Posted: Wednesday 7th August 2013 by BrianEversham
Cranefly, Nephrotoma flavescens, by Brian Eversham
Long cold spring, long hot summer - an overview of nature's winners and losers in these strange climactic times
I hope you’re enjoying the summer, despite some of the strangest weather we’ve seen. Wildlife’s response to the long winter, cold spring, extreme heatwave and heavy rains has been mixed. The lack of ladybirds and wasps hit the headlines last month, but the wider picture is more complex. Many insects which should be plentiful in July and August are almost absent - I have never seen so many empty flowerheads of wild carrot, hogweed and ragwort. These wonderful nectar sources are usually thickly crowded with masses of soldier-beetles, flower-beetles and hoverflies, but these are all very scarce this year. And talking to friends who run a moth trap, it was among the worst springs and early summers on record for moths, though things have improved in July.
Above: Gatekeeper butterfly, Pyronia tithonus, at Old Sulehay and Cuckoo bumblebee, Bombus (Psythirus) sylvestris, male, on hemp-agrimony, Eupatorium cannabinum, at Woodwalton Fen
Conversely, one species of tiger cranefly, top, has been conspicuously abundant and attracted media interest. The mid-summer butterflies such as Ringlet and Gatekeeper are doing well, and lots of Peacock, Purple Hairstreak and Common Blue butterflies have emerged in the last couple of weeks. Silver-washed Fritillaries have re-appeared at several of our woodlands (after small numbers in previous years - so, they are probably established and breeding now, rather than wanderers), and the magnificent Purple Emperor has turned up at Woodwalton Fen and Brampton Wood, about 20 miles from the well-known Northants site.
Bumblebee numbers have picked up, with the appearance of the first males of the year, and on some sites, large numbers of Cuckoo Bumblebees (nest parasites of the true bumblebees) are feeding on the thistle and teasel. There’s also a hint that there might have been a wave of migration from mainland Europe, too, with quite a few Silver Y moths around, the overnight appearance of large numbers of Marmalade hoverflies on fennel in my garden, and the occasional report of Painted Lady butterflies (which are almost all visitors to Britain).
The underlying story is one of long-term weather impacts on populations. A few species which have several generations in a year, such as greenfly and some slugs, can build up large populations within a summer. Most other insects, and many birds and mammals too, breed only once a year. If their breeding season is disrupted by bad weather or food shortages, it has knock-on effects for several years following. So, the absence of soldier-beetles and some butterflies is probably a consequence of 2012’s cold and wet spring. By contrast, the craneflies, whose larvae - leather-jackets - live in the soil and feed on the roots of grasses, benefited from the wet season.
I’ve focussed on insects, partly because they make up the vast majority of wildlife species. But other, more flamboyant wildlife, such as birds and bats, mostly feed on insects, so a bad spring for caterpillars will probably have meant a devastating breeding season for songbirds. Our woods may be rather quiet next spring…