2003 BUTTERFLY REPORT

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BUTTERFLY REPORT, 2003

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2003 BUTTERFLY REPORT ROB PARKER Described by Butterfly Conservation as “A vintage year for butterflies”, 2003 has indeed been an outstanding season for most species in Suffolk. The reasons are fourfold: 1. A mild winter allowed the survival of a high proportion of overwintering eggs, larvae, pupae and hibernating adults from the (below average) 2002 season. 2. The abrupt transition to a hot, dry summer meant that many species emerged en masse, causing peak numbers to exceed the norm by some 10 to 15%. 3. The continuation of the hot, dry conditions was ideal for the multi-brooded species to reproduce well, and some had an extra brood. 4. Superimposed on this, was an excellent year for migrants, with an exceptional influx of Painted Lady arriving in May and their progeny emerging in July. The net result was an abundance of butterflies; enough for the man in the street to notice, and to catch the attention of the local media. Suffolk’s Biodiversity Action Plan (BAP) species all had strong seasons, and most of our resident species fared well too. Weather Average temperatures were up on historic averages in every month of the season, sunshine was materially up from January to April, and rainfall was significantly low in August and September. Table 1 shows month by month temperature and sunshine for East Anglia, presented as anomalies compared to averages over the period 1961 to 1990. During the season, rainfall almost ceased on 11 August and after 15 dry days qualified for 11 continuous days of absolute drought, through to 5 September, when there was a switch to local deluges. Days of rain (>1 mm) measured close to Bury St Edmunds are shown below. The Suffolk summer passed without interruptions from gales, contributing to what was overall an unusually favourable climate for lepidoptera. Table 1 Month May June July August September

Max Temp Anomaly Deg C 17·6 21·9 23·1 24·3 20·9

% +1·7 +2·7 +2·0 +3·2 +2·4

Sunshine hrs 197 220 204 233 224

Anomaly Rain days Rain days % +3 +13 +8 +27 +56

av 9 8 8 8 8

at BSE 12 11 11 2 4

Sources: www.metoffice.gov.uk/climate and local meteorologist Alan Messem.

Trans. Suffolk Nat. Soc. 40 (2004)


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