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Butterfly Season Report

It seems strange writing a butterfly report in early January when the onslaught of bitter westerly winds brings biting cold air and spiteful rain over Ireland. The species we have are hardy survivors well adapted to cope with our uncertain weather and this uncertainty was a major feature of 2011.

The record low temperatures at the end of 2010 left us early in 2011 and a benign January and February offered hope for a warm spring which duly arrived. A bright sunny March and a spectacular April followed. However this glorious weather ended early in May and a cold summer followed with the exception of 3 days of warm sunshine in early June. Only occasional sunny days occurred during June, July [an especially cold month] August and September. A period of good weather occurred near the end of the flight season at the end of September and early October with temperatures in the low twenties on some days. This allowed some species that over-winter as adults to feed up in advance of the coldest months.

The favourable spring conditions produced remarkable early records. One such record is a Pearl-bordered Fritillary on 14/04 with the previous earliest date recorded date in Ireland being 21/04. The first Dingy Skippers were reported on April 14/04 from Roscommon and Offaly. This species, like the Pearl-bordered Fritillary usually appears in May. The two species were still found in June because the cool conditions in May lengthened the flight period.

Other butterflies were reported emerging early; the Small Tortoiseshell [19/02], Peacock and Brimstone [21/02], Holly Blue [24/02], Comma [16/03], Green-veined White [22/03], Orange-tip [26/03], Small White [27/03], Speckled Wood [28/03], Wall Brown [10/04], Green Hairstreak [15/04; still on the wing in late July on Achill], Cryptic Wood White and Large White [17/04], Common Blue and Clouded Yellow [19/04], Small Blue [26/04, still abundant at Portrane in late June], Small Heath [29/04; usually seen later in May]. The earliest record to hand for the Wood White [leptidea sinapis] is 25/04 when 9 were seen at Gortlecka but it is most likely that the butterfly first emerged earlier in April.

The Narrow-bordered Bee Hawkmoth, a striking bee mimic, is usually seen later in May and in June but large numbers were seen on their sites during April with females already busy laying their eggs on Devil’s-bit Scabious.

The early spring records were followed on 8/05 with the Marsh Fritillary [late May is more usual].The latest recorded date for this fritillary was 9/07 [Fahee North, Clare]. Bizarrely, a Marsh Fritillary was seen in Britain in mid-September, two months after its flight period there should be over for the year.

However the cold summer put an end to most of the unusually early emergence dates. The Small Skipper was recorded a little earlier in 2011. It was first sighted on 29/06 when 4 males were seen. This is the earliest recorded emergence date for Ireland. The previous earliest Irish record is 02/07 in 2010.

The Large Heath was recorded first on 03/06 and this species is now mainly a June flyer. Past Irish records show a flight period from late June to mid-August while the flight period in Britain is given as “mid-June on most lowland sites…lingering well into August” [Thomas & Lewington, 2010]. In Ireland the Large Heath is found in numbers on its sites from early June and recent records suggest that its flight ends around mid-July.

The Meadow Brown was recorded first on 31/05, the Ringlet on 08/06 in Wexford, the Grayling on 09/07 near Ballyvaughan, County Clare and the Hedge Brown on 12/07 at The Raven, County Wexford. The Dark Green Fritillary was first reported on 06/06 at Brittas Bay, County Wicklow and it was still being reported in early September showing an extended flight period while the Silver-washed Fritillary was first recorded on 02/07 at The Raven, an exceptionally warm, dry site. The Essex Skipper was seen on 09/07 and the Purple Hairstreak was first recorded on 13/07.

July 24th was the first recorded date for the Brown Hairstreak; this date is not unusually early; on 26/07 in 2010 13 male Brown Hairstreaks were counted at Gortlecka, County Clare. The Brown Hairstreak is the last of the single-brooded butterflies to emerge but species that are multi-brooded will produce butterflies that emerge later.

These include the Small Tortoiseshell, Common Blue, Speckled Wood and others. The Small Tortoiseshell’s first generation flew throughout June and produced the next generation that appeared throughout August. Most will over-winter as adults but some of these will produce a third brood that become adult butterflies during October. It is impossible to distinguish second and third brood Small Tortoiseshells flying together in October but the third brood individuals are likely to have a fresher appearance.

The good weather late in the season produced surprises. Plenty of Silver Y moths, a migrant species were abundant in late September. Clouded Yellows arrived on the Wexford coast in numbers while a Queen of Spain Fritillary was recorded in Waterford on 18/10; the last Irish record of this continental butterfly was in 1960.

The recent arrivals, the Small and Essex Skippers and Comma appear to be doing well. The Comma, unlike the two skippers is not a colonial species so it is not usual to see large numbers in any one place [highest number recorded at one time in 2011 is 4] so the low numbers reported do not necessarily reflect its status. During 2011 the Comma was seen in March, April, July-October inclusive, all in County Wexford.

The first species recorded in 2011 was the Red Admiral on 12/01 and the second was the Painted Lady on February 12/02. The last adult butterfly seen during 2011 was the Red Admiral seen on 19/12. The Red Admiral was especially evident during August and September and in some warmer coastal areas may now be a permanent resident. Egg-laying is being reported along the Dublin coast late in the year and these appear to be surviving the winter. It is overwhelmingly a migrant from warmer areas in Europe and North Africa and most individuals leave our shores for these areas during August/September. Nonetheless it is interesting to note that the Red Admiral seems now set to be the first and last adult butterfly we see each year.

Finally, what species did well during 2011? Numbers of most summer butterflies were generally down but the Common Blue, Ringlet and Small Heath appeared in good numbers. The Small Copper appeared in good numbers but not in the abundance it enjoyed during 2010. From Clare [Sharon Parr] and Donegal [Bob Aldwell] come reports that the Dark Green Fritillary did well with reports from The Burren of huge numbers. Most butterflies were well down on numbers seen in 2010. The weather during the summer and autumn months is an obvious reason and a knock on effect into 2012 may be seen in lower numbers of Small Tortoiseshell, Peacock and Brimstone seen in spring because the numbers of these species that over-winter as adults will reflect 2011’s conditions. Recovery in population sizes will be achieved by warmer conditions. It should be borne in mind that fluctuations in population sizes are a response to a number of factors of which weather is important but the key factor influencing butterfly populations’ size and existence is changes in their habitats.

I thank everyone who recorded butterflies during 2011 with special thanks to David Nash and the excellent “butterflyireland” website run by the Dublin Naturalists’ Field Club.

Jesmond Harding 2012