August 2018 has returned to us the more typical Irish summer conditions but the heat earlier in the summer means that there are high numbers of butterflies flying now, which developed quickly in the warm weather that prevailed during the immature life stages. One very important butterfly flying now and during September is the Wall Brown, a butterfly that has seen a marked decline in distribution and range in Ireland since the mid-1980’s. Before the mid-1980’s it was found throughout Ireland in the general countryside but is now mainly restricted to the most free-draining, driest, thinly-vegetated areas such as sand and gravel quarries (probably also found in dimension stone and aggregate stone quarries ), sand dunes, dry coastal heaths, rocky areas such as limestone pavement, dry limestone and acid grassland and the driest areas of cutover bogs. It is absent from many areas inland that it occupied in the past, such as along tracks worn to bare earth on farmland, dry hedge banks and lanes and at the edge of country roads edged by stone walls. It is feared extinct in Northern Ireland where it was last recorded at a coastal site in County Down in 2015. It remains numerous in County Donegal, where, according to excellent recorders, there has been no decline.
The Wall Brown may return to the broader countryside as it is a mobile butterfly and can fly great distances when the urge to move exists. We include two photographs of this lovely butterfly. It is often seen in low numbers but occasionally a dozen or more will be seen concentrated in an area of suitable habitat. It is a sun-loving butterfly. Males are eye-catching. If you see one, he will usually be seen flying low ahead of you, landing periodically to bask against bare surfaces. It holds its wings in a shallow V as it flies. After flying along a track or a stone wall for many metres, it will often turn and fly back, pausing to bask briefly before resuming its patrol. When direct sunlight is dimmed by cloud, the butterfly lands and basks briefly before closing its wings. It is only then that a close approach is usually possible. The female looks similar but is paler overall and does not have the dark brown diagonal band across the upper side of the forewing. Note the presence of white-pupils on black eye-spots. The presence of eye-spots shows its membership of the Satyridae or the “Browns” (regarded by taxonomists as a subfamily of Nymphalidae which includes the fritillaries and vanessids). Other members of the subfamily Satyridae include the Meadow Brown and Speckled Wood.
The Wall Brown shows a similar decline in Britain. It is presumed extinct in Surrey, for example, a southern county that holds many sites containing apparently suitable habitats. Box Hill was one of the last Surrey sites it survived on, and the site continues to hold well-drained, sparsely vegetated grassland one associates with the butterfly. It is the mystery of its decline that adds to the alarm as we have no idea what measures are needed to help it to recover. If you see one on your walk along a country road, on your ramble through flower-rich sand dunes, a cliff walk or anywhere else please let us know, according to the details we need for a valid record; for what is needed please check our website here: https://butterflyconservation.ie/wp/records/
Biodiversity Ireland Issue 17 Spring/Summer 2018 published by the National Biodiversity Centre contains an article by Dr Tomás Murray promoting butterfly recording for the Butterfly Atlas 2021.
The article contains this bleak statistic of Ireland’s declining butterflies: “Ireland (is) identified as being in the top five countries for declines in both widespread and specialist species, out of 21 countries assessed”.
It continues: “For the 15 species where we have sufficient information, our monitoring schemes reveal that seven of those species are in decline compared to three increasing, two stable and three that are too variable to assess”.
Is it that bad?
From what I see on sites I visit regularly, and from parts of the countryside I see from time to time, there are changes in butterfly populations. Without even attempting any population monitoring, it is clear that butterfly populations have undergone significant changes. This is evident when observing the changes in land use. Habitat specialists, in particular, are unlikely to survive for long in areas where their habitats are altered or destroyed by being replaced by golf courses, built on, afforested, drained, mined, cleared, modified by application of chemical fertilisers, ploughed and re-seeded, etc. In habitats not directly altered or destroyed, butterflies can be affected by gradual changes, especially by successional changes in vegetation and by changes to adjoining land such as flooding, drainage, tree-felling or tree-planting, planting of invasive plant species (such as cotoneaster) and other alterations. Natural factors such as coastal erosion, severe in some areas, results in changes to habitats and sometimes to the destruction of high-value conservation land.
