NBMP annual reports - background information

The information below is common to all recent annual reports, with only minor modifications. To avoid too much duplication and to reduce the size of the reports, from the 2008 report onwards the following background information on the NBMP will be omitted and replaced with links to this web page. We hope this page will also serve as a useful reference for anyone looking for information on the aims, objectives and scope of the National Bat Monitoring Programme.

Aims and objectives of the monitoring programme

The aim of the monitoring programme is to provide annual population trend data, with specified confidence limits, for each resident bat species in the UK.

Long term objectives

1. To implement existing monitoring projects annually and produce annual population trends.

2. To identify drivers behind identified population changes.

3. To develop new surveys that increase species coverage and are suitable for volunteer participation.

4. To deliver population trends at national, regional and local scales.

5. To increase the funding base to ensure that the programme is sustained over the longer term.

6. To develop and coordinate a pool of trained volunteers throughout the UK to implement surveys and become involved more actively in conservation.

7. To ensure the programme's data are used to inform and influence government environmental policy.

Contribution to practical and policy themes and issues

Although bat population monitoring data are needed to inform bat conservation policy they also contribute knowledge to a wider suite of environmental assessments that allow the UK to report against targets and objectives within the framework of national legislation and international Conventions, Directives and Agreements.

Collection of reliable information that delivers an accurate picture of the state of UK bats and contributes, in conjunction with other species' programmes, to a wider environmental evaluation lies at the core of the monitoring programme.

International initiatives and directives

Convention on Migratory Species (Bonn Convention 1979) and the EUROBATS 1991 Agreement

Obligations under the EUROBATS Agreement place considerable emphasis on monitoring and sharing information. Monitoring methodologies developed and tested by the monitoring programme and dissemination of accumulated knowledge through running international workshops help meet these fundamental obligations.

The Convention on Biological Diversity (CBD)

This is the most comprehensive global agreement and Article 7 requires signatory parties to ‘identify components of biodiversity....and monitor, through sampling and other techniques, the components of biological diversity identified'. The monitoring programme's approach fits closely with the principles of the Convention.

European Communities Directive 92/43/EEC, on the Conservation of Natural and Semi-natural Habitats and of Wild Flora and Fauna (The Habitats Directive)

All European bats are listed on Annex IV of the directive and 5 UK bat species are listed on Annex II (‘strictly protected'). Member States must maintain and restore ‘favourable conservation status' of species listed in Annexes II, IV and V. Favourable conservation status is defined as ‘the sum of the influences acting on the species concerned that may affect long-term distribution and abundance.' Article 11 of the Directive states that ‘Member States shall undertake surveillance of the conservation status of the natural habitats and species referred to in Article 2 with particular regard to priority natural habitat types and priority species.' The programme's data will help inform judgements on FCS for bats.

Pan-European Biological and Landscape Diversity

As a contribution to the European Action Programme for Threatened Species (Action Theme 11 of the Pan-European Biological and Landscape Diversity Strategy), a new Red Data Book (RDB) of European vertebrates is in preparation. Our monitoring data will contribute to this theme.

National obligations and initiatives

Sustainable Development

In 1994, the government published its Strategy for Sustainable Development, following commitments made at the Earth Summit of 1992. The programme helps deliver commitments made to develop a set of indicators which link environmental impacts with socio-economic activity. Local Authorities, as part of the Local Agenda 21 initiative, are developing a set of indicators for use at local level. The reliance of bats on artificial structures for roosts and their interaction with roads makes them ideal indicators of Regional Sustainable Development.

Global Warming

In the recently published ‘Review of UK and Scottish Surveillance and Monitoring Schemes for the detection of climate-induced Changes in Biodiversity' funded by the Scottish Executive and Defra, (Riley et al., 2003) bats were identified as good climate change indicators and the monitoring programme as a robust mechanism for monitoring those changes.

Biodiversity Action Planning Process

This is a target-orientated process and monitoring data are required to judge whether conservation actions have been successful. The BAP process completed a review of targets in 2006 and the lists of priority species have also been reconsidered in the light of current knowledge. The population trend information collected by the NBMP was used to inform both reviews to ensure that the correct bat species are covered by the BAP process and that targets set are realistic.

Monitoring approach

The main monitoring techniques employed by the programme are summarised in Table 1 below:

Table 1 NBMP survey details

Survey	Start year	Survey period	Site selection method
Pipistrelle Colony Count	1997	6th June - 25th June	Known roosts
Brown long-eared bat Colony Count	2001	6th June - 25th June	Known roosts
Serotine Colony Count	1997	6th June - 25th June	Known roosts
Natterer's bat Colony Count	2000	6th June - 25th June	Known roosts
Lesser horseshoe bat Colony Count (Welsh counts coordinated by CCW)	1998	29th May - 17th June	Known roosts
Greater horseshoe bat Colony Count (NE/CCW; coordinated by BCT since 2005)	1997	7th July - 21st July	Known roosts
Field Survey (noctule/serotine/pipistrelle)	1998	1st July - 30th July	Random 1km squares
Waterway Survey (Daubenton's bat)	1997	1st August - 30th August	EA River Habitat Survey sites
Hibernation Survey	1997	January/February	Known or potential hibernacula
Bats and Roadside Mammals Survey	2005	May - September	Self-selected 15km squares
Woodland Survey	2005	July - September	SAC sites for barbastelles plus other woodlands with suitable habitat

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. Monitoring sites where the species of interest is not present can help identify if populations are expanding into new areas.

