Radipole Butterflies - 2013

This excellent summery of the 2013 butterfly season has been sent to me by our volunteer Allan Neilson. He also very kindly sent through photographs but technology has failed me and I can't currently post them. I'll try to add the photos soon! In the meantime, I'm sure you'll enjoy reading Allans summery of a very interesting year!

As the days get shorter and the nights longer and colder it’s good to remember warmer times and what symbolises them better than butterflies? They’re not top of most people’s list of creatures to count on a wetland but since 1977 RSPB staff and local volunteers have surveyed the Radipole Lake reserve in the heart of Weymouth for butterflies. The data goes to, via Butterfly Conservation (Dorset), the UK Butterfly Monitoring Scheme.

Up to 22 species of butterfly can be seen at Radipole in a normal year: mainly the familiar ‘garden’ species such as red admiral, peacock and large (cabbage) white etc. Holly, common and small blues, speckled wood and a smattering of other grassland ‘browns’ plus the occasional large skipper make up the rest. Very rarely individuals of chalkhill blue, silver-studded blue, grayling or green hairstreak wander on to the reserve.

After a cold winter followed by a very cold spring butterfly enthusiasts throughout Britain feared 2013 would be a disastrous year but July warmth and the August heat-wave came to the rescue, big-time. With the bonus of a warm September, Radipole had its best year since 1989 with a total 977 individuals of 18 species recorded.

The beautiful orange-tip, despite being a spring-flyer, and comma had their best-ever year and nine other species since the 1980s or early-90s. As a result of the cold spring, though, the first record for orange-tip was six weeks later than in 2012!

Small tortoiseshell populations have declined over the past two decades: some to 1/5 of their 1990 level. At Radipole the 2013 total was up 3.5 times compared to 2010-12, apparently matching the rest of the UK. Experts have suggested that more adults than usual successfully overwintered, emerged to breed in good numbers in spring and that their offspring and then a third generation also emerged in periods of good weather during the summer and early autumn. Fingers crossed that 2014 doesn’t show this to be a “flash-in-the-pan”.

Some people dislike the sight of ivy on a tree but it provides food and shelter for a host of wildlife including caterpillars of holly blue that feed on the flowers and overwinter as pupae under the tree-bark. No great surprise then that the first sighting of holly blue this year was near an ivy-covered tree on the Buddleia Loop.

The beautiful clouded yellow has ‘invasion years’ about once a decade when large numbers cross the channel with most making landfall on the coast of Dorset. Barely a handful of these get into the reserve-records but this year a pale helice form of the female was spotted - a first!

Our butterflies don’t simply disappear during the winter and different species adopt different tactics to get through the colder months. Some hibernate as adults, some overwinter as pupae and others simply migrate. Flitting across a flowery meadow it looks as though they can barely fly in a straight line, let alone cross many miles of sea. But remember that in 2009 hosts of painted ladies, another migrant species recorded at Radipole and which started their journey in North Africa, were recorded flying north from Iceland: the only butterfly species ever recorded there.

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In last year’s ‘State of Nature Report’ experts reported that 56% of the 54 species of butterfly assessed in England have decreased over the last 50 years. The RSPB can help them by looking after reserves like Radipole Lake but we can all lend a helping hand in our own gardens too. Visit www.homes.rspb.org.uk to get loads of ideas how you can join in saving nature.