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Survey coverage

UK site network

The total site network for all surveys completed up to 2016 is 6,330 sites. In 2016, 960 of our dedicated NBMP volunteers completed surveys at a total of 1,984 sites. (Site figures do not include Sunset/Sunrise Survey, as sites are less clearly defined for this survey.) This is a slight decrease on the number of sites surveyed in 2015 (-1.9%).

The map shows the distribution of all NBMP volunteers who took part in surveys in 2016.

Distribution of active NBMP volunteers 2016

We also encourage new volunteers to get involved in the NBMP by taking part in our Sunset / Sunrise Survey. In 2016, 161 Sunset/Sunrise Surveys were completed by at least 119 volunteers. Bats were recorded on 153 surveys (95%) and six bat roosts were located. Click here to view a map of Sunset/Sunrise site distribution in 2016.

Value of the volunteer contribution to the NBMP

In 2016 volunteers taking part in our four core surveys (Field Survey, Waterway Survey, Roost Count and Hibernation Survey) contributed approximately 17,700 hours of their time, representing an in-kind contribution to the NBMP of £264,760a. The equivalent cost of these surveys if they were undertaken by professional ecologists would be £653,332b.

Repeat sites

For the core surveys (Field Survey, Waterway Survey, Roost Count and Hibernation Survey), 1838 sites (93%) had been surveyed in at least one previous year (repeat sites). There was a very slight overall increase compared to 2015 when 92% of sites surveyed were repeat sites. 

Maximising the number of sites that are surveyed for at least two years is a priority for NBMP, as data from a site can only contribute to species trends once it becomes a repeat site.

The table shows the number of sites both in the network and surveyed in 2016 compared to 2015, and the levels of repeat survey sites for each survey type. Click here to view maps of the distribution of sites in the network for each survey type. Click on the survey or species names in the table to view maps of site distribution in 2016.

UK NBMP survey coverage 2016

Survey type No. sites in network 2016 Total sites surveyed 2016 Total sites surveyed 2015 % change in sites surveyed from 2015 to 2016 % repeat sites 2016
Field Survey 891 231 233 -0.9 93.9 
Waterway Survey  1370 333 344 -3.2 93.7
Hibernation Survey  1184 564 545 +3.5 96.3
Woodland Survey (barbastelle)  49 16  16 0

100

Roost Counts:     
Greater horseshoe bat 38 30 32 -6.3 93.3
Lesser horseshoe bat  357 193 187 +3.2 94.3
Common pipistrelle  628 194 219 -11.4 92.3
Soprano pipistrelle  484 164 185 -11.4 91.5
Unidentified pipistrelle sp. 757 73 76 -3.9 82.2
Natterer's bat  101 41 40 +2.5 92.7
Serotine  146 39 41 -4.9 97.4
Brown long-eared bat  221 69 75 -8.0 97.1
Other species 104 37 30 +23.3  64.9
 All surveys 6330 1984  2023
-1.9 93.4

Country level site networks

The NBMP produces trends for Great Britain and at country-level where sufficient data are available. Reporting of trends at country level is possible providing the sample size is sufficient. Power analyses were completed for the NBMP in 2001, and from these it was recommended that a core of 30-40 sites need to be surveyed annually for any given survey to provide sufficient data for trends to be calculated that will detect changes in populations effectively (BCT, 2001). More recent power analysis has indicated that the sample size needed can vary between each species and survey. However, we use 30-40 sites as our initial target number of repeat sites at each geographical scale. Further power analysis would need to be carried out in order to more precisely assess the sample size needed at the country or regional scale for each species and survey method.

For more information on detecting population changes, click here.      