Some species are monitored using more than one of the survey methods. As a general rule, trends from the Field Survey and Waterway Survey are currently considered most robust, followed by the Hibernation Survey, and then Colony Counts. For full details of survey methods, robustness of different techniques, and how the monitoring sensitivity is influencing the frequency at which individual sites are surveyed, see the NBMP Annual Report 2007.

Colony Count results are treated with caution for species that are known to regularly switch between different roosts as this behaviour has the potential to affect the trends. Common pipistrelles are thought to have the most mobile colonies whereas horseshoe bats tend to be very faithful to a specific roost. This is illustrated in the table below which shows the percentage of roosts for each species where "No bats present this year" has been recorded at least once on the NBMP database.

The Bats and Roadside Mammals Survey and the Woodland Survey have not yet produced enough years' data to enable delivery of trends and assessment of robustness.

Table 2 Relative roost fidelity for species counted at NBMP Colony Count sites

Species	No of roosts¹	No of roosts with status "No bats present this year" in at least one year²	Percentage
Common pipistrelle	346	72	20.8
Soprano pipistrelle	264	40	15.2
Natterer's bat	66	6	9.1
Serotine	67	5	7.5
Greater horseshoe bat	24	1	4.2
Brown long-eared bat	102	4	3.9
Lesser horseshoe bat	246	1	0.4

¹Roosts with a minimum of 5 bats for species with average roost size of <50 (serotine, Natterer's bat, brown long-eared) and minimum of 10 bats for species with average roost size of >50 (all other species) as smaller roosts are likely to be non-breeding roosts and therefore more mobile. Changes at these relatively small roosts are less likely to influence the species population trends.

²Figures exclude roosts known to have become unsuitable for bats

Species coverage

There is sufficient coverage to carry out robust statistical analysis on 11 resident UK species/species groups (Table 3). The difficulty in differentiating the two closely related Myotis species, whiskered and Brandt's bat, means that the data for these two species has been pooled for trend analysis and the trends assumed to be the same for both species, though further research is needed to verify this.

Table 3: Coverage of UK bat species by each monitoring method

Species	Colony Count	Field or Waterway Survey	Hibernation Survey
Greater horseshoe bat	B	-	B
Lesser horseshoe bat	A	-	A
Daubenton's bat	-	A	A
Brandt's bat	-	-	A
Whiskered bat	-	-
Whiskered/Brandt's bat	-	-
Natterer's bat	A	-	A
Bechstein's bat	-	-	C
Greater mouse-eared bat	-	-
Common pipistrelle	A	A	C
Soprano pipistrelle	A	A	C
Nathusius' pipistrelle	-	-
Serotine	B	A
Noctule	-	A
Leisler's bat	-	-
Barbastelle	-	-	C
Brown long-eared bat	A	-	A
Grey long-eared bat	-	-

Key:

A = encountered on more than 40 sites

B = encountered on between 10 and 40 sites

C = encountered on less than 10 sites

The following species are challenging to study and not yet incorporated fully within the NBMP. These species are now being targeted using new survey methods.

Bechstein's bat

This species has a close association with semi-natural woodlands but is difficult to survey for using standard monitoring techniques. The Bechstein's bat has a low intensity echolocation call, and tends to forage high up in the canopy; making it very difficult to pick up the bat's quiet calls on an ultrasound detector. This species is known to have very mobile, tree roosting colonies and is rarely encountered in hibernation sites.

A new survey technique has been developed which allows systematic surveying of this species for the first time. The technique uses an acoustic lure (the Sussex Autobat), to relay synthesized social calls of bats. Whilst holding territories, Bechstein's bats will respond to the Autobat, allowing them to be caught in a harp trap (Greenaway et al., 2001). This method is being used as the basis of a 3.5 year project (which began in September 2007) to assess the distribution of Bechstein's bat across its UK range and evaluate the potential for future population monitoring. This is an invasive technique and as such is conducted under a strict project licence. The protocol is designed to limit the possible stress and intrusiveness of the work. Click here for more information on the Bechstein's Bat Project.

