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Butterfly Season Report 2015

BUTTERFLY SEASON REPORT 2015

The Butterfly Season Report 2015 presents a view of the abundance of butterflies during 2015 relative to previous seasons, based on data received from recorders, mainly those who sent their records to Butterfly Conservation Ireland, but also based on records on the Butterflyireland website run by the Dublin Naturalists’ Field Club. A major influence on butterfly populations is weather conditions during the main butterfly flight season (March to October). The following overviews from Met Éireann provide a snapshot of conditions during 2015. Spring (March, April, and May) is described as “cool everywhere, wet and sunny in most parts.” Sunshine means that butterflies can be active especially in sheltered habitats that heat up in direct sunlight. Summer conditions (June, July and August) are summarised as “cool everywhere, wet and windy in most parts” with “summer mean temperatures all below average.”  There were some sunny and warm days especially in June and in early July but this did not persist and overcast conditions mainly prevailed.  While many reports of butterflies were received during these months, few were of high numbers. Autumn (September, October and November) is described as “drier, windier and milder than normal in many places.” Bright, settled weather resulted in regular sightings being reported until early November.

While a range of factors such as parasitism, conditions on the continent that influence migration and land management affect butterfly populations, weather has the most obvious influence. The vagaries of our weather deliver differing experiences of butterfly numbers from year to year and within a year. Good weather early and late in the flight season produced an impression of high numbers because common conspicuous species fly then. Small Tortoiseshells, Peacocks and Speckled Woods were abundant in April and September.

However below average summer temperatures produced an unspectacular year. Nevertheless, there were more reported sightings of some species than in 2014. The Large White fared better in 2015; following a collapse in previous years its parasites declined too allowing the butterfly to increase. Cryptic Wood White, Small White and Green-veined White showed increases on 2014 records. The Brimstone was also prominent in records. Wood White records were few but low recording levels are implicated. The blues and hairstreaks showed in reasonable and low numbers respectively. The Dingy Skipper, mainly a spring butterfly, did well. Small Skippers continue to be found in Kildare but in much lower numbers than 2014. Essex Skippers were reported from Wexford and Kildare but not in large numbers.

The fritillaries appear to have fared well; reports from the Burren suggest that the Pearl-bordered Fritillary, no doubt assisted by the sunny April, had a good showing on transects there. The Silver-washed Fritillary generally appeared later than in previous years, its emergence probably delayed by the cooler conditions. It is noticeable that its flight season was more prolonged in 2015 with late records in mid-September, when in some warmer summers late August marked the end of its flight season.  Dark Green Fritillaries were numerous in the Burren, with over 100 counted along a kilometre of track in Clooncoose, County Clare on 5 July. Marsh Fritillary numbers varied according to site location. At the dunes on North Bull Island and on warm, dry limestone grassland at Collure, beside Lough Derravaragh the butterflies appeared in high numbers but on wetter inland sites numbers were much lower.

The brown butterflies which fly mainly in summer appeared in lower numbers than in the previous two years. The Ringlet did well, but records of high numbers were fewer than 2014. A very interesting illustration of the impact of habitat management on butterfly populations comes from Newbridge Park, County Dublin on a transect monitored by John Lovatt; an area of sward allowed to grow wild in Newbridge Park, County Dublin yielded 754 Meadow Browns on 15 July 2014; the same area, but cut in June 2015 yielded only 33 on July 25 2015!  The Meadow Brown performed similarly to the Ringlet overall. There are very few Grayling records in recent years, including 2015, and it needs to be looked for in 2016, to see if it is in trouble. It favours dry, free-draining rocky and sandy terrain with sparse vegetation with fine-bladed grass species, such as Sheep’s Fescue and Red Fescue. It is chiefly a coastal dune inhabitant (here Marram Grass is recorded as a host-plant) but inland it can be found in quarries, on rocky areas even near bogs and on limestone pavement. The Wall Brown which favours similar habitats continues to appear in low numbers; we await a recovery. Since the 1980’s it appears to have retreated to its optimal habitats. There were few Large Heath records reflecting reduced recording. The Small Heath had quite a good year with most reports from late May to late July and few records after early August. (Note: the brood structure of the Small Heath is complicated, may not be well understood in Ireland and may have changed since the 1980’s. Its recorded flight period in 2015, 21 May to 18 September may represent two overlapping generations while individuals seen in September might be a partial third generation arising from eggs laid in May). It was another poor year for the Hedge Brown (Gatekeeper) with low numbers and few records. Its status must be a concern and there appears to be no obvious reason why it has remained so restricted in its Irish range while it has spread northwards in England. Indeed, it may be retreating from the northern limits of its Irish range (in August 2013 and July 2015 it was not found at Old Bawn (Newtown), south of Cahore Point, County Wexford where it was recorded by this author in the late 1990’s and early 2000’s)

Migrants mainly disappointed; there were many Red Admiral records but few Clouded Yellow and Painted Lady sightings despite predictions of abundance for the latter.