It is easy to be pessimistic for the future of our butterfly populations, especially about our habitat specialists. My recent visit to the area south of Lough Corrib, County Galway engendered much despondency in me. This area, north of the N59 towards Lough Corrib between Moycullen and Oughterard contains a variety of habitats, especially bog, calcareous grassland, limestone pavement, scrub and woodland. A number of important habitat specialists have been recorded from the area. These include the Brimstone, Dingy Skipper, Brown Hairstreak, Small Blue, Pearl-bordered Fritillary (in the 1980’s), Marsh Fritillary and Large Heath.
On my visit, I encountered many new, often out-sized individual houses (with boundaries starkly proclaimed by laurel and Leylandii hedging) imposed on what appeared to have once been great habitat. I observed peat being gouged out of the bogs, parts of which have been converted to fairly unproductive agricultural grassland. Rough walls, composed of natural limestone pavement and boulders ripped from rare karst habitats are frequent in the area. It appears that few areas of untouched limestone habitat remain. In one area I examined off the local road from the N59 to Carrowmoreknock, bog grades into limestone grassland, limestone outcrops and scrub habitats. Flowers characteristic of grassy bog and limestone grassland almost have their petals touching. But the limestone pavement that once existed is no more, the limestone slabs torn up to form monumental walling. The area has clearly lost some value. It is likely that Grayling and perhaps even Pearl-bordered Fritillary flew here, but no longer. However, clearing the limestone pavement appears to have rebounded on the farmer, as that area is now buried in dense scrub. Marsh Fritillary breeds on the sward where bog grades into limestone grassland, quite likely assisted by the livestock grazing taking place.
When special habitats like these are degraded or destroyed despair deepens, as the count of precious places with their associated butterflies decreases. Once limestone pavement is ripped up, there is no chance of restoration. The habitat is gone. There are species that will not survive when this damage is done. There will be no return.
Some habitats of special character are designated as Special Areas of Conservation and therefore legally protected. However, the Special Area of Conservation that lies west of Carrowmoreknock, Gortnandarragh Limestone Pavement, has been damaged by quarrying and conversion of part of the area to farmland. Protection clearly needs to be enforced! Even when sites are protected they are sometimes unmanaged leading to undesirable successional changes in the vegetation, causing habitats to deteriorate. In the circumstances outlined above, it is easy to see that habitat specialists are likely to be in decline, and why.
What about the general countryside butterflies, the ones that breed in a broad range of habitats? Even a glance at the general farmed landscape suggests evidence for declines. Many semi-natural grasslands formerly very rich in butterflies are ploughed and re-seeded with one or two grass species and heavily fertilised. Some remaining semi-natural grasslands are heavily dosed in fertiliser annually, resulting in a habitat that excludes many of the food plants butterflies and moths need. Some semi-natural grassland has been ploughed up and planted with non-native conifers. Hedges and hedge banks are severely cut or even removed. Ponds and wet areas are drained or farming ceases, and formerly good habitats that were well managed by rough cattle grazing deteriorate. The inappropriate management of our public spaces, such as parks and canal banks where vegetation is cut when butterflies are feeding and breeding are further examples of drivers of decline. Given these grim circumstances, why are some butterflies doing well?
Firstly, let consider the species that are showing increases in population size (abundance) and in distribution (area occupied). Based on my observations, the resident species that I believe are showing increases in population size and distribution are Cryptic Wood White, Brimstone, Holly Blue, Peacock, Comma and Silver-washed Fritillary. The Speckled Wood is likely to be stable or possibly increasing. While the article quoted above mentions that three species are increasing, I believe that six species are increasing. Interestingly, all of these are found in woodland and woodland edges but other habitats are used by some of these butterflies. Wooded areas are increasing in Ireland. Some are arising from the abandonment of farming, some are planted, some existing woods are spreading and some woodland is new, developing on cutover bogs and on limestone pavement.
To take each of these butterflies in turn, the Brimstone is benefitting from the development of its larval food plants on cutover bogs. The food plants are developing in areas that used to be wet raised bogs and the spread of the butterfly into these areas suggests a genuine increase in distribution. The development of scrub containing the Brimstone’s food plants on eskers, rough hillsides, abandoned quarries and on limestone pavement is also helping the butterfly.
The reasons for the Holly Blue’s increase are harder to assess. It was, before the 1990’s, largely restricted to old woodland near the coast in Ireland but has spread inland to hedges, wooded lanes and even rural gardens, although it was found in large urban gardens before the period of expansion. The increase in woodland is likely to be a factor but a warming climate is likely to be more significant. In Britain it is very rare or perhaps absent from Scotland and rare in Northern England, reflecting its sensitivity to cooler climates.
