2009 was a spectacular year for heath fritillary butterflies. I mentioned it here in my blog at the time.
But going back to the RSPB Reserves Review of 2010 there is a more detailed article about how phenomenal an event it was and how we manage the Blean Woods NNR ( with Forestry Commission, Natural England, the Woodland Trust, Kent Wildlife Trust, Kent County Council, Canterbury City Council and Swale Borough Council). Our work is supported by Viridor Credits. And our mate, Martin Warren the Chief Executive of Butterfly Conservation is the person whose research underpins the management of the site for this very rare and localised insect.
Cow-wheat is the food plant for heath fritillaries. We coppice the wood in c6ha patches every 15-20 years. This allows five years of cow-wheat growth and then a period when the coppice grows, shades out other growth and leaves , when coppiced, bare ground for the cow-wheat to reestablish. So the butterfly is chasing cow-wheat patches around the wood. Wide sunny rides provide highways for movement between cow-wheat patches and some glades are left permanently.
2009 was a really spectacular year at Blean - the butterfly numbers were something like 10 times higher than in other 'peak' years.
Yes, there probably will be a crash in numbers either next year or the year after, that is quite normal for insects and small mammals like voles etc. However the fact that the peak for this year is ten times other previous peaks would strongly indicate the woodland management for the butterfly is "bang on".
Are Heath Frits like Marsh Frits carrying a parasite so they will crash next year as the parasite numbers increase as well?