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21 Jun 2017

Endangered Butterfly Expansion Success

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In June 2014 Butterfly Conservation Ireland, having assessed the habitat at a coastal site in County Meath as suitable for the endangered Small Blue released a small number of adults. The first release occurred on 7 June with a second release one week later. No further release was made. Since 2007 the donor site, Portrane, has sustained massive habitat loss due to erosion of the east facing sand dunes at Portrane. Since 2007, over 90% of the Small Blue habitat on the affected dunes  have been removed by the sea. Meanwhile, the dunes along County Meath coast lacked the Small Blue, despite the presence of the sole larval foodplant, Kidney Vetch, growing in highly suitable situations over an extensive area.

On their release on 7 June  females began to lay immediately, indicating the site’s suitability. However, searches of the release site in 2015 and 2016 which took place in overcast conditions failed to find any trace of the butterfly. The sunny weather on 20 June, when the temperature peaked at 20 Celsius, made for excellent search conditions. The release site was searched and seven butterflies were seen, including an egg-laying female. She was photographed ovipositing (see below) on a west facing plant adjoining a sand track; the release site was chosen because it contains the food plant growing among grassland vegetation with areas of bare sand, (the butterfly does not appear to favour areas with a very high density of the food plant, probably because the micro-climate is not warm enough) the site is sheltered and has a west facing slope. A further visit on 21 June revealed three egg-laying females.

The butterfly has not expanded far beyond the release site; its area of occupation has expanded only a few metres north and south of the release point. This indicates a high degree of loyalty to the natal area. The smallness of the area occupied (it was searched for in the area around the site  and not found) also suggests that the butterfly is not mobile and/or may have a low rate of reproductive success. The butterfly lays only one egg on each flower head and may only lay on one flower head per plant. On 21 June two females were observed rejecting a number of food plants, presumably because these already held an egg. This results in females moving from the original release zone in search of suitable food plants, and in turn to an increase in the the butterfly’s distribution as the population grows. In time it may expand to occupy all the available habitat along this stretch of coastline. Along the Dublin coast the Small Blue has not shown significant mobility; it has not, for example, expanded its Dublin distribution to include Bull Island, a site that has existed for around 150 years. This may be due to the  absence of suitable habitat between Bull Island and the closest population north of this, at Howth. The Small Blue may be sedentary throughout Ireland,  emphasizing how important it is to protect the breeding habitat of one of our most endangered species.

We will continue to monitor the Meath population. At this point it appears to be a conservation success to savour.

Small Blue, County Meath.©J.Harding.

Egg-laying female, County Meath.©J.Harding.

Small Blue habitat in County Meath.©J.Harding.

15 Jun 2017

Event Report: Donabate and Portrane

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BCI’s Donabate trip was held during warm sunshine with a balmy southerly wind.

We walked the beach to reach the southern extremity of the dunes and entered the dunes close to Malahide Estuary. The area has extensive dunes, some very tall, and a salt marsh, dry on the day of our visit. Part of the area is occupied by a golf course, and the dunes there appeared, from our vantage point, to be in better condition for flora than the ranker areas where we stood. The site still holds flora alongside tracks and near or at the summit of the dunes, but some disturbance of the dense Marram-dominated grassland, using livestock, is needed to restore the site. We found Small Blues among patches of Kidney Vetch, Common Blues around Common Bird’s-foot-trefoil and Small Heath among the pockets of finer grasses but the area could be so much more productive if managed properly. We were concerned to see invasive species, especially clematis, clambering over the native plants.

We appeal to coastal gardeners not to grow clematis, sycamore or Red Valerian.  These escape onto sand dunes and remove native vegetation that native moths and butterflies breed on.

Later, we went to Portrane’s dunes, much reduced by erosion, but where Small Blues are more numerous. Hummingbird Hawkmoths were laying eggs on Lady’s Bedstraw plants, by dipping their abdomens, while hovering, and depositing eggs singly. Four of these aeronautical masters were observed, a high number for any site in Ireland, and easily the highest number I have seen at one time. Maybe it is set to be a good summer!

Pyramidal Orchid, Donabate. ©J.Harding.

12 Jun 2017

Moths and Butterflies to look for in June

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June is a strange month for butterflies.

The month is the first month of summer but it is a strangely quiet month for butterflies in Ireland and Britain. The dam-burst of Orange-tips, Brimstones, Green-veined Whites, Holly Blues, Pearl-bordered Fritillaries, Peacocks and others is all but over leaving a quiet landscape, seemingly flat after the frenetic explosion of spring.

June does have its jewels but unlike spring’s butterflies, it is often necessary to venture into the habitats of special character to admire them. While a typical sunny hedge-bank or sympathetically managed garden will play host to most of the spring species, June’s butterflies are choosier. You must look in Ireland’s bogs, unspoiled wet meadows, limestone grassland, flower rich dunes along our coasts for June’s beauties. Here are some of the species that can be found in June in some of our finest habitats. Later in the month, look for the Six-spot and Narrow-bordered Five-spot Burnet Moths, both day-flying, and Dark Green Fritillaries.

To appreciate the beauty of these species below, click twice on the image for an enlarged image.

Cinnabar Moth, North Bull Island, Dublin.©J.Harding.

Marsh Fritillary, North Bull Island, Dublin.©J.Harding.

Green Hairstreak, North Drehid, Kildare.©J.Harding.