The extraordinary garden of Robert Donnelly and Jane Doughty boasts enormous butterfly populations, with hundreds of butterflies counted for Butterfly Conservation Ireland’s National Garden Butterfly Survey annually. On just one day, 27 August 2020, 154 Small Tortoiseshells were counted, feasting on native flowers such as Hemp Agrimony Eupatorium cannabinum. Less frequent garden visitors, such as Cryptic Wood White, Small Copper, Comma, and Silver-washed Fritillary also make Robert and Jane’s garden at Little Eden in County Kilkenny their home.
But Little Eden is not just looking after local butterflies. The garden’s fruit and vegetable yield generated €793.42 from neighbours and passers-by, which Robert and Jane have kindly donated to Butterfly Conservation Ireland. Their help is timely, as we are currently arranging fencing for the front boundary of the reserve in Lullybeg in northwest Kildare to improve the security of the area to ensure grazing livestock needed to conserve the grassland habitats are better contained.
Butterfly fund-raising at Little Eden. Photo Jane Doughty.
A great thanks to Robert and Jane for all they do for butterflies local and national. The joy of seeing beautiful butterflies in our gardens and beyond, like this Red Admiral, depends on the care for nature shown by Jane, Robert, and all our members and supporters.
Every year, up to this, I have been contacted by one media outlet or another to explain where our butterflies are and why aren’t we seeing them. The interviewer typically prefaces his or her question with, “When I was a child I saw plenty of butterflies, so why am I seeing so few today?”
This year, 2023, is the first year that I was not asked this question. On the contrary, people commented happily about finding large populations adorning gardens and elsewhere this summer (but not in spring) and taking delight at seeing so many. Are they right, or is this just an impression formed by seeing butterflies when people have time off, like during August? Butterfly abundance peaks do not occur at the same time every year, so the poor weather in July is likely to have pushed peaks into August when the weather improved, and people had time to notice.
The familiar Small Tortoiseshell loves human company. This lovely butterfly is feeding in our gardens now, and entering our houses to seek roost and over-wintering sites. It appears to have thrived in 2023. But over the period 2008 and 2022, it has declined by 36%.
Let’s leave the butterfly year of 2023 to the annual report we publish under the Report heading. The National Biodiversity Data Centre (NBDC) has published the Irish Butterfly Monitoring Scheme Newsletter for 2022, the warmest year on record. What do the findings tell us?
Firstly, just a quick word on how the information is obtained. The Irish Butterfly Monitoring Scheme (IBMS) involves walking a fixed route (transect) on a weekly basis from 1st April to 30th September each year when weather conditions are favourable. The number of the different butterfly species seen along different sections of each transect are recorded. These records are the basic data upon which the analysis is based. The IBMS tracks population and phenology (time of flight) trends in Irish butterflies, detecting the impacts of factors such as land use and climate change on the Irish butterfly population.
A reduced effort transect scheme, the Five Visit Monitoring Scheme (FVMS) helps to capture abundance. (Several Butterfly Conservation Ireland (BCI) members are involved in these important schemes and BCI runs its own recording scheme which provides data on distribution).
The results in the 2022 report do not make for happy reading.
The multi-species index which estimates the overall direction of change in the butterfly population using Ireland’s most common resident butterflies (15 species) shows that once again there was a moderate decline (-57%) in the number of butterflies flying in 2022 when compared with the baseline year of 2008 (the start of the monitoring scheme). Only the Holly Blue Celastrina argiolus showed an increase in the last 10 years (+149%), with all other species showing uncertain, stable or moderately declining trends.
Holly Blue male on Common Heather, often called Ling. This butterfly has probably benefited from the warming climate.
It is important to note that the multi-species index is a useful index to show overall trends in population changes of common butterflies of the wider countryside. However, it does not generate sufficiently reliable data to track how the populations of our more localised or specialised butterfly species are changing. This is because there is currently not enough data being recorded for these species. To capture adequate information on these species additional species-specific schemes (like the Marsh Fritillary Monitoring Scheme) are needed.
Fertiliser and herbicide use are removing habitat for the Green-veined White which will also be at risk from drought caused by drier summers predicted as a result of climate change.
The greatest declines during the period 2008-2022 are the Green-veined White (-81%), followed by Meadow Brown Maniola jurtina (-74%), Ringlet Aphantopus hyperantus (-72%), Large White Pieris brassicae (-71%), and Small Heath Coenonympha pamphilus (-68%). Aside from the Small Heath which has lost the status of being a wider countryside butterfly, all of these are, which suggests that there are significant problems in our environment. These are widespread butterflies, which suggests a widescale environmental crisis. Butterfly abundance will rise and fall naturally from year to year, but these declines span 14 years and are persistent.
Cryptic Wood White feeding on Bush Vetch. Given their comparatively low prevalence in our ecosystems, bees, butterflies and moths preferred the plant family Fabaceae, which includes Bush Vetch, Common Bird’s-foot-trefoil and other wild peas. Removal of these plants using herbicides and mowing is disastrous.