The Peacock has probably benefited from the increase in warmth too, suggested by its increase in a cooler Northern Ireland which has been ongoing since the mid-1990’s. It is still found in smaller numbers there than further south. The increase in nitrate fertiliser usage over the past few decades benefits its larval food plant, the Stinging Nettle, which may be more vigorous, numerous and nutritious as a result. The Comma, a recent and continuing colonist, is likely to be benefiting from the same factors as the Peacock. There may be additional factors behind the Comma’s rise. It may have developed a preference for use of the abundant Stinging Nettle as a larval food plant, rather than relying on plants such as Hop, which is rare in Ireland.
The Silver-washed Fritillary is a woodland butterfly, breeding on violets growing in well-lit woods. When plantation forestry is cut down, the non-crop tree species are frequently left to grow among newly sown sapling trees, ensuring that woods are not clear-felled and that some shade remains. The light admitted after decades of darkness may make some of these areas suitable for the Silver-washed Fritillary especially a few years after re-planting. Edging conifer plantations with native trees may create habitat, even if this is simply a thin belt of woodland adjoining the arboreal slums of mature, modern non-native coniferous plantations. Even when plantations do not have a cosmetic band of native broadleaf trees added, a scattering of willow and birch seed often germinates along the edges, with Silver-washed Fritillary habitat developing over the following two decades. The growth of tall scrub and trees on abandoned farmland creates habitat too. The butterfly is turning up in the new semi-natural woods colonising the cutover bogs and tall scrub on limestone pavement. Some of these areas now boast large and extensive populations. In addition, some conifer plantation woodland planted on bogs develops poorly, with some trees dying after 20-30 years, leaving gaps that open up the ground to light and suitable vegetation. The dark cloud cast by the demise of Large Heath’s wet bog habitat is the Silver-washed Fritillary’s silver lining.
The Cryptic Wood White loves to fly and breed along sunny herb-rich wood edges, so is in its element along the access tracks through woods and along the edges of new wooded areas. The fact that it looks superficially like some other white species may result in it being under-recorded, but I believe it is doing well. It even shows up in my garden!
To guess which species are in decline is depressingly easy. I will mention a few here. The Dark Green Fritillary cannot be doing well in its main habitats. Its preferred habitat, unfertilised flower-rich grassland is quite rare now outside the coasts. For the same reason, Dingy Skipper, Small Blue, Common Blue, Small Heath, Wall Brown and many other semi-natural grassland dwellers must be in trouble. There are likely to be additional reasons for the fall and fall of the Wall Brown but these are not clearly understood.
However, we need hard data. My observations do not count without robust, scientifically reliable statistics. The records being sent to Butterfly Conservation Ireland from 2017 to 2021 will be used along with records collected by Butterfly Conservation Northern Ireland and the National Biodiversity Data Centre to compile an All-Ireland Butterfly Atlas in 2021. Please send us your butterfly records. We explain how to do this here: https://butterflyconservation.ie/wp/records/
We have images of all Ireland’s butterflies here to help you identify our butterflies: https://butterflyconservation.ie/wp/gallery/
The other measures you can take concern habitat protection and habitat development. Report any damaging activity you see taking place on any protected site to the National Parks and Wildlife Service. Insist on receiving information on how your concerns are followed up. The full list of Special Areas of Conservation and Special Protection Areas are here: https://www.npws.ie/protected-sites.
The data you send us will be used to create the Atlas and to update the Ireland Butterfly Red List, due to be updated in 2020. Armed with this data, we will be able to press the state for better protection and management of our landscapes so that there will still be some wildlife-rich areas for you and your children to enjoy and for our butterflies and moths to live in.
August is a busy month on the reserve at Lullybeg. Some butterfly species are busily feeding as adults or as larvae, racing to feed up for the winter. Other species are feeding to build reserves for migration or breeding. Individual adult butterflies of some species can either over-winter as adults or breed now (Small Tortoiseshell) while other species may breed now or prepare to migrate (Red Admiral). The potential for this flexibility may depend on a range of circumstances (such when the adult emerged) and conditions (weather, the condition of the larval food plant, etc). These complications and possibilities add variety and interest, and the observer can scan for clues as to the strategy used by species that have the capacity to be flexible. These clues will be seen in the behaviour. Are the male butterflies concentrating on feeding or on establishing territories and pursuing potential mates? Are females focussing on feeding or fluttering around the larval food plants?
