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.