Overview and main changes
A re-structuring of the format to the guidelines has been adopted to improve accessibility for readers. New sections and chapters include:
• Elements that influence survey design.
• Species core sustenance zones.
• Preliminary ecological appraisal for bats.
• Framework for assessing suitability.
• Bat roost inspection surveys for trees.
• Acoustic surveys at potential swarming sites.
• Advanced licenced bat survey techniques.
• Data analysis and interpretation.
• Protocol for collecting droppings for DNA analysis.
Two chapters have been omitted from the 3rd edition:
• Surveying major infrastructure projects.
• Surveying proposed onshore wind turbine developments (until this guidance is available, the 2nd edition of the Bat Survey Guidance and it’s wind farms chapter is still applicable).
Main changes to survey design and recommendations
Preliminary ecological appraisal
The criteria for assessing the potential suitability of a proposed development site for bats has been updated with a clear distinction between roosting habitats and commuting and foraging habitats, and their level of suitability to support bats.
Preliminary bat roost assessment
Preliminary tree roost assessments, are more explicitly defined with recommendations for assessing potential roost features and methods, survey effort, timings and the requisite experience required to assess trees from the ground and above ground level.
Bat roost survey
The main updates to this chapter include a reduction in the number of surveys required to establish the presence or likely absence of bats.
• Low potential roosts: one dusk emergence or pre-dawn re-entry survey between May and August (not September)
• Moderate potential roosts: one dusk emergence and a separate pre-dawn re-entry survey between May and September. At least one of the surveys should be completed between May and August.
• High potential roosts: a combination of three dusk emergence and pre-dawn re-entry surveys between May and September. At least two surveys should be completed between May and August.
The recommended maximum duration of dusk emergence surveys has also decreased whilst there has been a minor increase in the maximum duration of pre-dawn re-entry surveys.
However, critically for project timescales, multiple surveys must now be completed throughout the recommended survey period, with a minimum interval of two weeks between surveys, unless there are specific ecological reasons to schedule surveys closer together.
In relation to establishing the foraging and commuting value of a site, the guidance continues to categorise sites as having low, moderate or high value for species of bats. However the size of the site is no longer taken into consideration and the corresponding number of surveys required has increased:
• Low suitability habitat for bats: one survey visit per season (spring – April/May, summer – June/July/August, autumn – September/October).
• Moderate suitability habitat for bats: one survey visit per month (April – October).
• High suitability habitat for bats: up to two surveys per month (April – October).
• Low suitability habitat for bats: one location per transect with data to be collected on five consecutive nights per season (spring – April/May, summer – June/July/August, autumn – Sep/Oct).
• Moderate suitability habitat for bats: two locations per transect with data to be collected on five consecutive nights per (April – October).
• High suitability habitat for bats: three locations per transect with data to be collected on five consecutive nights per month (April – October).
There is also a reduction in the maximum duration of dusk transect surveys and an increase in pre-dawn transect and automated detector surveys.
From a users perspective it is clear that BCT have worked closely with professional ecologists across the board to provide an updated guidance that utilises the latest in research, field methodologies and best practice. However, as with any guidance, the content is only as good as the current level of understanding.
Collins, J. (ed.)(2016) Bat Surveys for Professional Ecologists: Good Practise Guidelines (3rd edn). The Bat Conservation Trust, London.