Bat Group Surveys

This survey project aimed to increase the network of regularly surveyed sites across London and monitor more bat species than ever before. Volunteers with all levels of experience, from beginners keen to learn new skills, to more experienced members took part.

Survey summary

The survey involved walking a roughly triangular transect (divided into twelve stops and walks) within a 1km square and attempting to identify all bat species encountered and counting numbers of bat passes. The survey methodology was based on the NBMP Field Survey. This expanded survey was successfully trialled in 2008 at RSPB Rainham Marshes and Holland Park, and a very similar methodology has been used with great success at the London Wetland Centre.

Survey methodology

  • Begin the survey 20 minutes after sunset.
  • Record temperature, cloud cover and wind speed. (At the end of the survey record whether it rained at all).
  • Tune one detector to 50 kHz (for smaller bat species) and the other to 25 kHz (for larger species).
  • Start at spot 12 and walk at a moderate pace towards spot 1. When a bat is heard tune the detector up and down in order to hear the call more clearly and identify the species. Species identification tips will be provided.
  • On the survey form record all species heard or seen and the number of passes. A bat pass is a continuous stream of echolocation calls indicating a bat flying past.
  • If constant activity is heard estimate the number of times a bat flies past, or note down as “continuous” if there is too much activity to enable an estimate of number of passes.
  • Passes are counted rather than number of bats as these are easier to estimate.
  • On reaching spot 1 stop for two minutes and record bat species and number of passes.
  • Continue along your route, counting all bat passes between spots (when walking) and for two minutes at each spot (when stationary), until you finish back at spot 12.