Barbastelle

The Woodland Survey began with a pilot investigation into the feasibility of monitoring barbastelles at three woodland sites supporting known breeding populations in 2004. Two of these sites were special areas of conservation (SACs) and one was a national Nature Reserve (NNR). The feasibility study concluded that it should be possible to monitor breeding barbastelle bats, and also some of the other bat species that occur alongside them within woodlands, using frequency division/heterodyne detectors on walked transects. A National Bat Monitoring Programme Woodland Survey protocol was subsequently devised to trial at additional sites. The aim of the survey was also to try to find barbastelles in woodlands where they may not have been previously recorded.

In 2005 the woodland survey was tested more widely using a continuous walking transect methodology at the three sites included in the original study, along with an additional eight sites. Surveyors were asked to walk a looped transect through a woodland for approximately one hour in three separate survey periods between July and September. The heterodyne detector tuning was set at 32 kHz in order to pick up barbastelle echolocation calls and a simultaneous recording was made from frequency division to a recorder. Post-survey sound analysis was carried out for all species encountered.

For a summary of the first three years of this ongoing survey see the NBMP Annual Report 2007.

Nathusius' pipistrelle

The development of a broadband detector technique for surveying Nathusius' pipistrelle is being piloted as part of the expansion of the NBMP's coverage of UK species (more information on the Nathusius' pipistrelle survey page). Currently this species is occasionally encountered on the Bats and Roadside Mammals Survey. In a separate initiative, distribution data are collected and presented at http://www.nathusius.org.uk/.

Leisler's bat

In 2008 the Field Survey was modified for Northern Ireland so that Leisler's bat is monitored in place of noctule and serotine. The fact that noctule and serotine are not considered to be present in Ireland should make identification of Leisler's bat with heterodyne detectors fairly simple. Initial uptake has been limited but still an improvement on participation in the standard Field Survey in Northern Ireland, which suggests that making this survey more relevant to Northern Ireland has been at least partially successful, and further efforts to promote this survey there would be worthwhile. Elsewhere, investigation needs to be made into the extent to which Leisler's bat is under-recorded due to confusion with noctule and serotine as these three species are challenging to separate. Outside of its stronghold in Ireland, Leisler's bat is thought to be widespread and rare though locally common to the east of London, in the Derbyshire/South Yorkshire area, Dumfries and Galloway and the Isle of Man (BCT 2001). Significant breeding populations have also been recorded in Bristol, Kent, Suffolk, Oxfordshire, Sheffield, Essex and Worcestershire (Harris & Yalden, 2008). Elsewhere, the use of time expansion detectors has suggested that Leisler's bats are more common than noctules in parts of West Yorkshire (John Gregory, pers comm.) and South West London (Briggs et al, 2007). In 2007 the Bats and Roadside Mammals Survey produced 83 Leisler's bat records compared to 116 noctule records, which suggests that, within its range, Leisler's bat is reasonably abundant compared to noctule (Russ et al, 2007). Leisler's bat was recorded in 10 of the 17 counties included in the 2007 survey and was as commonly encountered as noctule in Kent, Avon and Cornwall. The employment of broadband detectors as standard on field surveys will increase the possibility of monitoring Leisler's bat, and steps to quantify the potential error associated with noctule/Leisler's bat misidentification may be useful.

Rare species

Grey long-eared bat and greater mouse-eared bat are too rarely recorded in the UK to allow analysis of population trends. Both species are represented in the NBMP by a few records from hibernation sites. In the case of greater mouse-eared bat, the hibernating male annually recorded at a site in Southern England is the only individual of this species currently known in the UK. The NBMP team collects ad-hoc records of rare UK species and also vagrants including Kuhl's pipistrelle, parti-coloured bat, pond bat and Savi's pipistrelle.

References

Bat Conservation Trust (2001) The UK's National Bat Monitoring Programme - Final report 2001. Bat Conservation Trust, London. DEFRA Publications, PB 5958A (available at www.bats.org.uk/pages/nbmp_reports.html)

Bat Conservation Trust (2007) The National Bat Monitoring Programme - Annual Report 2006. Bat Conservation Trust, London. (available at www.bats.org.uk/pages/nbmp_reports.html)

Briggs, P.A., Bullock, R.J. & Tovey, J.D. (2007) Ten years of bat monitoring at the WWT London Wetland Centre - a comparison with National Bat Monitoring Programme trends for Greater London, The London Naturalist 86, 47-70

Greenaway, F., Hill, D., & Fitzsimons, P.J.R. (2001) Bats of Ebernoe Common. Held by The Sussex Wildlife Trust

Harris, S. & Yalden, D.W. (ed) (2008) Mammals of the British Isles: Handbook, 4^th Edition. The Mammal Society, Southampton.

Russ, J., Briggs, P.A., Wembridge, D. (2007) The Bats and Roadside Mammals Survey 2007: Final Report on Third Year of Study. Bat Conservation Trust, London. (available at www.bats.org.uk/pages/nbmp_reports.html)