Event Report: Bull Island Visit

Leaden skies with some bright patches offered hope for at least a dry spell for our Bull Island outing today. We assembled at the roundabout (luckily I brought my net as an identification point!) and headed north along a sandy track. Deep pink Common Vetch and splashes of buttercup flowers gave a sharp contrast against the muted green of the wall of grasses that edges the path but little else was in bloom.

We reached the ‘Alder marsh’, which was very dry, and soon Marsh Fritillary larvae were observed. These were fully grown and sluggish or stationary. Most were on dry grass, some on the foodplant, the Devil’s-bit Scabious. Most of the larvae will have pupated and a few adult butterflies may have emerged but the sun needed to coax any that have reached adulthood did not appear. The larvae remaining are most likely infected by a parasitoid wasp that prolongs the larval stage so that the wasp can delay its own emergence to coincide with the availability of the next generation of Marsh Fritillary larvae which will be present after mid-July. We eventually found a chrysalis, in the open, attached to the upper surface of a foodplant leaf (an untypical pupation site). A Drinker Moth larva,  a Common Lizard and a delightful and stunning Cinnabar Moth were found. We managed to place the moth it in a jar where it eventually settled for a photo shoot!

The Marsh Fritillary breeding site is in excellent condition. The sward is open, contains a range of heights and has a high density of foodplant growing among dry, warm sward litter, ideal for larval basking. There is plenty of nectar on the way, with Common Bird’s-foot-trefoil beginning to flower. Cutting and removal of the highly invasive Sea Buckthorn has also improved the habitat-congratulations are due to the site managers for this vital conservation intervention.

It would have been wonderful to see the beautifully patterned adults but we might see them next weekend at Lullymore. It was a lovely day for conversation and it was lovely to be in such a warm and engaging company. The constant singing of the skylarks provided a delightful atmosphere. The view from the marsh looking northwards to Howth is uninterrupted rural Dublin at its finest. You’d never think the capital city is just behind you!

Thank you for everyone who joined our outing and made it special.

Marsh Fritillary on Bull Island, 12 June 2017.© J.Harding.

Burren Delights

At this time of year, the Burren in Counties Clare and Galway is a rewarding place for any butterfly enthusiast. The Burren, an area of exposed carboniferous limestone contains the best habitats in Ireland for most of Ireland’s butterflies, including many of our rarest species.

Much of the Burren remains unspoilt by modern farming. The ground is largely inaccessible to modern machinery and much of the region is legally protected by the designations under the Habitats’ Directive.

The warm limestone and fertile soil pockets produce a wide range of plants that moths and butterflies need for nectar and food for their larvae.

The main habitats for butterflies in the Burren are open scrub and woodland on limestone, limestone pavement with pockets of soil and open limestone grassland. Areas of heathland and species-rich wetland also exist.

I spent much of last Saturday enjoying the butterflies that live in an especially warm, dry, sheltered area near Clooncoose valley containing open limestone pavement, patchy open scrub backed by tall scrub. The air temperature barely reached about 14 Celsius making this warm site the ideal spot to look for these newly-emerging spring species. This is one of my reliable spots, where year after year I am guaranteed to see my target butterflies.

I did not see the Pearl-bordered Fritillary anywhere else in Clooncoose valley that day. I knew the ‘Pearl’ must be running late this year. In 2009 I saw it in numbers in the valley as it abounded in the glorious heat of April that year.  But this lovely creature is highly variable in its emergence. The pupa can last a little over a week when the weather is good but the pupal stage can last a month, perhaps longer, in cold weather.

Fortunately, I saw three pristine males. They spent time basking quite frequently between low patrolling flights and the occasional brief pause to feed on the golden Common Bird’s-foot-trefoil blooms. The orange-red wings of this butterfly are a sharp neon on the soft grey limestone and really needs to be admired. This is our rarest native resident and is so specialised there seems little chance of it expanding its distribution in Ireland.

A less dramatic butterfly, the Wood White, also flies low to the ground but instead of the rapid flight of the Pearl-bordered Fritillary, you will notice a feeble, floppy flight. It looks as though it will float to the ground, depleted of vigour but it shows an unexpected resilience for a dainty flyer by staying airborne for long periods. This delicate white is somewhat less restricted in its distribution but is confined to scrub and woods on limestone habitats in Clare, Galway and perhaps Mayo.

A third butterfly, much more widespread than the previous two species, is the Dingy Skipper. In the Burren, this moth-like butterfly is represented by a subspecies, baynesi which is unique to the area. It is paler than the Dingy Skippers found elsewhere. Its paleness helps it to melt into the limestone, aiding its blending ability. This subspecies is recognised widely as a distinct butterfly. The Dingy Skippers I observed were darting about, chasing each other and the Pearl-bordered Fritillaries, all eager to locate a mate.

Interestingly, I saw only one female Dingy Skipper and no female Wood White or Pearl-bordered Fritillary, suggesting that we are very early in the flight period of all three, as the earliest females typically start to emerge a day or two after the first males appear.

Later, two new Small Coppers appeared, their shiny copper adding their glamour to the scene.

All these species have in common a liking for warm, dry well-drained ground found in the Burren, our greatest butterfly haven. If you want to see these butterflies, visit in good weather during May.

Pearl-bordered Fritillary basking on limestone at Clooncoose, County Clare.© J. Harding.
Pearl-bordered Fritillary: note the seven pearls bordering the outer edge of the hindwing; these give the butterfly its English name. © J.Harding.
Dingy Skipper subspecies baynesi, which is unique to the Burren. © J. Harding.
Wood White, a rarity headquartered in the Burren. © J. Harding.
An early season Small Copper basking on dry vegetation, Clooncoose, County Clare. © J. Harding.