Following two years with barely any immigrant butterflies, it was with some excitement that we received one of the largest influxes of Painted Lady for many years. Conditions were favourable in North Africa, and a large build-up of the population occurred early in 2009. By early April they were observed moving north across Spain in large numbers, and some isolated worn specimens turned up in Suffolk from 19th April. The first significant multiple sightings along the Norfolk and Suffolk coasts came on 15th May, and thereafter they dispersed inland, with singles being seen daily in the King’s Forest, Thetford.

Sunday 24th May was something special. All across Suffolk, observers watched a mass migration. Streams of fast-flying butterflies moving in small clusters, passed by for hours on end. Generally they were flying determinedly at about waist height across open country, climbing to pass over trees or houses, and moving on without stopping to take nectar. This is classic behaviour for migratory flight, but is not often seen widely in East Anglia. The individual butterflies were so worn that people had difficulty identifying them at first glance. Here are a few clippings from observations that reached me on that day, under a blue sky, and the warmest day of the year, until then.

Wenhaston: “Just seen PL migration in action in this country for the first time. On Black Heath this morning, in superb weather, I counted 182 flying fast and low up and over the summit ridge across a 40m wide front. All were on a WNW heading and in one hour from 09.30 BST”.

Beccles: “Birders’ web site reports: ‘large influx of PLs along Norfolk and Suffolk coast this morning, including c.100 per hour at Beccles”

“A constant westerly passage through Beccles at 12:00, increasing in numbers per hour”.

Mutford: “I managed 67 in 15 minutes watching from my garden, then a move to a more open area south of the village produced 164 in ten minutes. All were heading steadily North-west.”

Saxmundham: “My husband and I have just counted over 200 (yes two hundred) Painted Ladies between 11am and noon flying over our garden from slightly east of south to slightly west of north in a straight line. Mostly in ones, twos and threes. They are still coming though not quite so frequently.”

Rushmere St Andrew: “Has there been another influx of Painted Lady butterflies? I counted a steady stream of 22 in half an hour heading strongly north through our garden this morning.”

Dunwich and Westleton Heaths: “Large numbers crossing the roads back north towards Lowestoft this morning. They were all over the place. Whether the PLs were coming in off the sea here so early in the day or were flying northwards up the coast is not clear at this stage.”

Broom Hill Hadleigh: “Some 500 passing northwards during a period of one and a half hours in threes & fours”.

Thetford Forest: “1130 for 4 hours, Over 500 flying high over the pines, all moving in the same direction, not stopping”.

Beyton:“1120 to 1320. Hundreds in all, flying fast at about 4ft & moving from SE to NW, sweeping up over houses & down the other side”.

Bury St Edmunds Continental market morning: “A dozen individuals on the move noticed at roof top height”.

Bury St Edmunds afternoon: “Eight singles passed over during my transect walk, 1530 to 1600, all flying low, heading NW”.

“Steady stream through our field in Little Blakenham today”.

“It seems that Large Whites and Red Admirals are flying west too but in less numbers than Painted Lady”.

The migration continued through the following day, as the butterflies moved north-west across Suffolk, and more and more people noticed them. Meanwhile, a similar invasion was arriving along the South Coast of England, and also moving north. Butterfly Conservation organised a UK-wide morning watch for Sat 30th May, but this was an anti-climax in Suffolk, as the majoriNovember 19, 2011 9:14xhausted, and glad to pause to take nectar and recuperate.

As for the total numbers, several attempts have been made to offer a reasoned estimate, and figures from 10 million to 50 million have been suggested for the UK as a whole. From local observations, it would seem that the butterflies did not arrive across a broad front, but came in streams, often following routes like the Waveney valley, but with broad areas in between which did not see the same intensity. This makes it difficult to guess at totals. Certainly, after landfall, most paused for an overnight stop, and the next day’s overflights were not always fresh arrivals. The first waves were mostly very battered and short of wing scales, but later arrivals seemed to be in better shape, though not pristine.

Ten days after the influx, Painted Ladies were still to be found in most villages, but mostly as singletons lingering. The immigration was over.

With any luck, many eggs will have been laid on Suffolk’s abundant thistles, and we shall have the pleasure of seeing a second generation later this summer.