A highlight of 2015 is the expansion of the Comma, a colonist. The Comma’s advance in its south-eastern strongholds in Wexford and Carlow continues. It appears to be strongly double-brooded promising a steady spread. Keep an eye on your nettle patch, Buddleia and Ice Plant for its lovely scalloped outline and the deep orange/brown upper-side colours found in the second brood flying from September.

An important new report, The State of the UK’S Butterflies 2015, has just been published by Butterfly Conservation and the Centre for Ecology and Hydrology. The survey schemes used to count butterflies are the UK Butterfly Monitoring Scheme (UKBMS) and The Butterflies for the New Millennium (BNM). The UKBMS uses transect counts, timed counts, egg and larval web counts to assess trends in butterfly abundance (population size). The BNM recording scheme gathers butterfly sightings from recorders (similar to the BCI website records).This scheme comprises over 11 million records from 1690 to today, with 2.97 million obtained in the most recent survey (2010-2014). These are used to track changes in occurrence (distribution). The impressive amount of data and the analysis models used suggest that the findings must be taken very seriously and the findings corroborate much of what is stated above, even though our review covers only 2015 and is based on a relatively small number of records. Thus, the decline of the Hedge Brown in Ireland reflects the findings of UK abundance surveys; between 1976 and 2014 the UKBMS recorded a 41% decline in abundance. Between 2005 and 2014 this figure is -44%. This is despite an increase in distribution in the UK (15% from 1976-2014 but just 1% from 2005-2014, suggesting that its expansion has fizzled out). The Hedge Brown is a wider countryside species in the UK but is described in the report as a butterfly “that seems to be faring particularly badly.” While it appears that climate warming has allowed it to spread northwards and increase the area of its distribution, it has declined in number. The decline in population of this grassland/scrub edge species could be the result of habitat loss/change and other less obvious changes, such as increased presence of nitrogen in rainfall or in surface runoff from fertilised areas especially arising from heavy rain.

Interestingly, other species in the UK in decline in both population size (abundance) and distribution (occurrence) include the Small Blue, Green Hairstreak, Brown Hairstreak, Marsh Fritillary, Wall, Small Heath and all of these showed in lower numbers in Ireland in 2015, and in recent years. Furthermore, some species that are thriving  in the UK, such as the Silver-washed Fritillary, are performing well here too, suggesting overall a good deal of similarity in what is happening to  butterfly populations in the UK and Ireland.

In order to be more certain of the fortunes of our butterflies in Ireland we need more records. Please send, and continue to send us your records. Send these to conservation.butterfly@gmail.com

Let us know:

your name/s,

date of find,

species found,

the life stage/s found,

numbers seen,

location the butterfly/moth was found (e.g. townland name, site name, county), six figure grid reference, including the letter identifying the 100,000 metre grid square in which the location lies (see http://www.gridreference.ie/ or Discovery Series maps),

weather conditions

and any other interesting comments you wish to provide.

Example: John Smith ( 14/06/12). 14 Small Blues, 15 Small Heaths, Portrane sand dunes, O254515, County Dublin. Small Blues feeding on Kidney Vetch and Creeping Thistle. Sunny, light breeze, 18 Celsius.

Finally, we thank everyone who recorded butterflies from 2012-2015 who made this report possible.

References

Butterfly Conservation Ireland (2015)2013-2015 Records. Butterfly Conservation Ireland. Online at:  http://www.butterflyconservation.ie/wordpress/?page_id=1978. Accessed 19 December 2015.

Dublin Naturalists’ Field Club (2015) Records. Dublin Naturalists’ Field Club. Online at:

http://www.butterflyireland.com/RECORDS.aspx Accessed 19 December 2015.

Fox, R., et al (2015). The State of the UK’s Butterflies 2015. Butterfly Conservation and the Centre for Ecology and Hydrology, Wareham, Dorset.

Met Eireann (2015) Season Reports 2015. Met Eireann. Online at: http://www.met.ie/climate/monthly-weather-reports.asp Accessed 19 December 2015.

EVENTS REPORT 2015

Please see website for reports of our outings in 2015.