Glasgow & SW Scotland Butterflies

Glasgow & SW Scotland Branch Website

February 27, 2011

Light Trapping for Rannoch Sprawler at Loch Rannoch in 2012

Filed under: Moths — Andrew Masterman @ 1:14 pm
UPDATE 2012: Further survey work is planned for the weekend of 23-25 March 2012 to search for Rannoch Sprawler along the south-east quadrant of Loch Rannoch and to do some further survey work on the north side further away from the road and behind the MacDonald Loch Rannoch Hotel. If you would like to get involved, please email andrewmasterman@hotmail.com
 
RESULTS 2012: A total of 77 Rannoch Sprawler were obtained in 2012 during four nights trapping. The map below shows the trapping results for 2011.
In 2011, the result of the four nights light trapping at 19 different points was a total of 33 Rannoch Sprawler which were caught in seven different 1 km squares five of which were new.

In 2012, the result of four nights trapping at 29 different points was a total of 77 Rannoch Sprawler in eight different 1 km squares four of which were new.
 
These results show that Rannoch Sprawler occurs in at least 12 different 1 km squares at Loch Rannoch and sometimes occurs in large numbers. These are very positive results.
 
 
The first British specimen of Rannoch Sprawler was taken at Rannoch in the spring of 1854 and it is currently known from four different areas of Scotland: the Rannoch area; near Braemar; on Speyside; and in Glens Affric and Moriston.
Distribution of Rannoch Sprawler in Scotland
Distribution of Rannoch Sprawler in Scotland
The Rannoch Spawler is a large and impressive noctuid which occurs in two forms: a grey Speyside form and a reddy Rannoch form.
Grey Speyside form of Rannoch Sprawler on left and red Rannoch form on right. Credit John Knowler.
Grey Speyside form of Rannoch Sprawler on left and red Rannoch form on right. Credit John Knowler.
Butterfly Conservation commissioned survey work in 2010 on rare moths in the Rannoch area as part of the Moths Count project funded by the Heritage Lottery Fund and many other partner organisations. The results for Rannoch Sprawler are presented below.
The flight period of the Rannoch Sprawler is from March to mid-April when it can be caught using light traps or you can search for adults on the south side of the trunks of large birch trees during the day. Waring & Townsend Moths Field Guide suggests it can take as long as six hours to find one Rannoch Sprawler using this daytime search method. Daytime searches for Rannoch Sprawler on the south sides of the trunks of large birch trees were unsuccessful in 2010. While some distinguished Scottish Lepidopterists have been heard to lament the loss of traditional Lepidoptera methods such as searching the trunks of trees for moths during the daytime, there is such a thing as being a Luddite! In the case of Rannoch Sprawler, using a light trap is a much more efficient method than daytime searches of birch trunks and therefore the author is using this method in 2011 to confirm that Rannoch Sprawler is present in the areas of suitable habitat which were identified in 2010.
The habitat of the Rannoch Sprawler is mature open birch woodland with large trees. Waring & Townsend suggest that both downy and silver birch are used and that downy birch is used at Rannoch. However, the surveys in 2010 revealed that silver birch and not downy birch occurs at the sites of the historical records. The photos below show such silver birch habitat on the north side of Loch Rannoch and a close-up of the trunk of one silver birch tree which has large crevices and knobbly bits at the bottom.
Birch Woodland occupied by Rannoch Sprawler on north side of Loch Rannoch
Birch Woodland occupied by Rannoch Sprawler on north side of Loch Rannoch
Close-up of Silver birch trunk in woodland occupied by Rannoch Sprawler
Close-up of Silver birch trunk in woodland occupied by Rannoch Sprawler
The map below shows the areas around Loch Rannoch which were identified as containing suitable habitat for Rannoch Sprawler in 2010 plus the sparse historical Rannoch Sprawler records. The areas of apparently suitable habitat are large and light trapping across these areas is required in 2011 to confirm that Rannoch Sprawer is present. Click here for a Word document file containing this map which can be printed out and taken into the field.
Distribution of Rannoch Sprawler records around Loch Rannoch and areas of habitat.
Distribution of Rannoch Sprawler records around Loch Rannoch and areas of habitat.
Permission to use light traps in the shaded areas on the north side of Loch Rannoch has been obtained so there is an opportunity here to catch a very rare and spectacular moth if you have not already had the priviledge of recording this large majestic noctuid! If anyone is keen to bag the red ‘Rannoch’ form of the Rannoch Sprawler during the latter half of March when I plan to trap there over 2 or 3 nights, please email andrewmasterman@hotmail.com .
You can get a budget room for £43 a night for a mid-week stay at the Loch Rannoch Hotel , Kinloch Rannoch if you book online, or there are very scenic wild camping spots at the east end of Loch Rannoch at Kinloch Rannoch.
RESULTS Posted 1 April 2011
Trapping took place on the nights of 21, 22, 23 & 28 March 2011. Heath traps were placed at a total of 19 different points and Rannoch Spawler found at 12( 63%) of these random sites within suitable habitat. A total of 33 Rannoch Sprawler were caught in seven different 1 km squares, five of which were new 1 km squares for Rannoch Sprawler.
Eight and nine individual Rannoch Sprawler were caught in two traps on the 28 March 2011 suggesting that Rannoch Sprawler is very numerous at these sites around Loch Rannoch. However, the two squares above Kinloch Rannoch, NN6559 & NN6659 had both Silver & Downy Birch whereas the squares further west were dominated by Silver Birch. The habitat in these two squares seemed less good with fewer old Silver Birch trees and this was confirmed by the absence of Rannoch Sprawler at four trapping sites in NN6559 and at one of the trapping sites in NN6659. But overall, there is certainly large areas of suitable habitat for Rannoch Sprawler as well as large populations of the moth which is shown by the large trap totals at some sites.
Many thanks to Greg & Andy Fitchett for trapping over two nights with four Heath Traps and to Stan Campbell for attending.
Results of trapping for Rannoch Sprawler in 2011
Three Rannoch Sprawler caught in a Heath trap & placed on a Birch trunk
Three Rannoch Sprawler caught in a Heath trap & placed on a Birch trunk

