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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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