2005 Butterfly Report

by Rob Parker

2005 was the hottest year the Northern Hemisphere bas ever experienced, according to climatologists. However, the Suffolk weather was not hot compared to 2003, and was sufficiently erratic to spoil the butterfly season for some species, with heavy rain at unwanted moments. It was an ordinary year for our commonest residents, a depleted year for the Vanessids and an unusually poor year for migrants. The progressive decline of Grayling and Wall Brown continued, and most observers commented on a boring, poor, unexciting or disappointing season.

Fortunes were mixed for our scarcer species, with encouraging records from fresh sites for White Admiral and White-letter Hairstreak, ups and downs for Dingy Skipper and a big down for the Silver-studded Blue at Purdis Heath.

A couple of rare aberrations were found in the wild, and further excitement resulted from the discovery that Purple Emperor was flying in Suffolk (following releases made in earlier years). Meanwhile, counts from transects showed that numbers were not down by as much as casual observation led one to think. Overall then, 2005 has been notable only for a handful of unusual sightings; generally it has been a year of low butterfly numbers.

Weather

Average temperatures were again about a degree up on historic averages, but sunshine was only average. Rainfall was low initially, but it was wetter than average in the summer. The table below shows mean temperature, sunshine for and rainfall for East Anglia, all presented as anomalies compared to averages over the period 1961 to 1990. Spring warmth opened the season nicely, but some very wet days inhibited recording activity in summer. Autumn was warm and extremely sunny; sadly there were very few butterflies on the buddleia, but there were plenty of Red Admirals well into November.

Monitoring the BAP Species

This year's Dingy Skipper survey got off to an excellent start, with a record count at the Wordwell/King's Archery colony, but a worrying count of just one at RAF Barnham, where grazing by sheep has just been introduced. The Silver-studded Blue survey was blighted by a false start and heavy rain, resulting in incomplete counts at the Minsmere sites. Results elsewhere were mixed, with two newly colonised sites apparently in good health, but a very worrying deterioration at Purdis Heath, where no one saw more than 6. The White-letter Hairstreak was again rather well recorded in 2005, with 9 sightings from

Table 1. 2005 Weather for East Anglia

Mean Temp Anomaly Sunshine Anomaly Rainfall Anomaly

Season Deg C % up hrs % mm % Winter 04/05 5.6 1.2 193.9 115 98.9 69 Spring 9.4 1.2 435.0 98 109.4 79 Summer 16.5 0.9 552.4 97 152.4 98 Autumn 12 1.5 386.8 121 170.9 105

Source: www.meroffice.gov. uk/ climate/ uk Anomalies are measured against the 1961 to 1990 averages.

previously unknown sites. Over the period since 1995, records have now been made from 84 tetrads, although not all of these represent established colonies, and the steady increase is a measure of recording effort rather than a genuine spread of the species. Separate detailed accounts for each of the BAP species are available as annexes [Not attached].

Migrants

It was a poor year for migrants, with Painted Lady appearing in very low numbers. There were only 16 Clouded Yellow sightings, and no Camberwell Beauties or Queen of Spain Fritillaries.

Swallowtails

Two adult Swallowtails were seen, one at Trimley and the other on the outskirts of Ipswich. There was no recurrence of the flurry of sightings made in 2004, and no reports oflarvae.

Residents

Orange-tips, Holly Blues and Green Hairstreaks all did well in spring, although Holly Blues were not so numerous in the second brood. By summer, the shorrage of Small Tortoiseshells, Peacocks and Commas was a topic of general awa~eness, and it is possible that they are suffering from the spread of the parasitic Tachinid fly Sturmia be/la. Again, there was a very poor showing of the Wall, although the Grayling and Small Heath did not deteriorate below their low 2004 numbers. The White Admiral had a strong year, with sightings in 31 terrads, including 6 in totally new sites, following a year that produced a partial second brood. :rhe Small Tortoiseshell, noted in 66% of tetrads visited, remains our most widely reported butterfly, though it was closely challenged by the Speckled Wood and Green-veined White.

Purple Emperor.

The surprising discovery of Purple Emperors flying in Theberton Woods was found to be the result of clandestine releases dating from 2000. It remains to be seen whether they can establish a sustainable breeding population in the wild.

Early/Late Records

Spring brought only one earlier than ever record a Brown Argus on April 28th. Autumn was mild, sunny and extended, with the Browns flying later than usual - on October 6th, both Meadow Brown and Gatekeeper were still on the wing. This is later than previous records by just a day for Meadow Brown, but by 10 days for Gatekeeper. Speckled Woods, Large Whites, Commas and Peacocks were all to be seen in sunny spells, but it was Red Admirals that were most noticed, with 33 records in November/December.

Geographic Coverage

Records were received from 493 tetrads, which is better than 2002 and 2003, but does not match last year's high of 530. In all, some 295 recorders contributed, and "regulars" were joined by new faces, some from SNS, others through BC's Spring Survey, and a good number through participation in the BTO's Garden Bird Watch, which encouraged butterflies to be noted alongside birds. Our distribution maps are improving as an increased number of observers record butterfly numbers, rather than simply presence.

Speckled Wood

by Beryl ]ohmon