Wild spring baffles butterflies


This year's wild spring weather has baffled our butterflies: some species have emerged earlier than usual while others have been delayed by the deluge. A warm March saw a number of spring specialists emerging very early, but these butterfly-friendly conditions were followed by the wettest April on record. The wet weather has continued well into May and delayed the typical emergence periods of many species. Cold, damp weather makes butterflies less active, reducing feeding and mating activity. If the wet conditions persist they could affect the breeding success of some species later in the year.

Butterfly Conservation records emergence dates each spring. This year the Small Blue was one of the species to benefit from the mild winter and warm March. The butterfly was seen on March 30th on the Isle of Wight — one of the earliest dates ever recorded for the species. The Small Blue typically emerges in mid-April in warmer years and early May when conditions are cooler. The rapidly declining Wood White was seen on April 10th in Surrey — the species normally emerges in late April or May. The threatened Pearl-bordered Fritillary was also recorded earlier than usual. But these early emergences soon slowed to a trickle as April became a record-breaking washout.

Glanville Fritillary (Pete Eeles).

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The Common Blue and Brown Argus, which are seen in mid-April in warm years, were not reported until early May. And the Marsh Fritillary and Adonis Blue, which both emerged in the final week of April in 2011, were not seen until the second week of May this year. The threatened Small Pearl-bordered Fritillary and Glanville Fritillary also seem to have returned to more normal emergence dates after several very early years. The wild weather experienced during the first quarter of 2012 could have a dramatic effect on butterflies as the year unfolds.

Richard Fox, Butterfly Conservation Surveys Manager, explained: "Overall, butterflies have experienced an unusual spring so far — the mild winter and very warm March led to some extremely early emergences, but the cold, wet April delayed the emergence of other species. The worry about this April is that the butterflies that did emerge will have poor breeding success due to the bad weather. Unless conditions improve in the next few weeks their opportunities to breed will be very limited and, therefore, we may see population crashes later in the year or next spring. Time will tell. Last year we had a hot spring and a poor summer. This year we're having a poor spring, so let's hope the summer is better."

The public can watch butterfly emergence at first hand this May with Butterfly Conservation. The charity is running Save Our Butterflies Week — a series of events highlighting the conservation work that is helping to secure the future of UK butterflies.

Written by: Butterfly Conservation