caught at Portmoak

One Scottish bat species we haven’t recorded at Portmoak (it tends to be found mostly south of the Forth-Clyde line) is the Noctule, which is a shame, as I think it would feel at home. It’s Scotland’s largest bat, with a wingspan of 37-40cm, usually found flying high, catching beetles and other large flying insects. A powerful flier, it’s relatively long and narrow wings allow it to fly fast and cover long distances whilst hunting making it a good contender to be the ASH-25 of the bat world (7).

The powerful long wing of a Noctule

Schleicher ASH-25 (photo credit Alexander Schleicher GmbH)

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(1) Instrument flight rules - flying in the dark, fog, cloud etc.
(2) A very widely-used training glider, with benign handling characteristics. On days when nothing much else is flying there's likely to be one or two trundling around on instructional flights.
(3) A high performance glider, often used for long-distance cross-country flights.
(4) An old and much-loved glider type, built of plywood and canvas, with broad wings and slow, maneuverable flight.
(5) G-DDRV is a K-8 based at Portmoak and still flown regularly. I own a share in her and on a calm day she's a joy to fly.
(6) Chief Flying Instructor, the person responsible for flight safety and  a 'chat' with whom often means you've crossed a line somewhere!
(7) A very high performance glider - think Lamborghini with wings!