For an example of a butterfly that can be flexible in its approach at this time of year, let us look at the Small Copper. The second generation of this species is flying now. This elegant little butterfly is now breeding. Some of the butterfly’s offspring may, if sunlight, temperature and food plant quality are suitable, become adult butterflies this year. These will fly in late September and in October. If the conditions do not allow for a third generation of the Small Copper or are marginal, most or all of the autumn larvae will endure winter hunkered down deep in the vegetation to resume feeding when spring arrives. These will reach the adult state next May or early to mid-June. I counted eleven of these sparkling starlets on the reserve today, a good tally for a butterfly usually recorded in low single figures.
Several butterfly species have their entire population in the larval stage now. The Marsh Fritillary butterfly is strengthening its population at Lullybeg, with 31 larval nests found on the reserve so far. I watched larvae feeding today, some outside their webs, nibbling in unison at the upper epidermis of the leaves of their sole food plant, Devil’s-bit Scabious. Some larvae are in their first instar while others have moulted their skins once to reach the second instar. The larvae may need to reach a healthy weight before their final moult later in autumn when they reach the fourth instar. Some species will not survive winter unless the larva reaches a certain instar before cold weather bites. The Speckled Wood is an example of this urgency. I suspect that the Small Heath larva must also reach a certain stage before winter if it is to survive.
Some butterflies don’t have these worries. The last Dark Green Fritillaries of the season was probably the tattered trio I saw on August 3rd. Their larvae, and the larvae of its bigger cousin, the Silver-washed Fritillary, hatch after two weeks, consume the eggshell and hibernate. The larva fasts for at least seven months before seeking violets to feed on. However, the larvae do have some concerns. They must not be discovered by birds, beetles or spiders. They must hope that their mothers placed them in the best conditions for over-wintering and feeding when the time comes. For the Silver-washed Fritillary, the egg-site is a cool, shady spot on a tree trunk, often on moss or half-hidden by ivy or in a crevice in a tree trunk. The Dark Green Fritillary lays her precious egg among dense, cool grass tufts with violets close by or among the tangle of grass. The cool conditions are chosen so that the tiny unfed larva does not shrivel in the August and September heat.
Life is simple for Brimstone butterflies. Feed up. That’s all they need to do. There is no complicated multi-brood strategy for our longest-lived adult butterfly. Just get as much Common Knapweed and Devil’s-bit Scabious nectar as possible before vanishing in September or October until the sun’s heat returns in mid-March.
There is so much going on now, with vast flights of ladybirds, bees, flies, dragonflies. All are racing against summer’s diminishing hour-glass. Before the sands of summer slip through your fingers, get out and savour what’s left.
Here we are in August, a month of grandeur for the special jewels of our landscapes. Below are some butterflies found this month, all recently photographed. What a summer we continue to have!
Common Blues are seemingly everywhere, even turning up in gardens where some are breeding. Some individual Common Blues are much smaller than they should be, no doubt products of drought conditions reducing the food available to the larvae. I peered hard at a couple today, so diminutive as to suggest a Small Blue.
Small Coppers are widespread but not numerous but this is typical of this lovely creatures population dynamic. No photograph can really represent its sparkling copper upper surfaces, so here I opt for a more sombre photograph of its undersides, still elegant and interestingly distinct from British populations. British Small Coppers usually have brown rather than grey undersides with a lesser defined, more subdued reddish hindwing band than the ones that grace our flowers.
Peacocks seem to be launching a takeover attempt at the moment. I am rarely shocked at their population sizes on good sites but the swarm encountered at a special site recently left me gaping in admiration as a blur of reds, golds and purples swirled in the sunshine! Never spray your nettles, the plant it breeds on!
The Brimstone is out in numbers now in its midland haunts, dawdling for several minutes at favoured Common Knapweed blooms, oblivious to bees jostling for their share.
Small Tortoiseshells are just beginning to show up in gardens, fields, parks and wood edges now, and will build their numbers to outnumber the Peacocks. Alas, when this happens, we know autumn is upon us!