The good news is that the heath fritillary has enjoyed another splendid season, marginally better than last year’s excellent total. The graph below shows how numbers have built up rapidly over the past three years from a nadir in 2016-7. Although populations collapsed at several normally reliable colonies, these losses were more than made up for by healthy numbers at other sites, and by strong colonisations of several recently-managed areas – coppice and ride verges – where the butterfly’s food-plant, cow-wheat, has moved in. What goes up doesn’t necessarily have to come down, but a glance at the graph suggests that the butterfly is a dynamic species, so it wouldn’t be surprising if a crash or, less worryingly, a gentle downward slide were to occur before long.
Here’s another graph, but unfortunately heading in the opposite direction. I last wrote about common spotted orchids two years ago, lamenting their apparently inexorable decline on the reserve, and June’s survey confirms that this attractive species is heading towards local extinction. The so-called orchid glade held only 61 plants, compared to 2034 in its glory days just twelve years ago, so it may soon be time to think up a new name for this small clearing. An incredibly dry spring evidently hasn’t helped, as many of the plants were very short, with weedy little flower spikes.
The drought was proving stressful for other species, and devil’s bit scabious, which doesn’t flower until late summer, was wilting badly, and some of the cow-wheat was beginning to suffer, which could be bad news for the caterpillars of the heath fritillary. Fortunately, a return to cooler conditions and the advent of much-needed rain in early June were sufficient to stave off serious repercussions, at least for the time being.
An interesting consequence of lockdown can be seen from the reserve’s access track: with Kent College closed for an indefinite period, there was no point in mowing its sports field, and the grass was simply allowed to grow, that is until about 70 sheep from the college’s farm were introduced in June, creating a slightly surreal spectacle as they calmly grazed the football pitches and running tracks!
Wilted devil’s bit scabious, the leaves twisted to reveal their paler undersides.
Part of the orchid glade in its glory days.
Heath fritillary on a common spotted orchid.
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