Butterflies bamboozled by 2011's weird weather


The record-breaking weather of 2011 bamboozled our butterflies and moths, with many species appearing much earlier and later than in a typical year. The hot, dry spring, combined with the second warmest autumn on record, saw butterflies on the wing from early March to mid-December.

Threatened species such as the Pearl-bordered Fritillary and Grizzled Skipper benefitted from extended flight periods by emerging weeks ahead of their normal dates as spring temperatures soared. The endangered Black Hairstreak typically emerges in June but was seen in May — the earliest emergence on record — and the Lulworth Skipper, which is restricted to southern Dorset, was also on the wing seven weeks earlier than normal.

Pearl-bordered Fritillary (Pete Eeles).

The balmy conditions of September and October saw a huge influx of migrant moths from Southern Europe. The spectacular Humming-bird Hawk-moth is thought to have enjoyed its best ever year in the UK. More than 9,000 records were sent to Butterfly Conservation, beating the previous 2006 high of 6,500.

Unseasonably warm winter weather has seen Red Admirals still on the wing in the run-up to Christmas, while some spring moths have emerged months ahead of schedule. It was hoped that the warm spring would produce a bumper butterfly summer, but Butterfly Conservation's Big Butterfly Count revealed that the number of common species was down by around 11% as they struggled in the coldest summer for 18 years.

But the effects of the record-breaking spring were still felt in some places. Several single-brooded species were recorded much later than normal: such as a rare Marsh Fritillary seen in mid-September, almost eight weeks after the butterfly should have disappeared for the year.

The second warmest autumn on record saw a huge influx of migrant moths from Southern Europe, with exotic species such as the Crimson Speckled and Vestal moths recorded into October. The UK recorded the largest number of rare Flame Brocades for 130 years, with a colony discovered at a secret location in Sussex.

And the unusual sightings are continuing well into December. Red Admirals are still regularly being seen and the unseasonably warm winter has prompted some species to hatch before Christmas, weeks ahead of schedule.

Spring Usher moths together with Hebrew Character and Common Quaker have been reported regularly since November — months earlier than they are supposed to appear.

Butterfly Conservation Surveys Manager Richard Fox said: "The weather is a matter of life and death for butterflies and moths, and 2011 has been a year of extremes. It's too soon to tell exactly how the UK's butterflies and moths have fared but the signs are that spring species, including many threatened butterflies, benefited from the hot weather in April and May. In contrast, most summer-flying species struggled to survive in the cold and damp. Autumn brought a reprieve for our beleaguered butterflies and moths, with many native species able to extend their flight periods or squeeze in an extra brood, as well as the arrival of marvellous migrant moths from overseas."

Written by: Butterfly Conservation