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Common pipistrelle trends for Scotland

Scotland-level population trends for common pipistrelle from the Field Survey and the Roost Count are shown on this page.

Population trends are also produced for common pipistrelle for Great Britain and England.


Field Survey

Scotland index of common pipistrelle population from Field Surveys

Common pipistrelle Field Survey trend Scotland

Note: The graph above shows the unsmoothed index value for each year (green crosses), the smoothed trend (solid line) and 95% confidence intervals (dotted lines). The smoothed trend for 2016 is shown as a dashed line to indicate that it is provisional.

The smoothed index is currently 19.5% above the 1999 base year value, equivalent to an annual increase of 1.1%. The smoothed index has fluctuated above and below the baseline, but at no point has it differed significantly from the baseline year due to the low precision associated with this trend. Overall there has been no significant change in the smoothed index since 1999. However the number of sites monitored by the Field Survey in Scotland is small and the level of uncertainty associated with the smoothed index is high, meaning trends for common pipistrelle in Scotland may be difficult to detect using data from the Field Survey.

Data from 76 sites contribute to the trend analysis in Scotland.


Roost Count 

Scotland index of common pipistrelle population from Roost Counts

Common pipistrelle bat roost trend Scotland

Note: The graph above shows the unsmoothed index value for each year (green crosses), the smoothed trend (solid line) and 95% confidence intervals (dotted lines). The smoothed trend for 2016 is shown as a dashed line to indicate that it is provisional.

The smoothed index is currently 63.3% below the 1999 base year value, equivalent to an annual decrease of 5.7%. There has been a significant decline in the smoothed index since 1999. However it is likely that this species' frequent roost switching results in a negative bias in the Roost Count trend (see Robustness of Monitoring) and this trend is not therefore considered a reliable measure of population change for this species. We are currently investigating the causes of this negative bias in more detail and exploring ways to correct it (see Developments and Future Directions).

Data from 64 sites contribute to the trend analysis in Scotland (sites surveyed in two or more years).


Return to Common pipistrelle population trends; Report home page; Contents page

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