Without great changes to farming methods, this is unlikely to change. The causes are not provided by the IBMS data but we can see that our farmed landscape is doused with herbicide, pesticide and synthetic fertilisers. These damage vegetation and butterflies; there is scientific evidence for this, as well as the more subjective, anecdotal support derived from personal experience.
A damp grass field near my home supported common countryside butterflies such as Orange-tip Anthocharis cardamines, Green-veined White Artogeia napi, Cryptic Wood White Leptidea juvernica and the Small Copper. Intensification began to occur. The vegetation was topped early one year to tackle rushes Juncus spp. This did not impact the butterflies but this spring herbicide was applied. It completely removed Common Sorrel Rumex acetosa (Small Copper foodplant), Cuckooflower Cardamines pratensis (Orange-tip and Green-veined White foodplant) and most if not all vetches especially Meadow Vetchling Lathyrus pratensis (Cryptic Wood White). I observed none of these species in this field in 2023. Even when herbicide is not used, nitrates play havoc with many butterflies.
While the EU Nitrates Directive has cut organic nitrates that can be applied to 220kg of nitrate per hectare, this figure is above the safe physiological tolerance level of the larvae of the six butterfly and moth species (Small Copper, Sooty Copper Lycaena tityrus, Speckled Wood Pararge aegeria, Small Heath, Blood Vein Timandra comae and Straw Dot Rivula sericealis) studied by Susanne Kurze and her colleagues.
The Small Copper belongs to the same butterfly family as the Common Blue. It breeds on Common and Sheep’s Sorrel, both dock species. This beautiful, active butterfly is widely distributed but rarely numerous in any one place. The Small Copper is vulnerable to intensification practices on farms.
The Kurze study showed declines in the survival of all six species when fed on sorrels and grass (depending on the moth or butterfly) when their plants were given between 150 and 300 kg N ha−1 year−1. At the higher rate, the sorrels died. The survival rate of the Small Copper was nearly 50% lower in the group fed on N300 than those fed on unfertilised plants. Grass-feeding species also suffered. The survival rate in the Small Heath and Speckled Wood declined by one-third under both nitrogen treatments compared with unfertilised plants. Interestingly, some Speckled Wood larvae survived to pupation but the Small Heath larvae that died did not live longer than 45 days or reach pupation. The most sensitive species was the Straw Dot. Its survival rate declined by half between the control and the N150 treatment and about 80% between the control and the N300 treatment.
The Sooty Copper (female), a European species, proved highly sensitive to increased fertility. Photo taken in Tuscany J. Harding
This study only scratches the surface. It did not deal with the impacts of these fertiliser concentrations on the overall vegetation in the wild, or the effect of more vigorous plant growth on soil and above-ground temperatures, all of which can also be expected to influence survival rates.
There is a great need for sustainable farming. Stocking rates are absurdly high, maintainable only by massive fertiliser inputs which poison wildlife, pollute water and add to global warming gases.
There is certainly no excuse for continuing to kill off our planet’s most beautiful animals. We waste about one-third of our food, so we are grossly over-producing and over-consuming. Our butterflies don’t need it and nor do we.
Key References:
Judge, M and Lysaght, L. (2023). The Irish Butterfly Monitoring Scheme Newsletter, Issue 15. National Biodiversity Data Centre.
Kurze, S., Heinken, T. & Fartmann, T. 2018, “Nitrogen enrichment in host plants increases the mortality of common Lepidoptera species”, Oecologia, vol. 188, no. 4, pp. 1227-1237.
After being drenched and underwhelmed by daytime maxima of 13°C during July and August our early September sunshine and warmth is a serious restorative. Today we are looking at 22°C to 26°C; yesterday temperatures climbed above 27°C in some areas; that’s more like it!
Met Eireann tells us that July 2023 was “very wet, cool and dull.” In fact, it was the wettest July on record. The highest temperature recorded in July was on one day, July 7th, and was 24.1 °C in Fanad, County Donegal. While August had better weather, it was not a classic summer month. Described as “mild and changeable” the temperatures were above average nearly everywhere but so was rainfall. Poor Newport in County Mayo had 29 wet days during August!
This doesn’t look like our butterflies should have had a good year, given what our ‘summer’ weather was like, and if I include June this was much better (warmest June on record at most weather stations, with average rainfall). Athenry, County Galway and Shannon Airport, County Clare experienced 27 consecutive days with maximum air temperatures > 20.0 °C, ending on Saturday 24 June. Some of our summer flying butterflies had a spectacular year, with some very high abundance reported to Butterfly Conservation Ireland.
On September 3rd, for example, 246 Small Tortoiseshells were reported from Lullymore, and hundreds of Small Whites and hundreds of Small Tortoiseshells were seen on a wildlife-friendly farm near Maynooth. Red Admirals and Commas are booming too, Green-veined Whites, which love moist, damp habitats, are up, and so are Meadow Brown and Ringlet populations. Holly Blue seems to be thriving and spreading. Early in August, I counted 91 Brimstones just in a small area in Lullybeg; there must have been hundreds of this highly localised butterfly in the bogland in northwest Kildare.
