Glasgow & SW Scotland Butterflies

Scottish Natural Heritage have run a butterfly transect at Glasdrum NNR as part of the UK Butterfly Monitoring Scheme (BMS) each year since 1992 except for 1997. The BMS runs from the 1st week of April to the last week of September each year and each week is numbered from 1 to 26. From 1992-2002, the number of weeks surveyed was not high but the number of weekly visits since 2002 has been good (Fig. 1).

Figure 1 Number of weeks surveyed each year 1992-2009

Figure 2 Annual Totals of Chequered Skipper

The second important UK BAP species is Pearl-bordered Fritillary which is most common along the wayleave. 2009 was a reasonably good year for this species with a total of 15 (Figure 3).

Figure 3 Annual totals of Pearl-bordered Fritillary.

Figure 4 Maximum weekly counts of Mountain Ringlet

The other butterfly species which occur at Glasdrum are presented below in decreasing order of abundance.

Scotch Argus is the most numerous butterfly species despite having a relatively short flight period from mid-July to late September. This is a stunning butterfly when newly emerged but most individuals tend to look very worn and tatty by late August. The highest annual total was 1579 back in 1995 and 516 were seen in 2009 (Figure 5).

Figure 5 Annual totals of Scotch Argus

 The Small Pearl-bordered Fritillary is the second most numerous butterfly at Glasdrum and also has quite a short flight period occurring from mid-May to early July. The highest total of 433 occurred in 2005 and 146 were seen in 2009 (Figure 6).

Figure 6 Annual totals of Small Pearl-bordered Fritillary

The Speckled Wood is butterfly which has 2 or 3 generations at Glasdrum being found from late April  to September which results in high annual totals. The highest total was 239 in 2003 and 155 were seen in 2009 making it the third highest year (Figure 7).

Figure 7 Annual totals of Speckled Wood

Figure 8 Annual totals of Green-veined White

The Peacock is the commonest butterfly along the transect in April and early May and a second generation occurs during August and September. Figure 9 shows annual counts of Peacock along the transect and there were no records prior to 1998. There are two factors here. One is that April visits were not made during the early years of the transect and the second which is more influential is that the Peacock was quite rare in Argyll prior to 2000 but has become much more common since then. The 46 Peacock in 2009 is the fourth highest total.

Figure 9 Annual totals of Peacock

The Small Heath occurs at Glasdrum during May to July and the peak year was in 1998 with 67.  While numbers from 2004 to 2008 were quite high, the Small Heath population at Glasdrum crashed in 2009 for some reason (Figure 10).

Figure 10 Annual totals of Small Heath

Meadow Brown is found in low numbers along the transect in mid-summer. The largest number of Meadow Brown were found in 1992 and the 12 recorded in 2009 was the sixth highest on record (Figure 11).

Figure 11 Annual totals of Meadow Brown

Dark Green Fritillary is found in small numbers along the Glasdrum transect during mid-summer. The highest total of 26 occurred in 1995 and 2009 with 10 was joint 8th highest (Figure 12).

Figure 12 Annual totals of Dark Green Fritillary

Figure 13 Annual totals of Green Hairstreak

Orange Tip is a harbinger of spring at Glasdrum as well as other parts of the branch area but only occurs in small numbers. As it is a species of more open countryside and roadsides, only the odd one or two manage to get into the woodland glades at Glasdrum.  Also, the Orange Tip is a butterfly that is responding to climate warming and expanding northwards in Scotland and this trend is evident in the numbers since 1992 along the Glasdrum transect (Figure 14).

Figure 14 Annual totals of Orange Tip

A further five species have only occurred in a proportion of the years 1992-2009 and are shown in Figure 15. Small White has only been since in three years and has not been seen since 2000. Common Blue has been seen in eight years and in every year since 2003. The migrant, Red Admiral has been seen in seven years scattered across the 1992-2009 period and four were seen in 2009. Painted Lady has been seen in eight years and 2009 has of course been a good year for this migrant. Despite this, the 2009 total of just five is the second largest on record as 13 were recorded in 2004. Small Copper has been seen in every year since 2003. Small Tortoiseshell has only been seen twice along the transect, one in 1992 and another singleton in 2007. Marsh Fritillary has been seen just once in 1992 when two were spotted. And just one Grayling has been spotted at Glasdrum in 2007.

Figure 15 Annual totals of scarce species

Written by committee member, Andrew Masterman

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