February 13, 2011

Welsh Clearwing Surveys at Loch Rannoch 2011

Filed under: Moths — Andrew Masterman @ 3:29 pm

Welsh Clearwing is a spectacular moth which is a wasp-mimic and its UK stronghold is in Wales where it was first found at Llangollen in 1854.

Welsh Clearwing    Credit:  John Knowler

Welsh Clearwing Credit: John Knowler

Welsh Clearwing was first recorded in Scotland in the Rannoch area in 1867. There are scattered populations in Scotland: the Rannoch area; the Trossachs; Perth; and Glens Affric and Moriston.

Distribution of Welsh Clearwing in Scotland

Distribution of Welsh Clearwing in Scotland

Butterfly Conservation commissioned survey work in 2010 on rare moths in the Rannoch area  as part of the Moths Count project funded by the Heritage Lottery Fund and many other partner organisations. The results for Welsh Clearwing are presented below.

The easiest method of detecting Welsh Clearwing is by searching for exit holes on the south facing aspects of birch trunks. These exit holes which are created by the emerging adults can be numerous and may persist for many years. Searches for exit holes and pupal exuviae (the empty pupal cases which can sometimes be found protruding from the exit holes) increased the number of 1 km squares with Welsh Clearwing in the Rannoch area from seven to 16 which includes two new sites (Killichonan & Innerhadden) away from the previously one known site with Welsh Clearwing: Finnart on the south-west side of Loch Rannoch.

 

Three sites around Loch Rannoch where old Welsh Clearwing exit holes were found in 2010.

Three sites around Loch Rannoch where old Welsh Clearwing exit holes were found in 2010.

 

In Wales and Staffordshire, both Silver and Downy Birch are used (Graham, 2007) but in the Rannoch area, while both birch species are present, Welsh Clearwing exit holes were only found on Downy Birch. In the Trossachs too, Welsh Clearwing is only found on Downy Birch.

Aas and Riedmiller (1994) describe the bark of Downy Birch as “Red-brown at first, becoming greyish-white with brown or grey horizontal banding. Sometimes bark stays brownish even in large trees”. Their description of the bark of Silver Birch is “Shiny, reddish brown at first, later turning pinkish or white with pale grey horizontal markings and dark grey scales, with deep fissures and knobbly bumps towards base of tree”.  A Downy birch trunk riddled with Welsh Clearwing exit holes is shown below while Silver Birch trees tend to have larger crevices and are less horizontally banded.

Downy Birch trunk riddled with Welsh Clearwing exit holes.

Downy Birch trunk riddled with Welsh Clearwing exit holes.

Another difference between Silver and Downy Birch is the tree shape with Silver Birch generally being slender and taller up to 30 m high with branches angled sharply upwards and the outer branches curve downwards such that the foliage appears to elegantly cascade downwards. In contrast, Downy Birch are shorter up to 20 m tall with branches either angled upwards or more horizontal and they don’t curve downwards towards the tip giving the tree a much more compact and less attractive profile. However, both Silver and Downy Birch can hybridise with each other producing intermediate forms which are difficult to identify (Aas and Riedmiller,1994).