So what can we expect this month? Top of the list is the Small Tortoiseshell, which is everywhere now, even in the Sutton area in Dublin, where the butterfly has gone into a second brood for the first time in many years, thanks probably for July’s bountiful rain and the boost to Stinging Nettles.
Small Tortoiseshells will often feed together in gardens during September.
The highest numbers of the year are present now but this abundance will be brief. While they are busy feeding, they gain weight and their flight is considerably slower, especially in the cooler temperatures expected as September advances. It is risky to stay on the wing for too long, as dragonflies and birds are eager predators of butterflies. In the past few days, Small Tortoiseshells have entered buildings to look for a secluded nook to pass the winter in. In fact, some will find a spot, retain a topographical memory of its location, and fly out to resume feeding, safe in the knowledge that they know where they will hunker down. Experiments carried out in England show that the Small Tortoiseshell relies on its memory to relocate important sites.
They do not always choose well. A centrally heated building will awaken them in autumn, and deceive the butterfly into the idea that spring is here. Capture and release is not the advised approach; capture and relocation in a cool place is the best policy. A plastic lidded box lined with absorbent kitchen roll in the bottom of the fridge is a good place; no air holes are needed. Release them in March when a warm spell, predicted to last a few days, arrives.
This Small Tortoiseshell is readying himself for winter.
By contrast with the Small Tortoiseshell boom, Peacocks on the wing are few in number. Most are in hibernation and will stay put despite the blandishments of high September temperatures and nectar. This poor Peacock looks the way we might feel after a bad day. Remarkably, this butterfly flew away, albeit awkwardly, after the photo was taken. Staying out late is risky, as pointed out earlier!
A Hard Day’s Night! This Peacock has likely suffered an avian assault. Find a dark tree trunk, a hollow trunk, a cave, a pipe, or a disused building quickly!
Another butterfly that passes the winter in the adult stage, the Brimstone, is similarly out there in greatly reduced abundance. Most of them are concealed in evergreen foliage, blending with their leaflike wings to aid blending. We will see a few still feeding, and these are wisely very close to over-wintering cover.
This Brimstone was observed on September 4th, feeding quite sedately. This suggests he will feed for a few more days before hibernation. Brimstones that are about to move into cover for the rest of the year are often skittish, nervous feeders.
Green-veined White butterflies really suffer from droughts, but not this year. Here is a male on Devil’s-bit Scabious, his forewings packed with citral (C10H16O), a pheromone used to seduce a female. It is a powerful, sweet fragrance, easily detected by a human, so it must be an all-enveloping experience for a female Green-veined White. This butterfly is still breeding and the species will pass the winter as a caterpillar.
Green-veined White on Devil’s-bit Scabious. Females have two spots on each forewing, males have one.
And now for something different! The next two butterflies are migrants. Unlike our resident butterflies, these two are not cold-adapted species. Unlike our resident natives, these do not have a rest phase in their life cycle and are continuously brooded, which means they breed and grow throughout the year. In more technical language, they do not undergo a diapause phase. If a butterfly cannot delay breeding, it requires the correct conditions to reproduce throughout the year. These conditions are not currently available in most of northern Europe, so an escape strategy must be applied. Migration is a way to avoid the onset of unsuitable conditions. In spring and summer, the heat in North Africa and parts of Southern Europe drives some migrants north to find the conditions needed.
The Red Admiral is our most regular migrant butterfly. It occurs in Ireland from about March to November and they leave during the autumn months. When the herbaceous flowers are gone, it uses ivy nectar, sap runs and overripe fruit for sustenance. There are still Red Admiral larvae on nettles so we will see the adults for some weeks yet.
A Red Admiral caterpillar in early September. The caterpillars are polymorphic. The commonest forms I have seen are the olive form shown here and the black form.This Red Admiral is feeding in my garden along with two others. None have shown any mating behaviour, which is an indication of a migratory intent!
The lovely Clouded Yellow is a visitor too, but in smaller numbers and often later in the year, especially during September and October. In some years a mass arrival followed by breeding occurs. In these years, they arrive earlier, usually from April onward.
In years when they arrive later, the Clouded Yellow does attempt to breed, but it is likely that the attempts fail as the temperatures drop. But the butterfly is a delight to see whenever it appears. This female was seen in Lullymore by Pat Wyse and Fionnuala Parnell, enjoy!
Clouded Yellow, Lullymore, 2nd September 2023. Photo Pat Wyse.
Back to our resident butterflies, the Comma is beginning to hatch its second generation which flies during autumn. This makes it unique among our butterflies. We will say more about the Comma in our October post, but keep a close eye on ripe blackberries and ivy in the coming weeks.
Comma on Devil’s-bit Scabious.
The heatwave during the first week in September has coaxed migrants from southern Europe to journey north. This Vestal is one of four to visit a garden in County Meath on 7th September. The colour of this moth is strongly influenced by the temperature experienced by the pupa with bright specimens like this one the result of hotter conditions, suggesting that this one is from the Mediterranean area of Europe or North Africa. It is mainly a nocturnal moth but can be found on grass stalks during the day.
Vestal. It breeds on docks and Knotgrass.
All photos by J. Harding except Clouded Yellow P. Wyse.
