Black Hairstreak (Satyrium pruni)
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© Nick Greatorex-Davies
In Britain the Black Hairstreak is a rare butterfly with a very restricted distribution. It is a sedentary and elusive butterfly of old Blackthorn (Prunus spinosa) scrub in woodland or on, or adjacent to, woodland edges. (For further details on this species see http://www.butterfly-conservation.org/).
Status details :
Status since 1995 is Stable with a decrease of -34.4%
Status over the last 20 years is Stable with a decrease of -17.2%
Status over the last 10 years is Stable with a decrease of -78.1%
Log collated index plot
This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in
populations from year to year, and is scaled so that the average index over the whole series is equal to 2
(horizontal line). For greater detail about how this index is derived, click on the green question mark above.
Trend description :
Although this normally canopy dwelling butterfly is recorded occasionally on transects, the transect method is not suitable for monitoring changes in its abundance. The species has been recorded on only 12 UKBMS transects to date and has only been recorded regularly on a annual basis at more than one site for the past ten years or so and reflects the restricted distribution of this species. The limited data shows that the Black Hairstreak has been increasing at monitored sites with superb counts in recent years such as 2010.
This map shows the distribution between 1995 and 2016. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway
This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.
This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.
In total, Black Hairstreak has been recorded from 65 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 10 sites, with an average index of 2 individuals per site.
For 6 of these sites, Black Hairstreak has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.
In 2016, 43 individuals were recorded from 8 sites, producing annual indices at 7 of these.
Links to counts
This map shows the trend in abundance at particular transect sites for which data has been received within the last five years. Trends (increasing, declining or stable) are assessed at sites where the species has more than five years of annual index data. Use the option boxes below to view plots for individual sites.
Links to lists of sites with particular statuses
|Stable sites (8)|
|Increasing sites (2)|