The two new sites with Welsh Clearwing exit holes present on Downy Birch trunks, Killichonan and Innerhadden, were discovered during nine random examinations of birch trees around Loch Rannoch. At one further site, only Downy Birch trees were found, but at the remaining six sites, only Silver Birch were present indicating that Silver Birch is dominant along large parts of the banks of Loch Rannoch.

Random sites around Loch Rannoch searched for Welsh Clearwing.

Random sites around Loch Rannoch searched for Welsh Clearwing.

 Given these results, it is unlikely that other new Welsh Clearwing sites will be found along the banks of Loch Rannoch but it is possible that Downy Birch may be present higher up the slopes above Loch Rannoch, so venturing away from the roadside might lead to new Welsh Clearwing sites. On the NBN gateway, there are two 10 km squares to the west of Loch Rannoch with historical Welsh Clearwing records (no specific details available) which need to be explored for presence of Downy Birch and Welsh Clearwing: NN35 and NN45.

Nine random sites around Loch Tummel were searched for Downy Birch and Welsh Clearwing but only Silver Birch trees were found so it is unlikely that Welsh Clearwing is present around Loch Tummel.

Raondom sites around Loch Tummel searched for Downy Birch and Welsh Clearwing.

Raondom sites around Loch Tummel searched for Downy Birch and Welsh Clearwing.

The map below shows the distribution of trees with Welsh Clearwing exit holes around Finnart found during survey work in 2010. New exit holes can be identified by their perfectly round shape and size (10 mm in diameter- see photo below) and fresh edges and a presence of a pupal exuvium (see photo below)  is also proof of occupancy by Welsh Clearwing in the current year. But in some of the 1 km squares below, only old exit holes were found which could mean that Welsh Clearwing is no longer present as these exit holes can persist from many years. Click here for a Word Document containing the Finnart map below which you can print out and take into the field.

Distribution of Downy Birch trees with Welsh Clearwing exit Holes at Finnart

Distribution of Downy Birch trees with Welsh Clearwing exit Holes at Finnart

A perfectly round fresh Welsh Clearwing exit hole.

A perfectly round fresh Welsh Clearwing exit hole.

A Welsh Clearwing pupal exuvium at Finnart on 30 June 2010

A Welsh Clearwing pupal exuvium at Finnart on 30 June 2010

Adult Welsh Clearwing are not easy to find (none found in 2010) but a Welsh Clearwing pheromone lure is available which makes finding adult Welsh Clearwing males easy in areas where they are present. This pheromone lure (termed SCO) can be pre-ordered before April from Anglian Lepidoptera Supplies and this is very effective at attracting male adult Welsh Clearwing during the flight period: late June to July.  Use of this pheromone lure is recommended for 2011 searches in those areas where only old exit holes were found in 2010. At Finnart, these are the following 1 km squares: NN5257; NN5455; NN5355: NN5224 and two further squares with birch woodland but which were not searched in 2010 need to be checked as well, NN5225 and NN5125.

A few new exit holes and one pupal exuvium were found at the first new site in 2010: Killichonan NN5556. At the second new site, Innerhadden, only old Welsh Clearwing exit holes were found so use of the pheromone lure is also required in square NN6657. The extent of this new site was not fully explored in 2010 so the 1 km squares either side also need exploring but it is suspected that these other squares only contain Silver Birch trees.  Click here for a Word Document containing the Innerhadden map below which you can print out and take into the field.

Welsh Clearwing exit holes present in Downy Birch at Innerhadden

Welsh Clearwing exit holes present in Downy Birch at Innerhadden

Welsh Clearwing is a rare moth only found locally at a few sites in Scotland (see Scottish Distribution map at the top of the page). However, it may be under-recorded to some extent, so if you visit the Rannoch area to familiarize yourself with the sort of open birch woodland it occupies and the appearance of the exit holes - trees with exit holes are common in areas in which Welsh Clearwing occurs  - you will be able to recognise potential new sites when you are out and about in the Highlands of Scotland.

References

Aas, G and Riedmiller, A. 1994. Trees of Britain and Europe. Collins Nature Guide.

Graham,A.N. 2007. Welsh Clearwing Synanthedon scoliaeformis on Berwyn, Montgomeryshire. CCW Contrct Science Report. Countryside Council for Wales, Bangor.

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