The table below provides further information on survey coverage in 2016 at a country level. Country level trends are calculated where sufficient data were available and are included in this report. We are exceeding our basic target of 30 repeat sites in England for all surveys except for the greater horseshoe bat Roost Count. In Wales, we are exceeding this target for the Hibernation Survey and the lesser horseshoe bat Roost Count. In Scotland we are exceeding this target for the Waterway Survey. A power analysis commissioned by Scottish Natural Heritage further demonstrated that the trend for Daubenton's bat estimated from Waterway Survey data and the trends for common and soprano pipistrelle estimated from Roost Count data had low or medium levels of sample error and could therefore be considered statistically robust (although not necessarily free of bias, see Robustness of Monitoring). These trends are included in a Trend Note published by Scottish Natural Heritage in 2015. Here we present additional Scottish trends for common and soprano pipistrelle estimated from Field Survey data. Of the survey methods used to monitor common and soprano pipistrelle, the Field Survey is considered to most reliably reflect the underlying population trend. However the number of Field Survey sites monitored in Scotland is small and therefore the confidence intervals associated with these trends are wide, reflecting a high degree of uncertainty. Increasing the number of Field Survey sites monitored in Scotland in the future is a priority. Samples sizes in Northern Ireland are currently too small for any species trends to be calculated. 

Country level NBMP survey coverage 2016

Survey type England Scotland Wales Northern Ireland Channel Islands
Field Survey 200 (189) 18 (16) 8 (7) 1 (1) 4 (4)
Waterway Survey 249 (237) 35 (33) 19 (15) 30 (27) 0
Hibernation Survey 398 (381) 25 (24) 141 (138) 0
Roost Counts:          
Greater horseshoe bat 30 (28) - 5 (5) -
Lesser horseshoe bat 80 (72) - 113 (110) - -
Common pipistrelle 150 (140) 22 (20) 22 (19) 0
Soprano pipistrelle 111 (102) 26 (24) 21 (20) 6 (4)
Pipistrelle sp. 56 (47) 10 (8) 4 (3) 3 (2) 
Natterer's bat 37 (34) 3 (3) 1 (1) 0
Serotine 38 (37) - 1 (1) -
Brown long-eared bat 51 (49) 11 (11) 5 (5) 2 (2)
Total for all surveys 1400 150 340 42 4

Note: no. of repeat sites in brackets

a Volunteer contribution calculated using the daily rate given for unskilled and skilled volunteers by the Heritage Lottery Fund in their application guidance (Dec 2013), and assuming a 7.5 hour day.

b Equivalent professional contribution calculated using the mid-point of the daily rate range for an Assistant Ecologist (lowest level of experience) and Ecologist given by CIEEM in the guidance to members, and assuming a 7.5 hour day.

 

Survey coverage maps

These maps show survey coverage of core NBMP surveys in 2016 and the overall site network for the following surveys:

Field Survey

Distribution of Field Survey sites 

231 sites were surveyed in 2016 (shown in red), representing 25.9% of the total Field Survey site network (other sites in the network are shown in yellow).

Field Survey site coverage

For more detailed maps showing which species were recorded at Field Survey sites in 2016, click here.

Waterway Survey

Distribution of Waterway Survey sites 

333 sites were surveyed in 2016 (shown in red), representing 24.3% of the total site network (other sites in the network shown in yellow). Northern Ireland sites are from the All-Ireland Waterway Survey, run by Bat Conservation Ireland, and funded in NI by the Northern Ireland Environment Agency.

Waterway Survey coverage
For a more detailed map showing sites where Daubenton's bat was recorded in 2016, click here.

Hibernation Survey

Distribution of Hibernation Survey sites 

564 sites were surveyed in 2016 (shown in red) representing 47.6% of the total site network (other sites in the network are shown in yellow).

Hibernation Survey site coverage
To see more detailed maps of 2016 Hibernation Survey results by species, click here.

Roost Count

Distribution of all Roost Count sites

A total of 840 sites were surveyed in 2016 representing 29.6% of the site network. 

Roost Count site coverage
Maps showing the distribution of Roost Count sites surveyed in 2016 by species can be found here.

 

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