1 Mixed fortunes for butterflies 28 <strong>The</strong> <strong>Nature</strong> <strong>of</strong> <strong>Scotland</strong>
It has been another poor summer weather-wise for most <strong>of</strong> the country, with perhaps the far west and north being the exception. Dr. Tom Prescott <strong>of</strong> Butterfly Conservation <strong>Scotland</strong> explains how a disappointing summer has impacted on some <strong>of</strong> our favourite insects. 1 In the UK, the chequered skipper is found only in <strong>Scotland</strong>. “How have our butterflies fared in 2012?” <strong>The</strong> answer is that we don’t quite know the definitive answer yet. <strong>The</strong> results are still coming in from the sixty or so butterfly transects that are walked weekly across <strong>Scotland</strong> during the summer, mainly by volunteers, to monitor populations. A tale <strong>of</strong> two summers Wettest Scottish readings Kirkcudbrightshire: 599.2mm (average is 305.6mm) Dumfriesshire: 573.2mm (average is 281.5mm) Wigtownshire: 514.5mm (average is 255.0mm) Driest Scottish readings Caithness:171.4mm (average is 192.4mm) Sutherland: 225.2mm (average is 272.7mm) Ross & Cromarty: 246.8mm (average is 315.7mm) Summer snippets Edinburgh received 214% <strong>of</strong> its average rainfall this summer. Glasgow 156% and Eskdalemuir 154%. Conversely, the north-east mainland and Western Isles received only 65% and 80%, respectively. Source: Crown Copyright Met Office. However, we do know that poor weather reduces opportunities for adult butterflies to fly, mate and for the females to lay eggs, resulting in reduced breeding numbers. In addition, it is not just the adults that require warm and dry weather as the development and growth <strong>of</strong> the caterpillars are limited in cold and wet weather, resulting in increased mortality due to predation and disease. This can also result in species emerging on the wing later than normal. <strong>The</strong> vast majority <strong>of</strong> <strong>Scotland</strong>’s thirty-two resident butterflies have an annual life-cycle. That means it takes a year for them to complete their transformation from egg to caterpillar to pupa to adult. As a result, the adults that we see this year <strong>of</strong>ten reflect the breeding success <strong>of</strong> the previous season, so 2013 may be a poor year. By contrast, in ‘good’ years some species are able to respond quickly by having two generations in a year. Scarce migrants Some <strong>of</strong> the commonest butterflies found in towns and gardens are migrants, including the red admiral and painted lady, which have ventured here from further afield. <strong>The</strong>y are unable to survive our winter, and thus we are reliant on new colonists every year, but they require settled weather, usually with a trailing wind, to reach <strong>Scotland</strong>. <strong>The</strong> absence <strong>of</strong> these conditions this year has meant that they have been very scarce, adding to the general lack <strong>of</strong> butterflies. <strong>The</strong> poor weather also restricts the activities and tests the patience <strong>of</strong> even the most enthusiastic butterfly recorder, who needs to have the flexibility to dash out in those all too brief spells <strong>of</strong> sunshine. Nevertheless, many <strong>of</strong> <strong>Scotland</strong>’s butterflies are designed for this weather as we have a number <strong>of</strong> northern species, including Scotch argus, northern brown argus and mountain ringlet, that favour a cooler climate and are absent in the warmer south. In addition, Scottish species have adapted to our cooler weather and fly at lower temperatures. As a result, Scottish butterfly recorders are permitted to walk their transects at a lower minimum temperature than their counterparts south <strong>of</strong> the border. Northern species <strong>of</strong> butterfly also respond quickly to brief spells <strong>of</strong> sunshine. For instance, it can be staggering to see hundreds <strong>of</strong> Scotch argus rise up out <strong>of</strong> the grass in a woodland clearing as the sun emerges from behind a cloud. However, it is not all doom and gloom. A survey organised by Butterfly Conservation <strong>Scotland</strong> <strong>of</strong> the chequered skipper, a rare butterfly that in the UK is found only in <strong>Scotland</strong>, discovered the butterfly to be present at twenty-three new locations. For more information about <strong>Scotland</strong>’s butterflies and to get involved visit www.butterfly-conservation.org/scotland or email scotland@butterflyconservation.org www.snh.gov.uk 29