Lullybeg Reserve Report
The Lullybeg transect was walked from April to the end of September and the results have been forwarded to the National Biodiversity Data Centre. The figures outside brackets refer to all butterflies counted on the site while figures inside the brackets are transect counts.
A total of 695 adult butterflies [1053 in 2010] were counted during a total of 25 visits [20 visits in 2010].
Cryptic Wood White=0
These figures illustrate a severe decline in population sizes in most species. The cold weather from May to late September is undoubtedly the major reason. The average temperature for the transect walks in 2011 was 15.64 degrees Celsius.
The main cause of concern during 2011 was the decline of the Marsh Fritillary on the site. We hoped that the great work done by Eamon Mulhall in removing tall scrub that was casting direct shade on the north bank of the Crabtree River and other scrub removal and grazing by Philip Doyle’s cattle would improve the Marsh Fritillary habitat and lead to an increase in the population but instead a dramatic decline has occurred.
Yet the season began with great promise with the mild and bright weather of February and March culminating in a gloriously sunny April that
provided excellent conditions for accelerated larval development. These conditions led to a record early emergence of the adults. The first 2 adults were seen on May 8th. This is the earliest date it has been recorded in the area since recording began here in 1995. However, the adults that emerged so early due to the weather during spring were now at a major disadvantage; a polar air mass led to prolonged cold with overcast conditions and bitter winds.
Fears for the population were added to by the autumn web counts. During the spring of 2011 17 larval webs were counted but during the autumn of 2011 only 5 webs were found. While this looks very alarming this reduction is mirrored elsewhere in Ireland. In 2009 81 larval webs were counted in Pollardstown Fen, County Kildare but only 4 were found there this autumn . In Clare, the Termon Marsh Fritillary larval nest count yielded over 60 nests while only 2 were found in September 2011. No webs were found on Dunshane Common; last year 39 larval webs were counted.
The collapse cannot be attributed to any changes on these sites; it is almost certain that the prolonged cold conditions that prevailed throughout the flight period in May, June and early July had a devastating impact. Several fresh adults were found on Lullybeg in the webs of Funnel Spiders and the higher than the usual predation recorded is likely to be due to the butterfly being unable to fly in the cold conditions. Prolonged cold weather makes grassland butterflies vulnerable to predation especially by arachnids. It is hoped that the population will see a recovery following what we hope will be more typical conditions in 2012.
The site continues to produce the unexpected; a Large Heath was recorded on June 20th.There is some Cottongrass on the site and perhaps the species might colonise the reserve. However its habitat in Ireland is wet, intact bogland. The Wall Brown continues to exist on the site but in low numbers. The individual seen in spring was a female found in suitable egg-laying terrain on steep, south facing sparsely vegetated banks of the silt pond.
The two other Lullybeg butterflies that have a threat category assigned to them on the Ireland Red List No.4 [a list published by the National Parks and Wildlife Service detailing the conservation status of Ireland’s butterflies] are the Dingy Skipper and Small Heath. Both are rated as “Near Threatened”. Both continue to thrive at Lullybeg with numbers of Dingy Skipper slightly up on 2010’s totals. In addition two species bucked the downward trend to show a huge increase on 2010’s totals; these are the Common Blue up from 42 to 81 and the Ringlet up from 94 to 185.These rises may be traced to habitat changes. The grazing and poaching of species-rich grassland containing the Dingy Skipper’s and Common Blue’s favoured larval foodplant [Bird’s-foot-trefoil] is a likely cause of the increase while the Ringlet was helped
by the removal of heavy scrub on the river’s south bank as this area contains the tall, lush grasses needed by the species. The Ringlet is also resistant to cool Irish summers and likes wet summers. In fact the butterfly will fly in light rain and hot dry summers do not favour it.
The rest of the reserve’s butterfly species saw declines. Cold weather means multi-brooded species are less likely to produce as many generations as are possible during favourable weather. Cold weather prolongs the length of the immature stages making predation more likely resulting in smaller numbers of individuals.
Another effect of prolonged cold is extending the flight period resulting in greater wear and tear and increased exposure to predation. The Brimstone and Peacock will feed later into the autumn when weather is poor because of the need to build up reserves for over-wintering. Both butterflies were active in October at Lullybeg but this is unusual. The Peacock usually disappears by mid-September and the Brimstone follows with the previous latest record for Lullybeg being September 20th. It is likely that numbers of Peacocks, Small Tortoiseshells and Brimstones will be lower during the coming spring.
The reserve is in excellent condition thanks to the efforts of our members, helpers from the Kildare Branch of BirdWatch Ireland and our partners Bord na Móna. During 2010 members cleared scrub on the southern area of the site and this was followed up by cattle grazing during September to remove ranker grasses and break up some turf to allow for germination of finer grasses and wild flowers. We are very grateful to Philip Doyle who supplied the cattle to enable our conservation work to continue and to Bord na Móna for their assistance especially Eamon Mulhall who assisted with the machine work we needed and Catherine Farrell, who liaises closely with Butterfly Conservation Ireland.