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Monitoring approaches

The NBMP is an integrated programme that employs a number of different survey methods. This approach means that, for some species, bats are surveyed at more than one stage of their annual life cycle. As a general rule, trends from the Field Survey and Waterway Survey are currently considered most robust, followed by the Hibernation Survey, and then Roost Counts.

A sampling approach is used on all surveys with the assumption that trends occurring in sample sites reflect trends occurring in the general population. Theoretically this assumption is strongest when sample sites are chosen at random and where a proportion of sites do not contain the species of interest, such as for the Field Survey. Monitoring sites where the species of interest is not present can help identify if populations are expanding into new areas.

The main monitoring techniques employed by the programme and their survey periods and site selection methods are summarised here:

NBMP survey details

Species monitored

Start year

Survey period

Site selection and survey method

Roost Count

common pipistrelle, soprano pipisrelle, serotine, Natterer's bat, brown long-eared bat, greater horseshoe bat, lesser horseshoe bat

1997 (Natterer's bat: 2000, brown long-eared bat: 2001)

6th - 25th June (lesser horseshoe: 9th May - 27th June, greater horseshoe: 7th - 21st July

Known roosts

Roost emergence counts

Field Survey

noctule, serotine, common pipistrelle, soprano pipistrelle


1st July - 30th July

Stratified random 1km squares

Walked transect with heterodyne bat detector

Waterway Survey

Daubenton's bat


1st August - 30th August

River Habitat Survey sites

Walked transect with heterodyne bat detector

Hibernation Survey

greater horseshoe bat, lesser horseshoe bat, Daubenton's bat, Natterer's bat, whiskered/Brandt's bat, brown long-eared bat


January/February (data also now included from December to March)

Known or potential hibernacula

Internal hibernacula survey

Bats and Roadside Mammals Survey / iBats UK

(not currently running)


May - September

Self-selected transects

Car survey with time expansion bat detector 

Woodland Survey



July - September

SAC sites for barbastelles (plus other woodlands with suitable habitat surveyed up to 2010)

Walked transect with broadband bat detector

Nathusius' Pipistrelle Survey

Nathusius' pipistrelle

(not currently running - superceded by the project below)



Lakes/lochs allocated from UK Lakes online database (website no longer live)

Walked transect with broadband bat detector

National Nathusius' Pipistrelle Project

Nathusius' pipistrelle


Spring to autumn, avoiding key breeding period

Sites with known/likely Nathusius' pipistrelle presence

Harp trapping survey

Continue to Robustness of monitoring

Return to Report home page; Contents page


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