Field Survey

Quality Control

All data were collected using a standardised methodology. Heterodyne detectors are used as this survey method enables a wide range of volunteers to collect data for the purpose of producing species population trends. Participants are provided with training and resources to aid species identification but it is not possible to verify records from this survey. The data do not provide a complete picture of bat distribution, but should be considered as a sample of sites from across the UK. These data are not intended to replace systematic local surveys and data held by local records centres.

Method steps

1. Surveyors walk a roughly triangular route in a randomly allocated 1km square on two evenings in July to record noctule, serotine, common pipistrelle and soprano pipistrelle bat activity with a heterodyne bat detector. In Northern Ireland, Leisler’s bat is counted instead of noctule and serotine. The number of common and soprano pipistrelle passes is counted for two minutes at 12 stopping points along the transect. The number of noctule and serotine passes (Leisler’s bat in NI) is counted while walking between stopping points.

The NBMP Field Survey collects data from a stratified random sample of 1km squares across the UK. Survey coverage is lower in areas with fewer volunteers or with less accessible terrain such as upland areas.