Suffolk Natural History, Vol. 46
48
2009 BUTTERFLY REPORT ROB PARKER After two poor years, 2009 came as something of a relief. For most species, it has been a decent season, and the major immigration of Painted Lady was very welcome. Only for a few species has it been a poor year, and long-term declines account for some of these. Good recording effort has resulted in meaningful coverage for the whole of the 5-year period. Annexes A and B provide analysis of the season’s results and compare them with previous years. Weather The winter was colder than recent mild years, and even below average judged by historic averages, with February bringing frosts, cold winds and snow. In all, air frosts occurred 38 times in East Anglia. Thereafter, things improved, and 15 March was warm enough to bring out first butterfly sightings for many observers. Spring was warmer, sunnier and drier than 2008. The summer figures in the table below are averages, and mask the reality that July was very wet (15 rainy days), whereas August and September were unusually dry, creating conditions of drought for some larval host plants. Table 1. 2009 Weather for East Anglia Season Winter 08/09 Spring Summer Autumn
Mean Temp
Anomaly Sunshine Anomaly Rainfall
Anomaly
Deg °C
Deg °C
hrs
%
mm
%
3·5 10·0 16·8 12·0
-0·8 1·4 0·8 1·4
179 547 622 348
103 121 107 107
134 85 154 162
91 63 103 94
Source: www.metoffice.gov.uk/climate/uk Anomalies are measured against the 1971 to 2000 averages [updated baseline]. The shortage of sunny April days with temperatures of above 16 °C (at the SNS weather station in Boxford) again explains why transect walkers had difficulty in getting any walks in within the stipulated weather criteria. May was slightly better, but there were still twelve days that failed to meet the basic butterfly flight criteria, delaying the emergence of species that had passed the winter as pupae. In June there were 13 days that provided little opportunity for flight, or pairing. The frost and snow of December (the coldest December for 15 years) will be bad news for some species, particularly overwintering Red Admirals. However it could also kill parasitic fly and wasp species, once again bringing benefits for host species next year.
Trans. Suffolk Nat. Soc. 46 (2010)