The results generated by the various recording schemes for butterflies have started to appear over the last few weeks. Looking across these it is possible to establish an idea of how 2010 shaped up and it seems that many species benefited from the hot June and July weather, which followed on from a cold winter.
As I noted in one of last summer’s columns, the summer heat helped species like White Admiral, which were able to shorten the time spent as a mature caterpillar and chrysalis and so reduce the levels of predation, a key factor to determining the size of the summer generation. Other butterflies, notably some of our less common species, also did well, with the Silver-washed Fritillary delivering the big success story for East Anglia. It appeared across the region in good numbers, re-establishing itself at some sites after a long gap.
Many of our familiar species did less well, especially immigrants like Red Admiral and Painted Lady, numbers of which were both very much down on the 2009 influx that grabbed the headlines. Such short-term fluctuations are not cause for concern. Some species exhibit regular changes in abundance that are shaped by parasite populations. The Holly Blue, for example, has populations that cycle depending on how common a particular small parasitic wasp happens to be. When the Holly Blue enjoys a good year, this allows the parasite to do well, meaning that the levels of parasitism will be greater the following year; this, in turn, brings the Holly Blue population back down.
Being able to see longer-term trends is a key component for any attempts to conserve our butterfly populations. This is where systematic recording schemes, like the Wider Countryside Butterfly Survey, carried out by volunteers from Butterfly Conservation and the BTO (many of the BTO’s bird recorders revisit their survey squares to record butterflies for this survey). Less common species are monitored by coordinated counts at key sites, as is the case with the Silver-studded Blue monitoring that takes place on some of the Norfolk heaths. Volunteers provide a key role in this work, working in collaboration with researchers to keep tabs on these changing populations.
Most butterflies are fairly straightforward to identify, meaning that (with a little training) you can make a valuable contribution to the work of organisations like Butterfly Conservation. If you would like to get involved in some of the butterfly recording work taking place across the county, or simply want to find out more about Norfolk’s butterflies, then why not contact the Norfolk branch of Butterfly Conservation. Visit www.norfolk-butterflies.org.uk or contact Chris Dawson on 01603 545092 if you would be interested in helping with their Wider Countryside Butterfly Survey.