Small scale manual bat activity survey

Biodiversity Net Gain assessment | Habitat and fauna surveys | Preliminary Ecological Appraisal (PEA)

Applied Ecology was appointed to complete a preliminary ecological appraisal, follow-up faunal surveys and a biodiversity net gain assessment of a proposed 21 home residential development within the grounds of an existing property in Berkshire.

As part of the faunal survey work, Applied Ecology completed a series of after dark bat activity surveys of a derelict residential dwelling to assess its use by roosting bats as the building was to be removed as part of development planning.

A team of three experienced Applied Ecology bat surveyors each equipped with a high resolution thermal video camera linked to a lap-top computer to record and view live video footage staked out the property to watch for bats emerging from the building from 15 minutes before sunset until 90 minutes after sunset in line with best practice bat survey guidance.  Typically, it is too dark to see bats emerging from a building with the naked eye from 25-30 minutes after sunset, and use of the thermal cameras enabled the surveyors to see clearly in the dark throughout the entire survey.  Post survey analysis of thermal video recordings, surveyor notes and bat calls recorded by time synchronized electronic bat detectors positioned around the perimeter of the building enabled accurate identification of bat roost locations.

The surveys verified the presence of small day roosts of three bat species: brown long-eared bat Plecotus auritus; common pipistrelle Pipistrellus pipistrellus; and soprano pipistrelle P. pygmaeus that were filmed emerging from window frame gaps, verge gaps and gaps under roof tiles around the property.

  1. At 20 minutes after sunset it was still just possible to see bats with the naked eye.
  2. At 40 minutes after sunset the building was too dark to see bats emerging with the naked eye, but bats could still be clearly seen using the thermal video camera.
  3. Biodiversity Net Gain (BNG) pre-development baseline habitat map.
  4. BNG post-development habitat map.